LANDFORM STABILITY DURING PLEISTOCENE INTERGLACIALS IN THE ANTARCTIC McMurdo DRY VALLEYS: A REGIONAL CLIMATE MODELING STUDY

The interpretation of Antarctica’s Pleistocene climate, and response of the ice sheets, deviates due an inconsistency in Quaternary climate records. Although the climate records are sparse, the apparent inconsistency centers where we have perhaps the most spatially dense records of paleoclimate in Antarctica, the Ross Embayment.

The McMurdo Dry Valleys (MDV) are a predominantly ice free region within the Transantarctic Mountains which extend along the western flank of the Ross Embayment. The preservation of Miocene and Pliocene landscapes (sublimation polygons, shallow ash deposits, buried glacier ice, cold based drifts, and rectilinear slopes) at high elevations in the MDV provides convincing evidence for sustained cold-polar desert conditions since the mid-Miocene.

At apparent odds with the MDV terrestrial record is evidence for much warmer conditions during Marine Isotope Stage 31 (MIS31) interpreted from the ANDRILL MIS off-shore core. Massive diatom units suggest an absent Ross Ice Shelf, elevated summertime sea surface temperatures (a 4-8°C increase), and perhaps a significantly reduced West Antarctic Ice Sheet.

Here I investigate the thermal regime required for achieving long-term preservation of landscapes in the MDV and predict whether landscapes could exist during the warmer interglacials. Specifically, this study calculates the range of temperatures necessary for preserving sublimation polygons and the underlying glacier ice in Beacon Valley, Antarctica. Initial thermal modeling results show that mean summer atmospheric temperatures of ≥-5°C would result in abundant surface snow melt resulting in modification of the sublimation polygons. Such increase in temperatures for an extended duration would also result in melt along the upper surface of the underlying glacier ice.

To investigate if long-term stability of sublimation polygons at high elevations in the MDV is in fact consistent with an absence of ice shelves and warming of the Ross Sea during MIS31 as interpreted by the ANDRILL community, I ran a series of paleoclimate simulations using a regional climate model (RegCM3) to predict Antarctic climate during this interval. Initial model results show that the increase of atmospheric temperatures in the MDV during MIS31 is insufficient to alter sublimation polygons.