Linking midlatitudes eddy heat flux trends and polar amplification
Linking midlatitudes eddy heat flux trends and polar amplification
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DOI：
10.1038/s41612-020-0111-7
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发表时间：
2020-02-19
影响因子：
9
通讯作者：
Polvani, Lorenzo M.
中科院分区：
文献类型：
--
作者：
Chemke, Rei;Polvani, Lorenzo M.
涡旋热通量起着从低纬向高纬输送热量的重要作用，从而影响中纬度气候。最近和预计的极地变暖及其对经向温度梯度的影响，表明涡旋热通量可能减弱。我们在这里通过重新分析和最先进的全球气候模型来研究这个问题。在北半球，我们发现在过去的40年里，涡旋热通量已经显著减弱。我们进一步表明，这种减弱出现在2000年左右的内部变化中，我们将其归因于温室气体的增加。相比之下，在南半球，我们发现涡旋热通量显著增强，我们将这种增强与最近南大洋表面温度的数十年降温联系在一起。最先进的气候模型无法模拟这种冷却，这使它们无法捕捉到观测到的南半球涡旋热流的增强。模型和再分析之间的这种差异提供了一个明确的例子，说明极地地区的模型偏差如何影响中纬度气候。
Eddy heat fluxes play the important role of transferring heat from low to high latitudes, thus affecting midlatitude climate. The recent and projected polar warming, and its effects on the meridional temperature gradients, suggests a possible weakening of eddy heat fluxes. We here examine this question in reanalyses and state-of-the-art global climate models. In the Northern Hemisphere we find that the eddy heat flux has robustly weakened over the last four decades. We further show that this weakening emerged from the internal variability around the year 2000, and we attribute it to increasing greenhouse gases. In contrast, in the Southern Hemisphere we find that the eddy heat flux has robustly strengthened, and we link this strengthening to the recent multi-decadal cooling of Southern-Ocean surface temperatures. The inability of state-of-the-art climate models to simulate such cooling prevents them from capturing the observed Southern Hemisphere strengthening of the eddy heat flux. This discrepancy between models and reanalyses provides a clear example of how model biases in polar regions can affect the midlatitude climate.