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PSTG Document SAR Science Requirements for Ice Sheets

SAR Science Requirements for Ice Sheets (V1.0) – May 17, 2013

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SAR Science Requirements for Ice Sheets

A recommendation to the Polar Space Task Group (PSTG)

V1.0 -‐ May 2013 Coordinating Author and Point of Contact for this document: Bernd Scheuchl Associate Project Scientist Department of Earth System Science University of California, Irvine Croul Hall Irvine, CA 92697-‐3100 e-‐mail: [email protected] (A list of supporters and contributing authors is provided in Appendix H) Executive Summary Following the successful internationally coordinated SAR data acquisitions over ice sheets during the International Polar Year 2007/2008, efforts are undertaken to continue data acquisitions in the spirit of collaboration. The Polar Space Task Group (PSTG) is succeeding the IPY coordinating body of international space agencies, Space Task Group (STG). The PSTG SAR Coordination Working Group was created to address the issue of SAR data acquisitions in the cryosphere. This document outlines the SAR data requirements for the ice sheets of Antarctica and Greenland. The general requirements have been presented at the first SAR Coordination Working Group in November 2012. Here, more detailed, sensor specific recommendations on SAR acquisitions are made in response to a SAR Coordination Working Group request. The sensor specific recommendations are summarized in the appendix (A, B, C, and D) and will form the basis for the ongoing discussions of the SAR Coordination Working Group. Relevant areas containing ice caps are mentioned in appendix E, but are not the focus of this document.



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Table of Contents

1 Introduction ....................................................................................................................... 4 2 Science Requirements ..................................................................................................... 5 Observation Requirements .................................................................................................. 7 2.1 General Recommendations ................................................................................................. 7 2.2 Current and Upcoming SAR Missions .............................................................................. 8

3 Antarctica ............................................................................................................................ 9 3.1 General Observation Requirement .................................................................................. 9 3.2 Reduced Observation Requirement (if sensor capacities require scale down) 9 3.3 Science Mission Requirement (assuming no conflicts with other priorities) 10 3.4 Specific Considerations -‐ Antarctica ............................................................................. 10 3.5 Recommendation for X-‐band High-‐Resolution Acquisition Super Sites -‐ Antarctica .......................................................................................................................................... 10 3.5.1 TerraSAR-‐X specific Recommendation ................................................................................ 12 3.5.2 TanDEM-‐X specific Recommendation .................................................................................. 12 3.5.3 COSMO SKYMED specific Recommendation ..................................................................... 12

3.6 RADARSAT-‐2 Recommendations -‐ Antarctica ........................................................... 13 3.7 Sentinel-‐1 Recommendations -‐ Antarctica ................................................................. 13 3.8 ALOS-‐2 Recommendations -‐ Antarctica ....................................................................... 15

4 Greenland ......................................................................................................................... 16 4.1 General Observation Requirement ............................................................................... 16 4.2 Reduced Observation Requirement (if sensor capacities require scale down) 16 4.3 Science Mission Requirement (assuming no conflicts with other priorities) 17 4.4 Specific Considerations -‐ Greenland ............................................................................. 17 4.5 Recommendation for X-‐band High-‐Resolution Acquisition Super Sites -‐ Greenland ......................................................................................................................................... 18 4.5.1 TerraSAR-‐X Specific Recommendation ............................................................................... 22 4.5.2 TanDEM-‐X Specific Recommendation .................................................................................. 22 4.5.3 COSMO SKYMED Specific Recommendation ..................................................................... 22

4.6 RADARSAT-‐1 Recommendations -‐ Greenland ........................................................... 22 4.7 Sentinel-‐1 Recommendations -‐ Greenland ................................................................. 22 4.8 ALOS-‐2 Recommendations -‐ Greenland ....................................................................... 23

5 Data Available ................................................................................................................. 24 6 References ........................................................................................................................ 25 7 Acronyms .......................................................................................................................... 27 8 Appendix A: Summary of Recommendations for RADARSAT-‐1 and RADARSAT-‐2 .......................................................................................................................... 28 8.1 Antarctica ............................................................................................................................... 28 8.2 Greenland ............................................................................................................................... 28

9 Appendix B: Summary of Recommendations for High-‐Resolution X-‐band Sensors (TerraSAR-‐X, TanDEM-‐X, and COSMO-‐Skymed) ........................................ 29



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9.1 TerraSAR-‐X specific Recommendation ........................................................................ 29 9.2 TanDEM-‐X specific Recommendation .......................................................................... 29 9.3 COSMO SKYMED specific Recommendation ............................................................... 29 9.3.1 Antarctica ......................................................................................................................................... 29 9.3.2 Greenland ......................................................................................................................................... 30

10 Appendix C: Summary of Recommendations for Sentinel-‐1 ........................ 31 10.1 General Recommendations ........................................................................................... 31 10.2 Ramp-‐up Phase Recommendations (Antarctica and Greenland) ..................... 31 10.3 Sentinel-‐1 Recommendations -‐ Antarctica ............................................................... 32 10.4 Sentinel-‐1 Recommendations -‐ Greenland .............................................................. 32

11 Appendix D: Summary of Recommendations for ALOS-‐2 ............................. 33 11.1 ALOS-‐2 Recommendations -‐ Antarctica ..................................................................... 33 11.2 ALOS-‐2 Recommendations -‐ Greenland .................................................................... 33

12 Appendix E: Areas Containing Mountain Glaciers and Ice Caps ................. 34 12.1 Background and Overview ............................................................................................ 34 12.2 Canadian Arctic .................................................................................................................. 35 12.2.1 General Observation Requirement (ideal case) ............................................................ 35 12.2.2 Reduced Observation Requirement (given sensor capacities) .............................. 35

12.3 Svalbard and Russian Arctic .......................................................................................... 36 12.3.1 General Observation Requirement ..................................................................................... 36 12.3.2 Reduced Observation Requirement (given sensor capacities) .............................. 36

12.4 Mountainous Glaciers (Andes, Rocky Mountains, Himalaya-‐Karakoram-‐TienShan, Patagonia, New Zealand Alps, European Alps, Alaska) ................................. 37 12.4.1 General Observation Requirement ..................................................................................... 37

13 Appendix F: ALOS-‐2 Basic Observation Scenario ............................................ 38 14 Appendix G: Ice sheet Requirements Mentioned in the Scientific and Institutional Literature ...................................................................................................... 39 14.1 Summary of recommendations of IGOS report ....................................................... 39 14.2 EOS Science Plan 1999 .................................................................................................... 39 14.3 Global Inter-‐agency IPY Polar Snapshot Year (GIIPSY) ....................................... 40 14.4 From Cryos Theme Report (2007) .............................................................................. 41 14.5 GCOS report implementation plan – 2010 update ................................................. 42 14.6 GCOS report implementation plan – 2011 update – supplemental details ... 43 14.7 Fringe 2011 ......................................................................................................................... 46 14.8 ISMASS 2012 ....................................................................................................................... 47 14.9 ESA-‐CliC-‐EGU Earth Observation and Cryosphere Science Conference .......... 47 14.10 NASA .................................................................................................................................... 47

15 Appendix H: Contributing Authors and Affiliations ....................................... 48



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1 Introduction The International Polar Year 2007/2008 represented an opportunity for international space agencies to coordinate data acquisitions of the cryosphere through the Space Task Group (STG) and through this process to provide a historical data set. The success of the effort led to the formation of the Polar Space Task Group (PSTG) to succeed STG to transform a one-‐off opportunity into an ongoing effort to collect remote sensing data of the cryosphere. Input from the science community is coordinated with representatives from the science community represented at PSTG meetings. Here, we focus on the science requirements of ice sheets and how they can be met with SAR acquisitions. Ice sheets are acknowledged by WMO and UNFCCC as an Essential Climate Variable (ECV) needed to make significant progress in the generation of global climate products and derived information. The need to monitor the great ice sheets was identified in several prior publications:

• 1999 EOS Science Plan • 2001 Climate and Cryosphere (CliC) Science Coordination Plan • 2006 GIIPSY Science Requirements • 2007 IGOS Cryosphere Theme Report • GCOS Implementation plan for the global observing system for climate in

support of the UNFCCC (2010 update) • GCOS Systematic observation requirements for satellite-‐based data products

for climate (2011 update) • Preliminary scientific needs for Cryosphere Sentinel 1-‐2-‐3 products

(Preparatory material updated after the SEN4SCI workshop March 2011) In addition, the issue was raised at several meetings and workshops:

• Fringe 2011 (Panel Discussion), Frascati, IT, Sept. 2011 • IPY workshop Montreal (Panel discussion), Montreal QC, Apr. 2012 • PSTG-‐2, Geneva, CH, June 2012 • SCAR 2012, Portland, OR, July 2012 • ISMASS 2012, Portland, OR, July 2012 • The PSTG SAR Coordination Group meeting, Frascati, IT, Nov. 2012 • ESA-‐CliC-‐EGU Earth Observation and Cryosphere Science Conference, Frascati,

IT, Nov. 2012 • AGU 2012 Fall meeting, San Francisco, CA, Dec. 2012 • PARCA 2013, Greenbelt, MD, Jan. 2013



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2 Science Requirements In 2012, an ESA-‐funded project, ESA ice sheet CCI, conducted a literature review and user survey on ice sheet science requirements. Questionnaire responses were received from 67 scientists and a report was finalized by the Ice Sheet CCI team in August 2012. The following is a summary of user requirements and recommendations. It should be noted that the user survey specifically focused on Greenland, though many of the findings can be applied to Antarctica as well. A second user requirement survey specifically focused on Antarctica will be performed in the last half of 2013 as part of a scoping study for an intended future Antarctic CCI project. The results of this study will be made available to the PSTG as soon as they are collected. Summary of user recommendations [Ice Sheet CCI user requirement]:

1. The preferred priority by users is to have low resolution in the interior areas and a high resolution in the margin areas for both Surface Elevation Change (SEC) and Ice Velocity (IV). (other scenarios are also useful).

2. The regions of special interest include glaciers all around the margin of the GrIS, in particular focusing on the major fast-‐flowing ice streams and glacier systems: Jakobshavn Ice Stream, Helheim Glacier, Petermann Glacier, Kangerlugssuaq, and Nuuk Fjord Glaciers.

3. Open access to data is critical. If not, users will continue using publicly available datasets.

4. High-‐level datasets are needed, in particular for climate and ice flow modelers who have no special knowledge of satellite-‐based data.

5. NetCDF (CF-‐compliant) is by far the most popular choice, in particular by modelers, although there is also a request for simpler file formats. Most users use Matlab or Fortran as their preferred software.

6. Long and continuous records are needed, in particular for SEC. Ensuring long-‐lasting records, is an important issue and must be taken into account when planning future satellite missions.



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Table 1 shows a summary of user requirements for ice sheet essential climate variable parameters. These requirements refer to derived products as described. In the case of IV and Grounding Line Location (GLL), requirements for SAR data resolution will be more stringent (i.e. higher resolution required), as spatial averaging is generally performed during product generation. Table 1. User Requirements for Ice Sheet Essential Climate Variable parameters.

