Analysis of the Sedimentary and Geomorphic Signature of Retreating Tidewater Glaciers in Western Antarctic Peninsula Bays

The Antarctic Peninsula (AP) is the northernmost extent of the Antarctic continent. Due to the location of this small ice cap, it is being subjected to warming earlier than the Antarctic mainland and serves as a natural laboratory to study changes in glacial stability and the resulting sediment deposits. The AP is a rapidly changing area and assessing past responses to climate events in this region would enable us to predict more accurately future trends as climatic conditions fluctuate in the AP and in other areas in Antarctica. Sediment analysis coupled with Pb-210, Cs-137, and radiocarbon dating, as well as multibeam swath bathymetry and shallow seismic (CHIRP) were used to study the modern surface sediment distribution in Flandres Bay, the geomorphic seafloor features in bays throughout the AP, and Holocene sediment cores from Flandres, Collins, and Beascochea bays. In Flandres Bay, grain size coarsens from the inner to the outer bay. Discrete areas of the bay are affected differently by varying factors to distribute sediment; these factors include persistent fast sea ice, differential rates of primary productivity, and winnowing of fine grained sediments away from the bay. The geomorphology found in the seafloor of western AP bays indicates that bay geometry exerts a control on the number and type of landform features found in the bays. We identified networks of channels carved in bedrock, likely produced by subglacial meltwater channels, which highlights the presence of subglacial meltwater production in the northern AP region, possibly through several glacial cycles. Results from sediment core analysis from Collins Bay suggest deglaciation started before 9280 cal. yr B.P., while in Beascochea Bay deglaciation started much later, possibly around 5910 cal. yr B.P. A recent glacial advance was interpreted in the inner bay areas of Collins, Beascochea, and Flandres bays, roughly corresponding to the Little Ice Age. This conclusion is also supported by geomorphic features found in proximal bay areas which indicate a recent glacial advance. The modern glacial retreat is observed in most bays studied in the AP indicating a common forcing mechanism, likely the intrusion of warmer water melting the glacier fronts.