Large amounts of freshwater and nutrients pass through the Bering Strait to the Arctic Ocean, making the Bering Sea a crucial marginal sea of the North Pacific Ocean. The hydrography and biological production of the Bering Sea are strongly influenced by the amount of sea ice produced and melted. The sea ice extent and production exhibited large interannual variability but no visible trend until 2016 when a strong decrease began. However, records of sea ice before 1979 and the beginning of satellite-based estimates do not exist. In this paper, we devised a methodology using historical temperature and salinity data, supplemented by historical oxygen isotope (δ18O) data, to estimate sea ice melt and its temporal variability in the Bering Sea from 1950 onward. Our results, consistent with estimates of sea ice thickness, indicate that the sea ice melt volume has declined significantly —following lower sea ice extent and production— with a decrease between 35 and 50 km3 (from 442 km3) between pre-1980 and post-1980 climatologies. In particular, our meltwater time series reveals a decline of 160 km3 between 2012 and 2018, which also reflects the strong decrease in sea ice volume between 2016 and 2018 that numerous previous studies have highlighted. We also evaluated the change in the salinity of the Pacific Winter Water (PWW), whose formation is also related to sea ice production. The time series of PWW salinity exhibits a strong decreasing trend, with a freshening of about 0.3 between the mid-1950s and the mid-2010s, that we attribute to a combination of a reduced sea ice production and the freshening of the Alaskan Coastal Current water. The decline in meltwater volume and PWW salinity that we observed strongly influences the stratification over the Bering shelf, with a significant weakening of the stratification in coastal polynya regions, and a stronger and increasingly temperature-controlled stratification in the rest of the shelf. These changes could have adverse consequences on the biological productivity of the northern Bering Sea.

中文翻译：

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海洋观测揭示了白令海冰融水量和太平洋冬季水盐度的多年代际下降


大量的淡水和营养物质通过白令海峡进入北冰洋，使白令海成为北太平洋重要的边缘海。白令海的水文和生物生产受到产生和融化的海冰量的强烈影响。海冰范围和产量表现出较大的年际变化，但直到 2016 年开始大幅减少才出现明显的趋势。然而，1979 年之前的海冰记录和基于卫星的估计的开始并不存在。在本文中，我们设计了一种方法，使用历史温度和盐度数据，并辅以历史氧同位素 （δ18O） 数据，以估计 1950 年以来白令海的海冰融化及其时间变化。我们的结果与海冰厚度的估计一致，表明海冰融化量显着下降——随着海冰面积和产量的降低——在 1980 年之前和 1980 年后的气候学之间减少了 35 到 50 km3（从 442 km3）。特别是，我们的融水时间序列显示，2012 年至 2018 年期间减少了 160 km3，这也反映了 2016 年至 2018 年期间海冰体积的大幅减少，这是之前许多研究所强调的。我们还评估了太平洋冬季水 （PWW） 盐度的变化，其形成也与海冰的产生有关。PWW 盐度的时间序列呈现出强烈的下降趋势，在 1950 年代中期到 2010 年代中期之间更新了约 0.3，我们将其归因于海冰产量减少和阿拉斯加沿海洋流水的更新。 我们观察到的融水量和 PWW 盐度的下降强烈影响了白令大陆架的分层，沿海冰间湖地区的分层显着减弱，而大陆架其余部分的分层更强且温度越来越受控。这些变化可能会对白令海北部的生物生产力产生不利影响。