SEC IV GLL CFL Minimum spatial resolution

1-‐5 km 100 m – 1 km 100 m – 1 km 100 m – 500 m

Optimum spatial resolution

< 500 m 50 m 50 m 50 m

Minimum temporal resolution

annual annual annual annual

Optimum temporal resolution

monthly monthly monthly monthly

Minimum accuracy 0.1 – 0.5 m/yr

30 m/yr -‐ -‐

Optimum accuracy < 0.1 m/yr 10 m/yr -‐ -‐ What times are observations needed

All year All year All year All year

SEC – Surface Elevation Change IV – Ice Velocity GLL – Grounding Line Location CFL – Calving Front Location



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Observation Requirements The information provided in the following three chapters came out of a number of discussions within the science community and expertise gained during projects spanning the last 15 to 20 years.

2.1 General Recommendations A set of general recommendations is given below based on a discussion with Ian Joughin and Eric Rignot. Both have many years of expertise in the field and are PIs in current projects dealing with ice velocity mapping of the great ice sheets using spaceborne SAR data. Polarization: HH preferred Acquisition mode: Stripmap preferred, (a notable exception is Sentinel-‐1 IWS, a TOPS mode. See Sentinel-‐1 specific sections for details) Incidence angle range: Based on experience, 23 to 45 degrees worked fine (even 57 deg. to cover South Pole). Where possible, the same range of incidence angles should be used over individual glaciers and super sites to simplify result comparisons. Regional requirements may lead to specific preferences, specifically on smaller outlet glaciers in mountainous terrain. Acquisition strategy: Acquire at least some long tracks (i.e. coast to coast, rock to rock) to aid processing [4]. The remainder of this document outlines the post-‐IPY requirements. One aspect to be considered in this respect is the multi-‐purpose and commercial use of most SAR missions available. Requirements are therefore divided into 3 sections:

1. General Observation Requirements: Based on previous (particularly the IPY) experience, these data requirements should be manageable for space agencies, particularly if acquired in a coordinated fashion.

2. Reduced Observation Requirements: In case competing priorities of the various SAR missions do not allow a fulfillment of the general observation requirements, this set is hopefully manageable (could be enhanced with a prioritized list), while still preserving the science value of the data.

3. Science Mission Requirements: This set of requirements represents the ideal case of a mission with few (or no) competing priorities.



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2.2 Current and Upcoming SAR Missions Table 1 lists the sensors available or upcoming as of May 2013. Chapters 4 and 5 of this document outline sensor specific recommendations; these are summarized in the appendix. The following sections include a recommendation of super sites for high resolution X-‐band coverage (TerraSAR-‐X, TanDEM-‐X and Cosmo-‐Skymed) and a recommendation for large scale C-‐band coverage during the winter 2012/2013 (RADARSAT-‐1 and -‐2).

Table 2. List of currently operating and upcoming SAR missions.

Instrument Band Mission Duration

Space Agency

Left looking capability

Comments

RADARSAT-‐1 C 1997 -‐ 2013 CSA No (not operational)

Mission ended in late March 2013. Included here due to 2013 Greenland acquisitions.

RADARSAT-‐2 C 2007 -‐ ongoing

CSA Yes Commercial mission (PPP) may affect sensor availability

TerraSAR-‐X / TanDEM-‐X

X 2007 -‐ ongoing

DLR Yes Commercial mission (PPP) may affect sensor availability. 2 satellites acting 2 missions

Cosmo-‐Skymed

X 2007 -‐ ongoing

ASI No Commercial mission (PPP) may affect sensor availability

RISAT-‐1 C 2012 -‐ ongoing

ISRO Information not available

Access to science data unclear

RISAT-‐2 X 2009 -‐ ongoing

ISRO Information not available


HJ-‐1C S 2012 -‐ ongoing

NDRCC/SEPA Information not available


Sentinel-‐1 2 sats.

C Launch: 2013 +2015

ESA / EC No Government mission (PPP) may affect sensor availability

ALOS-‐2

L Launch: 2013 JAXA Yes Commercial mission (PPP) may affect sensor availability

SAOCOM 2 sats

L Launch 2014, 2015

CONAE Yes Collaboration with ASI (COSMO-‐Skymed)

RCM 3 sats

C Launch 2016 + 2017

CSA No Government mission – science access possible

DESDynI L Launch: 2021 NASA TBD Full science mission



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3 Antarctica The IPY effort marks the first time the entire continent was completely covered with interferometric SAR data. The effort led to a reference velocity map [6] as well as an InSAR-‐based grounding line product [7]. Both products represent measurements of changing geophysical parameters. The coastal regions of Antarctica are undergoing changes, particularly on the West Antarctic Ice Sheet [4,5,9]. Frequent coverage is therefore warranted. Interior regions with little change [10] also benefit from repeat acquisitions to increase the accuracy of measurements particularly in slow moving areas [4]. The size and geographic location of the area of interest requires a combination of left and right looking acquisitions to cover the area.

3.1 General Observation Requirement • Annual coverage of all of Antarctica with at least 3 consecutive cycles –

winter observations. More cycles are considered an asset. • More frequent (monthly) observations of critical areas with every possible

acquisition of selected tracks (Pine Island / Thwaites Glacier region; Antarctic Peninsula; Totten Glacier; please refer to Table 3 for more information).

3.2 Reduced Observation Requirement (if sensor capacities require scale down) • Plan for a full Antarctic coverage at least every 3 years. • Provide annual coverage of coastal regions (right looking: all coastal areas;

left looking: TAM + Ross and Ronne with their tributaries). • More frequent (monthly) observations of critical areas with every possible

acquisition of selected tracks

Figure 1. Prioritized coastal regions in Antarctica for a reduced acquisition

requirement (1: highest priority, 3: lowest priority).

1

2

3a

3b



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3.3 Science Mission Requirement (assuming no conflicts with other priorities) • Ongoing coverage of the visible area with coast-‐to-‐coast tracks

(right looking: coastal areas; left looking: Central Antarctica). • Acquisition of additional tracks covering large outlet glaciers with higher

resolution modes • Capture seasonal changes over major ice streams

3.4 Specific Considerations - Antarctica

• Plan for at least some coast-‐to-‐coast tracks to facilitate data processing and calibration [4]

• South of 80 degrees south (i.e. left looking visibility only): It is acknowledged that left looking acquisitions put additional strain on resources (change from right to left looking) and require careful planning and execution. A full coverage per year (3 consecutive cycles) would be considered an asset.

• L-‐band: Most critical in coastal zones and WAIS (C-‐band decorrelation is present for 24 and 35 day repeat orbit, however, 6 and 12-‐day repeat period of S-‐1 should reduce this problem in the future [24])

• C-‐band: Historically most impact in the interior, but coastal coverage is also recommended, particularly for missions with shorter repeat orbits.

• X-‐band: Continuation of current approach recommended (example: TerraSAR-‐X) – more frequent coverage of smaller, high impact regions + some limited basin wide coverage of selected regions (e.g. the TerraSAR-‐X left looking campaign in Antarctica).

3.5 Recommendation for X-band High-Resolution Acquisition Super Sites - Antarctica

This section was written in response to a PSTG SAR coordination group information request regarding X-‐band high-‐resolution sites for regular monitoring. The sensors addressed include TerraSAR-‐X, TanDEM-‐X and the COSMO SKYMED constellation. The PSTG SAR coordination group requested a list of sites recommended for frequent high-‐resolution observation. The following is a table comprised of existing TerraSAR-‐X time series resulting from super sites and AOI’s of individual PI’s augmented by recommendations from the larger community. While the list may seem extensive, it is targeted and the resulting spatial coverage is small. Glacier Names are taken from the following reference: USGS Antarctic Research Atlas (http://gisdata.usgs.gov/website/antarctic_research_atlas/).



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Table 3. Recommended Sites for X-band high-resolution acquisitions in Antarctica

Priority level: 3 (high 6) – acquisition every cycle (ongoing acquisitions) 2 (med 6) – 3-5 pairs per year (2 winter, 1 summer (or 2 winter, rest evenly spread)) 3 (low 27) – 1 pair per year (winter acquisition).

# Name Lat Lon DLR

(TSX) Priority Comment

1 PIG -‐75.18 -‐99.36 yes 3 WAIS 2 Thwaites Gl -‐75.31 -‐106.92 limited 3 WAIS 3 Pope -‐75.21 -‐111.45 limited 3 WAIS 4 Smith -‐75.11 -‐111.89 limited 3 WAIS 5 Kohler -‐75.03 -‐113.92 limited 3 WAIS 6 Institute Ice

stream -‐80.84 -‐73.00 no 1 WAIS – RONNE – left

7 Rutford Ice stream

-‐78.42 -‐83.11 no 1 WAIS – RONNE – left

8 Evans ice stream


9 Ferrigno ice stream


10 Venable Ice shelf

-‐73.2 -‐87.7 no 1 WAIS

11 DeVicq Gl. (Getz)

-‐74.8 -‐131.0 No InSAR 1 WAIS

12 Hull Gl. -‐75.1 -‐136.9 No InSAR 1 WAIS 13 Land Gl. -‐75.7 -‐140.94 No InSAR 1 WAIS 14 Ice stream

A/B -‐83.9 -‐164.1 Yes, one

regional InSAR coverage

1 WAIS – ROSS – left

15 Larsen B glaciers

-‐65.35 -‐62.0 Yes (but not regular)

3 AP (one single coastal coordinate provided; several glaciers to be monitored)

16 Glaciers feeding into Larsen C

-‐67.66 -‐62.55 Some limited InSAR

2 AP (single coordinate in the center of the ice shelf provided; several glaciers to be monitored)

17 Glaciers feeding into George VI

-‐71.00 -‐62.55 No for George VI, Yes for Wilkins IS

2 AP (single coordinate on the ice shelf provided; several glaciers to be monitored)

18 Denman Gl. -‐66.7 99.27 No InSAR 2 EAIS 19 Totten Gl -‐67.45 114.02 No 2 EAIS 20 Moscow

University Gl -‐67.38 119.12 no 2 EAIS

21 Cook Ice Shelf.

-‐68.68 152.19 no 2 EAIS

22 Foundation/Academy Gl.

-‐83.6 -‐61.0 no 1 EAIS – RONNE -‐ left

23 Recovery Gl. -‐81,0 -‐36.75 One regional coverage

1 EAIS – RONNE -‐ left

24 Slessor Gl. -‐79.9 -‐31.24 No InSAR 1 EAIS – RONNE -‐ left 25 Stancomb

Wills Gl. -‐75.4 -‐18.6 Some

limited InSAR

1 EAIS

26 Jutul-‐straumen Gl.

-‐71.74 0.9 yes 1 EAIS

27 Belgium Gl. (big feature

-‐70.91 27.07 No InSAR 1 EAIS



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# Name Lat Lon DLR (TSX)

