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A Stable Isotopic Investigation of a Polar Desert Hydrologic System, Mcmurdo Dry Valleys, Antarctica

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A Stable Isotopic Investigation of a Polar Desert Hydrologic System, Mcmurdo Dry Valleys, Antarctica View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by PDXScholar Portland State University PDXScholar Geology Faculty Publications and Presentations Geology 2-1-2006 A Stable Isotopic Investigation of a Polar Desert Hydrologic System, McMurdo Dry Valleys, Antarctica Michael N. Gooseff Colorado School of Mines W. Berry Lyons Ohio State University Diane M. McKnight University of Colorado at Boulder Bruce H. Vaughn University of Colorado at Boulder Andrew G. Fountain Portland State University See next page for additional authors Let us know how access to this document benefits ouy . Follow this and additional works at: http://pdxscholar.library.pdx.edu/geology_fac Part of the Geology Commons, Glaciology Commons, and the Hydrology Commons Citation Details Gooseff, M. N., Lyons, W., McKnight, D. M., Vaughn, B. H., Fountain, A. G., & Dowling, C. (2006). A stable isotopic investigation of a polar desert hydrologic system, McMurdo dry valleys, Antarctica. Arctic, Antarctic, And Alpine Research, 38(1), 60-71. This Article is brought to you for free and open access. It has been accepted for inclusion in Geology Faculty Publications and Presentations by an authorized administrator of PDXScholar. For more information, please contact [email protected]. Authors Michael N. Gooseff, W. Berry Lyons, Diane M. McKnight, Bruce H. Vaughn, Andrew G. Fountain, and Carolyn Dowling This article is available at PDXScholar: http://pdxscholar.library.pdx.edu/geology_fac/5 Arctic,Antarctic, and AlpineResearch, Vol. 38, No. 1, 2006, pp. 60-71 A StableIsotopic Investigation of a PolarDesert Hydrologic System, McMurdoDry Valleys, Antarctica Michael N. Gooseff* Abstract W. Berry Lyonst The hydrologic system of the coastal McMurdo Dry Valleys, Antarctica,is defined by Diane M. McKnightj snow accumulation,glacier melt, stream flow, and retention in closed-basin, ice-covered lakes. the Bruce H. During austral summersfrom 1993-1996 and 1999-2000 to 2002-2003, fresh Vaughnj snow, snow pits, glacier ice, stream water, and lake waters were sampled for the stable Andrew G. Fountain? and isotopes deuterium (D) and 180 in order to resolve sources of meltwater and the Carolyn Dowlingf interactions among the various hydrologic reservoirs in the dry valleys. This data set provides a survey of the distributionof naturalwater isotope abundanceswithin the well- *Correspondingauthor. defined dry valley system in which extends 20 km inland from Departmentof Geologyand Geological hydrologic Taylor Valley, McMurdo Engineering,Colorado School of Mines, Sound. The three major Taylor Valley lakes are not connected to one another Golden,CO 80401,U.S.A. hydrologically, and their levels are maintainedby glacial meltwaterinflow and perennial [email protected] ice-cover sublimation. At the valley scale, glacial ice, snow, stream, and lake waters tByrdPolar Research Center, become more depleted in 6D with increasing distance from McMurdo Sound (further OhioState University, Snow in accumulation zones is a result of ColumbusOH 43210-1002,U.S.A. inland). pack glacial heterogeneous, likely storm jInstituteof Arcticand Alpine Research, varying sources (continentalversus coastal), and, in general, snow pits, fresh snow Universityof Colorado, samples, and glacier ice are more depleted than stream waters. Within the lake basins, CO Boulder, 80309-0450,U.S.A. glacial ice source waters are depleted by as much as 6D and 86180compared of and 1110o 20o ?Departments Geology Geography, to lake waters. These results demonstratethe importanceof in-streamfractionation at the PortlandState University, scale. In-streamenrichment occurs direct fractionationfrom the Portland,OR 97207-0751,U.S.A. valley through evaporation channel and hyporheic exchange with isotopically enriched waters in the near-stream subsurfaceduring transportfrom the glacial source to lake. Furthermore,the results show that lake waters directly reflecttheir glacial ice sources, despite fractionationduring stream transport.Inter-annual comparisons of lake profiles suggest that lake waters are directly influenced by the isotopic composition and amount of stream flow during a season. Introduction Previousinvestigations of stable isotope distributionswithin dry valley hydrologic systems suggest that the use of isotopes is a The of stable study isotopes of water has provided a useful promisingtool for delineatingand quantifyingsources of water to method of discretizingtiming and source areas of the hydrologyof the lakes, as well as establishinghydrologic histories of the lakes temperatewatersheds (Hooper and Shoemaker,1986; Turneret al., (Matsubayaet al., 1979; Stuiver et al., 1981; Lyons et al., 1998a). 