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Active layer thickness was monitored along three ephemeral streams in the Taylor Dry Valley of Antarctica during the 1997–1998 summer season. Five to seven cross sections were established on each stream, and the thickness of the active layer was measured every 1.5 m over intervals ranging from 2 to 30 days. Active layer depths ranged from a minimum of 3 cm in early November to a maximum of 60 cm in late January, and the depth of the active layer increased rapidly as summer temperatures climbed above freezing. While there were significant differences in the thickness of the active layer among the three streams, the timing of rapid thaw was similar for all cross sections. Changes in active layer thickness were responsive to both daily and seasonal changes in air temperature. There was more rapid thaw under the areas with flowing water, suggesting a transfer of heat from meltwater into the underlying sediments, and some evidence of an insulating effect during cold periods. Active layer thickness was...

In the McMurdo Dry Valleys, glacial meltwater streams are a critical linkage between the glaciers and the lakes in the valley bottoms. This paper analyzes the physiographic characteristics and six years of discharge data from five streams in order to better characterize the dynamic inputs into Lake Fryxell, a closed basin in Taylor Valley. These feeder streams typically flow only for six to eight weeks during the summer, and streamflow is highly variable on an interannual as well as daily basis. During low flow years, the shorter streams contributed a higher proportion of the total annual inflow into the lake; this pattern may reflect the greater losses to wetting the hyporheic zone. Comparisons of the period of direct sun on the glacier faces with the time of peak flow suggested that solar position and melt from the glacier faces are the dominant controls on the diurnal fluctuations in streamflow. An analysis of streamflow recession showed considerable variability between streams and in some cases, over time. For example, recession coefficients for Canada Stream, a short stream with an incised channel, were fairly invariant with streamflow. In contrast, the recession coefficients for Lost Seal Stream, an unconfined, low gradient stream, increased significantly with increasing discharge. These observations lead to hypotheses for the control of streamflow dynamics in the McMurdo Dry Valleys by climate, solar position, and geomotphic factors.