摘要
随着全球气候变暖,北极海冰快速减退,北冰洋穿极流位置和强度正在发生明显的变化。本文利用海表地转流、海冰漂流、海冰密集度和海面风场计算了考虑海冰效应的北冰洋海洋表面应力分布,探讨了北冰洋穿极流的强度和源头位置变动机制。结果表明,穿极流冬季比夏季强,9月最弱,12月最强。2003—2014年间穿极流的年平均流速呈增强趋势,穿极流的源头海域逐渐从东西伯利亚海偏向西边的拉普捷夫海;典型强年比典型弱年有西向的趋势。影响穿极流强度年际变化的主要因素是海冰覆盖,海冰覆盖率越低,穿极流越强。2003—2014年间海冰覆盖率降低导致海表面应力增强,穿极流有变强趋势。影响穿极流强度季节变化的主要因素是海表面风场,冬季表海面风场较强,海表应力增强,穿极流也较强;夏季海面风场减弱,海表应力减弱,穿极流强度也随之减小。海面风场和海冰的变化共同影响了穿极流源头的位置变动,穿极流源头西移的原因:一是位于加拿大海盆上方的高压中心逐渐从波弗特海上空向西南方移动到靠近穿极流源头的俄罗斯沿岸,造成穿极流源头向西移动;二是北冰洋增温导致海冰加速融化,海冰覆盖率降低,加大了海表面应力,波弗特流涡增强,范围从加拿大海盆向西伯利亚海盆扩张,造成穿极流源头向西移动。
Rapid decline in Arctic sea-ice coverage suggests that the pathway and intensity of the Arctic Transpolar Drift(TPD)have changed evidently.In this study,we calculate sea surface stress in the Arctic by including the effects of both sea ice and surface ocean geostrophic currents to investigate variation in intensity and source region of the TPD.The TPD is stronger in winter than in summer and strongest(weakest)in Decem-ber(September).During 2003–2014,the annual mean velocity of the TPD increased,and the source area shifted westward from the East Siberian Sea to the Laptev Sea.The main factor affecting interannual variation of the TPD intensity is sea ice coverage;the higher the sea ice coverage,the weaker the TPD.The main factor affecting seasonal variation of the TPD intensity is the seasonal variation of surface winds.In winter(summer),the surface winds and sea surface stresses are strong(weak),as is the TPD intensity.Changes in surface winds and sea ice coverage jointly affect the source region of the TPD.During 2003–2014,the dominant factor controlling the westward movement of the TPD source was the Beaufort High,which moved southwestward from the Beaufort Sea toward the Russian coast, causing the TPD source to move westward. Rapid decline of sea ice coverage also caused westward movement of the TPD source. As sea ice melts, sea surface stresses increase, and the Beaufort Gyre expands from the Canada Basin to the East Siberia Sea, triggering the TPD source to move westward.
作者
田引
白学志
黄颖祺
Tian Yin;Bai Xuezhi;Huang Yingqi(College of Oceanography,Hohai University,Nanjing 210098,China)
出处
《极地研究》
CAS
CSCD
北大核心
2021年第4期529-544,共16页
Chinese Journal of Polar Research
基金
国家重点研发计划(2017YFA0604602)
国家自然科学基金(41676019)资助。
关键词
北冰洋
穿极流
海表面应力
Arctic Ocean
transpolar drift
sea surface stress