Priority Comment

in QML) 28 Shirase Gl. -‐70.17 39.1 No InSAR 1 EAIS 29 Lambert Gl. -‐73.27 66.96 no 1 EAIS 30 Philippi Gl. -‐66.8 87.75 No InSAR 1 EAIS 31 Holmes Gl -‐67.0 127.0 no 1 EAIS 32 Frost Gl. -‐67.0 129.0 no 1 EAIS 33 Mertz Gl. -‐67.8 144.2 Yes, one

coverage 1 EAIS

34 Ninnis Gl. -‐68.5 147.0 no 1 EAIS 35 David Gl. -‐75.36 161.0 No InSAR 1 EAIS 36 Mulock Gl. -‐79.0 160.0 no 1 EAIS 37 Byrd Gl. -‐80.43 158.03 Yes, full

trunk 1 EAIS – ROSS -‐ left

38 Nimrod -‐82.49 160.97 Yes, full trunk

1 EAIS – ROSS -‐ left

39 Beardmore Gl -‐83.6 171.8 Yes, full trunk

1 EAIS – ROSS -‐ left

Notes: No InSAR: some TerraSAR-‐X coverage available, but no InSAR pair. Regional coverage: more than one track acquired for larger area coverage. Full trunk: refers to regional coverage of TAM glaciers. 3.5.1 TerraSAR-X specific Recommendation It is recommended to expand current efforts with an InSAR background mission in Antarctica guided by the information above. Another recommendation is to provide broader access to data (similar to the recent Archive Data AO), without restriction on acquisition date. 3.5.2 TanDEM-X specific Recommendation The TanDEM-‐X Science Coordinator has identified a number of super sites where a data plan was prepared for multiple PI’s. It is recommended to continue data acquisitions for these super sites as long as the mission is in operation. 3.5.3 COSMO SKYMED specific Recommendation The COSMO SKYMED constellation allows the collection of one-‐day interferograms. This capability provides another opportunity for data acquisition with continental impact: Grounding line measurement around the Antarctic continent (or a portion thereof). The grounding line is the boundary, where an ice shelf changes from touching the ground to floating. This boundary has been mapped in the past [7], however, it will change as an ice stream undergoes changes and a repeat mapping campaign is important. It is an important aspect in glacier research and can be measured using differential interferometry. A big issue in this respect is data decorrelation. Data requirement: Two 1 day interferograms for each track (a total of 4 acquisitions). Large area coverage is not required (rather targeted coverage of the coastline guided by the existing grounding line + 25-‐50km inland). Options:

• Data acquisition around the entire coast



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• Data acquisition in specific areas (PIG/Thwaites/Smith/Kohler; Totten/Moscow University; Getz Coast; Lambert; Ferrignot)

3.6 RADARSAT-2 Recommendations - Antarctica Since the end of the ERS-‐2, ENVISAT ASAR, and ALOS-‐PALSAR missions, there has been no large-‐scale coverage of Antarctica. This data gap is widening and RADARSAT-‐2 is currently the only operational C-‐band sensor with the capability for large area coverage in the region (TerraSAR-‐X and COSMO-‐Skymed have limited basin-‐wide capability, but are better suited for targeted high-‐resolution super sites). Even with ALOS-‐2 and Sentinel-‐1 launched on Schedule, required commissioning will cause a data gap of potentially two more winters. The Canadian Space Agency (CSA) together with MDA have expressed their support in trying to minimize the impact of the limited data acquisition capability over the great ice sheets. Following several discussions with CSA and MDA and a better understanding of the priorities and limitations in place, a plan for acquisitions in Antarctica was implemented that includes:

• 2013 data acquisition in the Pine Island and Thwaites Glacier region on a more frequent basis

• 2013 data acquisition in the coastal regions of Antarctica with some limited left looking acquisitions to cover areas in the interior that are known to change.

Data acquisition is currently underway. The sensor will be in an eclipse during austral winter, which will limit acquisition opportunities. Following the eclipse, acquisitions are planned to resume.

3.7 Sentinel-1 Recommendations - Antarctica The Sentinel-‐1 constellation will be capable of large area coverage and is expected to make a significant contribution to ice sheet monitoring. The first of two SAR satellites is scheduled to be launched in late 2013. The Sentinel-‐1 mission’s full operations capacity will be reached with the two-‐satellite constellation. The second satellite is indicatively planned to be launched 18 months after the 1st unit (full operations capacity is expected by mid 2015). During the ramp-‐up phase following the launch of the first unit, SAR data will be provided for operations. On Sentinel-‐1, the TOPS technique is used both for the Interferometric Wide Swath (IWS) mode and the Extra Wide Swath (EWS) mode. The main goal of the TOPS is to overcome the limitations imposed by a standard ScanSAR mode (variation of SNR



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and azimuth ambiguity ratio along azimuth, scalloping etc.) by steering the antenna along track in azimuth. The IWS mode has been identified as potential compromise mode between sea ice and ice sheet community’s requirements. While the former prefers large area coverage and frequent revisits with less stringent demands on resolution, the latter prefers interferometric acquisitions at high resolution. One issue to resolve is that both communities are interested in the coastal zone. The ice sheet science community has expressed interest in working with S-‐1 IWS, however, the mode should be discussed more, pending analysis results for InSAR applications (a recommendation made during FRINGE 2011). The following recommendations are made for the standard operation phase:

• Four (4) consecutive coverages Stripmap once a year (during austral winter) in coastal areas

• Crossing orbits (i.e. near-‐simultaneous ascending AND descending coverage) would be considered an asset. If such data can be provided, they will be used.

• Frequent coverage using IWS mode (the entire visible area, as often as

possible). • Crossing orbits (i.e. near-‐simultaneous ascending AND descending coverage)

would be preferred.

• It is recommended to provide a network of long tracks (coast to coast, TAM to coast) to support velocity calibration. See [4] for further details.

During the ramp-‐up phase following satellite commissioning, the sensor capacity will be reduced. Due to the looming data gap since IPY, an early contribution by Sentinel-‐1a would greatly contribute to the post IPY data pool. A recommendation for the ramp-‐up phase is as follows:

• 2 consecutive (3 preferred) coverages in IWS mode as soon as possible during the ramp-‐up phase (considering austral winter). Crossing orbit not required. If coverage of the entire visible area is not possible due to conflicts and or other limitations, the margins shown in Figure 1 should be covered (priority regions 1 and 2). In addition, ice sheet edges (priority regions 3) should be covered.

• As the mission continues, recommendations below (particularly Stripmap coverage in coastal areas) should be considered even with only a single satellite in orbit.



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3.8 ALOS-2 Recommendations - Antarctica The ALOS-‐2 BOS (ice sheet relevant portions are presented in Appendix F) addresses crucial regions with high-‐resolution data once per year. The ScanSAR coverages would need to be further evaluated for their utility for ice sheet monitoring. Based on the BOS, the ice sheet science community recommends the following improvement w.r.t. ice sheet monitoring:

• Ideally, ALOS-‐2 would contribute a coverage of the entire coastal area (3 consecutive cycles) with high-‐resolution data once per year (thus expanding on the current plan to monitor the West Antarctic Ice Sheet once per year)

Recognizing that sensor load considerations may not allow the expansion of the coverage to the entire coast, the following recommendation is put forward for consideration:

• Adding Totten/Moscow University (EAIS)



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4 Greenland The IPY effort provided high-‐resolution time series of a number of large outlet glaciers as well as a complete coverage of Greenland [2,8]. The coastal regions of Greenland are undergoing significant changes [3,5]. Frequent coverage is therefore warranted. Unlike Antarctica, right looking imaging provides full coverage for Greenland. The community acknowledges that the sea ice monitoring requirements are not necessarily compatible with ice sheet monitoring requirements. The need to compromise is understood and the sensor specific recommendations were developed with these considerations in mind.

4.1 General Observation Requirement • Annual coverage of all of Greenland with at least 3 consecutive cycles –

Arctic winter observations. More cycles are considered an asset. Time of Year: December to March.

• A secondary full coverage each year would be an asset (3 cycles). Suggested timing for such a secondary campaign would be July-‐September. Less correlation can be expected due to summer conditions, but seasonal variability would be captured. More coverages in Arctic winter would also be an important science contribution (to reduce errors).

• More frequent observations of critical areas with every possible acquisition of selected tracks (see section 5.5).

• Acquire ascending and descending coverages. This aspect would allow the use of the interferometric phase for improved accuracy.

4.2 Reduced Observation Requirement (if sensor capacities require scale down) • Annual coverage of all of coastal Greenland with at least 3 consecutive

cycles (Arctic winter acquisitions preferable). • Full coverage every second year. • Provide additional coverages of coastal regions.



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Figure 2. Prioritized coastal regions in Greenland for a reduced acquisition

requirement (1: highest priority, 5: lowest priority).

4.3 Science Mission Requirement (assuming no conflicts with other priorities) • Ongoing coverage of the entire area (ascending and descending). • Acquisition of additional tracks covering large outlet glaciers with higher

resolution modes.

4.4 Specific Considerations - Greenland

• L-‐band: Most critical in Southern Greenland, specifically SE (C-‐band decorrelation was encountered when using 35 day repeat orbit data.) Full coverage desired. Long tracks (coast to coast) aid data processing and calibration.

• C-‐band: Full coverage desired. Long tracks (coast to coast) aid data

processing and calibration.

• X-‐band: Continuation of the current approach is recommended – more frequent coverage of smaller, high impact regions.

1

2

3

4

5



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4.5 Recommendation for X-band High-Resolution Acquisition Super Sites - Greenland

Response to PSTG SAR coordination group information request regarding X-‐band sites for regular monitoring The PSTG SAR coordination group requested a list of sites recommended for frequent high-‐resolution observation. The following is a table comprised of existing TerraSAR-‐X time series resulting from super sites and AOI’s of individual PIs (e.g. PI: I. Joughin) augmented by recommendations from the larger community. Glacier Names are taken from [8].



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Table 4. Recommended Sites for X-band High-Resolution Acquisitions in Greenland Priority level: 3 (high11) – acquisition every cycle (ongoing acquisitions) 2 (med16) – 3-5 pairs per year (2 winter, 1 summer (or 2 winter, rest evenly spread)) 3 (low26) – 1 pair per year (winter acquisition)

# Name Lat Lon DLR (TSX) Priority Comment 1 Kangerlussua

q 68.609 -‐32.97 Strip014 asc

Rel orb 163 Inc 43.4-‐45.8

3

2 Unnamed Deception O & Unartit

67.58 -‐33.56 Strip012 dsc Rel orb 156 Inc 39.8-‐42.4

2

3 Midgard Gl 66.41 -‐36.82 Strip009 dsc Rel orb 141 Inc 33.8-‐37.0

2

4 Helheim 66.47 -‐38.36 Strip010 asc Rel orb 148 Inc 36.0-‐38.8

3

5 No Name 65.74 -‐39.27 N/A 1 6 Ikertivaq Bay 65.62 -‐39.86 Strip010 dsc

Rel orb 50 Inc 35.9-‐38.7

2 (Bay center coordinates provided)

7 Koge Bugt Bay

65.17 -‐41.16 Strip008 dsc Rel orb 126 Inc 31.6-‐34.7

2 Note: one more track available

8 Graulv Gl 64.35 -‐41.55 Strip014 asc Rel orb 42 Inc 43.4-‐45.7

2

9 Gyldenlove Gl.

64.24 -‐41.59 Covered by the above

2

10 A.P.Bernstorff Gl., Maelkevejen Gl.

63.84 -‐41.73 Strip009 asc Rel orb133 inc33.8-‐36.8

2

11 Skinfaxe & Rimfaxe Gl.

63.25 / -‐42.03

63.25 / -‐42.03

Strip012 dsc Rel orb50 inc39.8-‐42.4 />>10

2 (center between the 2 termini)

