长江口夏季低氧区历年变化规律及影响因素探讨

Study on the variation trend and influencing factors of summer hypoxia off the Yangtze River Estuary

根据2010-2017年长江口及邻近海域夏季低氧区监测资料,分析长江口夏季低氧区发生位置、范围大小的年际变化特征,并对低氧区历年变化的影响因素进行初步探讨。结果显示:长江口外31°N,123°E附近海域几乎每年均会出现低氧区,低氧严重的年份在长江口北侧(32°N以北海域)会同时出现低氧区;长江口及邻近海域低氧区的历年变化很大程度上受台湾暖流影响,台湾暖流较强的年份,低氧区范围大,位置偏北;受台湾暖流影响导致的低氧区水动力环境变化以及台湾暖流底层黑潮次表层水的低溶解氧和高营养盐特性,是影响低氧区底层水体复氧和耗氧水平的重要因素,台湾暖流的强弱及其底层黑潮次表层水的特性对长江口及邻近海域夏季低氧区的年际变化具有至关重要的作用。

Based on the monitoring data of summer hypoxia off the Yangtze River Estuary from 2010 to 2017,this paper analyzed the interannual variation characteristics of the location and range of summer hypoxia off the Yangtze River Estuary, and discussed influencing factors of the annual variation of hypoxia. The results showed that the hypoxia existed almost every year in the sea area adjacent to the location of 123°E, 31°N off the Yangtze River Estuary. The hypoxia would reach the sea area north of 32°N off the Yangtze River Estuary when the hypoxia had gotten severely;the changes of the hypoxia range off the Yangtze River Estuary over the years were greatly affected by the Taiwan Warm Current, when the Taiwan Warm Current was strong, the hypoxia area was larger and its location was farther north off the Yangtze River Estuary;the changes of the hydrodynamic in the hypoxia area caused by the Taiwan Warm Current. The low dissolved oxygen and high nutrient characteristics of the sub-surface water of the Kuroshio in the bottom of the Taiwan Warm Current were important factors affecting the reoxygenation and oxygen consumption in the bottom water of the hypoxia area, the intensity of the Taiwan Warm Current and the characteristics of the subsurface water of the bottom Kuroshio played important roles in the interannual variation of summer hypoxia off the Yangtze River Estuary.