Mechanisms of the time-varying sea surface height and heat content trends in the eastern Nordic Seas
Mechanisms of the time-varying sea surface height and heat content trends in the eastern Nordic Seas
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DOI：
10.5194/os-2019-109
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发表时间：
2019-10
期刊：
影响因子：
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通讯作者：
S. Broomé;L. Chafik;J. Nilsson
中科院分区：
文献类型：
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作者：
S. Broomé;L. Chafik;J. Nilsson
抽象的。北欧海是北大西洋和北冰洋之间热量的主要海洋传送带。尽管亚极地北大西洋的年代际变化最近得到了极大的关注，特别是关于2000年代中期以来的冷却趋势，但人们对北部盆地下游的潜在联系知之甚少。利用过去25年(1993-2017年)卫星测高的海面高度，我们发现北欧海洋在多年到年代际的时间尺度上存在显著的变化。特别是，与1990年代初以来前十年的快速增长相比，自2000年代中期以来海面高度的区域趋势显示出放缓的迹象。这种变化在起源于大西洋的北欧海东部水域最为明显，根据水文地理学的估计，它与热量含量密切相关。此外，我们还建立了一个简单的北欧东部海热量收支公式，以讨论本地和远程变率来源的相对重要性；大西洋流入的温度异常平流被发现是主要机制。海洋热汇聚的概念模型仅以北欧海流入处的上游温度测量为输入，能够再现北欧海热含量年代际变化的关键方面。基于这些结果，我们认为与北大西洋上游次极地有很强的联系。然而，尽管北欧海和北大西洋次极地在2000年代中期的趋势转变是一致的，但北欧东部并没有出现趋势逆转，而是在本报告所述的最近十年中保持了较高的海面高度和热含量。
Abstract. The Nordic Seas is the main ocean conveyor of heat between the North Atlantic Ocean and the Arctic Ocean. Although the decadal variability of the Subpolar North Atlantic has been given significant attention lately, especially regarding the cooling trend since mid-2000s, less is known about the potential connection downstream in the northern basins. Using sea surface heights from satellite altimetry over the past 25 years (1993–2017), we find significant variability on multiyear-to-decadal time scales in the Nordic Seas. In particular, the regional trends in sea surface height show signs of a slowdown since mid-2000s as compared to the rapid increase in the preceding decade since early 1990s. This change is most prominent in the Atlantic origin waters in the eastern Nordic Seas and is closely linked, as estimated from hydrography, to heat content. Furthermore, we formulate a simple heat budget for the eastern Nordic Seas to discuss the relative importance of local and remote sources of variability; advection of temperature anomalies in the Atlantic inflow is found to be the main mechanism. A conceptual model of ocean heat convergence, with only upstream temperature measurements at the inflow to the Nordic Seas as input, is able to reproduce key aspects of the decadal variability of the Nordic Seas' heat content. Based on these results, we argue that there is a strong connection with the upstream Subpolar North Atlantic. However, although the shift in trends in the mid-2000s is coincident in the Nordic Seas and the Subpolar North Atlantic, the eastern Nordic Seas has not seen a reversal of trends but instead maintain elevated sea surface heights and heat content in the recent decade considered here.