Multi-decadal glacier surface lowering in the Antarctic Peninsula

From approximately 400 glaciers of the western
Antarctic Peninsula, no in situ records of mass balance exist and their recent contribution to sea level is consequently poorly constrained. We seek to address this shortcoming by using surface elevations from USGS and BAS airborne(1948–2005) and ASTER spaceborne (2001–2010) stereo
imagery, combined by using a rigorous semi-automated
registration approach, to determine multi-decadal glacier
surface elevation changes in the western Antarctic Peninsula
for 12 glaciers. All observed glaciers show near-frontal
surface lowering and an annual mean lowering rate of
0.28 � 0.03 m/yr at the lower portion of the glaciers during
the �4 decades following the mid-1960s, with higher rates
for the glaciers in the north-west parts of the Antarctic
Peninsula. Increased lowering of up to 0.6 m/yr can be
observed since the 1990s, in close correspondence to
increased atmospheric positive degree days. In all cases,
surface lowering reduces to zero within 5 km of the glacier
front at around 400 m altitude. This lowering may have
been at least partially compensated for by increased highaltitude accumulation.