Recent recovery of Antarctic Bottom Water formation in the Ross Sea driven by climate anomalies
Recent recovery of Antarctic Bottom Water formation in the Ross Sea driven by climate anomalies
复制标题
DOI：
10.1038/s41561-020-00655-3
复制
发表时间：
2020-11-16
影响因子：
18.3
通讯作者：
Macdonald, Alison M.
中科院分区：
文献类型：
--
作者：
Silvano, Alessandro;Foppert, Annie;Macdonald, Alison M.
根据对罗斯海现场和遥感数据的分析，相互作用的大气环流模式是导致南极大陆架上长达数十年的深水地层下降最近发生逆转的原因。南极底水（AABW）在几十年到千年的时间尺度上提供全球翻转环流的下肢，为深海通风，并吸收热量和碳。AABW起源于南极大陆架，在那里强烈的冬季冷却和海冰形成过程中释放的盐水产生密集的大陆架水，这些水下沉到深海。近50年来，AABW的盐度、密度和体积都有所下降，其中罗斯海的变化最为显著。这些变化归因于南极冰盖融化的加剧。在这里，我们使用现场观测来记录罗斯海形成的AABW的盐度，密度和厚度（即深度范围）的恢复，其属性与20世纪90年代观察到的相似。这种恢复是由于大陆架上海冰形成的增加造成的。2015年至2018年期间，与正南环模和极端厄尔尼诺现象的异常组合相关的异常风强迫引发了海冰形成的增加。我们的研究强调了AABW形成对远程强迫的敏感性，并表明气候异常可以驱动局部海冰形成的间歇性增加，从而抵消冰盖融化增加以减少AABW形成的趋势。
Interacting atmospheric circulation patterns are responsible for a recent reversal of a decades-long decline in deepwater formation on the Antarctic shelf, according to an analysis of in situ and remote sensing data from the Ross Sea.Antarctic Bottom Water (AABW) supplies the lower limb of the global overturning circulation, ventilates the abyssal ocean and sequesters heat and carbon on multidecadal to millennial timescales. AABW originates on the Antarctic continental shelf, where strong winter cooling and brine released during sea ice formation produce Dense Shelf Water, which sinks to the deep ocean. The salinity, density and volume of AABW have decreased over the last 50 years, with the most marked changes observed in the Ross Sea. These changes have been attributed to increased melting of the Antarctic Ice Sheet. Here we use in situ observations to document a recovery in the salinity, density and thickness (that is, depth range) of AABW formed in the Ross Sea, with properties in 2018-2019 similar to those observed in the 1990s. The recovery was caused by increased sea ice formation on the continental shelf. Increased sea ice formation was triggered by anomalous wind forcing associated with the unusual combination of positive Southern Annular Mode and extreme El Nino conditions between 2015 and 2018. Our study highlights the sensitivity of AABW formation to remote forcing and shows that climate anomalies can drive episodic increases in local sea ice formation that counter the tendency for increased ice-sheet melt to reduce AABW formation.