Sensitivity of Antarctic Circumpolar Current Transport and Eddy Activity to Wind Patterns in the Southern Ocean
Sensitivity of Antarctic Circumpolar Current Transport and Eddy Activity to Wind Patterns in the Southern Ocean
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DOI：
10.1175/jpo-d-14-0053.1
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发表时间：
2015-04-01
影响因子：
3.5
通讯作者：
Zika, Jan D.
中科院分区：
文献类型：
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作者：
Langlais, Clothilde E.;Rintoul, Stephen R.;Zika, Jan D.
近几十年来，南半球西风增强，与南环模态（SAM）的正趋势有关。然而，南极绕极流（ACC）的运输和涡旋场风强迫的响应仍然是一个有争议的话题。本研究使用全球涡旋允许的海洋环流模式驱动的理想化和现实的风强迫，探讨响应年际风加强。ACC的正压和斜压输送以及涡旋场的响应取决于风强迫变化的空间格局。在孤立的情况下，在ACC带上的西风带的增强导致增加的正压和斜压输送ACC信封内，涡动动能（EKE）的滞后增强。相比之下，在南极洲附近的风强迫的增加驱动器在很大程度上正压的变化，在运输沿着封闭的f/H等值线（“自由模式”），在涡动活动的变化不大。在实际强迫作用下，SAM和厄尔尼诺-南方涛动（ENSO）的相互作用影响了风异常的空间分布，特别是影响了ACC和沿着f/H等值线风应力变化的分区。本研究发现，在正SAM期间发生负或正ENSO可以抵消或加倍南极附近的风异常，改变ACC及其涡动场的响应。负ENSO和正SAM有利于EKE的增加，而正ENSO和正SAM导致正压输送的变化，没有涡动响应。
The Southern Hemisphere westerly winds have intensified in recent decades associated with a positive trend in the southern annular mode (SAM). However, the response of the Antarctic Circumpolar Current (ACC) transport and eddy field to wind forcing remains a topic of debate. This study uses global eddy-permitting ocean circulation models driven with both idealized and realistic wind forcing to explore the response to interannual wind strengthening. The response of the barotropic and baroclinic transports and eddy field of the ACC is found to depend on the spatial pattern of the changes in wind forcing. In isolation, an enhancement of the westerlies over the ACC belt leads to an increase of both barotropic and baroclinic transport within the ACC envelope, with lagged enhancement of the eddy kinetic energy (EKE). In contrast, an increase in wind forcing near Antarctica drives a largely barotropic change in transport along closed f/H contours ("free mode''), with little change in eddy activity. Under realistic forcing, the interplay of the SAM and the El Nino-Southern Oscillation (ENSO) influences the spatial distribution of the wind anomalies, in particular the partition between changes in the wind stress over the ACC and along f/H contours. This study finds that the occurrence of a negative or positive ENSO during a positive SAM can cancel or double the wind anomalies near Antarctica, altering the response of the ACC and its eddy field. While a negative ENSO and positive SAM favors an increase in EKE, a positive ENSO and positive SAM lead to barotropic transport changes and no eddy response.