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  • Zhang, X., and J. E. Walsh, 2006: Toward a Seasonally Ice-covered Arctic Ocean: Scenarios from the IPCC AR4 Model Simulations. J. Climate, 19, 17301747.

We have synthesized the sea ice simulations by the IPCC AR4 (Intergovernmental Panel on Climate Change, the 4th Assessment Report) models for the climate of the 20th century and for global warming scenarios. A large number of model simulations realistically captured the climatological annual mean, seasonal cycle and temporal trends of sea ice area over the Northern Hemisphere during 1979-99, although there is considerable scatter among the models. In particular, multi-model ensemble means show promising estimates very close to observations for the late 20th century. Model projections for the 21st century demonstrate the largest sea ice area decreases generally in the SRES (Special Report on Emission Scenarios) A1B and A2 scenarios compared with the B1 scenario, indicating large multi-model ensemble mean reductions of -3.54 1.66X105 km2/decade in A1B, -4.08 1.33X105km2/decade in A2, and -2.22 1.11X105km2/decade in B1. The corresponding percentage reductions are 31.1%, 33.4%, and 21.6% in the last 20 years of the 21st century, relative to 1979-99. Further, multiyear ice coverage decreases rapidly at rates of -3.86 2.07X105km2/decade in A1B, -4.94 1.91X105km2/decade in A2 and -2.67 1.7107X105km2/decade in B1, making major contributions to the total ice reductions. In contrast, seasonal (first-year) ice area increases by 1.10 2.46X105km2/decade, 1.99 1.47X105 km2/decade and 1.05 1.9247 X105 km2/decade in the same scenarios, leading to decreases of 59.7% and 65.0% of the multiyear ice area and increases of 14.1% and 27.8% of the seasonal ice area in the last 20 years of this century. Statistical analysis shows that many of the models are consistent in the sea ice change projections among all scenarios. The results include an evaluation of the 99% confidence interval of the model-derived change of sea ice coverage, giving a quantification of uncertainties in estimating sea ice changes based on the participating models. Hence the seasonal cycle of sea ice area is amplified and an increased large portion of seasonally ice-covered Arctic Ocean is expected at the end of the 21st century. The very different changes of multiyear and seasonal ice may have significant implications for the polar energy and hydrological budgets and pathways.


Last Updated: 2006-04-11

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