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Title: A temporal stable isotopic (d18O, dD, d-excess) comparison in glacier meltwater streams, Taylor Valley, Antarctica

Author
item Leslie, Deborah
item WELCH, KATHLEEN - The Ohio State University
item LYONS, WILLIAM - The Ohio State University

Submitted to: Hydrological Processes
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/29/2017
Publication Date: 7/21/2017
Publication URL: https://handle.nal.usda.gov/10113/5801793
Citation: Leslie, D.L., Welch, K.A., Lyons, W.B. 2017. A temporal stable isotopic (d18O, dD, d-excess) comparison in glacier meltwater streams, Taylor Valley, Antarctica. Hydrological Processes. 31(17):3069-3083. doi:10.1002/hyp.11245.

Interpretive Summary: The McMurdo Dry Valleys represent the largest ice-free, polar desert in Antarctica with a hydrologic system consisting of glacier ice, permafrost, lake water, snowpatches, and channelized streamflow. This study was undertaken to provide a clearer picture of seasonal subsurface water contributions to glacial melt streamflow and streamwater chemistry. Results showed that the concentrations of stable oxygen and hydrogen isotopes could be used to track the subsurface influence on streamwater chemistry. The influence of the subsurface zone was variable and increased throughout the 48-day melt season, except at higher streamflows. These findings have important ecological and biogeochemical as well as hydrological consequences for this fragile region. If warmer periods occur in the future, then there will be increased potential for streamwater contributions from undefined subsurface sources, which in turn could affect streamwater chemistry and ecology.

Technical Abstract: In this paper, we describe the importance of hyporheic dynamics within Andersen Creek and Von Guerard Stream, Taylor Valley, Antarctica, from the 2010-11 melt season using natural tracers. Water collection started at flow onset and continued, with weekly hyporheic zone sampling. The water d18O and dD values were isotopically lighter in the beginning and heavier later in the season. D-excess measurements were used as an indicator of mixing because an evaporative signature was evident and distinguishable between two primary end-members (glacier meltwater and hyporheic zone). Hyporheic zone influence on the channel water was variable with a strong control on streamwater chemistry, except at highest discharges. This work supports previous research indicating that Von Guerard Stream has a large, widespread hyporheic zone that varies in size with time and discharge. Andersen Creek, with a smaller hyporheic zone, displayed hyporheic zone solute interaction through the influence from subsurface hypersaline flow. Overall, the evolution of Taylor Valley hyporheic zone hydrology is described seasonally. In mid-December, the hyporheic zone is a dynamic system exchanging with the glacier meltwater in the channel, and with diminishing flow in January, the hyporheic zone drains back into the channel flow also impacting stream chemistry. This work adds new information on the role of hyporheic zone-stream interaction in these glacier meltwater streams.