Glacial history of Pyramid Trough, southern McMurdo Sound, Antarctica: Constraints on Koettlitz Glacier during the last glacial maximum and termination

Abstract

Reconstructions of past glacier extent and timing afford perspective on the efficacy of mechanisms thought to control ice-sheet fluctuations. Here, we present data concerning the interactions between the Antarctic Ice Sheet and a local glacier (Koettlitz Glacier) in the McMurdo Sound region of the western Ross Embayment and use this information to gain insight into driving forces of ice expansion in this sector during the last glacial maximum (LGM; 24–18 ka) and termination (18–13 ka). Our data suggest that a grounded ice sheet in McMurdo Sound at the LGM resulted not from expansion of local glaciers, such as Koettlitz, from the continent but rather from flow of marine-based ice into the sound from the Ross Sea. We infer that the relative importance of different forcing mechanisms, such as sea-level rise, ocean-temperature change, and accumulation variations, explains the contrasting behavior of the grounded marine ice sheet in the Ross Sea and local glaciers adjacent to McMurdo Sound, with Ross Sea ice responding primarily to marine forcing and local glaciers influenced strongly by accumulation.

Keywords

• Last glacial maximum
• Antarctic ice sheet
• Alpine glaciers
• Radiocarbon
• Lake-ice conveyor