Integrated SAR and lidar observations of the sea ice cover: Resolving the

contributions of thermodynamics and dynamics to the ice thickness

distribution

Ron Kwok, Jet Propulsion Laboratory

California Institute of Technology

IGARSS-2010Honolulu, HIJuly 25-30

2 Kwok

• Arctic Ocean ice cover• Ice thickness distribution

• Expression of dynamics (ice motion) and thermodynamics (growth and melt)

• Present observational capabilities• Motion and thickness

• Observational requirements• Coupled observation of motion and thickness at

appropriate time scales• Outlook - DESDynI

Topics

3 Kwok

Arctic Ocean sea ice cover

4 Kwok

Ice thickness distribution:Interplay of Dynamics and

Thermodynamics

5 Kwok

• Model Development/Improvements/Validation• Process Studies

• Ice Mechanics/Ice-ocean interactions• Deformation-induced ice production• Ocean interactions

• Sea ice area/volume balance• Ice growth and melt• Ice export

• Fram Strait, Nares Strait, Canadian Arctic Archipelago

• Narrow passages• Arctic Ecology

Ice motion and thickness observations

6 Kwok

Present Observational Capability of

Ice motion and thickness

7 Kwok

Ice Drift (Large scale forcing -> small-scale response)

L

(Kwok, 2002)

2000 km

100 km

Gradients in large-scale surface wind stress is often concentrated along quasi-linear fractures hundreds of kilometers long.

8 Kwok

Small-scale kinematics and ice production

10 km

10 km

Grid Cell AreaOne Grid Cell

Uncertainty in displacement requirement: 300 m

9 Kwok

Small-scale (~km) deformation along

fracture zones

10 Kwok

Animation of small-scale sea ice kinematics

11 Kwok

MEaSUREs

sea surface

snow

sea ice

sea water

air

Freeboard (ice / snow)

draft

thickness

sea water

air

Freeboard, snow depth and ice thickness

12 Kwok

ICESat (profiling lidar) and RADARSAT (image)

*Reference thickness estimated using ice age from RGPS

met

ers

freeboard

draft

ICESat track on RADARSAT image

Δt = 1 day

13 Kwok

Winter sea Ice thickness from ICESat

04 05 06 07 08

(Kwok et al., 2009)Thickness (m)

Greenland Greenland Greenland Greenland Greenland

MY = all ice with MY fraction>50%

14 Kwok

Trend in winter sea ice thickness:2004-2009

Thi

ckne

ss (

m)

Trend = -0.20 m/yr

MY fraction

0.8 mBetween 04-09

15 Kwok

• High resolution ice motion• Synthetic Aperture Radars

• RADARSAT not longer available, Envisat covers only part of the Arctic

• Need routine and reliable coverage of entire Arctic Ocean

• Sea ice thickness• Freeboard from lidars• ICESat provided only glimpses of the ice cover

(twice a year); mission ended last year• CryoSat-2 is now operational

• No coordinated acquisitions of ice motion and thickness

Limitations of current capabilities

16 Kwok

• DESDynI Mission• Synthetic Aperture Radar

• High-res imagery• Coverage of Arctic Ocean every 3-4 days

• Multi-beam Lidar• 25 m spots • Near simultaneous coverage of the sea ice

cover below 82 N• Monthly coverage of Arctic Ocean

• Allows coupled observation of ice motion and thickness

Sea ice observations with DESDynI

17 Kwok

• DESDynI SAR and lidar allow• Coordinated observations/mapping of motion and

thickness at length and time scales important for resolving the thermodynamic and dynamic processes

• Data products for• Monitoring of the changes in the relative

proportions of these processes associated with changing climate

• Model validation/assessments/improvements• Assimilation into global and regional models• Improved projection of global climate

Conclusions

18 Kwok

19 Kwok

Simulations with Elastic-Decohesion Approach

20 Kwok

• Joint project of the Alaska Satellite Facility and the Jet Propulsion Laboratory

• Continuation of REASoN project

• Project Objectives•To produce fine-scale sea ice motion ESDRs for the years 2004 through 2008. These products will add to the 7-year record of RADARSAT-1 data.

•To produce 3-day ice motion ESDRs of the northern Bering Sea from 1997-2008.

•To produce a record of high-resolution (100 m) image mosaics of the Arctic Ocean from 1991-2008 using available ERS-1, ERS-2, and RADARSAT-1 SAR imagery.

•To distribute, archive, and provide user services to promote and support the wide-spread use of these ESDRs.

Project Overview

6-day deformation fields of the Arctic Ocean ice cover

21 Kwok

Persistence in fracture patterns