Over the past 40 years, the Arctic sea ice minimum in September has declined. The period between 2007 and 2012 showed accelerated melt contributed to the record minima of 2007 and 2012. Here, observational and model evidence shows that the changes in summer sea ice since the 2000s reflect a continuous anthropogenically forced melting masked by interdecadal variability of Arctic atmospheric circulation. This variation is partially driven by teleconnections originating from sea surface temperature (SST) changes in the east-central tropical Pacific via a Rossby wave train propagating into the Arctic [herein referred to as the Pacific–Arctic teleconnection (PARC)], which represents the leading internal mode connecting the pole to lower latitudes. This mode has contributed to accelerated warming and Arctic sea ice loss from 2007 to 2012, followed by slower declines in recent years, resulting in the appearance of a slowdown over the past 11 years. A pacemaker model simulation, in which we specify observed SST in the tropical eastern Pacific, demonstrates a physically plausible mechanism for the PARC mode. However, the model-based PARC mechanism is considerably weaker and only partially accounts for the observed acceleration of sea ice loss from 2007 to 2012. We also explore features of large-scale circulation patterns associated with extreme melting periods in a long (1800 yr) CESM preindustrial simulation. These results further support that remote SST forcing originating from the tropical Pacific can excite significant warm episodes in the Arctic. However, further research is needed to identify the reasons for model limitations in reproducing the observed PARC mode featuring a cold Pacific–warm Arctic connection.
How Tropical Pacific Surface Cooling Contributed to Accelerated Sea Ice Melt from 2007 to 2012 as Ice Is Thinned by Anthropogenic Forcing
Authors:
Ian Baxtera,b, Qinghua Dinga,b, Axel Schweigerc, Michelle L’Heureuxd, Stephen Baxterd, Tao Wange,f, Qin Zhangd, Kirstin Harnosd, Bradley Marklea,b, Daniel Topala,b,g,h, and Jian LuiAffiliationsa Department of Geography, University of California, Santa Barbara, Santa Barbara, California
Affiliationsb Earth Research Institute, University of California, Santa Barbara, Santa Barbara, California
Affiliationsc Polar Science Center, Applied Physics Laboratory, University of Washington, Seattle, Washington
Affiliationsd NOAA/Climate Prediction Center, College Park, Maryland
Affiliationse Earth System Science Interdisciplinary Center, University of Maryland, College Park, College Park, Maryland
Affiliationsf NASA Goddard Space Flight Center, Greenbelt, Maryland
Affiliationsg Research Center for Astronomy and Earth Sciences, Institute for Geological and Geochemical Research, Budapest, Hungary
Affiliationsh Department of Meteorology, Eötvös Loránd University, Budapest, Hungary
Affiliationsi Atmospheric Sciences and Global Change Division, Pacific Northwest National Laboratory, Richland, Washington
Affiliationsb Earth Research Institute, University of California, Santa Barbara, Santa Barbara, California
Affiliationsc Polar Science Center, Applied Physics Laboratory, University of Washington, Seattle, Washington
Affiliationsd NOAA/Climate Prediction Center, College Park, Maryland
Affiliationse Earth System Science Interdisciplinary Center, University of Maryland, College Park, College Park, Maryland
Affiliationsf NASA Goddard Space Flight Center, Greenbelt, Maryland
Affiliationsg Research Center for Astronomy and Earth Sciences, Institute for Geological and Geochemical Research, Budapest, Hungary
Affiliationsh Department of Meteorology, Eötvös Loránd University, Budapest, Hungary
Affiliationsi Atmospheric Sciences and Global Change Division, Pacific Northwest National Laboratory, Richland, Washington
Received: 14 November 2018
Final Form: 6 September 2019
Published Online: 20 November 2019
December 2019
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