Dense-water production and overflow from an arctic coastal polynya in Storfjorden
Dense-water production and overflow from an arctic coastal polynya in Storfjorden
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Storfjorden 北极沿岸冰间湖的浓水产生和溢流
DOI：
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发表时间：
2013
期刊：
影响因子：
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通讯作者：
P. Haugan
中科院分区：
文献类型：
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作者：
R. Skogseth;I. Fer;P. Haugan
由于其反复出现的冰间湖，冬季的斯托峡湾是活跃盐水形成的场所。稠密、富含盐水的海水充满了峡湾的洼地，直至其岩床水平，随后像底部重力流一样下降，沿着地形向陆架断裂处延伸。盐水的形成和溢流表现出强烈的年际变化，受局部因素（例如预处理、冰形成速率和冰间湖位置）和大尺度因素（例如巴伦支海冬季冰盖和北大西洋大规模大气环流）的影响。现有的冰间湖和产冰模型利用卫星图像、风力数据和地表水文学，应用于 2002 年冬季，并预测大量盐水排斥与观测结果一致。从 5 年观测中获得的冰间湖模型的调整因子用于将计算时间延长至 33 年前。预计 2002 年的冰产量与前 4 年的平均值相差 5.4 个标准差，但仍能代表十年尺度的平均值和变化。 2002 年由此产生的强烈溢流是在其路径对面密集的水道测量站观察到的。在溢流路径的前 40 公里内观察到显着的夹带，使溢流水的密度异常降低了 0.18，并使横截面积增加了 2 倍。发现地转剪切是混合的部分原因。在下游更远的地方，夹带作用不太明显。溢流水的地转体积传输大约恒定在~0.06 Sv，与早期的估计一致。模型结果与现场数据相结合，提供了盆地内强迫、源条件的生成以及相应溢流之间的联系。
Storfjorden in winter is a site of active brine formation due to its recurrent polynya. The dense, brine-enriched waters fill the depressions of the fjord to its sill level and subsequently descend like a bottom gravity current, following the topography towards the shelf break. The brine formation and the overflow show strong interannual variability governed by both local factors, e.g., preconditioning, the rate of ice formation, and polynya location, and large-scale factors, e.g., Barents Sea winter ice cover and large-scale atmospheric circulation in the North Atlantic. An existing polynya and ice production model, making use of satellite images, wind data, and surface hydrography, is applied to winter 2002 and predicts large brine rejection in agreement with observations. Tuning factors for the polynya model obtained from 5 years of observations are used to extend the calculations to 33 years back in time. The ice production in 2002 is predicted to be 5.4 standard deviations away from the preceding 4 years' mean but still representative for the mean and variability of the decadal scale. The resulting strong overflow in 2002 is observed at densely spaced hydrographic stations located across its path. Significant entrainment is observed within the first 40 km of the path of the overflow, reducing the density anomaly of the overflow water by 0.18 and increasing the cross-sectional area by a factor of 2. The geostrophic shear is found to be partly responsible for the mixing. Farther downstream, entrainment is less significant. The geostrophic volume transport of the overflow water is approximately constant at ∼0.06 Sv, in agreement with earlier estimates. The model results combined with the field data provide a picture of the link between forcing, generation of the source conditions in the basin, and the corresponding overflow.