McMurdo Dry Valleys LTER: An overview of 1993-1994 research ...
References
Pace, M.L., G.A. Knauer, D.M. Karl, and J.H. Martin. 1987. Primary production, new production and vertical flux in the eastern Pacific Ocean. Nature, 325(6107), 803-804. Suess, E. 1980. Particulate organic carbon flux in the oceans: Surface productivity and oxygen utilization. Nature, 288(5788), 260-263. Wefer, G. 1989. Particle flux in the ocean: Effects of episodic production. In W.H. Berger, V.S. Smetacek, and G. Wefer (eds.), Productivity of the ocean: Present and past. New York: John Wiley and Sons.
Fischer, G., D. Fuetterer, R. Gersonde, S. Honjo, D.R. Ostermann, and G. Wefer. 1988. Seasonal variability of particle flux in the Weddell Sea and its relation to ice cover. Nature, 335(6189), 426-428. Karl, D.M., B.D. Tilbrook, and G. Tien. 1991. Seasonal coupling of organic matter production and particle flux in the western Bransfield Strait, Antarctica. Deep-Sea Research, 38(819A), 1097-1126.
McMurdo Dry Valleys LTER: An overview of 1993-1994 research activities ROBERT A. WHARTON, JR., Biological Sciences Center, Desert Research Institute, Reno, Nevada 89506
he McMurdo Dry Valleys are now a site within the Nationeral ecological understanding through studies of processes T al Science Foundation's Long-Term Ecological Research that may be better resolved in these simplified, end-member (LTER) network (Anonymous 1993; Wharton 1993). The environments (cf. more complex ecosystems). The two key perennially ice-covered lakes, ephemeral streams, and extenhypotheses for the McMurdo LTER during the first phase of sive areas of soil within the valleys are subject to low temperathe project are that tures, limited precipitation, and salt accumulation. The • the structure and function of the Taylor Valley ecosystems McMurdo LTER site (figure) is far colder and drier than any of are differentially constrained by physical and biological the 17 other established LTER sites. The dry valleys, therefore, factors, and represent "end-member" environments, which contain • the structure and function of Taylor Valley ecosystems are microbially dominated ecosystems that are simplified commodified by material transport. pared to other LTER sites. An important outcome of the The LTER project is addressing these hypotheses through McMurdo LTER research is its potential contribution to gen- systematic environmental data collection, long-term experi-
77.35,
77,45. 162"OO'
77,45. 163'45'
Map of Taylor Valley in southern Victoria Land, Antarctica, site of the McMurdo Dry Valleys Long-Term Ecological Research project.
ANTARCTIC JOURNAL - REVIEW 1994 224
ments, and model development. The research activities of the McMurdo LTER are divided into several disciplines, including physical, chemical, biological, modeling, and information science. During the 1993-1994 field season, 18 scientists deployed to McMurdo Station and Taylor Valley to conduct research associated with the LTER project. Scientists initiated core measurement programs to obtain baseline ecologically relevant data from glaciers, streams, soils, and lakes. This paper and the 10 following papers highlight some of the accomplishments of the 1993-1994 season, as well as projects related to LTER data and information management. Glacier meltwater is the predominant source of water to the streams and lakes in Taylor Valley, which lacks significant precipitation. In addition to recharging the lakes, this water carries dissolved gases and nutrients required by the biota. As discussed in the paper by Fountain, Vaugh, and Dana (Antarctic Journal, in this issue), the goal of the LTER glaciological program is to determine the mass balance and meltwater runoff of the Taylor Valley glaciers, all of which contribute significant water to the three major lakes (Fryxell, Hoare, and Bonney). During the 1993-1994 field season, Fountain and his colleagues established a network of surfacebased measurements on the Commonwealth, Canada, and Howard glaciers to determine mass balance and meltwater flow. Meteorological stations were also established on the Commonwealth and Howard glaciers. A cornerstone of the LTER aquatic ecosystem studies is the measurement of streamfiow. McKnight, House, and von Guerard (Antarctic Journal, in this issue) present streamfiow data for the 1993-1994 austral summer for three streams in Taylor Valley, located in each of the three lake basins (i.e., Fryxell, Hoare, and Bonney). Their data show large diet variations in the flow regimes of these streams and differences in the timing of streamfiow initiation. During the 1993-1994 field season, McKnight and colleagues established a comprehensive network of stream-gaging stations within Taylor Valley. Preliminary results indicate that several years of streamflow data will be necessary for development of reliable correlations between streams and for understanding the relationship between local