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Claudia M. Johnson

Abstract

Twenty-five years of Arctic sea ice data have been used in conjunction with data from the lower atmosphere (the surface and 700 mb) to establish some concurrent general circulation relationships. Five January climatologies for both maximum and minimum sea ice areas over the entire north polar cap were first determined. The differences between the two sets of mean atmospheric patterns were then found. The student's t-test was used to establish the statistical significance.

The results indicate that the wintertime (January–February) atmospheric circulation in the Pacific tends to be weaker during heavy ice conditions while the differences in the Atlantic are not as significant. These results are compared with GCM (general circulation model) simulations with similar maximum ice conditions.

Extremes in Arctic sea ice during January were also examined locally. Although extremes in sea ice between Greenland and northern Europe wore not found to be strongly associated with concurrent atmospheric changes, above-normal sea ice in the Bering Sea and the Davis Strait were found to be strongly associated with simultaneous surface northerly flow locally. The regional analysis also showed that above-normal ice is associated with intensification of the closest major low pressure centers and 700 mb troughs.

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John E. Walsh and Claudia M. Johnson

Abstract

Arctic sea ice data from the 1953–77 period are digitized onto a set of 300 monthly grids covering the polar cap. Each grid contains 1648 ice concentration points at a spacing of 1° latitude (60 n mi). The synthesis of the regional ice data sets is described.

The digitized data are used to evaluate quantitatively the normal seasonal cycle of ice extent, the 25 year extremes for winter and summer, and the longitudinal dependence of the variance and trend of ice extent. Interannual variations of ice extent exceeding 5° latitude are found at most longitudes. The time series of total Arctic ice extent shows a statistically significant positive trend and correlates negatively with recent high-latitude temperature fluctuations.

Empirical orthogonal functions of longitude are used to identify the major spatial and temporal scales of ice fluctuations within the 25-year period. The dominant spatial mode is an asymmetric mode in which the North Atlantic anomaly is opposite in sign to the anomaly over the remainder of the polar cap. A tendency for ice anomalies to persist for several months is apparent in the lagged autocorrelations of the amplitudes of the dominant ice eigenvectors. The month-to-month persistence of the ice anomalies is considerably greater than the persistence of the high-latitude meteorological anomaly fields of sea level pressure, surface temperature and 700 mb height.

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Molly Baringer, Mariana B. Bif, Tim Boyer, Seth M. Bushinsky, Brendan R. Carter, Ivona Cetinić, Don P. Chambers, Lijing Cheng, Sanai Chiba, Minhan Dai, Catia M. Domingues, Shenfu Dong, Andrea J. Fassbender, Richard A. Feely, Eleanor Frajka-Williams, Bryan A. Franz, John Gilson, Gustavo Goni, Benjamin D. Hamlington, Zeng-Zhen Hu, Boyin Huang, Masayoshi Ishii, Svetlana Jevrejeva, William E. Johns, Gregory C. Johnson, Kenneth S. Johnson, John Kennedy, Marion Kersalé, Rachel E. Killick, Peter Landschützer, Matthias Lankhorst, Tong Lee, Eric Leuliette, Feili Li, Eric Lindstrom, Ricardo Locarnini, Susan Lozier, John M. Lyman, John J. Marra, Christopher S. Meinen, Mark A. Merrifield, Gary T. Mitchum, Ben Moat, Didier Monselesan, R. Steven Nerem, Renellys C. Perez, Sarah G. Purkey, Darren Rayner, James Reagan, Nicholas Rome, Alejandra Sanchez-Franks, Claudia Schmid, Joel P. Scott, Uwe Send, David A. Siegel, David A. Smeed, Sabrina Speich, Paul W. Stackhouse Jr., William Sweet, Yuichiro Takeshita, Philip R. Thompson, Joaquin A. Triñanes, Martin Visbeck, Denis L. Volkov, Rik Wanninkhof, Robert A. Weller, Toby K. Westberry, Matthew J. Widlansky, Susan E. Wijffels, Anne C. Wilber, Lisan Yu, Weidong Yu, and Huai-Min Zhang
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