As part of the Long Term Ecological Research (LTER) project in the McMurdo Dry Valleys of Antarctica, a systematic sampling program has been undertaken to monitor glacial mass balance and meltwater flow. This data package includes stake height measurements to the surface of six glaciers (Canada, Commonwealth, Hughes, Suess, Howard, and Taylor) in Taylor Valley and one glacier (Adams) in Miers Valley, all of which are located in the McMurdo Dry Valleys of Antarctica. Most measurements began during the 93-94 field season. Adams measurements were established during the 14-15 field season. Measurements are ongoing except at Hughes and Suess Glaciers where monitoring ceased following the 08-09 field season. Monitoring the changes in these measurements over time provides a record of mass balance, and aids in determining the role of glaciers in the polar hydrologic cycle.
The goal of each summer season is to take measurements in early spring (Oct/Nov) and late summer (late January). This provides a measure of seasonal winter/summer changes of glacier mass. In some circumstances we have the opportunity or need to measure the glaciers in mid-season (Dec). View the dates the measurements were made at the following URL: http://mcmlter.lternet.edu/data/glaciers/timing/stkdates.pdf
Stakes were drilled into the snow and ice. Measurements are taken from the top of the stake to a round board that sits on the surface. The board, about 25 cm in diameter, is needed to average the surface height over a larger area because local roughness, especially on ice surfaces, can overwhelm the change in height since the last measurement. Roughness typically results from an "ablation well" around the stake, caused by enhanced solar absorption and subsequent longwave radiation from the stake. Measurements against the stake became meaningless. Methodology evolved to taking 4 replicated measurements at each stake. Height to the surface was then calculated from the sum of the distance from the top of the stake to the board, the board thickness, and subtracting the depression of the board into the snow If snow covered the ice surface, the snow depth was also measured. Procedures evolved to acquiring 4 - 8 replications around each stake. Typically, the final value of snow depth was the average of all measurements. In some cases, values were discarded because measurements were taken in hidden holes in the ice surface. Snow depth is important to record because the ice surface could have ablated prior to a snowfall. Therefore, to assess the mass balance at that stake, both ice surface change and snow depth is required.