12 Heimdal Gl. ? ? Strip006 asc Rel orbit 133 Inc 26.8 – 30.6 />10

2

13 Tingmiarmiut Fjord, Mogens Heinesen Bay

62.74 -‐43.13 Strip009 dsc Rel orb126 inc33.8-‐36.8

2 unnamed glacier in Mogens Heinesen Bay

14 Puisortoq Gl. 62.06 -‐42.42 Strip010 asc Rel orb042 inc 35.8-‐38.6

1

15 Unnamed Anorituup Kangerlua N,C,S

61.69 -‐43.23 Strip013 asc Rel orb118 Inc 41.6 – 44.1

2

16 Kangerluluk Gl.

61.12 -‐43.71 N/A 1

17 NoName1 SE corner

60.72 -‐43.78 N/A 1



20

# Name Lat Lon DLR (TSX) Priority Comment 18 NoName2 SE

corner 60.62 -‐44.20 N/A 1

19 Qooqqup Sermia and Kiattuut Sermiat


1

20 Qajuuttap Sermia


1 SW

21 Eqalorutsit Killiit Sermiat


1 Include the region SW of this (vel gap in the map)

22 Sermilik Brae 61.01 -‐46.94 Strip014 asc Rel orb103 inc43.2-‐45.7

1 End of gap

23 Ukaasorsuaq 61.95 -‐48.72 N/A 1 24 Avannarleq

Brae 62.21 -‐48.98 N/A 1

25 Kangiata Nunaata Sermia and Akullersuup Se;


3

26 Narsap Se. 64.64 -‐50.02 N/A 3 27 Russel

Gletscher 67.04 -‐49.87 Strip013 asc

Rel orb 103 Inc 41.70 – 44.03

2

28 Jakobshavn Isbrae


3 Strip014 dsc Rel orb20 inc43.5-‐45.6 />10 upstream Strip008 dsc Rel orb5 inc31.9-‐34.7 />10 trunk More tracks available

29 3 GL: Sermeq Kujalleq (middle)


1

30 Store Gl. 70.40 -‐50.54 Strip014 dsc Rel orb96 inc43.4-‐45.7

3

31 Rink Isbrae 71.75 -‐51.61 Strip012 asc Rel orb27 inc39.7-‐42.4

3

32 Upernavik Isstrom (System of 3 glaciers)


3 Note: This Region is an ESA ice sheet CCI test AOI and was therefore changed in priority

33 Kavifaat Sermiat

73.47 -‐55.20 Strip009 asc Rel orb27 Inc 33.9-‐36.7

1 Scene center given

34 Ussing Braeer 74.0 -‐55.46 Strip009 asc Rel orb27 Inc 33.9-‐36.7


35 Illullip Sermia



36 Hayes Gletscher

74.9 -‐56.9 Strip009 asc Rel orb 27 Inc 33.9-‐36.7


37 Sverdrup Gl. 75.58 -‐58.15 Strip010 dsc Rel orb127 inc35.9-‐38.8

2



21

# Name Lat Lon DLR (TSX) Priority Comment 38 Nansen Gl. 75.85 -‐58.49 Strip 009desc

Rel orb36 Inc 33.8 –36.9


39 Kong Oscar Gl.

76.01 -‐59.69 Strip008 dsc Rel orb112 Inc 31.7-‐34.9

2

40 Rink Gl 76.24 -‐60.70 Strip007 asc Rel orb 27 Inc 29.4-‐32.7

1 Scene Center Note: Do not confuse with Rink Isbrae

41 Morell Gl. 76.37 -‐62.29 Strip010 asc Rel orb 12 Inc 35.8-‐38.8


42 Carlos Gl. 76.48 -‐63.60 Strip011 Rel orb 88 Inc 37.8-‐40.7

1

43 Savissuaq Gl 76.45 -‐65.75 Strip011 asc Rel orb 164 Inc 37.9-‐40.7

1

44 Harald Moltke Brae

76.48 -‐67.14 Strip014 asc Rel orb 149 Inc 43.4 – 45.7

1

45 Heilprin Gl 77.60 -‐65.48 Strip007 asc Rel orb 103 Inc 29.4-‐32.6

1

46 Humboldt Gl. 79.76 -‐64.14 Strip 011 dsc Rel orb 82 Inc 38.1-‐40.5

1

47 Peterman Gl 80.74 -‐60.22 Strip012 asc Rel orb42 Inc 39.8 – 42.3

3 Scene center given Note: 80.70 / -‐60.37 Strip009 asc Rel orb 57 Inc 33.8 – 36.9 Scene center provided This orbit seems to provide slightly better coverage of the trunk, but: fewer scenes in archive (3 only in archive 2010)

48 Ryder Gl 81.25 -‐50 Strip014 asc Rel orb72 Inc 43.4-‐45.7


49 Academy Gl. 81.44 -‐32.21 Strip012 asc Rel orb 147 Inc 39.9-‐42.4


50 Hagen Brae 81.37 -‐27.92 Strip009 dsc Rel orb 96 Inc 33.9-‐36.7


51 Nioghalvfjerdsfjorden (79 North)

79.32 -‐22.06 Strip 011 desc Rel orb65 Inc 38.0-‐40.6


52 Zachariae Isstom

78.9 -‐21.37 Strip 008 desc Rel orb 141 Inc 31.8-‐34.7

3 Scene center given (One more pair upstream acquired)

53 Daugaard-‐Jensen

71.77 -‐29.15 Strip007 asc Rel orb 117 Inc 29.5–32.7

1 Scene center given Note: One pair upstream and one pair terminus also available

Note that if the line refers to a specific TerraSAR-‐X scene, neighboring glaciers that are not named here are also covered by the data.



22

4.5.1 TerraSAR-X Specific Recommendation It is recommended to expand current efforts with an InSAR background mission in Antarctica guided by the information provided in Table 4. Another recommendation is to provide broader access to data (similar to the recent Archive Data AO), without restriction on acquisition date. 4.5.2 TanDEM-X Specific Recommendation The TanDEM-‐X Science Coordinator has identified a number of super sites where a data plan was prepared for multiple PIs. It is recommended to continue data acquisitions for these super sites as long as the mission is in operation. 4.5.3 COSMO SKYMED Specific Recommendation For COSMO SKYMED it is recommended to acquire near-‐simultaneous ascending and descending one-‐day interferograms of selected outlet glaciers for high precision velocity measurements. Table 4 can provide guidance for the selection of sites.

4.6 RADARSAT-1 Recommendations - Greenland Since the end of the ERS-‐2, ENVISAT ASAR, and ALOS-‐PALSAR missions, there has been no large-‐scale coverage of Greenland. Even with ALOS-‐2 and Sentinel-‐1 launched on schedule, required commissioning will cause a data gap of potentially two more winters. The Canadian Space Agency (CSA) together with MDA, the Norwegian Space Centre (NSC), and KSAT have worked together to acquire RADARSAT-‐1 data over Greenland from January 2013 to the end of the mission in late March.

• The plan was to carry out a full coverage (3 repeat cycles, fine mode data) of the Greenland ice sheet during the 2012/2013 Arctic winter.

While a large portion of the data was acquired, the premature end of the mission in late March 2013 led to some data gaps. It is recommended to close these gaps using other missions between September and December 2013.

4.7 Sentinel-1 Recommendations - Greenland The Sentinel-‐1 constellation is described in detail in Section 3.7. The following recommendations are made for the standard operation phase:

• Four (4) consecutive coverages Stripmap once a year (during Arctic winter) in coastal areas



23

• Crossing orbits (i.e. near-‐simultaneous ascending AND descending coverage) would be considered an asset. If such data can be provided, they will be used.

• Frequent coverages using IWS mode (the entire visible area, as often as

possible). • Crossing orbits (i.e. near-‐simultaneous ascending AND descending coverage)

would be preferred.

• It is recommended to provide long, coast-‐to-‐coast tracks to support velocity calibration. See [4] for further details.

During the ramp-‐up phase following satellite commissioning, the sensor capacity will be reduced. Due to the looming data gap since IPY, an early contribution by Sentinel-‐1a would greatly contribute to the post IPY data pool. A recommendation for the ramp-‐up phase is as follows:

• 2 consecutive (3 preferred) coverages in S1-‐IWS mode during Arctic winter as soon as possible during the ramp-‐up phase. Crossing orbit not required. As the mission continues, recommendations below (particularly Stripmap coverage in coastal areas) should be considered even with only a single satellite in orbit.

4.8 ALOS-2 Recommendations - Greenland The ALOS-‐2 BOS addresses crucial regions with high-‐resolution data once per year. The ScanSAR coverages would need to be further evaluated for their utility for ice sheet monitoring. Based on the BOS, the ice sheet science community recommends the following improvement of the BOS w.r.t. ice sheet monitoring:

• Ideally, ALOS-‐2 would contribute a coverage of the entire coastal area (3 consecutive cycles preferably in Arctic winter) with high-‐resolution data once per year (thus expanding on the current plan to monitor the Northwest Coast of Greenland once per year)


• Adding the Southeast Coast of Greenland



24

5 Data Available Table 5 provides an overview of currently available InSAR based ice sheet products http://nsidc.org/data/measures/data_summaries.html All data sets are compiled using data from several international SAR missions and are an IPY contribution. Table 5. InSAR based Ice sheet products currently available at NSIDC. Product ID Principal

Investigator Data Set Title

NSIDC-‐0478 I. Joughin MEaSUREs Greenland Ice Velocity Map from InSAR Data http://nsidc.org/data/nsidc-‐0478.html

NSIDC-‐0481 I. Joughin MEaSUREs Greenland Ice Velocity: Selected Glacier Site Velocity Maps from InSAR http://nsidc.org/data/nsidc-‐0481.html

NSIDC-‐0484 E. Rignot MEaSUREs InSAR-‐Based Antarctica Ice Velocity Map http://nsidc.org/data/nsidc-‐0484.html

NSIDC-‐0498 E. Rignot MEaSUREs Antarctic Grounding Line from Differential Satellite Radar Interferometry http://nsidc.org/data/nsidc-‐0498.html

NSIDC-‐0525 E. Rignot MEaSUREs InSAR-‐Based Ice Velocity Maps of Central Antarctica: 1997 and 2009 http://nsidc.org/data/nsidc-‐0525.html

In addition to the above mentioned products, ice velocity products from the RADARSAT Antarctic Mapping Project (RAMP) are available online: http://bprc.osu.edu/rsl/radarsat/data/download.php?mission=mamm&path=VEL_PROD&tar=1 Future data sets include Essential Climate Variable (ECV) information from the ESA Ice Sheet Climate Change Initiative (CCI): http://www.esa-‐icesheets-‐cci.org/ The following references provide details on the data sets: Joughin, I., B. Smith, I. Howat, T. Scambos, and T. Moon. 2010. Greenland Flow Variability from Ice-‐Sheet-‐Wide Velocity Mapping. Journal of Glaciology 56(197): 415-‐430. http://dx.doi.org/10.3189/002214310792447734 Rignot, E., J. Mouginot, and B. Scheuchl. 2011. Ice Flow of the Antarctic Ice Sheet. Science 333(6048): 1427-‐1430. http://dx.doi.org/10.1126/science.1208336. Rignot, E., J. Mouginot, and B. Scheuchl. 2011. Antarctic Grounding Line Mapping from Differential Satellite Radar Interferometry. Geophyical Research Letters 38: L10504. http://dx.doi.org/10.1029/2011GL047109. Scheuchl, B., J. Mouginot, and E. Rignot. 2012. Ice Velocity Changes in the Ross and Ronne Sectors Observed Using Satellite Radar Data from 1997 and 2009. The Cryosphere (6): 1019-‐1030. http://dx.doi.org/10.5194/tc-‐6-‐1019-‐2012. Jezek, K.C. 2008. The RADARSAT-‐1 Antarctic Mapping Project. BPRC Report No., 22, Byrd Polar Research Center, The Ohio State University. Columbus, OH, 64 pages.



