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General Session 1: Physical oceanic processes: Dynamics and physical-biological-biogeochemical interactions |
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The impacts of internal waves on concentrations of nutrients and chlorophyll on Monterey Bay, California
GS1-39
Jiexin Xu* , South China Sea Institute of Oceanology, CAS
Fei Chai, Second Institute of Oceanography, SOA
University of Maine
Shuqun Cai, South China Sea Institute of Oceanology, CAS
Dongxiao Wang, South China Sea Institute of Oceanology, CAS
Presenter Email: manglo.xu@163.com
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| Internal waves are ubiquitous phenomenon in costal ocean, especially on continental shelf. They play a significant role in biological processes, yet how they influence the growth of biomass and how much the nutrients and chlorophyll change are still unclear. To study the impacts of internal waves on biological processes, a biogeochemical model CoSiNE coupled to a fully nonlinear nonhydrastatic three-dimensional physical model MITgcm (MIT general model) is applied to Monterey Bay, California.Model validation against in situ observations indicates the model is robust in reproducing physical processes. With the coupled model, the horizontal and vertical distribution of nutrients (e.g. NO3, SiO4, PO4) and chlorophyll throughout the water column during the generation and evolution of internal waves are analyzed. Model results show that, in horizontal, both nutrients and chlorophyll are peak at the shelf break during the generation of internal waves, and peak at the front of the waves as they travel onshore. More nutrients are transported from deep sea to continental shelf because of the strong mixing induced by generation of internal waves. When the crests of internal waves pass, concentration of NO3 in euphotic layer increases about 10%-20%. Increase of nutrients in euphotic layer favors the growth of phytoplankton. When nutrients are plenty, no significant differences can be seen between daytime and nighttime. A core with high chlorophyll concentration generates just above the trough of internal waves. Main effect of internal waves is to aggregate the phytoplankton. However, when system is nutrient limited, maximum chlorophyll concentration occurs about 4-5h after the trough of internal waves passes. The core with high chlorophyll concentration lies above the crest of internal wave, which make it possible to be observed by satellite. Because internal waves in Monterey Bay feature semi-diurnal period, the core only generates during daytime. This indicates that increase of nutrients by internal waves induces progressive development of biological processes. Increase of the concentration of chlorophyll is the interaction of physical processes and biological processes. As an important limited factor, light regulation is also discussed. Our study highlights the importance of taking into account the effect of internal waves in coastal area. |
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