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simulation suggests that Arctic sea ice extent anomalies of the magnitude observed
in the September 2007 minimum are plausible under 1990 forcing conditions. It is
reasonable to conclude that more severe anomalies are achievable with more acute
forcing conditions that are in excess of those of 1990.
1. INTRODUCTION
march to a minimum of 6.8 × 10 6 km 2 in September [ Serreze
et al. , 2007]. For the observational record, a sustained ice
pack averaging about 2 to 3 m in thickness [e.g., Bourke and
Garrett , 1987] has continuously covered the central Arctic
Ocean and portions of the surrounding marginal seas. Over
the record of satellite passive microwave observations of sea
ice cover beginning in 1979, the average sea ice extent has
trended downward at a rate of about 3% per decade [ Par-
The Arctic Ocean Basin (Figure 1) has received increased
attention in recent years because of observed, rapid changes
in its climate [ Serreze et al. , 2000]. Its perennial sea ice
cover is a signature characteristic. As shown in Plate 1,
Northern Hemisphere sea ice extent has historically varied
seasonally from a maximum cover of over 15.3 × 10 6 km 2 in
Figure 1. Map of the Arctic Ocean basin. The orography of the National Center for Atmospheric Research (NCAR)
ccSm3 is contoured every 250 m with local maxima indicated.
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