Abstract. The mass loss from the Greenland Ice Sheet has increased over the
past 2 decades. Marine-terminating glaciers contribute significantly to
this mass loss due to increased melting and ice discharge. Periods of rapid
retreat of these tidewater glaciers have been linked to the concurrent
inflow of warm Atlantic-sourced waters. However, little is known about the
variability of these Atlantic-derived waters within the fjords, due to a
lack of multi-annual in situ measurements. Thus, to better understand the
potential role of ocean warming on glacier retreat, reconstructions that
characterize the variability of Atlantic water inflow to the fjords are
required. Here, we investigate foraminiferal assemblages in a sediment core
from Upernavik Fjord, West Greenland, in which the major ice stream
Upernavik Isstrøm terminates. We conclude that the foraminiferal
assemblage is predominantly controlled by changes in bottom water
composition and provide a reconstruction of Atlantic water inflow to
Upernavik Fjord, spanning the period 1925–2012. This reconstruction reveals
peak Atlantic water influx during the 1930s and again after 2000, a pattern
that is comparable to the Atlantic Multidecadal Oscillation (AMO). The
comparison of these results to historical observations of front positions of
Upernavik Isstrøm reveals that inflow of warm Atlantic-derived waters
likely contributed to high retreat rates in the 1930s and after 2000.
However, moderate retreat rates of Upernavik Isstrøm also prevailed in
the 1960s and 1970s, showing that glacier retreat continued despite a reduced
Atlantic water inflow, albeit at a lower rate. Considering the link between
bottom water variability and the AMO in Upernavik Fjord, and the fact that a
persistent negative phase of the AMO is expected for the next decade,
Atlantic water inflow into the fjord may decrease in the coming decade,
potentially minimizing or stabilizing the retreat of Upernavik Isstrøm
during this time interval.
Productive detours – Atlantic water inflow and acoustic backscatter in the major troughs along the Svalbard shelf
