风和径流量对长江口缺氧影响的数值模拟

受自然和人类活动的影响,海洋缺氧现象日益严重,威胁着海洋生态环境,海洋缺氧问题已经引起了人们的广泛关注。本文应用区域海洋模式并耦合生态模式,对东海的生态系统进行了数值模拟和分析研究。与观测数据比较显示,该模型能较好地模拟长江口外生态变量的分布趋势。另外本文通过设置不同敏感性实验,探讨风和径流量对长江口底层缺氧现象的影响,结果分析表明,风和径流量对长江口外缺氧区的形成有显著的影响。径流量变化虽然对长江口外缺氧区的季节变化影响并不显著,但是对缺氧区域面积却存在显著的影响。径流量增加,水体层化增强,表层叶绿素浓度增加,最终导致缺氧区域范围扩展;径流量减小,水体层化减弱,表层叶绿素浓度减小,缺氧区域范围缩小。风向和风速的改变不仅影响长江口外缺氧区的季节变化,还影响缺氧区域面积。

The impact of river discharge and wind on the hypoxia off the Changjiang Estuary: A numerical modeling study

By the natural and human activities, the phenomenon of marine hypoxia has become increasingly serious, threatening the marine ecological environment. And the problem of marine hypoxia has caused wide attention. In this paper, a three-dimensional hydrodynamic model (ROMS) was coupled to a biogeochemical model to simulate and analyze the ecological system of the East China Sea. In comparison with the observation data, the model results can reasonably capture the physical and biochemical dynamics off the Changjiang River Estuary. In addition, the sensitive experiments were also used to examine the role that physical forcing (river discharge, wind speed, wind direction) play in controlling hypoxia in waters adjacent to the Changjiang River Estuary. The results show that the wind and river discharge have significant influences on the hypoxia off the Changjiang River Estuary. The seasonal cycle of hypoxia was relatively insensitive to synoptic variability in river discharge, but integrated hypoxic areas were sensitive to the overall magnitude of river discharge. Increased in the magnitude of river discharge led to enhance stratification and surface chlorophyll concentration, thereby greatly increased hypoxic area off the Changjiang River Estuary. In contrast, decreased in the magnitude of river discharge reduced the stratification and surface chlorophyll concentration and hence significantly decreased the hypoxic area. And variations in wind speed and direction had the greatest impact on the seasonal cycle of hypoxia and large impacts on the annually integrated hypoxic areas.