Recent dynamic changes on Fleming Glacier after the disintegration of Wordie Ice Shelf, Antarctic Peninsula
Abstract. The Antarctic Peninsula is one of the world`s most affected regions by Climate Change. Several ice shelves retreated, thinned or completely disintegrated during recent decades, leading to acceleration and increased calving of their tributary glaciers. Wordie Ice Shelf, located at the south-western side of the Antarctic Peninsula, completely disintegrated in a series of events between the early 1970s and the late 1990s. We investigate the long-term response (1994–2016) of Fleming Glacier after the disintegration of Wordie Ice Shelf by analysing various multi-sensor remote sensing datasets. Our analysis reveals that after two decades of accelerated glacier flow and dynamic thinning the glacier tongue partially ungrounded between January and March 2008. From 2010 to 2011 a further phase of gradual grounding line recession was observed. In total, the retreat of the grounding line between 2008 and 2014 amounted to ~ 6–9 km and caused ~ 68 km2 of the glacier tongue to go afloat. We attribute this to continuous dynamic thinning and pronounced basal melt at the grounding line, probably by a south-western Antarctic Peninsula wide oceanic warming. The bedrock topography revealed that a deep subglacial trough facilitated the grounding line retreat. In response to the ungrounding of the Fleming Glacier tongue we observed an upstream propagation of the acceleration of surface velocities and corresponding to a median speedup along the glacier's centreline of ~ 1.4 m d−1 (~ 29 %) between 2007 and 2011. The propagation of high velocities has not yet affected regions far upstream (~ 50 km) of the glacier. Current ice thinning rates (2011–2014) in areas below 1000 m altitude range between ~ 2.6 to 3.1 m a−1 and are 60–70 % higher than between 2004 and 2008. Our study shows that Fleming Glacier is far away from approaching a new equilibrium and that the glacier dynamics are not primarily controlled by the loss of the ice shelf anymore. Currently, the Fleming Glacier tongue is grounded in a zone of bedrock elevation of ~ −400 m, however, about 3–4 km upstream modelled bedrock topography indicates a retrograde bed which transitions into a deep trough of up to −1000 m at ~ 10 km upstream. Hence, this endangers much larger ice masses in the future and a huge potential for an increase in sea level rise contribution.