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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
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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
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3 Kwok
Arctic Ocean sea ice cover
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4 Kwok
Ice thickness distribution:Interplay of Dynamics and
Thermodynamics
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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
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6 Kwok
Present Observational Capability of
Ice motion and thickness
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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.
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8 Kwok
Small-scale kinematics and ice production
10 km
10 km
Grid Cell AreaOne Grid Cell
Uncertainty in displacement requirement: 300 m
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9 Kwok
Small-scale (~km) deformation along
fracture zones
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10 Kwok
Animation of small-scale sea ice kinematics
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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
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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
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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%
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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
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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
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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
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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
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18 Kwok
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19 Kwok
Simulations with Elastic-Decohesion Approach
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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
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21 Kwok
Persistence in fracture patterns