Sea Ice Lead Distribution from High Resolution Airborne Imagery
Abstract
NASA's Operation IceBridge Mission provides continuity of the sea ice thickness time series, between the now complete ICESat mission and the planned ICESat-2 mission, by utilizing airborne laser and radar altimetry measurements to improve estimates of snow and ice thickness. An essential step in deriving sea ice freeboard (and hence thickness) from altimetry measurements of sea ice elevation is the determination of local sea level. Discrimination of leads along-track is therefore critical for deriving the elevation of open water within leads and defining sea surface height. Here we provide an assessment of the lead mapping capabilities of the Digital Mapping System (DMS), a nadir-looking, high-resolution digital camera mounted on IceBridge aircraft. For a nominal aircraft operating-altitude around 500 m, the resolution of the DMS imagery is approximately 0.1 m. A novel lead detection algorithm was applied to DMS digital photography for unambiguous detection of leads within the sea ice pack and classification of lead type. The data were used to generate statistics on lead distribution and spacing, lead width, and areal coverage. We compare results from the Arctic multi-year ice pack with data gathered over the mainly seasonal ice pack of the Southern Ocean. We find that areal coverage of Antarctic leads is about 5 % and three times higher than in the Arctic (1.5 %). Both dynamic and thermodynamic modeling of the sea ice pack relies on knowledge of lead distribution to effectively model ice motion and interactions between the ocean and atmosphere. We describe the potential contribution our results can make towards the improvement of coupled ice-ocean numerical models. We discuss the application of lead discrimination for freeboard retrieval from satellite altimetry (e.g. CryoSat-2 and ICESat-2) and the use of lead distribution statistics for assessing sampling geometries employed by current airborne and future satellite laser altimeters to map the complex sea ice environment, including the multi-beam photon-counting approach proposed for ICESat-2.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2011
- Bibcode:
- 2011AGUFM.C52B..03F
- Keywords:
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- 0750 CRYOSPHERE / Sea ice;
- 0754 CRYOSPHERE / Leads;
- 0758 CRYOSPHERE / Remote sensing;
- 0794 CRYOSPHERE / Instruments and techniques