Ocean Shelf Exchange, NW European Shelf Seas: measurements, estimates and comparisons
Ocean Shelf Exchange, NW European Shelf Seas: measurements, estimates and comparisons
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DOI：
10.1016/j.pocean.2022.102760
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发表时间：
2022-02
影响因子：
4.1
通讯作者：
J. Huthnance;J. Hopkins;Bee Berx;A. Dale;J. Holt;P. Hosegood;M. Inall;S. Jones;B. Loveday;P. I. Miller;J. Polton;M. Porter;C. Spingys
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文献类型：
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作者：
J. Huthnance;J. Hopkins;Bee Berx;A. Dale;J. Holt;P. Hosegood;M. Inall;S. Jones;B. Loveday;P. I. Miller;J. Polton;M. Porter;C. Spingys
跨越大陆架边缘的运输增加了大陆架-海洋生产，消除了大气中的碳，并意味着海洋环流的活跃边界。我们估计相对较大的整体运输在三个对比部门的西北欧大陆架边缘：凯尔特海西南部的英国，马林-赫布里底群岛大陆架西部的苏格兰，西设得兰群岛大陆架北部的苏格兰。这些估计数来自FASTNEt项目（东北大西洋斜坡地形通量）的测量：漂流物、系泊海流计、漂流物分散和盐度调查的有效“扩散率”、有助于交换的速度方差的其他估计数。过程的贡献包括沿坡流、内波及其斯托克斯漂移、潮汐泵、涡旋、风驱动的表层和底边界层中的Ekman输运，整个大陆架边缘的交换量估计为几m2 s −1：如果从全球范围外推，即使是1 m2 s − 1也比海洋输运大，对大陆架-海洋和邻近海洋收支可能很重要。在我们的语境中，大多数交换都是在潮汐和其他周期在一天或更短的运动中进行的，因此只有在如此短的时间尺度上演化的水的性质才有效。尽管如此，横坡通量和低频运动（周期>两天）的交换量按全球标准来看是很大的，而且变化很大。最靠近陆架坡折的部署平均通量在0.3-4 m2 s −1之间;低频运动的平均交换为0.8-3 m2 s −1。更深更长时间的系泊和漂流物跨越500米深度，产生了更大的通量和高达20 m2 s −1的交换。这些输运的重要性取决于水或其内容物的独特性质，以及影响进一步输运的内部陆架-海洋环流。对于西北部的欧洲大陆架，跨大陆架边缘的运输使其不成比例的强大的CO2“泵”。复杂的背景下，和小规模的众多过程，使跨斜坡运输，意味着需要模型。测量的范围和持续时间仍然有限，但现在有各种各样的背景、特定条件、事件、过程和行为可用于支持模型验证，特别是在西北欧大陆架边缘周围。变异性仍然使得观测不足以对输送和交换进行稳定的估计，特别是如果按部门和季节划分的话;事实上，可能存在显著的年际差异。经过验证的高分辨率模式提供了最佳的时空覆盖前景，并可估计当前和未来陆架-海对邻近海洋的敏感性。
Transports across the continental shelf edge enhance shelf-sea production, remove atmospheric carbon and imply an active boundary to ocean circulation. We estimate relatively large overall transport across three contrasted sectors of north-west European shelf edge: the Celtic Sea south-west of Britain, the Malin-Hebrides shelf west of Scotland, the West Shetland shelf north of Scotland. The estimates derive from measurements in the project FASTNEt (Fluxes across sloping topography of the North East Atlantic): drifters, moored current meters, effective “diffusivity” from drifter dispersion and salinity surveys, other estimates of velocity variance contributing to exchange. Process contributions include transport by along-slope flow, internal waves and their Stokes drift, tidal pumping, eddies, Ekman transports in the wind-driven surface layer and bottom boundary layer.Overall exchange across the shelf edge is estimated as several m2s−1: if extrapolated globally even 1 m2s−1is large compared with oceanic transports and potentially important to shelf-sea and adjacent oceanic budgets. In our context, most exchange is in tides, and other motion with periods ∼ one day or less, and so effective only for water properties that evolve on such short time-scales. Nevertheless, cross-slope fluxes, and exchange by low-frequency motion (periods > two days), are large by global standards and also very variable. Deployment-mean fluxes nearest the shelf break were in the range 0.3–4 m2s−1; mean exchanges from low-frequency motion were 0.8–3 m2s−1. Deeper longer-term moorings and drifters crossing 500 m depth gave much larger fluxes and exchanges up to 20 m2s−1. These transports’ significance depends on distinctive properties of the water, or its contents, and on internal shelf-sea circulation affecting further transport. For the NW European shelf, transports across the shelf edge enable its disproportionately strong CO2“pump”.The complex context, and small scales of numerous processes enabling cross-slope transports, imply a need for models. Measurements remain limited in extent and duration, but widely varied contexts, particular conditions, events, processes and behaviours are now available to support model validation, especially around the north-west European continental shelf edge. Variability still renders observations insufficient for stable estimates of transports and exchanges, especially if partitioned by sector and season; indeed, there may be significant inter-annual differences. Validated fine-resolution models give the best prospect of spatial and temporal coverage and of estimating present-day and potential future shelf-sea sensitivities to the adjacent ocean.