Intermittent intrusions of Changjiang Diluted water in Hangzhou Bay modulated by intraseasonal winds and tropical cyclones

IF 2.6 3区地球科学 Q1 MARINE & FRESHWATER BIOLOGY

Estuarine Coastal and Shelf Science Pub Date : 2025-08-28 DOI:10.1016/j.ecss.2025.109525

Yi Wei , Kui Wang , Haiyan Jin , Wenbin Yin , Daji Huang , Jiliang Xuan , Bin Wang , Feng Zhou , Jianfang Chen

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引用次数: 0

Abstract

It is generally recognised that the north-easterly monsoon leads to greater intrusion of Changjiang Diluted Water (CDW) into Hangzhou Bay in winter than in summer, which strongly influences the hydrography of Hangzhou Bay. However, anomalously lower salinity (<10) and higher dissolved inorganic nitrogen (DIN) concentrations (1.9 mg L⁻¹) were observed in central Hangzhou Bay in summer (August 2019) than the salinity (>15) and DIN concentrations (1.5 mg L⁻¹) in winter (March 2022). A high-resolution, well-validated model has further revealed intermittent intrusions of CDW, characterised as intraseasonal (30–120 d) and episodic variations, resulting in a unique low-salinity and high-nutrient water mass in the north-central bay during summer. The intermittent intrusions are driven by the combined effects of the Changjiang discharge, intraseasonal winds, tropical cyclones, and tidal residual currents. The Changjiang discharge amplifies the effect of CDW intrusion on a seasonal scale, which is responsible for the large (>10) decline in summer salinity in the initial intrusion area of the northern bay mouth. The intraseasonal variation in the south-westerly monsoon in summer causes intermittent intrusion of the CDW, accompanied by variations in the Taiwan Warm Current. Intrusion of CDW is greatly enhanced during episodic events of strong northerly winds caused by tropical cyclones. This episodic intrusion can cause a decline in salinity in the initial intrusion area of up to 6 in approximately one week. After the CDW intrudes into the north central bay, the westward tidal residual current along the northern coast continuously transports the CDW toward the head of Hangzhou Bay.

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季风和热带气旋对杭州湾长江稀释水间歇入侵的调节

人们普遍认为，东北季风导致冬季长江稀释水（CDW）入侵杭州湾的程度大于夏季，这对杭州湾的水文特征产生了强烈的影响。而杭州湾中部夏季（2019年8月）盐度（> 10）和溶解无机氮（DIN）浓度（1.9 mg L−1）高于冬季（2022年3月）盐度（>15）和DIN浓度（1.5 mg L−1）。一个高分辨率、经过验证的模型进一步揭示了CDW的间歇性入侵，其特征是季节性（30-120 d）和偶发性变化，导致夏季中北部海湾出现独特的低盐度、高营养水团。间歇入侵是由长江流量、季内风、热带气旋和潮余流共同驱动的。长江径流在季节尺度上放大了CDW的入侵效应，这是造成北部湾口初始入侵区夏季盐度大幅下降的原因。夏季西南季风的季节内变化导致CDW的间歇性入侵，并伴随着台湾暖流的变化。在热带气旋引起的强北风的间歇性事件中，CDW的入侵大大增强。这种偶发性入侵可导致最初入侵区域的盐度在大约一周内下降高达6。CDW侵入中海湾北部后，沿北岸向西的潮余流不断将CDW向杭州湾头部输送。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

Estuarine Coastal and Shelf Science 地学-海洋学

CiteScore

5.60

自引率

7.10%

发文量

374

审稿时长

9 months

期刊介绍： Estuarine, Coastal and Shelf Science is an international multidisciplinary journal devoted to the analysis of saline water phenomena ranging from the outer edge of the continental shelf to the upper limits of the tidal zone. The journal provides a unique forum, unifying the multidisciplinary approaches to the study of the oceanography of estuaries, coastal zones, and continental shelf seas. It features original research papers, review papers and short communications treating such disciplines as zoology, botany, geology, sedimentology, physical oceanography.