Recent slowing of Atlantic overturning circulation as a recovery from earlier strengthening
Recent slowing of Atlantic overturning circulation as a recovery from earlier strengthening
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DOI：
10.1038/ngeo2715
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发表时间：
2016-07-01
影响因子：
18.3
通讯作者：
Wood, Richard A.
中科院分区：
文献类型：
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作者：
Jackson, Laura C.;Peterson, K. Andrew;Wood, Richard A.
大西洋纬向翻转环流（AMOC）在过去十年中已经大大减弱（1）。在过去的世纪里，一些减弱可能已经发生了（2），全球气候模型预测，人为气候变化会进一步减弱（3）。这种减弱可能对地表气候产生重大影响（4）。然而，基于历史条件的海洋模型模拟经常发现，直到20世纪90年代中期，倾覆率增加，然后下降（5）。因此，尚不清楚过去十年观测到的减弱是十年变率的一部分还是持续减弱（6）。在这里，我们研究了一个最先进的全球海洋再分析产品GloSea（5），它涵盖了1989年至2015年，与26.5度N的AMOC观测结果非常匹配，以前所未有的准确度捕捉了年际变化和年代际趋势。再分析数据将2004年4月至2014年2月的10年观测置于长期背景下，并表明所观察到的翻转环流的减少与先前增加后的恢复一致。我们发现，从拉布拉多海向南传播的密度异常是这些变化的最有可能的原因。我们的结论是，年代际变率可能在过去十年中观测到的AMOC下降中发挥了关键作用。
The Atlantic meridional overturning circulation (AMOC) has weakened substantially over the past decade(1). Some weakening may already have occurred over the past century(2), and global climate models project further weakening in response to anthropogenic climate change(3). Such a weakening could have significant impacts on the surface climate(4). However, ocean model simulations based on historical conditions have often found an increase in overturning up to the mid-1990s, followed by a decrease(5). It is therefore not clear whether the observed weakening over the past decade is part of decadal variability or a persistent weakening(6). Here we examine a state-of-the-art global-ocean reanalysis product, GloSea(5), which covers the years 1989 to 2015 and closely matches observations of the AMOC at 26.5 degrees N, capturing the interannual variability and decadal trend with unprecedented accuracy. The reanalysis data place the ten years of observations-April 2004 to February 2014-into a longer-term context and suggest that the observed decrease in the overturning circulation is consistent with a recovery following a previous increase. We find that density anomalies that propagate southwards from the Labrador Sea are the most likely cause of these variations. We conclude that decadal variability probably played a key role in the decline of the AMOC observed over the past decade.