Abstract. The Antarctic Peninsula is one of the world's regions most affected by
climate change. Several ice shelves have retreated, thinned or completely
disintegrated during recent decades, leading to acceleration and increased
calving of their tributary glaciers. Wordie Ice Shelf, located in Marguerite
Bay at the south-western side of the Antarctic Peninsula, completely
disintegrated in a series of events between the 1960s and the late 1990s. We
investigate the long-term dynamics (1994–2016) of Fleming Glacier after the
disintegration of Wordie Ice Shelf by analysing various multi-sensor remote
sensing data sets. We present a dense time series of synthetic aperture radar
(SAR) surface velocities that reveals a rapid acceleration of Fleming Glacier
in 2008 and a phase of further gradual acceleration and upstream propagation
of high velocities in 2010–2011.The timing in acceleration correlates with
strong upwelling events of warm circumpolar deep water (CDW) into Wordie Bay,
most likely leading to increased submarine melt. This, together with
continuous dynamic thinning and a deep subglacial trough with a retrograde
bed slope close to the terminus probably, has induced unpinning of the glacier
tongue in 2008 and gradual grounding line retreat between 2010 and 2011. Our
data suggest that the glacier's grounding line had retreated by
∼ 6–9 km between 1996 and 2011, which caused ∼ 56 km2 of
the glacier tongue to go afloat. The resulting reduction in buttressing
explains a median speedup of ∼ 1.3 m d−1 (∼ 27 %)
between 2008 and 2011, which we observed along a centre line extending between
the grounding line in 1996 and ∼ 16 km upstream. Current median ice
thinning rates (2011–2014) along profiles in areas below 1000 m altitude
range between ∼ 2.6 to 3.2 m a−1 and are ∼ 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 former ice shelf anymore. Currently,
the tongue of Fleming Glacier is grounded in a zone of bedrock elevation
between ∼ −400 and −500 m. However, about 3–4 km upstream
modelled bedrock topography indicates a retrograde bed which transitions into
a deep trough of up to ∼ −1100 m at ∼ 10 km upstream. Hence,
this endangers upstream ice masses, which can significantly increase the
contribution of Fleming Glacier to sea level rise in the future.