1987; Stewart and McDonnell, 1991), as well as glacial- and Forexample, Matsubaya et al. (1979) have foundthat saline lakes and snowmelt-dominatedwatersheds and Theak- (Epstein Sharp, 1959; pondshave evaporative-enriched6D and 6'80 isotopiccharacteristics stone, 1988; Theakstoneand Knudsen, 1989; Cooper et al., 1991, becausethey experiencemore ice-off time than freshwaterlakes and 1993;Theakstone and Knudsen, 1996; McNamara et al., 1997;Stichler pondsin the Dry Valleys. In theirstudy of stream-lakeinteractions in and Schotterer,2000). In glaciated watersheds,variations in stream Lake Fryxell, Miller and Aiken (1996) found that waters become isotope abundancesprovide informationon contributionsof snow isotopicallyenriched in 6D and 610 due to evaporationduring stream pack, glacial melt, and/ordirect precipitation to runoff. transportand evaporationduring summer open-water in the moatsof The hydrologyof the McMurdoDry Valleys polar desertis de- the lake, whereas isotopicallydepleted water may sink to the lake fined by glacial snow pack, glacier ice, intermittentvalley-bottom bottomswhen the moatsfreeze in autumn.The findingsof Millerand snow, streamflow, hyporheicwaters, and lake waters.The processes Aiken (1996) were confirmedby the findingsof Lorrainet al. (2002), thatcontrol the interactionsamong these storagelocations are glacial thatlake ice formationin a semi-closedsystem preferentially excludes meltwaterproduction, snow andice sublimation,stream and lake water isotopically depleted waters as freezing progresses downwards. evaporation,stream discharge,and hyporheicexchange. Hyporheic Further,Petit et al. (1991) suggest that D-excess in recentAntarctic exchange results in the mixing of stream water with near-stream snowfallcan be tracedto the latitudeof oceanicsource water. subsurfacewaters that are very enrichedin waterstable isotopes due to Ourapproach in the studypresented here was to conducta defined evaporativefractionation (Gooseff et al., 2003). Previoushydrologic surveyof the naturalabundance of waterstable isotopes withineach investigationsin the McMurdoDry Valleys polardesert have focused of the hydrologiccomponents (snow, glaciers,streams, and lakes) in on glacial meltwatergeneration (von Guerardet al., 1995; Conovitz orderto resolve sourceareas of meltwaterand the interactionsamong et al., 1998), stream-hyporheiczone interactions(Runkel et al., 1998; the various hydrologic compartmentsin the dry valleys. Here we McKnight et al., 1999; Gooseff et al., 2002, 2003), stream-lake presentdata of a surveyof stableisotopes of water(D and 180) from interactions(McKnight and Andrews, 1993), and lake hydrology the TaylorValley hydrologicbasins. Isotopicsamples of snow were (Chinn,1993; Bomblieset al., 2001). collectedin 1993 and 1996; glacier ice sampleswere collectedfrom 60 / ARCTIC,ANTARCTIC, AND ALPINE RESEARCH ? 2006 Regents of the University of Colorado 1523-0430/06 $7.00 Taylor Valley 13 N aylor79 Valley +5,6 4 FIGURE 1. Location map of Taylor Valley, Antarctica. Num- bers indicate stream locations: (1) Lyons Creek, (2) Santa Fe Stream, (3) Priscu Stream, (4) Andersen Creek, (5) Andrews Glaciers Creek, (6) Canada Stream, (7) Huey Creek, (8) Lost Seal di{ 2; E" Stream, (9) McKnight Creek, S3 miles (10) Aiken Creek, (11) Delta Stream, (12) Green Creek, and (13) Commonwealth Stream. Note that 1, 2, 4, 5, 6, and 12 the and ! go are very close to glaciers .,- 0 t5', k'm'5 km cannot easily be distinguished mt#o on the map. 1993 to 1997, stream water samples were collected during the austral All glaciers sampled in this study are alpine glaciers, except summers of 1993-1994, and 1999-2000. We also compare lake Taylor Glacier, a terminal glacier of the East Antarctic Ice Sheet. The isotopic profiles obtained in 2002 with previously published profiles. altitude of equilibrium lines (ELA) of the McMurdo Dry Valley These results provide a comprehensive understanding of the hydrologic glaciers vary systematically with distance from the coast (east to west) processes which support the persistent aquatic ecosystems within this with a gradient of -30 m/km (Fountain et al., 1999). This gradient is cold, dry environment. almost an order of magnitude greater than temperate glaciers. In Taylor Valley, there is an abrupt shift at --700 m which produces a local et The location of this shift SiteDescription gradient of -70 m/km (Fountain al., 1999). of gradient is related to the location of the Nussbaum Riegel, a ridge in The McMurdo Dry Valleys are located at --78oS latitude, on the the valley, which acts as a meteorological barrier.These steep gradients western edge of the Ross Sea (Fig. 1). The landscape is dominated by of the ELA indicate that these glaciers can be impacted differently by glaciers, open expanses of barren patterned ground, stream channels, changes in climate even through they are in relatively
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