Antarctic Sea Ice Thickness from Satellite Remote Sensing and In Situ Measurements, 20-R8181
Principal Investigators
Michael Lewis
Marius Necsoiu
Jorge Parra
Inclusive Dates: 10/01/10 – 9/07/12
Background — The cryosphere is intricately linked to the global climate system and the Earth's surface energy budget. Sea ice cover is a primary component of the polar oceans and is important to the global climate system due to its prominent role in the 'ice-albedo' feedback mechanism and other factors such as heat, gas, and momentum exchange between the ocean and atmosphere and buoyancy of ocean currents. Despite increased research focus in recent years, the Antarctic sea ice zone remains one of the least-known regions of the Earth's surface due to remote location, limited extent and infrequency of direct measurements, and difficulties in validation of remote sensing products.
This project involved direct collaboration with the British Antarctic Survey (BAS) and other international participants to obtain in situ sea-ice measurements during the IceBell program in November 2010. The data from this program were used to derive sea ice and snow cover thickness relationships in the Antarctic sea ice zone and ultimately improve satellite remote sensing products, allowing for improved long-term monitoring of the ice mass balance in the Antarctic sea ice zone.
Approach — The project had two tasks:
- participation in IceBell cruise aboard the JCR to obtain detailed snow and ice measurements that are coincident with airborne and satellite remote sensing measurements, and
- analyses of field campaign and satellite remote sensing data necessary to assess statistical relationships between surface elevation, snow depth, freeboard, ice thickness, and roughness with the ultimate goal of classifying sea ice types and calculating sea ice thickness from satellite altimetry and Synthetic Aperture Radar (SAR) returns.
The project was originally planned to coincide with NASA IceBridge flights acquiring both LiDAR and Snow (Ku band) radar along flight lines in the Bellingshausen Sea; however, unanticipated delays in the ship schedule precluded the overlap of IceBridge flights.
Physical and geophysical measurements were obtained on sea ice floes in the Weddell and Bellingshausen seas. Installing ice mass-balance buoys (IMBs) allowed tracking of sea ice floes for months following the cruise. The acquisition of TerraSAR-X radar, Envisat radar and AMSR-E passive microwave satellite data was coincident in time and location with IMBs. A methodology was developed to analyze radar decomposition products and correlate with surface elevation, snow depth, and freeboard to allow discrimination of the (positive or negative) freeboard condition. The freeboard condition was applied to an empirical model of sea-ice thickness developed for the Bellingshausen Sea resulting in a new method that aligns closely with actual ice thickness data on the studied ice floe.
Accomplishments —
- Successfully participated in the BAS IceBell sea ice cruise, collecting gridded surveys with geophysical measurements on 10 separate sites on 8 different sea ice floes in the Weddell and Bellingshausen Seas and placing 12 ice mass-balance buoys (IMBs) that drifted with the floes for months following the cruise.
- Coordinated the acquisition of 40 TerraSAR-X (X-band radar) images through the German Aerospace Agency, Envisat radar and AMSR-E passive microwave satellite data that were coincident in time and location with IMBs during the drift period.
- Developed a methodology to analyze decomposition products from TerraSAR-X datasets in the Bellingshausen Sea to derive a Shannon Entropy product for the sea-ice floes that was subsequently correlated with sea-ice type.
- Co-registered overlapping terrestrial scanning LiDAR datasets for all floe sites.
- Developed geostatistical relationships and probability distributions for sea-ice floes using surface elevation, snow depth, freeboard, and ice thickness for correlation with Shannon Entropy.
- Built successful relationships with a significant group of external collaborators who contributed to various aspects of the project. Specifically, this project has resulted in establishing/strengthening several very important international collaborations with investigators from BAS, Scottish Association of Marine Science (SAMS), German Aerospace Agency (DLR), Woods Hole Oceanographic Institute (WHOI), The University of Texas at San Antonio (UTSA), University of Manitoba (UM) and others and has resulted in several publications and proposals.
- Identified new avenues of research related to Antarctic sea ice that allow a multi-sensor approach to monitor sea-ice thickness from remotely sensed data sets with application to long-term climate change impact assessments.
