The North Icelandic Jet (NIJ) is the densest component of the Denmark Strait Overflow Water, feeding the abyssal limb of the Atlantic Meridional Overturning Circulation. Here, by using observational and numerical model data, we explore the formation of overflow water on the Icelandic shelf, the mechanisms involved, and its potential contribution to the NIJ. The sparse observational data on the western Icelandic shelf for the month of February shows top-to-bottom mixing on the shelf, distinct and well separated from the dense water offshore, with densities larger than 27.8 kg/m³ in some years. Using a 1-D mixing model and winter heat flux reanalysis, we suggest that waters with densities exceeding 27.8 kg/m³ are likely to be formed on the shelf in most years by the end of winter. High-resolution numerical model data shows that the transformation of the Atlantic inflow along the northwest Icelandic shelf generates a dense plume whose waters feed into the NIJ. The bulk of the plume cascades down-slope north of Iceland, funneled through deep cross-shelf troughs, with some cascading occurring west of Iceland as well. During years of strong cascading events (2008, 2013, and 2016), the modeled dense plume potentially feeds up to 21% of the NIJ transport at the Siglunes and Kögur sections. Back-tracked Lagrangian particle trajectories confirm that the western Icelandic shelf is a source of the NIJ. The dense plume transport and variability are found to be dependent on the total oceanic heat loss west of Iceland and along Denmark Strait.

中文翻译：

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冰岛陆架上的浓水形成及其对北冰岛喷流的贡献

冰岛北部急流 (NIJ) 是丹麦海峡溢流水中密度最大的部分，为大西洋经向翻转环流的深海分支提供水源。在这里，通过使用观测和数值模型数据，我们探索了冰岛大陆架上溢流水的形成、所涉及的机制及其对 NIJ 的潜在贡献。2月份冰岛西部大陆架的稀疏观测数据显示，大陆架自上而下混合，与近海稠密水区分开且分离良好，某些年份密度大于27.8 kg/m ³。使用一维混合模型和冬季热通量再分析，我们建议密度超过 27.8 kg/m ^{3 的水}到冬季结束时，大多数年份可能会在架子上形成。高分辨率数值模型数据显示，沿冰岛西北部陆架的大西洋流入的转变产生了密集的羽流，其水流进入 NIJ。大部分羽流沿着冰岛北部的斜坡向下倾斜，通过深的跨大陆架槽汇集，在冰岛西部也发生了一些级联。在多年的强级联事件（2008、2013 和 2016 年）中，模拟的密集羽流可能在 Siglunes 和 Kögur 部分提供高达 21% 的 NIJ 传输。回溯的拉格朗日粒子轨迹证实冰岛西部大陆架是 NIJ 的来源。发现密集的羽流传输和可变性取决于冰岛以西和丹麦海峡沿岸的海洋热损失总量。