The ice-covered lakes in the McMurdo Dry Valleys, a polar desert, rely on glacial melt for almost all their inputs. A recent study of Lake Fryxell suggests that in this environment even small changes in climate can impact biological productivity in the lake. Warmer weather (1) decreases ice thickness, boosting light penetration into the lake, and (2) increases glacial stream flow, providing more nutrient input—pulse events which together increase primary production in the lake.