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报告题目:Bottom boundary layer dynamics and its influences on biogeochemical processes over the Texas-Louisiana shelf

 

报告人:    Wenxia Zhang
        Department of Oceanography, Texas A&M University      
 
报告时间:2014年5月23日(星期五)09:30-11:00

 

报告地点:木兰船建大楼A211会议室

 

联系人:    孙薇  sunwei_0417@163.com

 

Abstract: The Mississippi and Atchafalaya Rivers discharge 530 km3 of fresh water and
950000 tons of nitrogen into the northern Gulf of Mexico every year. The
Texas-Louisiana shelf has historically been observed to be affected by
seasonal bottom hypoxia due to the combined effect of stratification from the
fresh water and eutrophication from the nutrients. The bottom boundary layer
is an unstratified thin layer above the sea floor, separated from the more
strongly stratified interior. Formation of a thin bottom boundary layer in the
presence of stratification and a sloping bottom is common, and well
characterized by theory. We show that the main pycnocline and the bottom
boundary layer play different roles but are both crucial for the formation of low
dissolved oxygen concentration in bottom waters. Bottom Ekman transport
excites buoyancy advection within the bottom boundary layer, resulting in
frontogenesis and convergence. These processes can alter the overlying flow
field and redistribute bottom material. Meanwhile, a new mechanism of
upwelling is detected—an upwelling driven by convergent flow generated from
the buoyancy advection within boundary layer—evident by a low oxygen
water intrusion.

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