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Mcmurdo LTER: Glacier Mass Balances of Taylor Valley, Antarctica ANDREW G

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Mcmurdo LTER: Glacier Mass Balances of Taylor Valley, Antarctica ANDREW G Dana, G.L., C.M. Tate, and S.L. Dewey. 1994. McMurdo LTER: The use Moorhead, D.L., and R.A. Wharton, Jr. 1994. McMurdo LTER: Primary of narrow-band spectroradiometry to assess algal and moss com- production model of benthic microbial mats in Lake Hoare, munities in a dry valley stream. Antarctic Journal of the U.S., 29(5). Antarctica. Anta rctic Journal of the U.S., 29(5). Doran, P.T., R.A. Wharton, Jr., S.A. Spaulding, and J.S. Foster. 1994. Powers, L.E., D.W. Freckman, M. Ho, and R.A. Virginia. 1994. McMurdo McMurdo LTER: Paleolimnology of Taylor Valley, Antarctica. LTER: Soil and nematode distribution along an elevational gradient Antarctic Journal of the U.S., 29(5). in Taylor Valley, Antarctica. Anta rctic Journal of the U.S., 29(5). Fountain, A.G., B.H. Vaughn, and G.L. Dana. 1994. McMurdo LTER: Priscu, J.C. 1994. McMurdo LTER: Phytoplankton nutrient deficiency Glacial mass balances of Taylor Valley, Antarctica. Antarctic Jour- in lakes of the Taylor Valley, Antarctica. Antarctic Journal of the nab! the U.S., 29(5). U.S., 29(5). Hastings, J.T., and A.Z. Butt. 1994. McMurdo LTER: Developing a geo- Welch, K., W.B. Lyons, J.C. Priscu, R. Edwards, D.M. McKnight, H. graphic information system access system. Antarctic Journal of the House, and R.A. Wharton, Jr. 1994. McMurdo LTER: Inorganic U.S., 29(5). geochemical studies with special reference to calcium carbonate McKnight, D., H. House, and P. von Guerard. 1994. McMurdo LTER: dynamics. Antarctic Journal of the U.S., 29(5). Streamfiow measurements in Taylor Valley, Antarctica. Antarctic Wharton, R.A., Jr. 1993. McMurdo Dry Valleys: A cold desert ecosys- Journal of the U.S., 29(5). tem.AntarcticJournabof the U.S., 28(4), 9-11. McMurdo LTER: Glacier mass balances of Taylor Valley, Antarctica ANDREW G. FOUNTAIN, U.S. Geological Survey, Denver, Colorado 80225 BRUCE H. VAUGHN, Institute ofArctic and Alpine Research, University of Colorado, Boulder, Colorado 80309 GAYLE L. DANA, Desert Research Institute, University of Nevada, Reno, Nevada 89506-0220 tudies of glacier hydrology are fundamental to the McMur- enhanced melt on the terminus cliff to the total glacier mass S do Long-Term Ecological Research (LTER) project. Precip- balance is unclear (Bull and Carnein 1970, pp. 429-446; Chinn itation occurs only as snow, commonly totaling less than 10 1987). To estimate the component of glacier mass lost to centimeters of snow a year in the valley bottoms (Keys 1980), meltwater, meteorological stations are being established on and usually sublimates before making any contribution to the glaciers to complement the four stations previously estab- streamfiow (Chinn 1981). Thus, glacial meltwater is the only lished in the valley bottom. From the meteorological data, we source of water to the perennially ice-covered and land- will be able to partition the total mass loss at a point, deter- locked lakes of the McMurdo Dry Valleys. Glacial meltwater mined from the stake measurements, into the components of supplies the lakes not only with water but also with dissolved sublimation, melting, and evaporation. The combination of gases, nutrients, and sediment. To predict streamfiow and low humidity and föhn winds descending from the polar nutrient supply to the lakes, the melt rate of the glaciers must plateau results in significant losses to evaporation and subli- be known. Glacier mass balance is important because it mation, such that meltwater may represent only 20 percent of directly affects glacier advance and retreat (Meier 1965, pp. the total mass loss (Bull and Carnein 1970). 795-805) and, therefore, the contact that some glaciers have Although inferring the mass balance and meltwater pro- with the lakes. duction from unmeasured glaciers is difficult, two comple- The goal of the glaciological program is to determine the mentary programs within the LTER project will help to con- mass balance and meltwater runoff of all the Taylor Valley strain the problem. First, streamfiow from most of the glaciers glaciers, which contribute significant volumes of water to the that drain to lakes is measured and summarized by McKnight major lakes. To accomplish this goal, we are establishing a et al. (Antarctic Journal, in this issue). These data will be used surface-based measurement program to determine the mass to check our measurements on monitored glaciers and our balance and meltwater runoff at a few glaciers and will infer predictions on unmeasured glaciers. Second, the point meas- the mass balance and meltwater at the remaining glaciers in urements of mass balance and meteorological variables will the valley. For temperate glaciers, summer is the ablation sea- be extrapolated to larger regions using satellite remote sens- son