5.4
Historical variability in Arctic surface air temperature records
James E. Overland, NOAA/PMEL, Seattle, WA; and M. Spillane and K. Wood
Surface air temperature records from 45 Arctic stations north of 64 N shows monthly anomalies of several degrees and large spatial teleconnectivity yet major seasonal and regional differences, based on time/longitude plots of temperature anomalies and principal component analysis(PCA). Warm springtime anomalies in the 1990s show greater longitudinal extent than previous decades in the 20th century. Explorers' logs from the Canadian archipelago in the 19th century show minor differences from present conditions, while NW Siberia and Scandinavia were cooler. Using monthly station data rather than winter or annual averaged gridded temperature fields highlights the importance of different record lengths in assessing Arctic change; for example PCA performed on 11 stations beginning in 1886, 20 stations beginning in 1912, and 45 stations beginning 1936, show instability in the spatial patterns selected. While often there is the well-known interdecadal negative covariability in winter between N.Europe/W.Siberia and Baffin Bay, long term changes in the remainder of the Arctic are most evident in spring. Meteorological analyses suggests that the major warming events of the 1930-1950s are due to intrinsic regional variability of the atmosphere, in contrast to the pan-Arctic structures of the 1990s. We hypothesize a conceptual model for decadal variability of the Arctic system consisting of stochastic behavior of the polar vortex. Feedbacks in the Arctic can act as partial multi-year memory for the vortex, while the vortex in turn is often driven by changes in north/south differences in radiational forcing.
Session 5, Observed Climate Change: Part I (Room 608)
Tuesday, 13 January 2004, 3:30 PM-5:15 PM, Room 608
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