PALEOCLIMATIC AND PALEOCEANOGRAPHIC CHANGES IN COLLINS BAY, ANTARCTICA

The Antarctic Peninsula (AP) has dramatically warmed and the majority of AP outlet glaciers have receded since the 1970’s. Relatively warm Circumpolar Deepwater (CDW) has been observed in the western AP, and questions of the relative importance of atmospheric vs. oceanographic controls on modern AP ice stability remain. Key to understanding the controls on modern AP glacial recession is the reconstruction of glacial response to past climate and ocean changes during the Holocene. Understanding long-term glacial stability will help in predicting future glacial response to climate variations.

Collins Bay is an open bay on the Graham Land coast, western AP. Sediment cores KC41 and JPC51, collected from inner and outer Collins Bay during N.B. Palmer cruise 07-03, are studied to reconstruct glacial and oceanographic changes during the Holocene. The variations in total organic carbon (TOC), nitrogen, and diatom assemblage and abundance are used to interpret depositional environments at the sub-centennial scale. By comparing the datasets with published records from other AP bays and fjords, we are able to test glacier sensitivity to warming in the western AP.

The combined core analysis indicates a minimum age of glacial retreat from Collins Bay ~9.3 cal. kyr. B.P. TOC and diatom abundance increased during glacial recession from ~8.8 to 6.0 cal. kyr. B.P. Little to no pebbles and low productivity from ~6.0 to 5.4 cal. kyr. B.P. may indicate ice shelf advance over the outer bay. A subsequent increase in productivity indicates open marine conditions from ~5.4 to 0.7 cal. kyr. B.P., possibly due to the incursion of the CDW. A sharp decrease in TOC and nitrogen may indicate the presence of an ice-shelf from ~0.7 to 0.2 cal. kyr. B.P., after which the ice-shelf receded to the present-day position. Ongoing analysis of diatom assemblages will help elucidate the past influence of the CDW, which upwells and melts the base of ice shelves in the western AP today.