ALBERT

Description: The mass loss from the Greenland Ice Sheet has increased over the past two decades. Marine-terminating glaciers contribute significantly to this mass loss due to increased melting and ice discharge. Rapid retreat periods of these tidewater glaciers have been linked to the concurrent inflow of warm, Atlantic derived waters. However, little is known about the 15 variability of Atlantic-derived waters within these 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 these 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 investigate the environmental characteristics that control species diversity and derive that it is predominantly controlled by changes in bottom water 20 variability. Hence, we provide a reconstruction of Atlantic water inflow to Upernavik Fjord, spanning the period 1925-2012. This reconstruction reveals peak Atlantic water inflow during the 1930s and again after 2000, a pattern that is similar to the Atlantic Multidecadal Oscillation (AMO). We compare these results to historical observations of front positions of Upernavik Isstrøm. This reveals that inflow of warm, Atlantic-derived waters indeed likely contributed to high retreat rates in the 1930s and after 2000. However, moderate retreat rates of Upernavik Isstrøm also prevailed in the 1960s/1970s, showing that retreat 25 continued despite 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 next ~10 years.

Description: This data set includes grain size analyses and SST reconstructions from core AXC1432 in Nørre Skjoldungensund, SE-Greenland. Furthermore it contains water temperatures calculated from mesurements from https://www.ICES.dk and from the HadISST dataset. Heat transport via ocean currents can affect the melting of marine-terminating glaciers in Greenland. Studying past changes of marine-terminating glaciers allows assessing the regional sensitivity of the Greenland Ice Sheet (GrIS) to ocean temperature changes in the context of a warming ocean. Here, we present a high-resolution multi-proxy marine sediment core study from Skjoldungen Fjord, close to the marine-terminating Thrym Glacier. Grain-size data is obtained to reconstruct the calving activity of Thrym Glacier, sortable silt is used as a proxy for fjord water circulation and sea surface temperatures (SSTs) are reconstructed from alkenone paleothermometry (Uk'37). Measurements of 210Pb, 137Cs and 14C indicate that the core covers the past 220 years (1796 CE to 2013 CE). Comparisons with modelled SST data (HadISST) and instrumental temperatures (ICES) suggest that the SST proxy record reflects temperature variability of the surface waters over the shelf and that alkenones are advected into the fjord. Additionally, average temperatures and the amplitude of fluctuations are influenced by alkenones advected from upstream the Irminger Current. We find that the SST record compares well with other alkenone-based reconstructions from SE-Greenland, and thus features regional shelf water variability. The calving activity as well as the terminus position of Thrym Glacier did not seem to respond to the SST variability. Limited ice-ocean interactions owing to the specific setting of the glacier would explain this. Instead, the fjord circulation may have been influenced by enhanced meltwater production as well as to larger scale changes in the AMOC.