An Extraordinary Katabatic Wind Regime at Terra Nova Bay, Antarctica

Abstract

Three years of automatic weather station observations for the months of February to April show that intense katabatic winds persistently blow across the western shore of Terra Nova Bay. The data demonstrate that the anomalously strong katabatic winds of Adelie Land are not unique, and thus strongly support the proposition that most of the cold boundary layer air from the ice sheet crosses the coastline in a small number of narrow zones. Furthermore the observations prove that katabatic winds can routinely blow for substantial distances across flat terrain in marked contrast to the abrupt dissipation previously monitored just offshore from East Antarctica. Winter wind conditions onset suddenly in mid-February and are characterized by negligible directional variations and by speeds mostly ranging between 10 and 30 m s?1. Katabatic winds at Terra Nova Bay both affect and are affected by the regional atmospheric circulation. This katabatic airflow is a time-averaged source of cold boundary layer air for the western Ross Sea. Maximum thermal contrast with the regional temperature field occurs between January and June. Temperature observations suggest that the katabatic winds at Inexpressible Island am primarily of the boratype throughout the year. Strong southerly geostrophic winds over the western Ross Sea appear to suppress the katabatic outflow during winter while weak zonal pressure gradients coincide with intensified katabatic drainage. This relationship is suggested to arise because clouds modulate the radiative production of cold surface air over the interior of the ice sheet.