| Although the McMurdo Dry Valleys (MDV) of Antarctica lie within an archetypal cold-desert climate, research presented here shows that the MDV are best divided into a series of microclimatic zones, with each zone fostering a unique suite of landforms and geomorphic processes that are produced by, and in balance with, local summertime environmental conditions. To quantify better the relationship between microclimates and landforms, we conducted a series of field-based and numerical-modeling studies designed (1) to elucidate landform response to potential climate warming, (2) to determine past climate variation by reconstructing former ice-volume changes of outlet glaciers draining the East Antarctic Ice Sheet, and (3) to describe the range of processes that both produce and modify near-surface ice in each microclimatic zone.;Results from a one dimensional heat diffusion equation coupled with a Mohr-Coulomb-based safety-factor model show that ice-cemented slope deposits in the upland microclimate zone would remain frozen, without failure from planar sliding, even if local summertime atmospheric temperatures were to warm by as much as 4 to 9°C. Given documented evidence for enduring geomorphic stability, the model results suggest that the maximum potential summertime warming in this zone since late Miocene time was ≤4 to 9°C. At lower elevations of the MDV, within the inland-mixed microclimatic zone, buried ice today experiences seasonal melting and modification via the formation of secondary ice; stream dissection, fan deposition, and active-layer cryoturbation also play major roles in modifying buried ice and overlying deposits. Finally, geomorphic analyses of nine moraines in Kennar Valley show that the East Antarctic Ice Sheet inland from the MDV has remained stable and robust (∼200 m of ice-elevation change) for at least the last ∼3.1 million years; chronologic control for the moraine sequence comes from cosmogenic 3He analyses of surface boulders. Taken together, the results suggest that the modern microclimatic zonation of the MDV has persisted for at least the last 3.1 million years, making it one of the most climatically stable regions on Earth. |
