Mapping and Characterization of Recurring Spring Leads and Landfast ice in the Beaufort and Chukchi Seas
Data will not be publicly available through this site until completion of the project. However, data and the final report from the the first project can be found at http://mms.gina.alaska.edu.
Map showing study regions for the leads and landfast ice components of the current project
Coastal flaw lead near Barrow, Alaska. Landfast ice is on the left and drifting pack ice on the right
Schematic showing morphology of landfast typical of the Chukchi and Beaufort Seas
The aim of this continuing study is to map and document the spatial and temporal distribution of recurring lead systems, coastal polynyas and landfast ice in the Beaufort and Chukchi Seas. The study region encompasses the entire northern coast of Alaska and parts of the Russian and Canadian coasts. This includes oil and gas leases sold in 2008 for which sea-ice information is lacking. The region and its sea ice cover are also of importance to protected marine mammals and birds. Dramatic reductions in Arctic summer sea ice extent since 2005 lend urgency to the need for improved knowledge and understanding of the physical sea ice environment in this region of the Arctic.
The methods we use for mapping and characterizing leads and landfast sea ice were developed during the first iteration of this project (AK-03-06, MMS-71707, active from 2004-2006), which covered a smaller study region for the period 1993-2004. The full description, final report and summary data for the first project are available at http://mms.gina.alaska.edu.
To determine the annual cycle of landfast sea ice extent, we examine co-located triplets of mosaicked Radarsat Synthetic Aperture Radar (SAR) imagery that span a period of approximately 20 days. We define landfast sea ice as that which is adjacent to the coast and remains stationary for the period spanned by the triplet. The SAR data allows us to delineate the seaward landfast ice edge (SLIE) at 100m spatial resolution approximately 30 times per season (approximately every 10 days). From these results, we can determine minimum, mean and maximum landfast ice extent on a monthly basis and calculate average dates of formation, stabilization and break up along different sections of the coast.
For analyzing lead patterns, we rely on Advanced Very High Resolution Radiometer (AVHRR) data. Our approach combines a qualitative analysis of characteristic patterns with quantification of the size, orientation, location and recurrence of individual leads. The qualitative analysis involves manual examination of daily images, which also allows the identification of cloud-free scenes suitable for digital image processing.
When the current project is complete, we will have analyzed mapped and characterized recurring leads within the study region for the period 1994-2008. The availability of Radarsat SAR data restricts the landfast ice analysis to the period 1996-2007, but we are also developing a using the PALSAR radar sensor on the ALOS satellite.
Investigator contact information:
Hajo Eicken, Lew Shapiro, Rudi Gens, Franz Meyer, Tom Heinrichs
University of Alaska Fairbanks
903 Koyukuk Dr., P.O. Box 757320
Fairbanks, AK 99775-7320
Phone: 907-474-7280 (HE), -7196 (LS)
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