Boundary-layer climate of the Darwin-Hatherton Glacial System, Antarctica: meso- and synoptic-scale circulations

The Transantarctic Mountain (TAM) glaciers that border the Ross Ice Shelf are important for the Antarctic Ice Sheet mass balance, but little is known about their climate. This research presents a climatology of the Darwin-Hatherton Glacial System (DHGS). Measurements from the longest reliably functioning automatic weather station in the TAM south of 78° latitude (2005–2011, excluding 2009) are used to describe the boundary-layer climate. Identified mesoscale features, denoted as downslope, humid, stagnant and anabatic winds, are profiled in terms of their character and frequency. The influence of the synoptic circulation on the boundary layer is investigated by comparing mesoscale feature frequencies to a set of synoptic pressure maps produced from Polar Weather Research and Forecasting model simulations and the self-organizing maps algorithm. Between April and September, the boundary layer is dominated by strong, dry, cold downslope winds (80%) that continuously flush the DHGS boundary layer preventing cold pools from developing, as is common in the McMurdo Dry Valleys. Humid winds, occurring under a variety of synoptic circulations, irregularly interrupt downslope winds, elevating air temperatures and specific humidity. Downslope winds begin to abate in October in frequency (24%) and strength, and humid winds become dominant (67%). A portion of humid winds in summer are mesoscale anabatic winds (15%) occurring after morning periods of downslope winds, and frequently under synoptic circulations whose pressure gradient is parallel to the TAM. The remaining 52% of humid winds generally persist for a day to multiple days, occurring more commonly under synoptic circulations whose pressure gradients are slack. The speed of downslope winds is influenced by synoptic circulation pressure gradient and orientation. The climate is similar to the Mulock Glacier, particularly from February to November. Changes to the synoptic circulation will impact the climate of these glaciers and their surface mass balance.