John Walsh received his B.A. in Mathematics from Dartmouth College in 1970 and his Ph.D. in Meteorology from M.I.T. in 1974. He spent a postdoctoral year at the National Center for Atmospheric Research. He was a faculty member at the University of Illinois for 30 years and, more recently, at the University of Alaska in Fairbanks. While at Illinois, he led a polar research group and coauthored an undergraduate textbook, Severe and Hazardous Weather. He also spent a year as the Chair in Arctic Marine Science at the Naval Postgraduate School in Monterey, CA.
At the University of Alaska Fairbanks, Walsh is currently the Chief Scientist of the International Arctic Research Center, the Director of NOAA’s Cooperative Institute for Alaska Research, and the Director of the University’s Center for Global Change. His recent research has addressed Arctic climate change; seasonal to decadal variability of sea ice; predictability of climate change in high latitudes; and changes in arctic weather in the context of climate change. In 2009 he received the Usibellli Distinguished Researcher Award from the University of Alaska.
Walsh was the lead author for the cryosphere chapter of the Arctic Climate Impact Assessment (2005), for the Polar Regions chapter of the IPCC’s Fourth Assessment Report (2007), and for the Arctic climate and modeling chapters of the Snow, Water, Ice and Permafrost in the Arctic (SWIPA, 2011) report of the Arctic Monitoring and Assessment Program. He is a Coordinating Lead Author for the Climate Science chapter of the 2013 U.S. National Climate Assessment. He has served as Associate Editor of the Journal of Climate, and is a fellow of the American Meteorological Society (AMS) and the American Association for the Advancement of Science (AAAS). He received the Editor’s Award from the AMS in 1992 and in 1999. He is a past member of the National Research Council’s Climate Research Committee and the Polar Research Board. He has co-chaired two reports of the Polar Research Board, including the recently released report on Seasonal to Decadal Predictions of Arctic Sea Ice. He has served on various panels of the National Science Foundation and other federal agencies, and has delivered invited lectures on arctic climate, both nationally and internationally.
Sea ice has emerged as the canary in the coal mine of climate change. Its summer extent in the Arctic has decreased by about 50% over the past decade, and the Arctic Ocean has undergone a regime shift from a cover of thick multiyear ice to a largely seasonal and much thinner ice cover. The recent loss is unprecedented in the periods of satellite and historical records of sea ice, and it also appears to be unique in paleo reconstructions spanning more than a thousand years. The change was driven by a “perfect storm” of warmer atmospheric and oceanic forcing, together with a boost from natural variability of wind-forcing in some years. However, the loss of sea ice is not apparent in some subarctic regions during the winter, nor has it occurred in the Antarctic region.
Signals of a response to the loss of sea ice are emerging in the ocean and the atmosphere. Ocean heat storage during the ice-free season not only contributes to a later freeze-up than in the past, but it also reduces the thickness to which first-year ice can grow. The vulnerability of this thinner ice to rapid spring melt is a manifestation of the ice-albedo-temperature feedback, which has long been postulated as a contributor to polar amplification of climate change. More notably for middle latitudes, the loss of sea ice appears to be triggering a reduction of the large-scale westerlies that characterize the atmospheric circulation in middle and subpolar latitudes. This response is consistent with increased persistence of departures from normal temperature and precipitation, resulting in anomalies of extreme weather during autumn and winter in heavily populated areas of the Northern Hemisphere.