Ocean stratification on Arctic shelves critically influences nutrient availability, essential for primary production. However, discerning the changes in stratification and their drivers is challenging. Through the use of a high-resolution ocean–sea-ice model, this study investigates the variability in stratification within the northeastern Chukchi Sea over the period from 1987 to 2016. Our analysis, validated against available observations, reveals that summers with weak stratification are marked by a warmer water column that features a saltier upper layer and a fresher lower layer, thereby diminishing the vertical density gradient. In contrast, summers with strong stratification are characterized by a cooler column with a fresher upper layer and a saltier lower layer, resulting in an increased density gradient. This variability is primarily driven by the timing of sea-ice retreat and the consequent variations in meltwater flux, with early retreat leading to less meltwater and saltier surface conditions. This factor significantly outweighs the influence of changes in circulation and associated lateral freshwater transport driven by the Bering Strait inflow. We also find that the synchronization of sea-ice retreat and Bering Strait inflow intensity is linked to the timing and strength of the Aleutian Low’s westward shift from the Gulf of Alaska to the Aleutian Basin in the early winter. These insights are crucial for understanding nutrient dynamics and primary production in the region. Furthermore, monitoring sea-ice retreat timing could serve as a useful proxy for predicting subsequent summer stratification changes.

中文翻译：

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了解楚科奇海东北部的海洋分层及其年际变化


北极陆架上的海洋分层严重影响了初级生产所必需的营养物质的可用性。然而，辨别分层的变化及其驱动因素具有挑战性。通过使用高分辨率海洋-海冰模型，本研究调查了 1987 年至 2016 年期间楚科奇海东北部层结的变化。我们的分析经现有观测结果验证，表明层结较弱的夏季以较温暖的水柱为特征，其上层盐分较高，下层较新鲜，从而减小了垂直密度梯度。相比之下，分层强烈的夏季的特点是较冷的柱体，上层较新鲜，下层较咸，导致密度梯度增加。这种变化主要是由海冰退缩的时间以及随之而来的融水通量的变化驱动的，早期退缩会导致融水减少和地表条件更咸。这一因素明显超过了白令海峡流入驱动的环流变化和相关的横向淡水输送的影响。我们还发现，海冰消退和白令海峡流入强度的同步性与初冬阿留申低气压从阿拉斯加湾西移至阿留申盆地的时间和强度有关。这些见解对于了解该地区的营养动态和初级生产至关重要。此外，监测海冰消退时间可以作为预测随后夏季分层变化的有用指标。