An Extreme Flood Event Marks a State Change in an Antarctic Aquatic Ecosystem

Takacs-Vesbach, Cristina

An Extreme Flood Event Marks a State Change in an Antarctic Aquatic Ecosystem

Tuesday, 24 January 2017: 11:20

Ballroom III-IV (San Juan Marriott)

Cristina D. Takacs-Vesbach¹, John E Barrett¹, Byron J Adams², Peter T Doran³, Andrew G Fountain⁴, William B Lyons⁵, Diane M McKnight⁶, John C Priscu⁷, Eric Sokol⁸, Martin L Vandegehuchte⁹, Ross A Virginia¹⁰ and Diana H Wall¹¹, (1)University of New Mexico, Biology Department, Albuquerque, NM, United States, (2)Brigham Young University, Department of Biology, Provo, UT, United States, (3)Louisiana State University, Department of Geology & Geophysics, Baton Rouge, LA, United States, (4)Portland State University, Portland, OR, United States, (5)Ohio State University Main Campus, Columbus, OH, United States, (6)University of Colorado at Boulder, Boulder, CO, United States, (7)Montana State University, Bozeman, MT, United States, (8)Institute of Arctic and Alpine Research, Boulder, CO, United States, (9)Swiss Federal Institute for Forest, Snow and Landscape Research, Research Unit Community Ecology, Birmensdorf, Switzerland, (10)Dartmouth College, Hanover, NH, United States, (11)Colorado State University, Fort Collins, CO, United States

Abstract:

Amplified climate change in polar regions is significantly altering polar ecosystems, yet there are few long-term records of ecosystem response. The McMurdo Dry Valley (MDV) region of Antarctica is a cold desert ecosystem, comprised of a mosaic of soils, glaciers, ephemeral melt-water streams and terminal ice-covered lakes. We use a ~30 year record to show that this ecosystem has exhibited a distinct response to a recent extreme climatic event. In 2002, a period of summer cooling that lasted over a decade, ended with a year of intense glacial melt and record stream flow caused by high temperatures and solar irradiance (“flood year”). Since 2002 summer air temperatures and solar radiation flux have had no discernable trend, exhibiting less variation than previously observed. The MDV aquatic systems exhibited distinct responses to this flood event. Before the flood, during the cooling phase, the ecosystem exhibited consistent and synchronous behavior: declining stream flow, increasing soil freeze-thaw cycles, decreasing lake levels, and thicker ice-cover on lakes, accompanied by a decrease in primary production in lakes and streams. After the flood, the MDVs entered a new ecosystem state of abiotic change defined by rising lake levels, lake ice thinning, and increasing stream flow generation. Biological responses to the flood and the climate shift varied; for example, one type of stream cyanobacterial mat immediately increased production after the flood year, but another type of stream mat and lake primary productivity responded asynchronously to the flood with different lags after the flood year. Based on predicted future climate scenarios, we expect the MDV region will experience more frequent and intense floods in the coming decades. These changes will continue to affect physical and biological aspects of the MDV aquatic system, which in turn may result in significant changes in the function and services of the surrounding terrestrial and marine ecosystems.