25

6 References

[1] GIIPSY Science Requirement document (Nov. 3, 2006) http://bprc.osu.edu/rsl/GIIPSY/documents/GIIPSY_Science_Sum_Nov_3.doc last accessed on May 21, 2012

[2] Joughin, I., B. Smith, I. M. Howat, T. Scambos, and T. Moon. 2010. Greenland Flow Variability from Ice-‐Sheet-‐Wide Velocity Mapping. Journal of Glaciology 56 (197), pp. 415-‐430.

[3] Moon, T., I. Joughin, B. Smith, I. Howat. 2012. 21st-‐Century Evolution of Greenland Outlet Glacier Velocities, Science, Vol. 336 (6081): pp. 576-‐578. doi 10.1126/science.1219985.

[4] Mouginot J., Scheuchl B., Rignot E. Mapping of Ice Motion in Antarctica Using Synthetic-‐Aperture Radar Data. Remote Sensing. 2012; 4(9):2753-‐2767.

[5] Pritchard, H. D., Arthern, R. J., Vaughan, D. G., and Edwards, L. A. 2009. Extensive dynamic thinning on the margins of the Greenland and Antarctic ice sheets, Nature, 461: 971–975, doi:10.1038/nature08471

[6] Rignot, E., J. Mouginot, and B. Scheuchl. 2011. Ice Flow of the Antarctic Ice Sheet, Science, Vol. 333(6048): 1427-‐1430. doi 10.1126/science.1208336.

[7] Rignot, E., J. Mouginot, and B. Scheuchl. 2011. Antarctic Grounding Line Mapping from Differential Satellite Radar Interferometry, Geophysical Research Letters, 38, L10504, doi:10.1029/2011GL047109.

[8] Rignot, E. and J. Mouginot. 2012. Ice flow in Greenland for the International Polar Year 2008-‐2009., Geophys. Res. Lett., doi:10.1029/2012GL051634, in press.

[9] Rott, H., Müller, F., Nagler, T., and Floricioiu, D. 2011. The imbalance of glaciers after disintegration of Larsen-‐B ice shelf, Antarctic Peninsula, The Cryosphere, 5, 125-‐134, doi:10.5194/tc-‐5-‐125-‐2011,

[10] Scheuchl, B., Mouginot, J., and Rignot, E., 2012. Ice velocity changes in the Ross and Ronne sectors observed using satellite radar data from 1997 and 2009, The Cryosphere, 6, 1019-‐1030, doi:10.5194/tc-‐6-‐1019-‐2012

[11] Fringe 2011 Workshop – Sorted Recommendations http://earth.eo.esa.int/workshops/fringe2011/files/FRINGE2011_Workshop_Recommendations_Final.pdf (last accessed on May 30, 2012)

[12] Gardner, A.S., Moholdt, G., Wouthers, B., Wolken, G.J., Burgess, D.O., Sharp, M.J., Cogley, J.G., Braun, C., Labine, C. 2011. Sharply Increased Mass Loss from Glaciers and Ice Caps in the Canadian Arctic Archipelago. Nature 473, pp. 357-‐360.

[13] Short, N.H and Gray, A.L. 2005. Glacier dynamics in the Canadian High Arctic from Radarsat-‐1 speckle tracking. Canadian Journal of Remote Sensing 31 (3), pp. 225-‐239.

[14] Van Wychen, W., Copland, L., Gray, L., Burgess, D., Danielson, B., Sharp, M. 2012. Spatial and Temporal Variation of Ice Motion and Ice Flux from Devon Ice Cap, Nunavut, Canada. Journal of Glaciology 58 (210), pp. 657-‐664.

[15] Hvidberg, C.S., et al., 2012 User Requirements Document for the ice_sheets_cci project of ESA's Climate Change Initiative, version 1.4, 29. May 2012. Report: ST-‐DTU-‐ESA-‐ISCCI-‐URD-‐001



26

[16] Stearns, L. A., Smith, B. E., and Hamilton, G. S. 2008. Increased flow speed on a large East Antarctic outlet glacier caused by subglacial floods, Nat. Geosci., 1, 827–831,

[17] IGOS, 2007. Integrated Global Observing Strategy Cryosphere Theme Report -‐ For the Monitoring of our Environment from Space and from Earth. Geneva: World Meteorological Organization. WMO/TD-‐No. 1405. 100 pp. http://igos-‐cryosphere.org/documents.html

[18] GCOS, 2010, Implementation plan for the global observing system for climate in support of the UNFCCC (2010 update), GCOS-‐138, (GOOS-‐184, GTOS-‐76, WMO-‐TD/No. 1523)

[19] GCOS, 2011, Systematic observation requirements for satellite-‐based data products for climate, 2011 update. Supplemental details to the satellite-‐based component of the “Implementation plan for the global observing system for climate in supoort of the UNFCCC (2010 update)”, GCOS-‐154

[20] Allison, I., Barry, R. G., and Goodison, B. E. (Editors), 2001. Climate and Cryosphere (CliC) Project. Science and coordination plan, Version 1, WCRP-‐114, WMO/TD No. 1053

[21] A Compilation of Recommendations from the IGOS Cryosphere Theme Report, 10 November 2011.

[22] Radic, V. and Hock, R., 2011. Regionally differentiated contribution of mountain glaciers and ice caps to future sea-‐level rise. Nature Geoscience, 4, 91–94, doi: 10.1038/ngeo1052

[23] Dowdeswell, J.A. and Hagen, J.O. 2004. Arctic ice masses. Chapter 15. In: J.L. Bamber and A.J. Payne (eds.). Mass Balance of the Cryosphere. Cambridge University Press, 712 pp.

[24] Hogg, A. E. Shepherd, S. Engdahl, M. Jung, H. S. 2013. CAFTS: A Coherence and Feature Tracking Study for Sentinel-‐1, Earth Observation and Cryosphere Science Conf. Frascati, Italy, 13-‐16 November 2012 (ESA SP-‐712, May 2013)

[25] Fernandez-‐Prieto et al. 2013. Earth Observation and Cryosphere Science: The Way Forward, Proc. 'Earth Observation and Cryosphere Science Conf.' Frascati, Italy, 13-‐16 November 2012 (ESA SP-‐712, May 2013)

[26] M.Drinkwater, K. Jezek, E.Sarukhanian, T. Mohr. 2011. IPY Satellite Observation Program, Chapter 3.1 in "Understandig Earth's Polar Challenges: International Polar Year 2007-‐2008", Summary report by IPY Joint Committee, WMO/ICSU, p. 361-‐370.

[27] Jezek, K.C. 2008. The RADARSAT-‐1 Antarctic Mapping Project. BPRC Report No., 22, Byrd Polar Research Center, The Ohio State University. Columbus, OH, 64 pages.



27

7 Acronyms ASI …… Agenzia Spaziale Italiana (Italy) AGU …… American Geophysical Union AOI …… Area of Interest BOS …… Basic Observation Scenario (ALOS-‐2) CCI …… Climate Change Initiative CFL …… Calving Front Location CliC …… Climate and Cryosphere Project CONAE …… Comisión Nacional de Actividades Espaciales (Argentina) CSA …… Canadian Space Agency DLR …… Deutsches Zentrum für Luft-‐ und Raumfahrt (Germany) EAIS …… East Antarctic Ice Sheet ECV …… Essential Climate Variable EGU …… European Geosciences Union EOS …… Earth Observing System ESA …… European Space Agency EWS …… Extra Wide Swath Mode (Sentinel-‐1) GCOS …… Global Climate Observing System GIIPSY …… Global Inter-‐agency IPY Polar Snapshot Year GLL …… Grounding Line Location GMES …… Global Monitoring for Environment and Security (now Copernicus) HH …… Horizontal transmit, horizontal receive IASC …… International Arctic Science Committee IGOS …… Integrated Global Observing Strategy InSAR …… Interferometric SAR IPY …… International Polar Year ISMASS …… Expert Group on Ice Sheet Mass Balance and Sea Level ISRO …… Indian Space Research Organisation IV …… Ice Velocity IWS …… Interferometric Wide Swath Mode (Sentinel-‐1) JAXA …… Japan Aerospace Exploration Agency KSAT …… Kongsberg Satellite Services MDA …… MacDonald, Dettwiler and Associates Ltd. MEaSUREs …. Making Earth System Data Records for Use in Research Environments (A NASA program) NASA …… National Aeronautics and Space Administration NDRCC/SEPA .. National Committee for Disaster Reduction and State Environmental Protection Administration of China NetCDF …… A set of software libraries and self-‐describing, machine-‐independent data formats that support the creation, access, and sharing of array-‐oriented scientific data NSC …… Norwegian Space Centre PARCA …… Program for Regional Climate Assessment PSTG …… Polar Space Task Group RAMP …… RADARSAT Antarctic Mapping Program SAR …… Synthetic Aperture Radar SCAR …… Scientific Committee on Antarctic Research SEC …… Surface Elevation Change STG …… Space Task Group TAM …… Transantarctic Mountains UNFCCC …… United Nations Framework Convention on Climate Change USGS …… United States Geological Survey WAIS …… West Antarctic Ice Sheet WMO …… World Meteorological Organization



28

8 Appendix A: Summary of Recommendations for RADARSAT-1 and RADARSAT-2

The Canadian Space Agency (CSA) together with MDA have expressed their support in trying to minimize the impact of the current limited data acquisition capability over the great ice sheets.

8.1 Antarctica Following several discussions with CSA and MDA and a better understanding of the priorities and limitations in place, a plan for acquisitions in Antarctica was implemented that includes:

• 2013 data acquisition in the Pine Island and Thwaites Glacier region on a more frequent basis.

• 2013 data acquisition in the coastal regions of Antarctica with some limited left looking acquisitions to cover areas in the interior that are known to change.

Data acquisition is currently underway. The sensor will be in an eclipse during austral winter, which will limit acquisition opportunities. Following the eclipse, acquisitions are planned to resume.

8.2 Greenland Since the end of the ERS-‐2, ENVISAT ASAR, and ALOS-‐PALSAR missions, there has been no large-‐scale coverage of Greenland. Even with ALOS-‐2 and Sentinel-‐1 launched on schedule, required commissioning will cause a data gap of potentially two more winters. The Canadian Space Agency (CSA) together with MDA, the Norwegian Space Centre (NSC), and KSAT have worked together to acquire RADARSAT-‐1 data over Greenland from January 2013 to the end of the mission in late March.

