Recent Water Mass Changes Reveal Mechanisms of Ocean Warming
Recent Water Mass Changes Reveal Mechanisms of Ocean Warming
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DOI：
10.31223/osf.io/npxkb
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发表时间：
2020-05
影响因子：
4.9
通讯作者：
J. Zika;J. Gregory;E. McDonagh;A. Marzocchi;L. Clement
中科院分区：
文献类型：
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作者：
J. Zika;J. Gregory;E. McDonagh;A. Marzocchi;L. Clement
近几十年来，地球系统中90%以上的额外热量都包含在海洋中。自2006年以来，新的观测项目揭示了海洋热含量变化的异质模式。目前还不清楚这种异质性有多少是由于热量被添加到海洋中并在海洋中混合，导致水团性质的物质变化，或者是由于循环的变化重新分配现有的水团。在这里，我们提出了一种新的诊断的“材料”和“重新分配”的贡献，区域热含量变化之间的2006年和2017年，是基于一个新的“最小变换方法”通知水质量变换和最优传输理论。我们表明，材料变暖具有很大的空间相干性。在任何地理位置，物质变化往往小于再分布的变化;然而，它在全球范围内的总和是海洋的净变暖，而再分布部分的总和，根据设计，为零。材料变暖在本分析的时间段内是稳健的，而重新分配的信号仅出现在少数地区的变化。在北大西洋，水团的变化表明物质大量变暖，而由于纬向翻转环流的减缓，再分配使副极地地区变冷。南大洋的变暖是由物质变暖和通过再分配向南的118 ± 50 TW的异常热输送所解释的。我们的研究结果表明，海洋热含量变化的近期预测，因此海平面变化将取决于理解和预测海洋再分配的变化。
Over 90% of the buildup of additional heat in the Earth system over recent decades is contained in the ocean. Since 2006, new observational programs have revealed heterogeneous patterns of ocean heat content change. It is unclear how much of this heterogeneity is due to heat being added to and mixed within the ocean leading to material changes in water mass properties or is due to changes in circulation that redistribute existing water masses. Here we present a novel diagnosis of the “material” and “redistributed” contributions to regional heat content change between 2006 and 2017 that is based on a new “minimum transformation method” informed by both water mass transformation and optimal transportation theory. We show that material warming has large spatial coherence. The material change tends to be smaller than the redistributed change at any geographical location; however, it sums globally to the net warming of the ocean, whereas the redistributed component sums, by design, to zero. Material warming is robust over the time period of this analysis, whereas the redistributed signal only emerges from the variability in a few regions. In the North Atlantic Ocean, water mass changes indicate substantial material warming while redistribution cools the subpolar region as a result of a slowdown in the meridional overturning circulation. Warming in the Southern Ocean is explained by material warming and by anomalous southward heat transport of 118 ± 50 TW through redistribution. Our results suggest that near-term projections of ocean heat content change and therefore sea level change will hinge on understanding and predicting changes in ocean redistribution.