climate and streamfiow. Microbial mat and moss communities are often found within and along the margins of streams in Taylor Valley. These communities are active during the austral summer when meltwater is present. Dana, Tate, and Dewey (Antarctic Journal, in this issue) report on a preliminary study that incorporated spectroradiometry to assess the distribution, biomass, and nutrient status of the stream communities. They measured the spectral and pigment characteristics of microbial and moss communities in the Canada Stream feeding Lake Fryxell. Initial results show the potential for using "close-range" remote-sensing techniques to study the ecological features of the stream communities. The McMurdo LTER lakes program is focused on understanding the environmental conditions and ecological processes of former and present lakes in the dry valleys. Paleolimnological studies provide important information about
the physicochemical and biological state of past lakes in the region. Doran et al. (Antarctic Journal, in this issue) report preliminary geochemical and biological data that help to put the present Taylor Valley lake environments into a historical perspective and to trace environmental change through time using lake bottom sediments. The water chemistry of the present dry valley lakes may also contain information about past environments. In addition, the chemistry of each lake profoundly affects the biota within the lake. Welch et al. (Antarctic Journal, in this issue) report on a comprehensive sampling regime initiated during the 1993-1994 austral summer to study the chemical and biological components of lakes Fryxell, Hoare, and Bonney (both east and west lobes). Welch and colleagues pay special attention to the effects of high vs. low biological activities on the production and dissolution of calcium carbonate in the lakes. Priscu (Antarctic Journal, in this issue) reports on a study designed to investigate phytoplankton nutrient deficiencies in several of the dry valley lakes. The nutrient bioassay experiments provide important data concerning nitrogen and phosphorus limitations in the dry valley lakes. Moorhead and Wharton (Antarctic Journal, in this issue) present results of a mathematical model that examines the productivity patterns of benthic microbial mats in Lake Hoare as a function of light intensity. Soils in the dry valleys are influenced by a variety of factors including climate, glacial movement, parent material, and site characteristics. During the 1993-1994 field season, Powers et al. (Antarctic Journal, in this issue) established an elevational transect on the south shore of Lake Hoare in Taylor Valley to examine spatial variation in soils and nematode abundance. Results from this study show that the input and accumulation of organic matter in dry valley soils may not be the main predictor of nematode abundance and diversity. Powers and colleagues suggest that nematode populations are most likely limited by soil age, salinity, moisture, as well as soil carbon and nitrogen content. The McMurdo Dry Valleys LTER is an explicitly synthetic effort—a comprehensive, multidisciplinary ecosystem study. Much of the data collected by the LTER is "geo-referenceable" and can be incorporated into a geographic information system (GIS) for data management and spatial analysis. Butt and Hastings (Antarctic Journal, in this issue) summarize the work to date on the development of a GIS for the McMurdo LTER. In a companion paper, Hastings and Butt (Antarctic Journal, in this issue) describe an experimental access system that allows LTER participants to manipulate the GIS database directly from desktop personal computers. The research reported here is supported by National Science Foundation grant OPP 92-11773. References Anonymous. 1993. NSF's Long-Term Ecological Research program: The antarctic connection. Antarctic Journal of the U.S., 28(4), 8-9. Butt, A.Z., and J.T. Hastings. 1994. McMurdo LTER: Developing a geographic information system database. Antarctic Journal of the U.S., 29(5).
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Dana, G.L., C.M. Tate, and S.L. Dewey. 1994. McMurdo LTER: The use of narrow-band spectroradiometry to assess algal and moss communities in a dry valley stream. Antarctic Journal of the U.S., 29(5). Doran, P.T., R.A. Wharton, Jr., S.A. Spaulding, and J.S. Foster. 1994. McMurdo LTER: Paleolimnology of Taylor Valley, Antarctica. Antarctic Journal of the U.S., 29(5). Fountain, A.G., B.H. Vaughn, and G.L. Dana. 1994. McMurdo LTER: Glacial mass balances of Taylor Valley, Antarctica. Antarctic Journab! the U.S., 29(5). Hastings, J.T., and A.Z. Butt. 1994. McMurdo LTER: Developing a geographic information system access system. Antarctic Journal of the U.S., 29(5). McKnight, D., H. House, and P. von Guerard. 1994. McMurdo LTER: Streamfiow measurements in Taylor Valley, Antarctica. Antarctic Journal of the U.S., 29(5).
