Fast and slow responses of Southern Ocean sea surface temperature to SAM in coupled climate models
Fast and slow responses of Southern Ocean sea surface temperature to SAM in coupled climate models
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DOI：
10.1007/s00382-016-3162-z
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发表时间：
2017-03-01
期刊：
影响因子：
4.6
通讯作者：
Holland, Marika M.
中科院分区：
文献类型：
--
作者：
Kostov, Yavor;Marshall, John;Holland, Marika M.
我们调查如何海洋表面温度（SST）在南极洲周围的南部环形模式（SAM）在多个时间尺度上的响应。为此，我们研究SAM和SST之间的关系在未扰动的前工业控制模拟耦合大气环流模式（GCM）包括在气候模拟相互比较项目第5阶段（CMIP 5）。我们开发了一种技术来提取南大洋SST（55 A度S-70 A度S）的SAM指数的一个假设的步骤增加的响应。我们证明了在许多GCM中，预期的SST阶跃响应函数在时间上是非单调的。在转变为正SAM异常之后，最初的冷却制度可以过渡到南极洲周围的表面变暖。然而，在CMIP 5集合中存在很大的差异。在某些模式中，阶跃响应函数从不改变符号，冷却持续存在，而在其他GCM中，SST异常仅在SAM阶跃增加后3年才从负值过渡到正值。这种模式间的多样性可能与南极洲周围季节性海冰区域的模式气候热海洋分层的差异有关。利用这种关系，我们使用观测数据的时间平均纬向和垂直温度梯度约束的真实的南大洋SAM的快速和缓慢的时间尺度上的响应。
We investigate how sea surface temperatures (SSTs) around Antarctica respond to the Southern Annular Mode (SAM) on multiple timescales. To that end we examine the relationship between SAM and SST within unperturbed preindustrial control simulations of coupled general circulation models (GCMs) included in the Climate Modeling Intercomparison Project phase 5 (CMIP5). We develop a technique to extract the response of the Southern Ocean SST (55A degrees S-70A degrees S) to a hypothetical step increase in the SAM index. We demonstrate that in many GCMs, the expected SST step response function is nonmonotonic in time. Following a shift to a positive SAM anomaly, an initial cooling regime can transition into surface warming around Antarctica. However, there are large differences across the CMIP5 ensemble. In some models the step response function never changes sign and cooling persists, while in other GCMs the SST anomaly crosses over from negative to positive values only 3 years after a step increase in the SAM. This intermodel diversity can be related to differences in the models' climatological thermal ocean stratification in the region of seasonal sea ice around Antarctica. Exploiting this relationship, we use observational data for the time-mean meridional and vertical temperature gradients to constrain the real Southern Ocean response to SAM on fast and slow timescales.