Proceedings Article | 13 October 2011
Proc. SPIE. 8175, Remote Sensing of the Ocean, Sea Ice, Coastal Waters, and Large Water Regions 2011
KEYWORDS: Hypoxia, Satellites, Oxygen, Data modeling, Earth observing sensors, Computer simulations, Physics, Databases, Data centers, Statistical analysis
Hypoxia has been widely observed in estuarine area and some reports have focused on the East China Sea over the past
decade. With the increasing nutrient load from Changjiang (Yangtze) River, a severe hypoxia zone was found in
summer. The mechanism and maintenance of hypoxia is due to the large density stratification caused by the significant
salinity difference between the fresh plume and salty water. Consumption of oxygen in bottom waters is linked to
biological oxygen demand fueled by organic matter from primary production in the nutrient-rich river plume. Hypoxia
occurs when this consumption exceeds replenishment by diffusion, turbulent mixing or lateral advection of oxygenated
water. The margins off the Changjiang are affected the most by summer hypoxia. Physical thermohaline stratification
plays an important role in the Changjiang shelf during summer. In this study, we discusses the relationship between
hypoxia and the stratification according to the surface temperature reversed from satellite, in situ observed data and time
series of profile data obtained from hypoxia buoy, which was especially designed for hypoxia identification. We
examined the occurrence of seasonal hypoxia in the bottom waters of river-dominated ocean margins off the Changjiang
River and compared the stratification procedure leading to the depletion of oxygen. A simulation for stratification was
performed to calculate the seawater temperature vertical profile. By collecting the historical investigated data, we
constructed a parametric structural model between surface and bottom temperature. Based on the parameterization of the
layered structure of seawater temperature vertical profile, the simulation method was used to calculate the parameter
distributions of stratification structure. When the real time outputs of SST and buoy-based profile were received, the
parametric model figured a set of major characteristic parameters of each profile directly: sea surface temperature, mixed layer depth, thermocline depth, and temperature gradient. Hence, the approach would achieve the goal of reconstructing the regional thermocline profile directly. The thermocline reflects the ocean temperature field's important physics characteristics, and can be used in analysis of the influence on the exchange of the oxygen.