Moorhead, D.L., and R.A. Wharton, Jr. 1994. McMurdo LTER: Primary production model of benthic microbial mats in Lake Hoare, Antarctica. Anta rctic Journal of the U.S., 29(5). Powers, L.E., D.W. Freckman, M. Ho, and R.A. Virginia. 1994. McMurdo LTER: Soil and nematode distribution along an elevational gradient in Taylor Valley, Antarctica. Anta rctic Journal of the U.S., 29(5). Priscu, J.C. 1994. McMurdo LTER: Phytoplankton nutrient deficiency in lakes of the Taylor Valley, Antarctica. Antarctic Journal of the U.S., 29(5). Welch, K., W.B. Lyons, J.C. Priscu, R. Edwards, D.M. McKnight, H. House, and R.A. Wharton, Jr. 1994. McMurdo LTER: Inorganic geochemical studies with special reference to calcium carbonate dynamics. Antarctic Journal of the U.S., 29(5). Wharton, R.A., Jr. 1993. McMurdo Dry Valleys: A cold desert ecosystem.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 McMurS do Long-Term Ecological Research (LTER) project. Precipitation occurs only as snow, commonly totaling less than 10 centimeters of snow a year in the valley bottoms (Keys 1980), and usually sublimates before making any contribution to streamfiow (Chinn 1981). Thus, glacial meltwater is the only source of water to the perennially ice-covered and landlocked lakes of the McMurdo Dry Valleys. Glacial meltwater supplies the lakes not only with water but also with dissolved gases, nutrients, and sediment. To predict streamfiow and nutrient supply to the lakes, the melt rate of the glaciers must be known. Glacier mass balance is important because it directly affects glacier advance and retreat (Meier 1965, pp. 795-805) and, therefore, the contact that some glaciers have with the lakes. The goal of the glaciological program is to determine the mass balance and meltwater runoff of all the Taylor Valley glaciers, which contribute significant volumes of water to the major lakes. To accomplish this goal, we are establishing a surface-based measurement program to determine the mass balance and meltwater runoff at a few glaciers and will infer the mass balance and meltwater at the remaining glaciers in the valley. For temperate glaciers, summer is the ablation season and winter, the accumulation season. In contrast, for the polar glaciers of the McMurdo Dry Valleys the austral summer is both the ablation and the accumulation season: they not only lose the most mass but also accumulate the most mass in summer (Chinn 1981). The mass balance is determined by measuring the surface density and the surface lowering against a network of stakes drilled into the glacier, including the vertical cliff of the terminus, and by measuring the mass of ice calving from the terminus cliff. The significance of
enhanced melt on the terminus cliff to the total glacier mass balance is unclear (Bull and Carnein 1970, pp. 429-446; Chinn 1987). To estimate the component of glacier mass lost to meltwater, meteorological stations are being established on the glaciers to complement the four stations previously established in the valley bottom. From the meteorological data, we will be able to partition the total mass loss at a point, determined from the stake measurements, into the components of sublimation, melting, and evaporation. The combination of low humidity and föhn winds descending from the polar plateau results in significant losses to evaporation and sublimation, such that meltwater may represent only 20 percent of the total mass loss (Bull and Carnein 1970). Although inferring the mass balance and meltwater production from unmeasured glaciers is difficult, two complementary programs within the LTER project will help to constrain the problem. First, streamfiow from most of the glaciers that drain to lakes is measured and summarized by McKnight et al. (Antarctic Journal, in this issue). These data will be used to check our measurements on monitored glaciers and our predictions on unmeasured glaciers. Second, the point measurements of mass balance and meteorological variables will be extrapolated to larger regions using satellite remote sensing. The latter is a particularly important task because of the difficulty in extrapolating meteorological measurements in mountainous terrain such as that in the dry valleys. In the 1993-1994 season, ablation stake networks were established on three glaciers: Commonwealth, Canada, and Howard (figure 1). Because of the large icefall and extensive crevasses on the upper Canada Glacier, emplacement of ablation stakes was limited to the fan of the lower glacier where it spreads out into the valley. It is on the glacier fan where most,
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Pace, M.L., G.A. Knauer, D.M. Karl, and J.H. Martin. 1987. Primary production, new production and vertical flux in the eastern Pacific Ocean. Nature, 325(6107), 803-804. Suess, E. 1980. Particulate organic carbon flux in the oceans: Surface productivity and oxygen utilization. Nature, 288(5788), 260-263. Wefer, G. 1989. Particle flux in the ocean: Effects of episodic production. In W.H. Berger, V.S. Smetacek, and G. Wefer (eds.), Productivity of the ocean: Present and past. New York: John Wiley and Sons.
