Climate links and recent extremes in antarctic sea ice, high-latitude cyclones, Southern Annular Mode and ENSO
Climate links and recent extremes in antarctic sea ice, high-latitude cyclones, Southern Annular Mode and ENSO
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DOI：
10.1007/s00382-011-1044-y
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发表时间：
2011
期刊：
影响因子：
4.6
通讯作者：
A. Pezza;H. Rashid;I. Simmonds
中科院分区：
文献类型：
--
作者：
A. Pezza;H. Rashid;I. Simmonds
本文研究了南部环模（SAM）与南部海冰范围（SIE）之间的气候联系，并讨论了驻波和天气涡旋在建立这种联系中的可能作用。在此过程中，我们使用了包括SIE空间相关性、涡旋流函数和风异常以及高纬度气旋强度统计在内的综合技术。研究表明，静止波可能会被与高纬度气旋相关的涡旋异常放大，从而在大多数（但不是全部）经度的SAM处于正相位时导致更多的海冰。在ENSO （La Niña年）期间也观察到类似的关联。虽然SAM/ENSO响应中的这种协同作用可能部分反映了南极洲周围波放大的优先区域，但气候记录的短范围不允许与SIE建立明确的因果关系。在驻波被放大的地区，观察到较强的极地气旋。这些更深的气旋将更有效地破裂并向赤道输出冰，但近海岸地区足够寒冷，可以让由此产生的冰迅速重新冻结。我们推测，如果全球变暖继续下去，一旦冰层变薄，同样的影响可能有助于逆转目前（正）南极SIE趋势，类似于在北半球观察到的情况。
In this article, we study the climate link between the Southern Annular Mode (SAM) and the southern sea-ice extent (SIE), and discuss the possible role of stationary waves and synoptic eddies in establishing this link. In doing so, we have used a combination of techniques involving spatial correlations of SIE, eddy streamfunction and wind anomalies, and statistics of high-latitude cyclone strength. It is suggested that stationary waves may be amplified by eddy anomalies associated with high latitude cyclones, resulting in more sea ice when the SAM is in its positive phase for most, but not all, longitudes. A similar association is observed during ENSO (La Niña years). Although this synergy in the SAM/ENSO response may partially reflect preferential areas for wave amplification around Antarctica, the short extent of the climate records does not allow for a definite causality connection to be established with SIE. Stronger polar cyclones are observed over the areas where the stationary waves are amplified. These deeper cyclones will break up and export ice equatorward more efficiently, but the near-coastal regions are cold enough to allow for a rapid re-freeze of the resulting ice break-up. We speculate that if global warming continues this same effect could help reverse the current (positive) Antarctic SIE trends once the ice gets thinner, similarly to what has been observed in the Northern Hemisphere.