Reconstructing hydrographic change in Petersen Bay, Ellesmere Island, Canada, inferred from SAR imagery

Abstract

Synthetic aperture radar (SAR) satellite imagery was used to reconstruct the change in limnological conditions adjacent to an Arctic ice shelf by examining the backscatter values of coastal ice in mid-winter scenes. High SAR backscatter values (>−6dB) suggest that an ice-dammed lake was present adjacent to the south coast of Petersen Bay from 1992 until 2005. Following a large calving event of the adjacent Petersen Ice Shelf (−8.07km2) in August 2005, the lake drained through a region where the ice shelf had separated from the coastline. This loss of freshwater and replacement of lake ice with sea ice along the southern coast of Petersen Bay were confirmed from analyses of ice core samples and conductivity–temperature–depth (CTD) profiles. The exception to this pattern was one distinct area where terrestrial streams entered the edge of Petersen Bay and freshwater continued to collect from 2006 to 2008. However, this ephemeral area of freshwater has not reformed since 2009 due to the persistence of open water events in Petersen Bay (observed in optical satellite imagery), which likely facilitated mixing of freshwater with sea water. Based on the continued break-ups of Petersen Ice Shelf and the frequency of open water events, it is unlikely that this ice-dammed lake will reform. The results of this study underscore the utility of SAR for reconstructing past hydrographic conditions in the water column below.