Fischer, G., D. Fuetterer, R. Gersonde, S. Honjo, D.R. Ostermann, and G. Wefer. 1988. Seasonal variability of particle flux in the Weddell Sea and its relation to ice cover. Nature, 335(6189), 426-428. Karl, D.M., B.D. Tilbrook, and G. Tien. 1991. Seasonal coupling of organic matter production and particle flux in the western Bransfield Strait, Antarctica. Deep-Sea Research, 38(819A), 1097-1126.
McMurdo Dry Valleys LTER: An overview of 1993-1994 research activities ROBERT A. WHARTON, JR., Biological Sciences Center, Desert Research Institute, Reno, Nevada 89506
he McMurdo Dry Valleys are now a site within the Nationeral ecological understanding through studies of processes T al Science Foundation's Long-Term Ecological Research that may be better resolved in these simplified, end-member (LTER) network (Anonymous 1993; Wharton 1993). The environments (cf. more complex ecosystems). The two key perennially ice-covered lakes, ephemeral streams, and extenhypotheses for the McMurdo LTER during the first phase of sive areas of soil within the valleys are subject to low temperathe project are that tures, limited precipitation, and salt accumulation. The • the structure and function of the Taylor Valley ecosystems McMurdo LTER site (figure) is far colder and drier than any of are differentially constrained by physical and biological the 17 other established LTER sites. The dry valleys, therefore, factors, and represent "end-member" environments, which contain • the structure and function of Taylor Valley ecosystems are microbially dominated ecosystems that are simplified commodified by material transport. pared to other LTER sites. An important outcome of the The LTER project is addressing these hypotheses through McMurdo LTER research is its potential contribution to gen- systematic environmental data collection, long-term experi-
77.35,
77,45. 162"OO'
77,45. 163'45'
Map of Taylor Valley in southern Victoria Land, Antarctica, site of the McMurdo Dry Valleys Long-Term Ecological Research project.
ANTARCTIC JOURNAL - REVIEW 1994 224
ments, and model development. The research activities of the McMurdo LTER are divided into several disciplines, including physical, chemical, biological, modeling, and information science. During the 1993-1994 field season, 18 scientists deployed to McMurdo Station and Taylor Valley to conduct research associated with the LTER project. Scientists initiated core measurement programs to obtain baseline ecologically relevant data from glaciers, streams, soils, and lakes. This paper and the 10 following papers highlight some of the accomplishments of the 1993-1994 season, as well as projects related to LTER data and information management. Glacier meltwater is the predominant source of water to the streams and lakes in Taylor Valley, which lacks significant precipitation. In addition to recharging the lakes, this water carries dissolved gases and nutrients required by the biota. As discussed in the paper by Fountain, Vaugh, and Dana (Antarctic Journal, in this issue), the goal of the LTER glaciological program is to determine the mass balance and meltwater runoff of the Taylor Valley glaciers, all of which contribute significant water to the three major lakes (Fryxell, Hoare, and Bonney). During the 1993-1994 field season, Fountain and his colleagues established a network of surfacebased measurements on the Commonwealth, Canada, and Howard glaciers to determine mass balance and meltwater flow. Meteorological stations were also established on the Commonwealth and Howard glaciers. A cornerstone of the LTER aquatic ecosystem studies is the measurement of streamfiow. McKnight, House, and von Guerard (Antarctic Journal, in this issue) present streamfiow data for the 1993-1994 austral summer for three streams in Taylor Valley, located in each of the three lake basins (i.e., Fryxell, Hoare, and Bonney). Their data show large diet variations in the flow regimes of these streams and differences in the timing of streamfiow initiation. During the 1993-1994 field season, McKnight and colleagues established a comprehensive network of stream-gaging stations within Taylor Valley. Preliminary results indicate that several years of streamflow data will be necessary for development of reliable correlations between streams and for understanding the relationship between local climate and streamfiow. Microbial mat and moss communities are often found within and along the margins of streams in Taylor Valley. These communities are active during the austral summer when meltwater is present. Dana, Tate, and Dewey (Antarctic Journal, in this issue) report on a preliminary study that incorporated spectroradiometry to assess the distribution, biomass, and nutrient status of the stream communities. They measured the spectral and pigment characteristics of microbial and moss communities in the Canada Stream feeding Lake Fryxell. Initial results show the potential for using "close-range" remote-sensing techniques to study the ecological features of the stream communities. The McMurdo LTER lakes program is focused on understanding the environmental conditions and ecological processes of former and present lakes in the dry valleys. Paleolimnological studies provide important information about
