Seasonal Changes in the North Atlantic Cold Anomaly: The Influence of Cold Surface Waters From Coastal Greenland and Warming Trends Associated With Variations in Subarctic Sea Ice Cover
Seasonal Changes in the North Atlantic Cold Anomaly: The Influence of Cold Surface Waters From Coastal Greenland and Warming Trends Associated With Variations in Subarctic Sea Ice Cover
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DOI：
10.1029/2019jc015379
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发表时间：
2019-12
期刊：
影响因子：
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通讯作者：
D. Allan;R. Allan
中科院分区：
文献类型：
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作者：
D. Allan;R. Allan
自1900年以来，全球海表温度（SST）平均上升了约1摄氏度，但北大西洋亚极地环流（SPG）附近50度附近的一个区域在同一时期下降了0.9摄氏度，这在温度异常图上产生了负特征，Rahmstorf等人（2015）将其通俗地描述为“冷团”（简称CB）。这种独特的长期地表变冷趋势在2月份最为明显，但在8月份，即使在炭黑震中也观察到净变暖，而炭黑本身也减少到仅仅是一个“变暖空洞”。碳当量强度的这些季节性变化是两个独立因素的产物：(1) CB区域特有的长期冬季冷却，这似乎与格陵兰岛沿海水域秋季的冷却有关；可信与夏季融水从冰山和海冰和(2)夏季温室效应来源于(a)大幅减少夏季北极海冰覆盖的辅助在过去的30年里,允许增强吸收阳光的新的开放水在夏天,(b)一个不寻常的时期增加夏季的辅助北极冰盖在20世纪早期海温基线测量,降低了从1900年开始,因此增加了计算线性海温随时间的变化率。这两种效应都可能导致观测到的北极变暖放大。
Worldwide sea surface temperatures (SST) have increased on average by about 1oC since 1900 with the exception of a region of the North Atlantic subpolar gyre (SPG) near 50oN which has cooled by up to 0.9oC over the same period, generating the negative feature on temperature anomaly maps which has been colloquially described by Rahmstorf et al. (2015) as the ‘cold blob’ (abbreviated here CB). This unique long term surface cooling trend is most evident in February but in August net warming is observed even at CB epicentre and the CB itself is reduced to a mere ‘warming hole’. These seasonal changes in the intensity of the CB are the product of two separate factors: (1) a long term winter cooling specific for the CB region which appears to be associated with cooling of Greenland coastal waters in autumn, plausibly linked to summer meltwater from icebergs and sea ice and (2) summer warming effects which derive from (a) dramatic reductions in summer sea ice cover in the sub‐Arctic over the last 30 years that allows enhanced absorption of sunlight by the new open water in summer and (b) an unusual period of increased summer sub‐Arctic ice cover in the early 20th century which lowers the SST baseline measured from 1900, thus increasing the calculated linear rate of change of SST with time. Both of these effects could contribute to the observed Arctic amplification of warming.