Effect of increasing Arctic river runoff on the Atlantic meridional overturning circulation:a model study
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摘要: 观测显示过去几十年间北极入海径流呈现增加趋势,CMIP5耦合模式预测表明21世纪北极入海径流仍会增加,在RCP8.5路径下,21世纪末北极入海径流量将会是1950年的1.4倍。本文利用冰-海耦合数值模式研究了北极径流增加对大西洋经向翻转环流的影响。基于两个数值实验的结果表明,如果北极入海径流按每年0.22%的速度(与RCP8.5路径下的速度相当)增加,大西洋经向翻转环流的强度在100、150和200年后将会分别减弱0.6(3%)、1.2(7%)和1.8(11%) Sv。北极入海径流增加导致大西洋经向翻转环流减弱的主要原因是,北极入海径流增加的淡水被输运到北大西洋后,会抑制北大西洋深层水的生成,这也会导致北大西洋深层水海水年龄的增加。Abstract: An increasing amount of freshwater has been observed to enter the Arctic Ocean from the six largest Eurasian rivers over the past several decades. The increasing trend is projected to continue in the twenty-first century according to Coupled Model Intercomparison Project Phase 5 (CMIP5) coupled models. The present study found that water flux from rivers to the Arctic Ocean at the end of the century will be 1.4 times that in 1950 according to CMIP5 projection results under Representative Concentration Pathway 8.5. The effect of increasing Arctic river runoff on the Atlantic meridional overturning circulation (AMOC) was investigated using an ocean-ice coupled model. Results obtained from two numerical experiments show that 100, 150 and 200 years after the start of an increase in the Arctic river runoff at a rate of 0.22%/a, the AMOC will weaken by 0.6 (3%), 1.2 (7%) and 1.8 (11%) Sv. AMOC weakening is mainly caused by freshwater transported from increasing Arctic river runoff inhibiting the formation of North Atlantic Deep Water (NADW). As the AMOC weakens, the deep seawater age will become older throughout the Atlantic Basin owing to the increasing of Arctic runoff.
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