the physicochemical and biological state of past lakes in the region. Doran et al. (Antarctic Journal, in this issue) report preliminary geochemical and biological data that help to put the present Taylor Valley lake environments into a historical perspective and to trace environmental change through time using lake bottom sediments. The water chemistry of the present dry valley lakes may also contain information about past environments. In addition, the chemistry of each lake profoundly affects the biota within the lake. Welch et al. (Antarctic Journal, in this issue) report on a comprehensive sampling regime initiated during the 1993-1994 austral summer to study the chemical and biological components of lakes Fryxell, Hoare, and Bonney (both east and west lobes). Welch and colleagues pay special attention to the effects of high vs. low biological activities on the production and dissolution of calcium carbonate in the lakes. Priscu (Antarctic Journal, in this issue) reports on a study designed to investigate phytoplankton nutrient deficiencies in several of the dry valley lakes. The nutrient bioassay experiments provide important data concerning nitrogen and phosphorus limitations in the dry valley lakes. Moorhead and Wharton (Antarctic Journal, in this issue) present results of a mathematical model that examines the productivity patterns of benthic microbial mats in Lake Hoare as a function of light intensity. Soils in the dry valleys are influenced by a variety of factors including climate, glacial movement, parent material, and site characteristics. During the 1993-1994 field season, Powers et al. (Antarctic Journal, in this issue) established an elevational transect on the south shore of Lake Hoare in Taylor Valley to examine spatial variation in soils and nematode abundance. Results from this study show that the input and accumulation of organic matter in dry valley soils may not be the main predictor of nematode abundance and diversity. Powers and colleagues suggest that nematode populations are most likely limited by soil age, salinity, moisture, as well as soil carbon and nitrogen content. The McMurdo Dry Valleys LTER is an explicitly synthetic effort—a comprehensive, multidisciplinary ecosystem study. Much of the data collected by the LTER is "geo-referenceable" and can be incorporated into a geographic information system (GIS) for data management and spatial analysis. Butt and Hastings (Antarctic Journal, in this issue) summarize the work to date on the development of a GIS for the McMurdo LTER. In a companion paper, Hastings and Butt (Antarctic Journal, in this issue) describe an experimental access system that allows LTER participants to manipulate the GIS database directly from desktop personal computers. The research reported here is supported by National Science Foundation grant OPP 92-11773. References Anonymous. 1993. NSF's Long-Term Ecological Research program: The antarctic connection. Antarctic Journal of the U.S., 28(4), 8-9. Butt, A.Z., and J.T. Hastings. 1994. McMurdo LTER: Developing a geographic information system database. Antarctic Journal of the U.S., 29(5).
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Dana, G.L., C.M. Tate, and S.L. Dewey. 1994. McMurdo LTER: The use of narrow-band spectroradiometry to assess algal and moss communities in a dry valley stream. Antarctic Journal of the U.S., 29(5). Doran, P.T., R.A. Wharton, Jr., S.A. Spaulding, and J.S. Foster. 1994. McMurdo LTER: Paleolimnology of Taylor Valley, Antarctica. Antarctic Journal of the U.S., 29(5). Fountain, A.G., B.H. Vaughn, and G.L. Dana. 1994. McMurdo LTER: Glacial mass balances of Taylor Valley, Antarctica. Antarctic Journab! the U.S., 29(5). Hastings, J.T., and A.Z. Butt. 1994. McMurdo LTER: Developing a geographic information system access system. Antarctic Journal of the U.S., 29(5). McKnight, D., H. House, and P. von Guerard. 1994. McMurdo LTER: Streamfiow measurements in Taylor Valley, Antarctica. Antarctic Journal of the U.S., 29(5).