• The plan was to carry out a full coverage (3 repeat cycles, fine mode data) of the Greenland ice sheet during the 2012/2013 Arctic winter.

While a large portion of the data was acquired, the premature end of the mission in late March 2013 led to some data gaps. It is recommended to close these gaps using other missions between September and December 2013.



29

9 Appendix B: Summary of Recommendations for High-Resolution X-band Sensors (TerraSAR-X, TanDEM-X, and COSMO-Skymed)

This section was written in response to a PSTG SAR coordination group information request regarding X-‐band high-‐resolution sites for regular monitoring. A single track selected at or upstream of the grounding line will provide vital information without requiring large area overage from the sensor in question. The sensors addressed include TerraSAR-‐X, TanDEM-‐X and the COSMO SKYMED constellation. Tables 3 and 4 of this document summarize a prioritized set of glaciers in Antarctica and Greenland for regular coverage with a high-‐resolution X-‐band sensor. The tables are comprised of existing TerraSAR-‐X time series resulting from super sites and AOI’s of individual PI’s augmented by recommendations from the larger community. While the list may seem extensive, it is targeted and the resulting spatial coverage is small.

9.1 TerraSAR-X specific Recommendation It is recommended to expand current efforts with an InSAR background mission in Antarctica guided by the information provided in Table 3. Another recommendation is to provide broader access to data (similar to the recent Archive Data AO), without restriction on acquisition date.

9.2 TanDEM-X specific Recommendation The TanDEM-‐X Science Coordinator has identified a number of super sites where a data plan was prepared for multiple PIs. It is recommended to continue data acquisitions for these super sites as long as the mission is in operation.

9.3 COSMO SKYMED specific Recommendation The COSMO SKYMED constellation allows the collection of one-‐day interferograms. This capability provides another opportunity for data acquisition with continental impact. 9.3.1 Antarctica COSMO SKYMED constellation provides an opportunity for grounding line measurement around the Antarctic continent (or a portion thereof). The grounding line is the boundary, where an ice shelf changes from touching the ground to floating. This boundary has been mapped in the past [7], however, it will change as an ice stream undergoes changes and a repeat mapping campaign is important. It is an important aspect in glacier research and can be measured using differential interferometry. A big issue in this respect is data decorrelation. Data requirement: Two 1-‐day interferograms for each track (a total of 4



30

acquisitions). Large area coverage is not required (rather targeted coverage of the coastline guided by the existing grounding line + 25-‐50km inland). Options:

• Data acquisition around the entire coast • Data acquisition in specific areas (PIG/Thwaites/Smith/Kohler;

Totten/Moscow University; Getz Coast; Lambert; Ferrignot) 9.3.2 Greenland For COSMO SKYMED it is recommended to acquire near-‐simultaneous ascending and descending one-‐day interferograms of selected Greenland outlet glaciers for high precision velocity measurements. Table 4 provides guidance for the selection of sites.



31

10 Appendix C: Summary of Recommendations for Sentinel-1

The Sentinel-‐1 constellation will be capable of large area coverage and is expected to make a significant contribution to ice sheet monitoring. The first of two SAR satellites is scheduled to be launched in late 2013. The Sentinel-‐1 mission full operations capacity will be reached with the two-‐satellite constellation. The second satellite is indicatively planned to be launched 18 months after the 1st unit (full operations capacity is expected by mid 2015). During the ramp up phase following the launch of the first unit SAR data will be provided for operations.

10.1 General Recommendations On Sentinel-‐1, the TOPS technique is used both for the Interferometric Wide Swath (IWS) mode and the Extra Wide Swath (EWS) mode. The main goal of the TOPS is to overcome the limitations imposed by a standard ScanSAR mode (variation of SNR and azimuth ambiguity ratio along azimuth, scalloping etc.) by steering the antenna along track in azimuth. The IWS mode has been identified as potential compromise mode between sea ice and ice sheet community’s requirements. While the former prefers large area coverage and frequent revisit with less stringent demands on resolution, the latter prefers interferometric acquisitions at high resolution. One issue to resolve is that both communities are interested in the coastal zone. The ice sheet science community has expressed interest in working with S-‐1 IWS, however, the mode should be discussed more pending analysis results for InSAR applications (a recommendation made during FRINGE 2011).

10.2 Ramp-up Phase Recommendations (Antarctica and Greenland) During the ramp up phase following satellite commissioning, the sensor capacity will be limited. Due to the looming data gap since IPY, an early contribution by Sentinel-‐1a would greatly contribute to the post IPY data pool. A recommendation for the ramp-‐up phase is as follows (valid for Antarctica and Greenland):

• 2 consecutive (3 preferred) coverages of the entire ice sheet (i.e. the visible area) in IWS mode as soon as possible during the ramp-‐up phase. (considering regional winter). Crossing orbit not required.

o For Antarctica coverage of the entire visible area may not possible due to conflicts and or other limitations. In this case the margins shown in Figure 1 should be covered (priority regions 1 and 2). In addition, ice sheet edges (priority regions 3) should be covered.

• As the mission continues, recommendations below (particularly Stripmap coverage in coastal areas) should be considered even with only a single satellite in orbit.



32

10.3 Sentinel-1 Recommendations - Antarctica The following recommendation are made for the standard operation phase:

• Four (4) consecutive coverages Stripmap once a year (during austral Winter) in coastal areas.

o Crossing orbits (i.e. near-‐simultaneous ascending AND descending coverage) would be considered an asset. If such data can be provided, they will be used.

• Frequent coverages using IWS mode (the entire visible area, as often as possible).

o Crossing orbits (i.e. near-‐simultaneous ascending AND descending coverage) would be preferred.

• It is recommended to provide a network of long tracks (coast to coast, TAM to coast) to support velocity calibration. See [4] for further details.

10.4 Sentinel-1 Recommendations - Greenland The following recommendation are made for the standard operation phase:

• Four (4) consecutive coverages Stripmap once a year (during Arctic winter) in coastal areas.

o Crossing orbits (i.e. near-‐simultaneous ascending AND descending coverage) would be considered an asset. If such data can be provided, they will be used.

• Frequent coverages using IWS mode (the entire visible area, as often as possible).

o Crossing orbits (i.e. near-‐simultaneous ascending AND descending coverage) would be preferred.

• It is recommended to provide long, coast-‐to-‐coast tracks to support velocity calibration. See [4] for further details.



33

11 Appendix D: Summary of Recommendations for ALOS-2

The ALOS-‐2 BOS addresses crucial regions with high-‐resolution data once per year. ALOS PALSAR data played a crucial role in ice velocity maps of Antarctica and Greenland [2,8]. The ScanSAR coverages would need to be further evaluated for their utility for ice sheet monitoring. The following recommendations for improvement are therefore made for the ALOS-‐2 BOS:

11.1 ALOS-2 Recommendations - Antarctica Based on the BOS, the ice sheet science community recommends the following improvement w.r.t ice sheet monitoring:

• Ideally, ALOS-‐2 would contribute a coverage of the entire coastal area (3 consecutive cycles) with high-‐resolution data once per year (thus expanding on the current plan to monitor the West Antarctic Ice Sheet once per year)


• Adding Totten/Moscow University (EAIS)

11.2 ALOS-2 Recommendations - Greenland Based on the BOS, the ice sheet science community recommends the following improvement of the BOS w.r.t. ice sheet monitoring:

• Ideally, ALOS-‐2 would contribute a coverage of the entire coastal area (3 consecutive cycles) with high-‐resolution data once per year (thus expanding on the current plan to monitor the Northwest Coast of Greenland once per year)


• Adding the Southeast Coast of Greenland



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12 Appendix E: Areas Containing Mountain Glaciers and Ice Caps

12.1 Background and Overview This main purpose of this document is to provide science and data acquisition requirements for ice sheets. The World Glacier Monitoring Service (WGMS) was represented at the 2012 PSTG meeting in Geneva regarding glacier requirements. Following some discussion during the public review phase of this document it was decided to include other regions than Antarctica and Greenland in this section. These regions include areas containing mountain glaciers and ice caps (in no particular order):

• Canadian Arctic • Svalbard • Russian Arctic • Iceland (glaciers in the area are affected by sub-‐glacial volcanism) • Himalaya • Alaska • Patagonia • European Alps and Norway

Shape files of all glaciers in the world are available from the Randolph Glacier Inventory (RGI) at: http://www.glims.org/RGI/ The dataset is undergoing improvements but provides an indication where glaciers are located. The following sections provide some general information and recommendations. It should be noted that recommended incidence angle ranges as well as acquisition intervals for velocity mapping depend on various factors (sometimes even within a region). For detailed acquisition planning it is therefore important to obtain region specific requirements.



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12.2 Canadian Arctic Ice masses located in the Canadian Arctic represent one-‐third of the global volume of land ice outside of the ice sheets, and have recently been identified as the largest contributor to sea-‐level rise outside of Greenland and Antarctica [12]. Despite this, relatively little is known about the motion of most of these ice masses, which limits understanding of their flux rates and how these and iceberg calving rates may change in a warming climate. As such, it is essential to continue acquisition of SAR imagery to provide up-‐to-‐date ice motion maps of the Canadian Arctic, to refine estimates of mass fluxes, and to aid in the interpretation of mass balance changes. It should be noted that RADARSAT-‐2 acquisition plans over the Canadian Arctic are already in place at CSA. Recommendations mentioned here are more general to raise awareness within PSTG. 12.2.1 General Observation Requirement (ideal case)

• Ongoing coverage of the entire AOI each year from October to May. • RADARSAT-‐2 Fine Wide mode (or equivalent), HH polarization is preferred. • High resolution (e.g. Radarsat-‐2 Ultrafine wide 3 m or equivalent mode)

monitoring of 15 target glaciers (tidewater/surge) within the AOI each year from October to May.

12.2.2 Reduced Observation Requirement (given sensor capacities)

• Annual coverage (RADARSAT-‐2 fide wide beam or equivalent mode) of the entire AOI with at least 4 consecutive cycles – January to May. More cycles are considered an asset.

• Ongoing acquisitions (RADARSAT-‐2 Ultrafine wide or equivalent mode) over 15 target glaciers (tidewater/surge) within the AOI from October to May.

Specific considerations: For RADARSAT and RADARSAT-‐2, expect conflicts for Canadian SAR missions due to other priorities (e.g., Canadian Department of National Defense, Canadian Ice Service). C-‐Band: Full coverage (RADARSAT-‐2 fine wide beam and ultrawide fine beam or equivalent mode) desired as previous studies have shown the utility of C-‐Band within the Canadian Arctic as well as maintaining continuity with current work [13,14].



