ALPINE GLACIER ADVANCE DURING MIS 11 IN THE MCMURDO DRY VALLEYS, ANTARCTICA

The McMurdo Dry Valleys (MDV) are home to one of the longest terrestrial records of glaciation in Antarctica. However, the record is discontinuous and spatially variable due to glacial reworking and erosion. Of the 15+ cold-based alpine glaciers that flow into Taylor Valley in the MDV, Stocking Glacier possesses the most complete suite of deposits, with six drop moraines distal to its terminus and ~1 km² of flowing ice-cored drift along its lateral margins. Ten dated samples from the outermost drop moraine yielded a cosmogenic ³He exposure age of 393 ± 35 ka, contemporaneous with marine oxygen isotope stage (MIS) 11. Stocking Glacier advances during warm intervals in response to increased snowfall and/or temperatures, similar to other MDV glaciers. During MIS 11, Stocking Glacier advanced ~500 m beyond its present location, corresponding to a minimal increase in surface area and indicative of similar regional climatic conditions during MIS 11 and the Holocene.

The lateral ice-cored drifts associated with Stocking Glacier were deposited later, likely during MIS 5 (~70–125 ka), contemporaneous with an advance of nearby Taylor Glacier, an outlet of the East Antarctic Ice Sheet. Elsewhere in the MDV, analogous lateral ice-cored drifts are presently forming where alpine glaciers terminate at the lateral margins of larger outlet glaciers. This glacial configuration can result in stagnation of ice and development of a protective debris cover. The ice-cored drifts around Stocking Glacier were likely deposited under these conditions, as Stocking and Taylor glaciers advanced and interacted with one another. This study highlights the importance of cold-based glacial dynamics on the development of buried glacier ice vs. deposition of drop moraines. The Stocking outer moraine is also the first well-dated MIS 11 glacial deposit in the McMurdo Dry Valleys, providing new insight into regional climatic conditions during a key interglacial interval.