Measuring Changes in the Vicinity of the Seal Nunataks Ice Shelf Remnant from Imagery and Altimetry

Abstract:

Analysis of repeated imagery and ICESat laser altimetry has enabled the ongoing losses from the northern Larsen ice shelf remnant to be assessed in detail. The remnant, the Seal Nunataks ice shelf (SNIS), has four ICESat tracks that cross it as well as adjacent tracks that cross Robertson Island (RI) and its remaining tributary, Rogosh Glacier (RG), on the Antarctic Peninsula. The altimetry data from ICESat (2003-2009) shows that elevation losses increase from west to east across the SNIS. Ice elevation differences suggest mean ice shelf thinning rates of up to 1.6 m a^-1 and reveal processes impacting the remaining shelf ice as well. Limited altimetry data across RG suggests elevation losses of almost 1 m a^-1 inland from the grounding zone with smaller losses further up the evolving tributary. Farther east, asymmetric elevation changes across RI suggest the magnitude of regional climate impacts vary distinctly depending on slope aspect.

Imagery analysis using Landsat 7 and ASTER images from 2001-2013 shows that ice area losses continued on the shelf remnant following the Larsen A break up in 1995 as well as after the Larsen B break up in 2002. The largest losses (~350 km²) occurred on the north side of the remnant in late 2004 into 2005 with smaller losses along the remaining margins. Despite a slight regional cooling recently and more persistent sea ice since early 2008 as seen in MODIS imagery, the SNIS is still losing ice along its margins and appears to be retreating past its pinning nunataks. In contrast to SNIS, RI has experienced minor ice area losses that suggest most of its ice is grounded and thus less directly impacted by ocean interactions. Combining these remote sensing data sets provides additional insights about ongoing ice loss processes in this part of the Antarctic Peninsula.