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12.3 Svalbard and Russian Arctic While much of the focus has been on the Greenland ice sheet, mountain glaciers and ice caps in the Arctic are at present, and will over the present century, be a large source of eustatic sea level change [22]. One of the large issues at present is to improve the knowledge of how the dynamics of ice masses may change due to warming. Svalbard is an Arctic archipelago at around 80°N and Austfonna and Vestfonna are the two major ice-‐caps on the second largest island (Nordaustlandet). These ice-‐caps represent one of the largest ice-‐covered areas in the Eurasian Arctic [23] and were the subject of various past studies on surface ice-‐velocity. As such, it is essential to continue acquisition of SAR imagery to provide up-‐to-‐date ice motion maps of Svalbard, to refine estimates of mass fluxes, and to aid in the interpretation of mass balance changes. 12.3.1 General Observation Requirement

• Annual coverage of the entire AOI with at least 4 consecutive cycles – January to May. More cycles are considered an asset.

• Stripmap mode (e.g. RADARSAT-‐2 Fine Wide HH polarization or equivalent) preferred.

• Sentinel-‐1 coverages in Stripmap during Arctic winter are preferred. 12.3.2 Reduced Observation Requirement (given sensor capacities)

• TOPS mode (ScanSAR like mode, e.g. Sentinel-‐1 IWS) annual coverage of the entire AOI with at least 4 consecutive cycles – January to May. More cycles are considered an asset.

Specific considerations: L-‐band: Most critical for InSAR (winter time, 2-‐3 consecutive cycles). Ascending and descending coverage -‐ this aspect would allow the use of the interferometric phase for improved accuracy. C-‐band: continuous acquisition desired, as an extension of ERS SAR and Envisat ASAR programs. RADARSAT (Standard mode -‐ 25 m or higher resolution), High-‐resolution Sentinel images.



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12.4 Mountainous Glaciers (Andes, Rocky Mountains, Himalaya-Karakoram-TienShan, Patagonia, New Zealand Alps, European Alps, Alaska)

So-‐called peripheral glaciers and ice caps are often characterized by very steep topography and comparably small glaciers, limiting the applications of microwave data for surface velocity estimation. However, the increasing resolution of SAR sensors enables mapping of surface flow and velocity changes over time even for smaller mountain glaciers and glaciers surges. ALOS PALSAR 46-‐day repeat winter imagery, TerraSAR-‐X 11-‐day to 5 months interval acquisition and ERS/ENVISAT images with one year time separation have been successfully been applied using intensity feature tracking techniques. Shorter wavelengths are known to perform less in the accumulation area of glaciers where few structures are present. For surface velocity mapping, the optimal time interval is dependent on sensor spatial resolution, sensor frequency, glacier flow velocity as well as observable structures and feature preservation over time. On the other hand, radar sensors are used on mountainous glaciers for improved mapping of debris-‐covered glaciers using coherence images acquired over a short-‐repeat period in summer (on the order of days). In the past, ALOS-‐1 PALSAR 46-‐days coherence images were found to have the most suitable contrast. In the future, it is expected that a similar procedure can be applied to Sentinel-‐1 12 day image pairs. 12.4.1 General Observation Requirement

• Ongoing coverage of mountain glaciers (Andes (incl. Patagonia), Rocky Mountains, Himalaya-‐Karakoram-‐TienShan, New Zealand Alps, European Alps, Alaska) during summer months.

• Stripmap mode is preferred (C-‐ or L-‐band) or high-‐resolution X-‐band data. • For surface velocities at least one repeat winter coverage of glaciers • Ascending and descending coverage to minimize layover/shadowing effects

Specific considerations: • For surface velocities of fast Alaskan (e.g. Hubbard, Columbia, Bering) and

Patagonian outlet glaciers short repeat intervals (max. 22 to 24 days) and at least 4-‐5 observations per year are preferred due feature deformation of fast flow and known flow acceleration during summer

• Annual high-‐resolution coverage with short observation interval of tidewater glaciers in Alaska (e.g. Stikine and Juneau Icefields) and Patagonia

• In case of many surging and advancing glaciers in a region (e.g. Karakoram) one very high resolution repeat coverage with 11/12-‐day repeat has proofed to be suitable

• Specific acquisitions on demand for other glaciers showing surge type behaviour (e.g. Alaska, Svalbard)

It should be noted that for Sentinel-‐1 the proposed acquisition strategy is in line with GMES requirements (e.g. hazard assessment related to slope instability).



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13 Appendix F: ALOS-2 Basic Observation Scenario

The two slides shown here were obtained from the following presentation: Ake Rosenqvist, Masanobu Shimada, Shinichi Suzuki, Fumi Ohgushi, Hiroki Nishi, Kaoru Tsuzuku, Tomohiro Watanabe ALOS-‐2 Basic Observation Scenario (BOS) (Update 131112) K&C Science Team meeting KC#18 – 7-‐9 Nov 2012



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14 Appendix G: Ice sheet Requirements Mentioned in the Scientific and Institutional Literature

14.1 Summary of recommendations of IGOS report Recommendations: Development of Ice Sheet Observations R6.1 Implement a C-‐band synthetic aperture radar optimized for SAR interferometry and capable of measuring the velocity field of the whole of the Greenland and Antarctic Ice Sheets. Data from this system would also provide new estimates on grounding lines, ice edge and shear margin positions.

14.2 EOS Science Plan 1999 Chapter 6: The Cryosphere



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14.3 Global Inter-‐agency IPY Polar Snapshot Year (GIIPSY) In 2006, the Space Task Group identified remote sensing requirements for IPY in the Global Inter-‐agency IPY Polar Snapshot Year (GIIPSY) Science Requirement document [1]: The primary objective of these plans is to advance polar science by obtaining another critical benchmark of processes in the Arctic and Antarctic during the IPY and to set the stage for acquiring future benchmarks beyond IPY. The technical objective is to coordinate polar observations with spaceborne and in situ instruments and then make the resulting data and derived products available to the international science community. [1]

GIIPSY Science Goal: Understand the polar ice sheets sufficiently to predict their response to climate change. [1]

GIIPSY Science Objectives: Polar glaciers and ice sheets are rapidly changing. Fast glaciers and ice streams located in Southern Greenland along with fast glacier and ice shelves around West Antarctica and the Antarctic Peninsula are accelerating, thinning and retreating. Satellite data to be collected during the IPY will provide additional benchmark, legacy data sets to document the change. The data sets will also help better understand the climatological and glacial dynamic processes that control rapid changes in flow. Documenting trends and quantifying glaciological processes are important because the phenomena of rapid increases in ice sheet flow are not presently incorporated into global climate models. [1]

The SAR observation objectives were identified for IPY [1]:

GIIPSY Observation objectives (SAR/InSAR) Satellite data acquisition objectives for Greenland and Antarctica in 2007 and 2008 include: • Winter observations (2007 and 2008) of the viewable area at L-‐band

for InSAR mapping (3 consecutive cycles) and seasonal single-‐cycle SAR observations.

• Winter Pole to coast InSAR observations (3 consecutive cycles each in 2007 and 2008) at C-‐band for measuring the surface velocity field.

• X-‐band and C-‐band observations of select fast glaciers for studies based on InSAR, seasonal SAR, and high spatial resolution DEMS [1].



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14.4 From Cryos Theme Report (2007) The following table provides current measurement capabilities and observational requirements for ice sheet parameters. In some cases observational requirements are listed separately for satellite and in situ observations because of different applications. Codes are as follows: C = Current Capability, T = Threshold Requirement (Minimum necessary), O= Objective Requirement (Target), L = Low end of measurement range, U = Unit, H = High end of measurement range, V = Value, cl = climate, op = operational. Summary of current/planned capabilities and requirements for ice sheet parameters (excerpt only with focus on SAR and InSAR)



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14.5 GCOS report implementation plan – 2010 update Key Need 3: International and intergovernmental organizations need to incorporate the relevant Actions in this Plan within their own plans and actions. Key Need 5: Parties are encouraged to establish effective institutional responsibilities for oceanographic and terrestrial observations at the national level. Key Need 10: Parties should ensure regular and timely submission of climate data to International Data Centres for all ECVs. Key Need 25: Parties are urged to support the sustained operation of satellite instruments and the sustained generation of the satellite-‐based products relevant for terrestrial ECVs. Essential Climate Variable (ECV) Ice Sheets:



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14.6 GCOS report implementation plan – 2011 update – supplemental details

From Chapter: 3.3.4. ECV Ice Sheets Our understanding of the timescale of ice-‐sheet response to climate change has altered dramatically over the last decade. Rapid changes in ice-‐sheet mass have surely contributed to abrupt changes in climate and sea level in the past. The mass balance loss of the Greenland Ice Sheet increased in the late 1990s to 50 gigatonnes per year (Gt yr-‐1), in 2005 to 150 Gt yr-‐1, and to more than 250 Gt yr-‐1 for the most recent observations in 2010. The mass for Antarctica as a whole is close to being in balance, but with a likely net loss since 2000 at rates of a few tens of gigatonnes per year. There are large mass-‐budget uncertainties from errors in both snow accumulation and calculated ice losses for Antarctica (±160 Gt yr-‐1) and for Greenland (~±35 Gt yr-‐1). Observations show that Greenland is thickening at high elevations because of a (predicted) increase in snowfall, but this gain is more than offset by an accelerating mass loss, with a large component from rapidly thinning and accelerating outlet glaciers. Recent observations show a high correlation between periods of heavy surface melting and increase in glacier velocity. A possible cause is rapid meltwater drainage to the base of the glacier, where it enhances basal sliding. An increase in meltwater production in a warmer climate will likely have major consequences on ice-‐flow rate and mass loss. Recent rapid changes in marginal regions of the Greenland and West Antarctic ice sheets show mainly acceleration and thinning, with some glacier velocities increasing more than twofold. Many of these glacier accelerations closely followed reduction or loss of their floating extensions known as ice shelves. Efforts should be made to (i) reduce uncertainties in estimates of mass balance and (ii) derive better measurements of ice-‐sheet topography and velocity through improved observation of ice sheets and outlet glaciers. This includes utilizing existing satellite interferometric synthetic aperture radar (i.e. InSAR) data to measure ice velocity; using observations of the time-‐varying gravity field from satellites to estimate changes in ice-‐sheet mass (e.g. GRACE satellite); surveying changes in ice-‐sheet topography using tools such as satellite radar (e.g. Envisat and Cryosat-‐2), future laser missions (e.g. ICESat-‐2), and use of wide-‐swath altimeters. Monitoring the Polar Regions with numerous satellites at various wavelengths is essential to detect change (e.g. of melt area) and to understand processes responsible for the accelerated mass loss of ice sheets and the disintegration of ice shelves (e.g. to estimate future sea-‐level rise). Driven by accelerated ice-‐sheet mass loss observed today, recent estimates using space-‐based gravity field measurements show an increase of the ice-‐sheet contribution to total cryospheric sea-‐level rise (which includes contributions from the melting of glaciers and permafrost). In addition to satellite observations, in situ measurements (e.g. of firn temperature profile and surface climate) are equally important in assessing surface mass balance and understanding recent increases in mass loss. The following is required for this ECV:



