A coastal transect of McMurdo Dry Valleys snow and firn: marine and terrestrial influences on glaciochemistry

Samples of snow and firn from accumulation zones on Clark Glacier, Commonwealth Glacier, Blue Glacier and Victoria Upper Glacier in the McMurdo Dry Valleys (�77–788S and 161– 1648E), Antarctica, are evaluated chemically and isotopically to determine the relative importance of local (site-specific) factors versus regional-scale influences in defining glaciochemistry. Spatial variation in snow and firn chemistry confirms documented trends within individual valleys regarding major ion deposition relative to elevation and to distance from the coast. Sodium and methylsulfonate (MS), for example, follow a decreasing gradient with distance from the coast along the axis of Victoria Valley (350–119�g L for Na; 33–14�g L for MS); a similar pattern exists between Commonwealth Glacier and Newall Glacier in the Asgaard Range. When comparing major ion concentrations (e.g. Na, MS, Ca2) or trace metals (e.g. Al, Fe) among different valleys, however, site-specific exposures to marine and local terrestrial chemical sources play a dominant role. Because chemical signals at all sites respond to particulates with varying mixtures of marine and terrestrial sources, each of these influences on site glaciochemistry must be considered when drawing temporal climate inferences on regional scales.