HR: 13:55h
AN: U33B-02    [Abstracts]
TI: The Recent Arctic Warm Period
AU: * Overland, J E
EM: james.e.overland@noaa.gov
AF: NOAA/Pacific Marine Environmental Laboratory, 7600 Sand Point Way NE, Seattle, WA 91115, United States
AU: Wang, M
EM: muyin.wang@noaa.gov
AF: University of Washington/JISAO, 7600 Sand Point Way NE, Seattle, WA 98115, United States
AB: Arctic winter and spring surface air temperature (SAT) anomalies and associated sea level pressure fields have a decidedly different spatial pattern at the beginning of the 21st century (2000-2007) than in the 20th century; we suggest calling this recent interval the Arctic warm period. The record minimum sea ice extent of summer 2007 is not a one year event, but is part of this extended period. Another example of the warm period is that the spring melt date as measured at the North Pole Environmental Observatory (2002-2007) is 7 days earlier than the records from the Russian North Pole stations (1937-1987), statistically different at 0.05. A main proximate cause of the warm period is an atmospheric dipole pressure anomaly pattern over the Arctic with anomalous winds blowing toward the central Arctic, suggesting a contribution from warm air advection to the regional loss of sea ice. Such persistence in the atmospheric flow pattern also suggests the importance of other climate memory processes such as ocean and sea ice advection contributing to the reduction of sea ice. The 20th century in contrast was dominated by the two main mid-latitude climate patterns, the Arctic Oscillation/Northern Annular Mode (AO/NAM) and the Pacific North American-like (PNA*) pattern. Positive phases of these patterns contribute to warm anomalies in the Arctic primarily over their respective eastern and western hemisphere land areas, as in 1989-1995 and 1977-1987. A hint of the importance of northward anomalous flow to unusual central Arctic warming comes from the late 1920s-1930s which also developed the dipole pressure pattern. The 21st century warm period is not inconsistent with IPCC AR4 model projections of SAT in amount and Arctic-wide extent.
DE: 0750 Sea ice (4540)
DE: 1616 Climate variability (1635, 3305, 3309, 4215, 4513)
DE: 1621 Cryospheric change (0776)
DE: 3349 Polar meteorology
SC: Union [U]
MN: 2007 Fall Meeting