First year sea ice: here today, here tomorrow

What can be learned from sea ice in the Barrow region?

Bonnie Light

Polar Science Center

APL/UW

Science and Education Opportunities for

an Arctic Cabled Seafloor Observatory

February 7- 8, 2005

2004/106 - 04/15 at 22 :10 UTCSatellite: Terra - Pixel size: 1km

1150 km x 850 km

Radarsat-1 Standard Beam #4 SAR image

June 19 2004

pixel size=100 meters

1024 x 1024 pixels (102.4 x 102.4 km).

                                                                                                                                                                                                                  

29 May 2001

 

                                                                                                                                                                                                                  

10 June 2001

  

                                                                                                                                                                                                                  

                                                                                                                                                                                                                  15 June 2001

   

                                                                                                                                                                                    22 June 2001

                                                                                                                                                                                                                  

29 May 2001

 

                                                                                                                                                                                                                  

10 June 2001

  

                                                                                                                                                                                                                  

                                                                                                                                                                                                                  15 June 2001

   

                                                                                                                                                                                    22 June 2001

June 2002

Land-fast ice• Seasonal

• Significant impact on terrestrial processes, such as coastal permafrost heat budget, vegetation patterns, and indigenous subsistence activities

• Rich history of surface ice observations

• Ice is stationary most of the time, but is shaped by dynamic events that can occur very quickly

• e.g., ice push, breaking from coast• understanding very important to local community• useful for studying thermodynamics

• Arctic Coastal Ice Processes: www.arcticice.org

• Barrow ice cam http://www.gi.alaska.edu/~eicken/he_proj/BRWICE/bcam1.htm

• Barrow Coastal Sea Ice Radar

Mass balance studies on land-fast ice

Perovich, D.K., T.C. Grenfell, H. Eicken, J.A. Richter-Menge, M. Sturm, K. Ligett, K. Frey,  G.A. Maykut, B. Elder, A. Mahoney, J. Holmgren, K. Claffey, T. George, Arctic Coastal Processes Data Report 2001 CD-ROM, October, 2001.

- ~ 100 km off shore

- Dynamic environment: opening, ridging, rafting

- Dynamics complicate study of thermodynamics

- No IABP buoys this close to shore

- Aerosonde observations (Curry et al.)

Pack Ice

• Flaw zone occupies space between land-fast ice and coherent pack ice

• Very dynamic

• Westward-drifting ice encounters fewer landmasses (and hence less resistence) once it passes Pt Barrow (semipermanent polynya)

• Adequate predictions of ice integrity and an understanding of behavior of ice in flaw zone is of critical importance to community

• Areal extent of zone increasing in regions where retreat of perennial ice is pronounced

• Flaw zone has received less detailed or long-term study than land-fast or pack ice

Flaw zone

Determination of SLIE (Seaward Landfast Ice Edge)

The SLIE determined from mosaics between 3 and 27 April 2003

The SLIE determined from mosaics between 23 February and 19 March 2003

The SLIE determined from mosaics between March 16 and 18 2000. In the center of the mosaic the SLIE coincides with a lead separating moving sea ice from ice that had remained stationary since February 23. To the east, the SLIE coincides with a line along which differential movement of ice was observed with

little/no open water.

Landfast ice/leads project (Eicken and colleagues) http://mms.gina.alaska.edu/Ice_classification.html

SLIEs delineated for 2001, 2002, and 2003. The color of the line represents the number of SLIEs occurring within 1 km of each other. Hi co-occurrence values indicate regions where the SLIE is more stable. It seems that there are stable nodes along the SLIE, separated by regions of more variability, suggesting that grounded ridges do not occupy the entire SLIE.

2001

2002

2003

• Trends in ice concentration show increases in winter, decreases in summer (1979-2000).

What’s the problem?

http://nsidc.org/data/seaice_index/

Figure 8. Spatial patterns of the trends in the annual thermodynamic growth and net advection for the 16-yr period 1988–2003. The sum of these two fields gives the trend in the mean ice thickness seen in Figure 4a.

Figure 4. Trend in the ice thickness for the 16-yr period 1988–2003 for all ice, level ice, and ridged ice.

The Dramatic Thinning of Arctic Sea Ice, 1988-2003R. W. Lindsay and J. ZhangPolar Science Center, University of Washington, Seattle, WASubmitted to Journal of Climate, 15 November 2004

• Need to understand relative roles of dynamics and thermodynamics

• First-year ice is here to stay and may even be the dominant ice type of the future

If we want to understand these changes...

• Study Flaw Zone

– A better understanding of flaw zones will yield insight into Arctic-wide change

– Snow accumulation on ice in conjunction with thinner ice may be causing regional flooding, inducing top-surface snow-ice formation

– SIZs could begin to resemble Antarctic conditions- implications for biodiversity

• Study at fixed location in Western sector (e.g. Barrow)

– Significant advantage to establishing a “node” in this dynamic environment

How can we progress?

• Acoustic sensors» ULS (1D)» Scanning ULS (2D)?» ADCP

• Radiative sensors» Passive: Upward looking radiometers» Active: LIDAR» Frazil formation within water column» Optical sediment “traps”

• Visual sensors» Upward looking camera with active lighting

– Important to look where there is plenty ice motion» Need climatology

– 1-D and 2-D observations – don’t forget about land-fast ice, it is still relevant

Approaches

Mean annual wind direction frequency distribution (%)for non-calm observations.

Figure from mahoney et al.

Figure 4: The seaward landfast ice edges (SLIE's) delineated from 31 gradient difference images for the whole study region from east of Point Lay to the Mackenzie Delta. See text for explanation.

Barrow lat/long: 71° 17'N / 156° 46' W