THE GEOCHEMISTRY OF UPLAND WETLANDS AND PONDS, TAYLOR VALLEY, ANTARCTICA

Wetlands and small ponds are common features in upland areas (>300m a.s.l.) near alpine glaciers and annual snow packs in Taylor Valley (~78°S), Antarctica.  Although the lakes and streams at lower elevations of Taylor Valley have been investigated since the 1960s, until recently there has been little interest in these upland aquatic systems.  Recent work documented the organic matter distribution and its dynamics in these systems (Moorhead et al., 2003; Moorhead, in review), and suggested that inundation and desiccation are important features of these systems.  In this paper, we present the first investigation of the geochemistry of these ponds in the uplands of Taylor Valley.  Most of the ponds and wetlands are Na-Cl waters suggesting the main source of ions is from marine aerosol and glacier/snow melt.  A few ponds are calcium-rich indicating an input from chemical weathering.  Chloride concentrations vary from 0.2 to 104 Mm indicating that many of the ponds have been evapoconcentrated over time.  The few d¹⁸O data that we have also indicate evaporation and sublimation are important processes in these systems.  Because of their elevations, these ponds are very sensitive to climate variations.  During warmer austral summers these systems expand, adding moisture to the soils and organic matter to the landscape; during colder times they wane in size and become more saline.  We present a model to explain sensitivity of these systems to temperature changes.