Sources and Deposition Processes Linking Atmospheric Chemistry and Firn Records from Four Glacier Accumulation Zones in the McMurdo Dry Valleys, Antarctica

• Main Author: Williamson, Bruce R.
• Format: Text
• Language: unknown
• Published: DigitalCommons@UMaine 2006
• Subjects: glaciochemistry; climatic changes; Earth Sciences; Glaciology; Antarctic; Ross Sea; McMurdo Dry Valleys; East Antarctic Ice Sheet; Blue Glacier; Commonwealth Glacier; Victoria Upper Glacier; Clark Glacier; Antarc*; Antarctica; E. Antarctica; Ice Sheet
• Online Access: https://digitalcommons.library.umaine.edu/etd/108; https://digitalcommons.library.umaine.edu/context/etd/article/1105/viewcontent/WilliamsonBR2006.pdf

Samples of snow and firn from accumulation zones on the Victoria Upper Glacier, the Clark Glacier, the Commonwealth Glacier and the Blue Glacier in the McMurdo Dry Valleys (~77 to 78º S and 161 to 164º E), Antarctica, are evaluated chemically and isotopically to determine the relative importance of local (site-specific) factors versus regional-scale climatic influences in defining regional glaciochemistry. Two approaches for distinguishing these controls are examined: comparing chemical concentrations using multivariate statistical analysis, and examining the effect of physical filtration (capturing particulate material largely originating in close proximity to each site) on sample values. These techniques provide constraints for interpretation of connections between Dry Valleys climate and the broader Ross Sea and East Antarctic Ice Sheet climate systems. Spatial variation in snow and firn chemistry confirms documented trends within individual valleys regarding ion deposition relative to elevation and to distance from the coast. The results here, however, demonstrate that intra-valley trends break down when chemistry is compared among valleys. Temporally, major ions (with the exception of methane sulfonate and to a lesser extent calcium ion) yield common seasonal signals at each site for the time period 1989 - 2002. Trace metals have concentration peaks offset from ion peaks; using Empirical Orthogonal Function (EOF) analysis to clarify this distinction, a secondary climate pattern accounting for ~13% to 33% of dataset variability contains opposing deposition patterns for 10-cm averages of major ions compared to corresponding 10-cm samples of trace metals. Differing resolutions between these data sets, however, dictate caution in this assessment. Site-specific exposure to marine and local chemical sources plays a dominant role over trends in elevation or in distance from the coast in defining snow and firn chemistry along the coastal axis of the Dry Valleys. Physical filtration of samples from the Victoria ...