2006 Annual Meeting and Arctic Forum | Abstracts

Arctic Sea Ice Simulations in the 20th Century and in Global Warming Scenarios

Xiangdong Zhang^1
1International Arctic Research Center, University of Alaska Fairbanks, 930 Koyukuk Drive, Fairbanks, AK, 99775, USA, Phone 907-474-2675, Fax 907-474-2643, xdz@iarc.uaf.edu

Sea ice is an essential component of the climate system and an outstanding indicator of global climate change. Recent dramatic shrinking of arctic sea ice cover has drawn much attention scientifically and societally. Remarkable global warming has been manifested in the polar region, which may continue and be further amplified, leading to a rapid decrease of sea ice cover or an ice-free summer in the Arctic Ocean, as projected in global warming scenarios.

The decreased sea ice cover would naturally result in significant climate consequences by changing energy budgets and hydrological cycle; for example, altering atmospheric circulation regimes and impacting the North Atlantic deep convections and Meridional Overturning Circulation. In this study, we analyzed changes of the arctic sea ice cover based on the multiple model outputs for the IPCC AR4 (Intergovernmental Panel on Climate Change, the 4th Assessment Report), which was archived by PCMDI (Program for Climate Model Diagnosis and Intercomparison).

We first examined the arctic sea ice simulations for the climate of the 20th century (20c3m) and validated the model's performance against observations. Considering availability of accurate sea ice measurements by satellites, we selected a period of 1979-99 from ensemble means of each model's simulations and compared model results with observational data. Then, we investigated changes of sea ice area in the 20th century and in the 21st century under global warming scenarios (SRES A1B, SRES A2, and SRES B1). The results demonstrated various capabilities of the participating models in simulating sea ice climatology. A number of models relatively captured realistic sea ice climatology, while a few models noticeably overestimated or underestimated sea ice cover. Nevertheless, most models show encouraging results in portraying decreasing sea ice during 1979-1999. In the global warming scenarios, all the models indicated a pronounced reduction of sea ice cover from 2000 to 2100 through out the Arctic Ocean. Generally, the strongest sea ice decrease occurs in the SRES A1B and A2 scenarios and the weakest occurs in SRES B1. Close examination shows that a ice-free Arctic Ocean in the summer can be expected in the later 21st century in a number of models, while sea ice is relatively stable and can survive in summer in other models.