Effect of AMOC collapse on ENSO in a high resolution general circulation model
Effect of AMOC collapse on ENSO in a high resolution general circulation model
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DOI：
10.1007/s00382-017-3756-0
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发表时间：
2018-04
期刊：
影响因子：
4.6
通讯作者：
M. Williamson;M. Collins;S. Drijfhout;R. Kahana;J. Mecking;T. Lenton
中科院分区：
文献类型：
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作者：
M. Williamson;M. Collins;S. Drijfhout;R. Kahana;J. Mecking;T. Lenton
我们在一个允许涡流的高分辨率气候模式实验中观察了厄尔尼诺南方涛动(ENSO)的变化，在该实验中，使用淡水软管切断了大西洋子午线环流(AMOC)。当AMOC关闭时，ENSO模式东移，其周期变得更长更规则。这种东移可以归因于赤道太平洋平均状态的异常东埃克曼输送。这种输送的辐合加深了热带东太平洋的温跃层，增加了温度异常弛豫时间，导致ENSO周期延长。这一异常的Ekman输送是由于经向海面温度偶极子关闭引起的地面偏北风异常引起的。与先前用该模型的早期版本进行的研究不同，该研究显示在AMOC关闭实验中ENSO幅度增加，这里的幅度保持与AMOC在控制状态下相同。我们将这种差异归因于不同模式中减少的随机强迫的响应的变化，这与温度异常的减少的阻尼值相竞争。在新的高分辨率模型中，这些影响近似抵消，导致幅度不变。
We look at changes in the El Niño Southern Oscillation (ENSO) in a high-resolution eddy-permitting climate model experiment in which the Atlantic Meridional Circulation (AMOC) is switched off using freshwater hosing. The ENSO mode is shifted eastward and its period becomes longer and more regular when the AMOC is off. The eastward shift can be attributed to an anomalous eastern Ekman transport in the mean equatorial Pacific ocean state. Convergence of this transport deepens the thermocline in the eastern tropical Pacific and increases the temperature anomaly relaxation time, causing increased ENSO period. The anomalous Ekman transport is caused by a surface northerly wind anomaly in response to the meridional sea surface temperature dipole that results from switching the AMOC off. In contrast to a previous study with an earlier version of the model, which showed an increase in ENSO amplitude in an AMOC off experiment, here the amplitude remains the same as in the AMOC on control state. We attribute this difference to variations in the response of decreased stochastic forcing in the different models, which competes with the reduced damping of temperature anomalies. In the new high-resolution model, these effects approximately cancel resulting in no change in amplitude.