Jung Hae Kun, Kim Changsin, Kim Beom Sik, Shim Jeong Hee, Han In Seong, Lee Chung Il, Kim Dongyoung
Ocean climate and Ecology Research Division, National Institute of Fisheries Science, Busan, 46083, Korea.
Department of Marine Ecology and Environment, Gangneung-Wonju National University, Gangneung, 25457, Republic of Korea.
Sci Rep. 2025 Aug 23;15(1):30986. doi: 10.1038/s41598-025-16226-8.
Stratification is a fundamental process influencing nutrient availability and biological productivity in coastal marine ecosystems. In this study, we examine multi-decadal variability in winter stratification and nutrient distribution within Western margin of the East Sea (WES), using observational data collected between 1990 and 2023. Stratification characteristics were quantified using the Brunt-Väisälä frequency (N²), with particular focus on changes in intensity and the depth of maximum stratification. These variables were then analyzed in relation to environmental factors such as upper-layer temperature, surface wind speed, and East Korea Warm Current (EKWC) transport. Over the study period, stratification intensity increased at an average rate of 1.1% per year, while the maximum stratification depth shoaled by approximately 0.6% annual trends that became more pronounced after 2015. These shifts were closely linked to enhanced thermal stratification and increased EKWC volume transport. Enhanced stability of the water column was accompanied by reduced vertical mixing, which in turn intensified the nitrate gradient between surface and subsurface waters. The most marked nitrate accumulation was observed near 100 m, where stratification was strongest. This study highlights how physical oceanographic changes during winter can regulate nutrient supply prior to the spring bloom, potentially influencing seasonal productivity in marginal seas. The results emphasize the importance of long-term monitoring of vertical structure in assessing the ecological impacts of ocean variability.
分层是影响沿海海洋生态系统中养分可用性和生物生产力的一个基本过程。在本研究中，我们利用1990年至2023年期间收集的观测数据，研究了东海西部边缘（WES）冬季分层和养分分布的数十年变化。使用布伦特-维萨拉频率（N²）对分层特征进行量化，特别关注分层强度和最大分层深度的变化。然后将这些变量与诸如上层温度、表面风速和东朝鲜暖流（EKWC）输运等环境因素相关联进行分析。在研究期间，分层强度以每年1.1%的平均速率增加，而最大分层深度以每年约0.6%的趋势变浅，这种趋势在2015年后变得更加明显。这些变化与增强的热分层和增加的EKWC体积输运密切相关。水柱稳定性的增强伴随着垂直混合的减少，这反过来又加剧了表层水和次表层水之间的硝酸盐梯度。在分层最强的100米附近观察到最明显的硝酸盐积累。这项研究强调了冬季物理海洋学变化如何在春季水华之前调节养分供应，可能影响边缘海的季节性生产力。结果强调了长期监测垂直结构在评估海洋变化的生态影响方面的重要性。
