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Arctic sea ice is a key indicator of the state of global climate because of both its sensitivity to warming and its role in amplifying climate change. Accelerated melting of the perennial sea ice cover has occurred since the late 1990s, which is important to the pan-Arctic region, through effects on atmospheric and oceanic circulations, the Greenland ice sheet, snow cover, permafrost, and vegetation. Such changes could have significant ramifications for global sea level, the ocean thermohaline circulation, native coastal communities, and commercial activities, as well as effects on the global surface energy and moisture budgets, atmospheric and oceanic circulations, and geosphere-biosphere feedbacks. However, a system-level understanding of critical Arctic processes and feedbacks is still lacking. To better understand the past and present states and estimate future trajectories of Arctic sea ice and climate, we argue that it is critical to advance hierarchical regional climate modeling and coordinate it with the design of an integrated Arctic observing system to constrain models.
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Download Supplemental Figure 1 as a PDF; also reproduced below.
Supplemental Figure 1. September 2002 mean sea ice thickness (m) from selected CMIP3 models, the NAME model, and observed sea ice extent.
Supplemental Figure 1 shows the mean September ice-thickness results from selected CMIP3 models and the NAME model. The satellite-derived mean September 2002 ice extent from the National Snow and Ice Data Center (NSIDC) is also shown for reference. The CMIP3 models show a wide range of ice-thickness distributions, as well as the extent of sea ice, during the September 2002 period. Recalling that September 2002 was a record-breaking minimum at the time, it is important to note that none of the CMIP3 models shows a realistic pattern of sea ice similar to the NSIDC ice-extent distribution. Results from CCSM3 runs show too little ice in the eastern Arctic and too much and too thick ice in the East Siberian Sea. CGCM3 and GFDL results have various deficiencies in representing the proper sea ice extent and also show unrealistic ice-thickness distributions, with predominately too thin sea ice in the central Arctic. HadGEM1 appears to have the most realistic distribution among the CMIP3 models; however, there are some errors, with too great of an ice extent in the Labrador Sea and the Laptev Sea, and the thickness distribution is likely elevated.