Woods Hole Oceanographic Institution

Elizabeth B Kujawinski Behn

»Using stable isotope probing to characterize differences between free-living and sediment-associated microorganisms in the subsurface.
»DOM in Lake Superior
»Deepwater Horizon hydrocarbons in the marine environment
»Microbes and marine DOM, Ann. Rev. Mar. Sci. 2011
»Greenland ice sheet outlet glacier: Insights from a new isotope-mixing model
»Groundwater DOM, GCA 2011
»Dispersants & DWH, ES&T 2011
»FT-MS variability in DOM, Org Geochem 2010
»Predatory Flavobacteria, FEMS Microb Ecol 2010
»Greenland Ice Sheet DOM, GCA 2010
»Protozoa and bacteria in aquifers, FEMS Microb Ecol, 2009
»Source markers in DOM, GCA 2009
»Automated data analysis, Anal. Chem. 2006
»Marine DOM and ESI FT-ICR MS; Marine Chem 2004
»DOM extraction by C18; Org. Geochem. 2003
»Black carbon by ESI FT-ICR MS; ES&T 2004
»ESI FT-ICR MS review; Env. Forensics 2002
»Marine protozoan surfactants; Marine Chem. 2002
»ESI MS and NOM; Org. Geochem. 2002
»ESI FT-ICR MS & humic acids; Anal. Chem. 2002
»Protozoan DOM & PCBs; ES&T 2001
»Protozoa & Fe, Th, C; Aquat. Microb. Ecol. 2001
»PCB uptake by protozoa; AEM 2000

Bhatia, M. P., S. B. Das, E. B. Kujawinski, P. Henderson, A. Burke, and M. A. Charette.,

Seasonal evolution of water source contributions to the subglacial outflow from a land-terminating Greenland ice sheet outlet glacier: Insights from a new isotope-mixing model

, Journal of Glaciology, 57: 929-941, 2011

Little is currently known about the subglacial hydrological system beneath the Greenland ice sheet (GrIS). Evidence that a large fraction of annual surface meltwater may drain to the bed of the GrIS suggests that portions of the GrIS subglacial hydrological system may undergo a seasonal evolution, akin to those present beneath alpine glaciers, with significant geophysical and biogeochemical implications. The interaction of surface meltwater with the glacier bed alters its chemical composition from dilute snow- and ice-melt to chemically-enriched subglacial discharge waters. In theory, variations in solute concentrations could be used to infer the evolution of the subglacial drainage network by differentiating water source contributions. There is ample evidence, however, that chemical mixing models which rely on bulk, non-conservative properties such as electrical conductivity, are unreliable. Here we present results from a novel multi-component isotope mixing model to quantify the relative contributions of surface snow, glacial ice melt, and basal melt to the bulk meltwater discharge at a small (~ 5 km2) land-terminating outlet glacier along the western margin of the GrIS. This model utilizes radioactive and stable isotopes (7Be, 222Rn, 18O, D) as passive flow tracers coupled with stream discharge and meteorological measurements. Each of these tracers has a unique and predictable signal for the different source waters that ultimately contribute to the subglacial discharge. We also use the radioactive nature of 7Be (half-life 53.3 d) to constrain the meltwater transit time from the glacier surface to the ice margin at the onset of the summer melt season. Finally, we compare our model results to those obtained from using conservative ionic species as tracers in order to assess the applicability of this approach for hydrograph separation. Results illustrate (1) the potential of using radon and stable water isotopes to provide quantitative estimates of the snow, ice, and basal flow components, and (2) the presence of a constant basal flow component which is diluted first by snow-melt and then by increasing amounts of glacial ice melt as the season progresses. These results are consistent with the hypothesis that the Greenland ice sheet subglacial drainage system undergoes a seasonal evolution from a distributed drainage system to a more efficient channelized drainage system. The development of an isotope mixing model that can successfully differentiate water source contributions would complement existing geophysical methods used to study seasonally-evolving subglacial hydrological systems. A reprint is available from Journal of Glaciology here.

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