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Product T.4 Ice-‐sheet elevation changes, supplemented by fields of ice velocity and ice mass change Benefits • Reduction in significant errors to which existing estimates of Antarctic and Greenland mass balance are prone (some parts of Antarctica and Greenland ice sheets are subject to rapid change, especially the Antarctic Peninsula and coastal regions in west and east Greenland); • State-‐of-‐the-‐ice-‐sheets is a major unknown factor in determining the pace of sea-‐level change. Target Requirements Rationale: Requirements for ice sheet-‐related products are driven by the overall need to determine the mass balance of ice sheets and its change over time, and, more specifically, by: (1) the need for adequate spatial sampling of ice sheet topography and its changes (horizontal resolution can be coarser in the flatter inner ice sheet areas); (2) monthly sampling of total ice sheet behaviour (all parameters) to detect seasonal cycles; (3) the ability to detect rapid elevation changes and to trace a 10 per cent contribution to expected eustatic sea-‐level rise (i.e. 0.3mm/yr, roughly equivalent to 120 GT/yr mass balance loss), assuming uniform ice loss mainly off the Greenland ice sheet (resulting in 0.1m/yr accuracy); (4) the need for adequate characterization of (potentially non-‐linear) ice losses through outlet glaciers and other mechanisms through measurements of ice velocity and mass change; (5) the intent to detect 10 per cent of the currently estimated annual rate of mass change due to ice loss (about 100 GT/yr, roughly equivalent to 10km3/yr); and (6) the fact that for a lack of a well-‐established estimated historical trend for all variables, more specific requirements for stability cannot be stated at present. Currently achievable performance Surface elevation change: Accuracy 0.2m along satellite track (derived from radar altimetry); Ice velocity: Accuracy 25m/year (derived from SAR); Mass change: Accuracy 30km3/yr with 500km horizontal resolution (derived from gravity measure-‐ ments). Requirements for satellite instruments and satellite datasets FCDR of appropriate radar and laser altimetry; Supplemented by: • Radar measurements, for example through consideration of the use of SAR, especially interferometric SAR, to provide intermittent sampling of ice velocity and other detailed ice-‐field properties (surface-‐ height change, densification and vertical ice velocity); • Satellite-‐based gravity-‐field measurements, which should be further explored to detect time varying changes in mass of water and ice on land. Calibration, validation and data archiving needs • Needs for calibration should be identified by the CEOS WGCV, working with



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involved partners; • Validation through mass-‐balance closure estimates, reference point surveys, airborne laser altimetry, use of other sensors (optical, microwave, etc.) is required; • Aircraft laser altimeter (NASA ATM) missions are required for validation as well as in situ ground observations by automatic stations (surface height change, densification, vertical ice velocity); • Product archiving by the NSIDC World Data Center for Glaciology is essential. Adequacy/inadequacy of current holdings • Coastal regions of certain outlet glaciers in Greenland are not adequately covered by current satellite data, although surface-‐height changes in these regions are dramatic (>25m/year); • 5-‐km-‐resolution bed topography data by PARCA, ITASE and DEMs, with appropriate spatial resolution, are available and will be enhanced in the future. Immediate action, partnerships and international coordination • Exploitation of the knowledge base of several research programmes and organisations, including PARCA, CliC, IGOS Cryosphere, SCAR, and NASA Icebridge; • Identification of the international body that will coordinate this activity and develop a strategy for archiving data. Link to GCOS Implementation Plan [IP-‐10 Action T20] Ensure continuity of laser-‐, altimetry-‐ and gravity-‐satellite missions, adequate to monitor ice masses over decadal timeframes. Other applications • Laser altimeter missions have proven very useful for near-‐real-‐time monitoring of major rivers; • Interferometric SAR allows all-‐weather detection of land surface movements; • Gravity mission data have given insight into changes in land-‐based water storage and ocean currents.



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14.7 Fringe 2011 During Fringe 2011, a set of recommendations was made based on the session summaries with relation to Sentinel-‐1 for Ice and Snow [11]: ]. These recommendations largely focus on operational details of the mission in an effort to optimize coverage for achieving ice sheet science objectives similar to those outlined by GIIPSY. In particular, the recommendations focus on which operational modes to use. FRINGE2011: Recommendations related to: Sentinel-‐1 Preparatory Work [11] 5 S-‐1 TOPS coregistration issues over moving terrain should be studied. 6 Additional studies are needed to assess how the 6/12 day repeat-‐cycle of S-‐1 affects Ice Velocity tracking, and what is the trade-‐off between IWS and SM modes. FRINGE2011: Recommendations related to: S-‐1 Observation Scenario [11] 15 Ideally operate at HH-‐polarization and IWS-‐mode with ascending/descending

passes for full coverage of ice every cycle. • For ice sheet wide mapping, once a year is probably sufficient because large

changes in the interior regions are not expected. Yet you need sufficient data stacking to tackle motion of less than 1 m/yr (e.g. a couple of months of data).

• Do not forget the smaller glaciated areas: Sentinel-‐1 systematic mapping of ALL ice sheets and glaciers (Patagonia, Alaska, Himalaya, Alps, Svalbard, Canadian ice caps, etc.) decided a-‐priori, every cycle if possible, at the minimum by series of 4 consecutive cycles (3 for grounding line mapping, 4 in case of gaps), with coast-‐to-‐coast tracks.

• Be careful about assuming too much a priori which area matters and which does not -‐-‐> focus on all coastal regions as a threshold mission with a set of predefined tracks.

16 Select “super sites” for systematic acquisitions -‐ maybe following the TanDEM-‐X super sites definition (5 main outlet glaciers in Greenland; PIG, Thwaites, Totten and the Peninsula in Antarctica + Mountain glaciers in Himalaya, Patagonia, Alaska).

FRINGE2011: Recommendations related to: 3rd Party Mission Coordination [11] 38 Coordinate with RADARSAT-‐2 and RADARSAT Constellation Mission for coverage of the South Pole. 39 Coordinate with other space agencies for continuity measurements on specific “super sites” (rapidly changing areas), now that three InSAR missions are being phased out in 2011.



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14.8 ISMASS 2012 ISMASS 2012 Workshop (Portland, OR, July 14, 2012) Round Table Summaries related to SAR remote sensing of ice sheets. Round Table 1: Ice Sheet Mass Balance from Remote Sensing and GIA Remote Sensing: Key Points -‐ Required/continuous coverage of satellite MB observations. Round Table 2: Modeling of Ice sheet dynamics: Processing/Observation needs -‐ Lack of velocity data (evolving over time) -‐ is all data out there properly used?

14.9 ESA-CliC-EGU Earth Observation and Cryosphere Science Conference From the summary report: “Earth Observation and Cryosphere: The Way Forward” [25]: “... The sea ice community agrees that the coastal regions are important to have covered in EWS or IWS mode also during winter, but that a limited Strip-‐Map mode coverage for monitoring of the ice sheet margins could be accommodated without conflict with the sea ice requirements during the austral winter.”

14.10 NASA http://ice.nasa.gov/aboutCryosphere/ Cryospheric Science at NASA Now, with long-‐term observations available from satellites and aircraft, better understanding of key relationships within the Earth system, and continual improvements in remote-‐sensing technologies, the current program has established the following objectives:

• To improve our understanding of the mechanisms controlling the mass balance and dynamics of the Greenland and Antarctic ice sheets, including interactions with the ocean and atmosphere.

• To develop, validate and improve predictive models of the contributions of land-‐based ice to sea-‐level change.

• ... The Cryospheric Science Program is part of the Earth Sciences Division (ESD) in the Science Mission Directorate (SMD) at NASA Headquarters. It provides:

• Funding and oversight to competed, investigator-‐led, cryosphere-‐related scientific studies at universities, NASA centers and other institutions.

• ... • Investment in the development of satellite and airborne cryosphere-‐related

data products, including storage and distribution capabilities.



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15 Appendix H: Contributing Authors and Affiliations

Coordinating Author and Point of Contact for this Document: Bernd Scheuchl Associate Project Scientist Department of Earth System Science University of California, Irvine Croul Hall Irvine, CA 92697-‐3100 e-‐mail: [email protected] Supporters and Contributing Authors: The following is a list of persons who contributed directly to this effort. Jonathan L. Bamber Professor Bristol Glaciology Centre School of Geographical Sciences, University of Bristol, UK

Malgorzata Blaszczyk Researcher Faculty of Earth Sciences, University of Silesia Poland

Matthias Braun Professor Department of Geography University of Erlangen-‐Nürnberg Erlangen, Germany

David Burgess Research Scientist Geological Survey of Canada, Natural Resources Canada, Ottawa, Ontario, Canada

Luke Copland Associate Professor Department of Geography University of Ottawa, Ottawa, Ontario, Canada

Rene Forsberg, Head of Geodynamics, Geodynamics Dept. National Space Institute (DTU-‐Space) Lyngby, Denmark

Massimo Frezzotti Head, Antarctic Technical Unit (UTA) ENEA-‐UTA Rome, Italy

Noel Gourmelen Associate Professor Institut de Physique du Globe University of Strasbourg Strasbourg, France

Laurence Gray Adjunct Professor Department of Geography, University of Ottawa, Ottawa, Ontario, Canada

Anna Hogg Researcher School of Earth and Environment The University of Leeds Leeds, UK

Martin Horwath Researcher Institut für Astronomische und Physikalische Geodäsie Technische Universität München Munich, Germany

Kenneth C. Jezek Professor Byrd Polar Research Center, School of Earth Sciences The Ohio State University Columbus, Ohio, USA



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Ian Joughin Principal Engineer Affiliate Professor, Earth and Space Sciences Polar Science Center Applied Physics Lab University of Washington Seattle, WA, USA

Adrian Luckman Reader, School of the Environment and Society Department of Geography College of Science Swansea University Swansea, UK

Eric Larour Ice Sheet System Model Development Manager Jet Propulsion Laboratory Thermal and Cryogenics Engineering Section Pasadena, CA, USA

John Peter Merryman Boncori Scientist Division of Microwaves and Remote Sensing National Space Institute (DTU-‐Space) Lyngby, Denmark

Twila Moon Researcher Earth and Space Sciences Applied Physics Lab University of Washington Seattle, WA, USA

Mathieu Morlighem Assistant Project Scientist University of California, Irvine Department of Earth System Science Irvine, CA, USA

Jeremie Mouginot Associate Project Scientist University of California, Irvine Department of Earth System Science Irvine, CA, USA

Marius Necsoiu Principal Scientist Southwest Research Institute Research Associate Professor University of Bucharest

Frank Paul Senior Researcher Department of Geography University of Zurich Zurich, Switzerland

Wolfgang Rack Senior Lecturer -‐ Remote Sensing/Glaciology Gateway Antarctica, Centre for Antarctic Studies and Research University of Canterbury, New Zealand

Eric Rignot Professor Earth System Science University of California, Irvine Department of Earth System Science Irvine, CA, USA

Helmut Rott Professor Institute of Meteorology and Geophysics University of Innsbruck Innsbruck, Austria

Ted A. Scambos Senior Research Scientist, Lead Scientist National Snow and Ice Data Center CIRES, University of Colorado, Boulder Boulder, CO, USA

Andrew Shepherd Professor of Earth Observation School of Earth and Environment The University of Leeds Leeds, UK

Tazio Strozzi Senior Project Scientist Gamma Remote Sensing Research and Consulting AG Gümligen, Switzerland

Wesley Van Wychen Researcher Department of Geography University of Ottawa Ottawa, Ontario, Canada

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