Moorhead, D.L., and R.A. Wharton, Jr. 1994. McMurdo LTER: Primary production model of benthic microbial mats in Lake Hoare, Antarctica. Anta rctic Journal of the U.S., 29(5). Powers, L.E., D.W. Freckman, M. Ho, and R.A. Virginia. 1994. McMurdo LTER: Soil and nematode distribution along an elevational gradient in Taylor Valley, Antarctica. Anta rctic Journal of the U.S., 29(5). Priscu, J.C. 1994. McMurdo LTER: Phytoplankton nutrient deficiency in lakes of the Taylor Valley, Antarctica. Antarctic Journal of the U.S., 29(5). Welch, K., W.B. Lyons, J.C. Priscu, R. Edwards, D.M. McKnight, H. House, and R.A. Wharton, Jr. 1994. McMurdo LTER: Inorganic geochemical studies with special reference to calcium carbonate dynamics. Antarctic Journal of the U.S., 29(5). Wharton, R.A., Jr. 1993. McMurdo Dry Valleys: A cold desert ecosystem.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 McMurS do Long-Term Ecological Research (LTER) project. Precipitation occurs only as snow, commonly totaling less than 10 centimeters of snow a year in the valley bottoms (Keys 1980), and usually sublimates before making any contribution to streamfiow (Chinn 1981). Thus, glacial meltwater is the only source of water to the perennially ice-covered and landlocked lakes of the McMurdo Dry Valleys. Glacial meltwater supplies the lakes not only with water but also with dissolved gases, nutrients, and sediment. To predict streamfiow and nutrient supply to the lakes, the melt rate of the glaciers must be known. Glacier mass balance is important because it directly affects glacier advance and retreat (Meier 1965, pp. 795-805) and, therefore, the contact that some glaciers have with the lakes. The goal of the glaciological program is to determine the mass balance and meltwater runoff of all the Taylor Valley glaciers, which contribute significant volumes of water to the major lakes. To accomplish this goal, we are establishing a surface-based measurement program to determine the mass balance and meltwater runoff at a few glaciers and will infer the mass balance and meltwater at the remaining glaciers in the valley. For temperate glaciers, summer is the ablation season and winter, the accumulation season. In contrast, for the polar glaciers of the McMurdo Dry Valleys the austral summer is both the ablation and the accumulation season: they not only lose the most mass but also accumulate the most mass in summer (Chinn 1981). The mass balance is determined by measuring the surface density and the surface lowering against a network of stakes drilled into the glacier, including the vertical cliff of the terminus, and by measuring the mass of ice calving from the terminus cliff. The significance of
enhanced melt on the terminus cliff to the total glacier mass balance is unclear (Bull and Carnein 1970, pp. 429-446; Chinn 1987). To estimate the component of glacier mass lost to meltwater, meteorological stations are being established on the glaciers to complement the four stations previously established in the valley bottom. From the meteorological data, we will be able to partition the total mass loss at a point, determined from the stake measurements, into the components of sublimation, melting, and evaporation. The combination of low humidity and föhn winds descending from the polar plateau results in significant losses to evaporation and sublimation, such that meltwater may represent only 20 percent of the total mass loss (Bull and Carnein 1970). Although inferring the mass balance and meltwater production from unmeasured glaciers is difficult, two complementary programs within the LTER project will help to constrain the problem. First, streamfiow from most of the glaciers that drain to lakes is measured and summarized by McKnight et al. (Antarctic Journal, in this issue). These data will be used to check our measurements on monitored glaciers and our predictions on unmeasured glaciers. Second, the point measurements of mass balance and meteorological variables will be extrapolated to larger regions using satellite remote sensing. The latter is a particularly important task because of the difficulty in extrapolating meteorological measurements in mountainous terrain such as that in the dry valleys. In the 1993-1994 season, ablation stake networks were established on three glaciers: Commonwealth, Canada, and Howard (figure 1). Because of the large icefall and extensive crevasses on the upper Canada Glacier, emplacement of ablation stakes was limited to the fan of the lower glacier where it spreads out into the valley. It is on the glacier fan where most,
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