Heat Flux from the Yangtze River to the Sea and Its Ecological Effects
Through the extraction and analysis of Landsat 5,7 and 8 long time series remote sensing image data,the practical single channel algorithm was used to invert the monthly long series water temperature data set of the Yangtze River Estuary from 1997 to 2016.Meanwhile,based on the global runoff data,the annual monthly mean heat flux at the Yangtze River Estuary during the same period was calculated.The temporal and spatial variations and response characteristics to climate change and human thermal emission were analyzed.On this basis,combined with the global ocean surface temperature data and the Copernicus global ocean color and biogeochemical data set,the influence of the heat flux change from the Yangtze River to the sea on the offshore water temperature and the offshore ecological environment was explored.The results show that the total heat flux in the Yangtze River Estuary is 77.5 EJ per year,and the seasonal variation of heat flux is obvious.The heat flux mainly used for heat transport to the coastal area is significantly higher than that in other typical river systems,and the average annual heat input to the coastal area is estimated to be 6.1 EJ,and the warming effect is obvious.Compared with the coastal zone,the influence of the Yangtze River Estuary on the temperature of the coastal waters is greater and the influence on the spatial range is further.The spatial influence on offshore water temperature can be divided into two gradients,namely,the riverine strong influence zone with decreasing temperature (0-40 km) and the ocean strong influence zone with increasing temperature (more than 40 km).From 1997 to 2016,the temperature of the coastal waters of the Yangtze River Estuary as a whole increased first and then decreased.Further analysis shows that the heat flux change in the Yangtze River Estuary has a profound effect on the offshore water temperature (R2=0.7495),and is closely related to the offshore primary productivity (R2=0.9651),indicating that the heat input from the Yangtze River to the offshore water is an important factor regulating the offshore thermal environment and ecological environment.
Yangtze River Estuaryheat fluxenvironmental remote sensingcoastal ecological environment
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