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Taylor Valley is a cold, polar desert located in the McMurdo Dry Valleys, the largest ice-free area in Antarctica. For six to ten weeks a year, glacial meltwater streams flow through unconsolidated boulders and pebbles to perennially ice-covered closed-basin lakes. Because there is no overland flow or groundwater input, most chemical weathering reactions are restricted to the stream channels. Despite these limiting conditions, chemical weathering rates in the stream channels are similar to or higher than those in temperate-climate watersheds. These high rates in Taylor Valley suggest that temperature and precipitation are not the primary controls on chemical denudation. In this case, high stream discharges, high rates of physical weathering (e.g., frost action, salt weathering), and/or the interaction between the stream and hyporheic zone contribute to the high chemical denudation rates in the Taylor Valley stream channels.