Amplified climate change in polar regions is significantly altering regional ecosystems, yet there are few long-term records documenting these responses. The McMurdo Dry Valleys (MDV) cold desert ecosystem is the largest ice-free area of Antarctica, comprising soils, glaciers, meltwater streams and permanently ice-covered lakes. Multi-decadal records indicate that the MDV exhibited a distinct ecosystem response to an uncharacteristic austral summer and ensuing climatic shift. A decadal summer cooling phase ended in 2002 with intense glacial melt (‘flood year’)—a step-change in water availability triggering distinct changes in the ecosystem. Before 2002, the ecosystem exhibited synchronous behaviour: declining stream flow, decreasing lake levels, thickening lake ice cover, decreasing primary production in lakes and streams, and diminishing soil secondary production. Since 2002, summer air temperatures and solar flux have been relatively consistent, leading to lake level rise, lake ice thinning and elevated stream flow. Biological responses varied; one stream cyanobacterial mat type immediately increased production, but another stream mat type, soil invertebrates and lake primary productivity responded asynchronously a few years after 2002. This ecosystem response to a climatic anomaly demonstrates differential biological community responses to substantial perturbations, and the mediation of biological responses to climate change by changes in physical ecosystem properties.
The McMurdo LTER team gratefully acknowledges the funding support from the National Science Foundation for the initial LTER grant and subsequent renewals (award numbers 9211773, 9813061, 9810219, 0096250, 0423595, 0832755, 1041742 and 1115245). We are grateful for the numerous collaborators and students who helped carry out lab and fieldwork associated with this project, and thank the logistical and helicopter support contractors who have facilitated our field research in Antarctica since 1993 through the US Antarctic Program: Antarctic Support Associates, Raytheon Polar Services, Antarctic Support Contractors and Petroleum Helicopters.