摘要
长江口-东海陆架是全球最大的季节性低氧区之一,其对区域生物地球化学和生物生态过程具有显著影响,但目前对该低氧区在秋季消退期的变化过程和控制机制仍缺乏深入的认识。本研究利用2017年9月在东海陆架所获取的多学科调查资料,刻画了秋季该海域低氧区的空间分布和背景理化环境特征,并结合对水文动力和生物地球化学过程的分析,深入探讨了低氧区的控制因素。结果表明,秋季东海陆架中部(浙江近海40~60 m等深线范围内)存在一东北-西南向的底层溶解氧(DO)低值区(DO质量浓度<4 mg/L,最低值为2.52 mg/L),且低氧水在近岸侧呈现出一定的抬升趋势。该低氧区基本处于黑潮次表层水近岸分支(也称为台湾暖流底层水)的影响范围内,跃层和黑潮次表层水近岸分支外缘处的锋面限制了内部低氧水与上层水体及周围水体的氧交换,形成了东海陆架低氧区在秋季得以维持的水动力条件;黑潮次表层水近岸分支在浙江近海的涌升是导致东海陆架近岸侧中上层出现DO低值区的重要原因。秋季浙江近海低盐水的东南向离岸扩展和上升流所带来的营养盐为现场初级生产提供了重要的物质基础,进而在一定程度上影响着东海陆架低氧区的强度。同时,分析指出秋季随着黑潮次表层水近岸分支的南退与向海移动,东海陆架低氧核心区亦将进一步向南和离岸侧退缩甚至消亡。本研究可为深入认识秋季长江口-东海陆架低氧区的消退过程和控制机制等提供重要科学依据。
The Changjiang Estuary-East China Sea(ECS)shelf system is one of the world's largest seasonal hypoxic zones,significantly influencing regional biogeochemical and ecological processes.However,the variation processes and controlling mechanisms during its autumn decay phase remain a limited understanding.Using multidisciplinary survey data collected from the ECS shelf in September 2017,this study documents the spatial distribution of the hypoxic zone and the characteristics of physical and chemical environment in autumn.And through analysis of hydrodynamic and biogeochemical processes,the controlling factors of hypoxia are further investigated.Results reveal a northeast-southwest oriented bottom dissolved oxygen(DO)minimum zone(DO mass concentration<4 mg/L,minimum of 2.52 mg/L)over the mid-shelf off Zhejiang within the 40-60 m isobath,showing a certain uplift tendency on its nearshore side.This hypoxic zone is basically within the influence area of the Kuroshio subsurface water(KSSW)nearshore branch(also known as the bottom water of the Taiwan Warm Current).The pycnocline and front structures near the outer edge of this branch restrict oxygen exchange between the hypoxic water and the overlying and surrounding water,providing hydrodynamic conditions that sustain the hypoxia into the autumn.The upwelling of the KSSW nearshore branch is identified as a major cause of the mid-water hypoxia over the inner shelf.Furthermore,the nutrients transported by southeastward offshore expansion of low-salinity water and upwelling at Zhejiang coast serve as a critical material foundation for in situ primary production,which partly modulates the intensity of the hypoxic zone.It is also shown that as the KSSW nearshore branch retreats southward and seaward in autumn,the core of the hypoxic zone moves correspondingly southward and offshore,eventually dissipating.This study provides an important insight into the decay processes and controlling mechanisms of the hypoxic zone in the Changjiang Estuary-ECS shelf system during autumn.
作者
郑杨
韦钦胜
吴林妮
辛明
翟星
孙霞
谢琳萍
王保栋
Zheng Yang;Wei Qinsheng;Wu Linni;Xin Ming;Zhai Xing;Sun Xia;Xie Linping;Wang Baodong(Research Center for Ecology,First Institute of Oceanography,Ministry of Natural Resources,Qingdao 266061,China;Laboratory for Marine Ecology and Environmental Science,Qingdao Marine Science and Technology Center,Qingdao 266237,China;Qingdao Key Laboratory of Analytical Technology Development and Offshore Eco-Environment Conservation,Qingdao 266061,China)
出处
《海洋学报》
北大核心
2025年第11期42-56,共15页
基金
国家自然科学基金(U23A2033,41876085)
中央级公益性科研院所基本科研业务费专项资金资助项目(GY0220S3)
联合国“海洋十年”项目“亚洲近海溶解氧和缺氧研究(Coastal Oxygen and Hypoxia in Asian Waters)”和“黑潮与边缘海的交换及生态效应(Kuroshio Edge Exchange and the Shelf Ecosystem)”。
关键词
低氧区
黑潮次表层水
层化
锋面
上升流
生物地球化学过程
东海陆架
hypoxic zone
Kuroshio Subsurface Water
stratification
front
upwelling
biogeochemical process
East China Sea shelf
