Katabatic winds in the McMurdo Dry Valleys, Antarctica

Katabatic winds are a frequent phenomenon in Antarctica and they are also common in the McMurdo Dry Valleys along the margin of the East Antarctic Ice Sheet (77.5o S, 163oE). Much of the valley landscape has been modified by aeolian erosion and we recently suspect that katabatic winds largely control the winter mass loss (sublimation) from the glaciers. Finally, we believe these winds to be a major integrating factor in the ecosystem of the dry valleys where other integrating factors such as rainfall-runoff are absent. We examined the data (1993-1999) from 8 meteorological stations distributed through out the dry valleys for katabatic events. As expected, we found a greater frequency of events during the winter (Feb-Oct) at all stations. The frequency of katabatic events is quite variable with significant differences between valleys and within valleys. We infer the spatial differences are related to the strength of the katabatic event and local meteorological conditions. The pattern of wind flow in the weaker events tends to follow valley topography and skip over depressions in the valleys where strong inversions exist. Strong katabatic events do not seem to be affected as much by valley topography and continue their original northward trajectory over the valleys with little deviation. Winter winds have decreased in intensity since the start of our observations, but we are uncertain at this time whether it is due to less frequent and weaker katabatic events or due to an overall decrease in wind speed. At the same time an increase in winter temperatures are observed. Katabatic events bring adiabatically warmer and drier air and a decrease in the number of events may be the causal factor in our decreasing winter temperatures.