2008 Annual Meeting and Arctic Forum | Abstracts

Dipole Anomaly Drove the 2007 Arctic Sea Ice Minimum

Jia Wang¹, Jinlun Zhang^2
1Great Lakes Environmental Research Laboratory, National Oceanic and Atmospheric Administration, 2205 Commonwealth Boulevard, Ann Arbor, MI, 48105, USA, Phone 734-741-2281, Fax 734-741-2055, jia.wang@noaa.gov
²Polar Science Center, University of Washington, 1013 NE 40th Street, Seattle, WA, 98105, USA, Phone 206-543-5569, zhang@apl.washington.edu

The record low Arctic sea ice in the summer of 2007 is found to be triggered by the Arctic Dipole Anomaly pattern. This local, second-leading mode in the Arctic produced a strong meridional wind anomaly that drove more sea ice out of the Arctic Ocean during the summer of 2007 from the western to the eastern Arctic into the northern Atlantic.

We identify the Dipole Anomaly (DA) pattern in the Arctic atmosphere, and its relationship with winter sea ice motion, based on International Arctic Buoy Programme (IABP) dataset (1979-2004) and datasets from the National Centers for Environmental Prediction (NCEP) and the National Center for Atmospheric Research (NCAR) for the period of 1948-2007. The DA is the second-leading mode of EOF (empirical orthogonal function) of monthly mean SLP north of 70°N during the winter season (October-March) and accounts for 13% of the variance. One of its two anomaly centers is over the Canadian Archipelago; the other is situated over northern Eurasia and the Siberian marginal seas. Due to the DA’s strong meridionality, it becomes an important dynamic mechanism to drive both anomalous sea ice out of the Arctic Basin and cold air outbreaks into the Barents Sea, the Nordic Seas and northern Europe.

The PIOMAS (Pan-arctic Ice-Ocean Modeling and Assimilation System) was used to examine the response of sea ice motion to the 2007 DA forcing. The spatial patterns and temporal variations of sea ice are identified to be closely related to the DA. A new feedback loop in the western Arctic is proposed.