and winter, the accumulation season. In contrast, for the ing. The latter is a particularly important task because of the polar glaciers of the McMurdo Dry Valleys the austral summer difficulty in extrapolating meteorological measurements in is both the ablation and the accumulation season: they not mountainous terrain such as that in the dry valleys. only lose the most mass but also accumulate the most mass in In the 1993-1994 season, ablation stake networks were summer (Chinn 1981). The mass balance is determined by established on three glaciers: Commonwealth, Canada, and measuring the surface density and the surface lowering Howard (figure 1). Because of the large icefall and extensive against a network of stakes drilled into the glacier, including crevasses on the upper Canada Glacier, emplacement of abla- the vertical cliff of the terminus, and by measuring the mass tion stakes was limited to the fan of the lower glacier where it of ice calving from the terminus cliff. The significance of spreads out into the valley. It is on the glacier fan where most, ANTARCTIC JOURNAL - REVIEW 1994 226 7745 I 16200 16345 Figure 1. The Taylor Valley, southern Victoria Land, Antarctica. The upper limits of the glaciers on the north side of the valley are not shown. if not all, of the meltwater that reaches the streams is generat- The mass balance of both Commonwealth and Howard ed. The ablation of the terminus cliff of Canada and Howard Glaciers was negative during the November to January Glaciers, neglecting losses from calving events, is 5-10 times 1993-1994 summer season. Figure 3 shows the mass-balance greater than on the top surface of these glaciers. Ablation data from Commonwealth Glacier, excluding the ice cliff at from the glacier fan of Howard Glacier was almost twice that the terminus. The mass balance for Canada Glacier could not of either Commonwealth or Canada Glaciers (figure 2). We be calculated because the ablation stakes were limited to the speculate that the cause of this difference is the sunlight- fan region. shading patterns in the valley. We observed that the glaciers To estimate the magnitude and frequency of calving on the north side of the valley are shaded by the Asgaard events from the glacier terminus, automatic cameras were Range for part of the day, whereas the glaciers on the south positioned in front of the Commonwealth and Howard Glaci- side are less shaded by the lower elevation Kukri Hills. ers. Preliminary analysis of the photograph indicates that calving is infrequent. From late October to the end of January, 10 no calving events were detected at Commonwealth Glacier, and one event was detected at Howard Glacier. The effect of 8 Commonwealth Glacier 93-94 Summer Season 800 I 700 E C.) 600 I C 0 5 500 a 0 E c 400 S 0 (5 I 300 2 I S 200 I I S 100 Commonwealth Canada Howard 0 -10 -8 -6 -4 -2 0 2 Figure 2. The average mass change of the glacier fan, neglecting calv- Mass Balance (cm water) ing. The darker shading is the mass lost during November and December 1993 and the lighter shading is the mass lost during Janu- Figure 3. Mass balance of Commonwealth Glacier during the summer ary 1994. (cm denotes centimeter.) season of 1993-1994. (cm denotes centimeter.) ANTARCTIC JOURNAL - REVIEW 1994 227 calving on mass balance in Taylor Valley is probably small, ments. This work was supported by National Science Founda- unlike tidewater glaciers of Alaska. This is in agreement with tion grant OPP 92-11773. the conclusions of Bull and Carnein (1970). During the 1994-1995 season, the stake network will be extended on each of the three glaciers to improve measure- References ments of ablation from the terminus cliff. During the past sea- son (1993-1994), only one stake was drilled into the terminus Bull, C., and L.B. Carnein. 1970. The mass balance of a cold glacier: cliff of Howard Glacier, and only two stakes were drilled into Meserve Glacier, south Victoria Land, Antarctica. In International the cliff of Canada Glacier. In addition to the three currently Symposium on Antarctic Glaciological Exploration, International Association of Hydrological Sciences (publication 86). Exeter, UK: measured glaciers, mass balance of the lower Taylor Glacier International Association of Hydrological Scientists. will be measured because of its importance to the inflow of Chinn, T.J. 1987. Accelerated ablation at a glacier ice-cliff margin, Dry Lake Bonney. Sparse stake networks also will be placed on Valleys, Antarctica. Arctic and Alpine Research, 19(1), 71-80. some other glaciers to help extrapolate mass-balance mea- Chinn, T.J. 1981. Hydrology and climate in the Ross Sea area. Journal surements from the monitored glaciers to the other glaciers in of the Royal Society of New Zealand, 11(4), 373-386. Keys, J.R. 1980. Air temperature, wind, precipitation and atmospheric the valley. A meteorological station will be erected on the humidity in the McMurdo region.
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