PRELIMINARY ANALYSIS OF CHEMICAL WEATHERING IN GLACIAL MELTWATER STREAMS OF WRIGHT AND TAYLOR VALLEY, ANTARCTICA

The McMurdo Dry Valleys, Antarctica, are the coldest and driest regions on Earth, thus making them an extreme end-member climate for the study of chemical weathering. Recent publications have begun to investigate weathering reactions on stream water chemistry within this polar desert. The only water input for the stream channels is limited to the 6-12 week austral summer. We are studying the chemistry of glacial meltwater streams in Wright and Taylor Valley in order to further understand chemical weathering here. The catchments in the targeted areas drain granitoid basement and then flow through drifts with clasts of variable lithology.

Initial analysis of stream water from Clark Glacier, Wright Valley, shows increasing concentrations of several cations (Ca⁺, Na⁺, K⁺, Si⁺, Mg⁺) from the base of the glacier to 5 km downstream. Beginning at approximately 500 meters downstream from the glacier, element concentrations exhibiting the most pronounced increases downstream include Ca⁺, Na⁺, and K⁺. The Clark Glacier drainage system flows over the Brownworth Pluton and passes through Trilogy and Brownworth drifts. Both drifts are composed of similar amounts of granite and granodiorite clasts and the transition between these drifts along the drainage does not appear to influence the water chemistry data.

These preliminary results confirm the influence of silicate weathering along even this relatively short distance of the Clark Glacier drainage, as expressed most notably by the increases in Ca⁺ and K⁺. Marine aerosols from the Ross Sea likely provide the source for the increase in Na⁺. Our results provide the first published data on the Clark Glacier drainage, but parallel results from other chemical weathering studies involving various drainages throughout the Dry Valleys.

Initial analyses from other glacier meltwater streams within Wright and Taylor Valley indicate chemical trends that correlate with those from Clark Glacier. Our future research will focus on integrating the solute data with results from mineralogical and textural analyses of the sediment from these drainages, to further our understanding of the chemical processes operating within this polar desert. We will compare low temperature weathering models with field data to determine how temperature and sediment texture affect chemical weathering fluxes.