The decadal to multidecadal temperature variability of the intermediate (700–2,000 m) North Atlantic Subpolar Gyre (SPG) significantly imprints the global pattern of ocean heat uptake. Here, the origins and dominant pathways of this variability are investigated with an ocean analysis product (EN4), an ocean state estimate (ECCOv4), and idealized modeling approaches. Sustained increases and decreases of intermediate temperature in the SPG correlate with long‐lasting warm and cold states of the upper ocean with the largest anomalous vertical heat exchanges confined to the vicinity of continental boundaries and strong ocean currents. In particular, vertical diffusive processes along the boundaries of the Labrador, Irminger, and Newfoundland basins are important drivers of the recent intermediate depth warming trend observed during 1996–2014. The overall effect of those processes is captured by a one‐dimensional diffusive model with appropriate boundary‐like parametrization and demonstrated through the boundary‐focused downward propagation of a passive tracer in a 3‐D numerical simulation. Our results imply that the slow and quasi‐periodic ventilation of intermediate thermohaline properties and associated heat uptake in the SPG are not strictly driven by convection‐restratification events in the open seas but also receives a key contribution from boundary sinking and mixing. Increased skill for modeling and predicting intermediate‐depth ocean properties in the North Atlantic will hence require the appropriate representation of surface‐deep dynamical connections within the boundary currents encircling Greenland and Newfoundland.

中文翻译：

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北极次极北大西洋吸收热量的边界过程的重要性

中大西洋（700-2,000 m）北大西洋次极环流（SPG）的年代际到年代际温度变化显着地烙印了海洋热量吸收的全球格局。在这里，使用海洋分析产品（EN4），海洋状态估计值（ECCOv4）和理想化的建模方法研究了这种变化的起源和主要途径。SPG中间温度的持续升高和降低与上层海洋的长期温暖和寒冷状态有关，最大的垂直垂直热交换局限于大陆边界和强洋流附近。特别是，沿拉布拉多，艾明格和纽芬兰盆地边界的垂直扩散过程是1996-2014年期间观测到的近期中间深度变暖趋势的重要驱动力。这些过程的整体效果由具有适当边界样参数化的一维扩散模型捕获，并通过在3D数值模拟中无源示踪剂的边界聚焦向下传播来证明。我们的结果表明，SPG中中等热盐特性的缓慢准周期性通风以及相关的热量吸收并不是严格地由公海对流再定殖事件驱动的，而是边界下沉和混合作用的关键贡献。因此，要提高对北大西洋中深层海洋特性进行建模和预测的技巧，就需要在环绕格陵兰岛和纽芬兰岛的边界流内适当表述深层动力联系。