Physically modulated phytoplankton production and export at submesoscales in the oligotrophic South China Sea Basin  

作　　者：Zhonghua ZHAO Mengdi XU Bangqin HUANG Wenfang LU Hongshuai QI Feng CAI Yuwu JIANG 

机构地区：[1]State Key Laboratory of Marine Environmental Science,Xiamen University,Xiamen 361102,China [2]College of Ocean and Earth Sciences,Xiamen University,Xiamen 361102,China [3]Fujian Provincial Key Laboratory for Coastal Ecology and Environmental Studies,Xiamen University,Xiamen 361102,China [4]National Observation and Research Station for the Taiwan Strait Marine Ecosystem,Xiamen University,Xiamen 361102,China [5]School of Marine Sciences,Sun Yat-Sen University,Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai),Zhuhai 519000,China [6]Laboratory of Ocean and Coast Geology,Third Institute of Oceanography,Ministry of Natural Resources,Xiamen 361005,China

出　　处：《Science China Earth Sciences》2024年第8期2681-2698,共18页中国科学（地球科学英文版）

基　　金：supported by the National Key Research and Development Program of China (Grant No.2022YFA1004404);the National Natural Science Foundation of China (Grant Nos.U22A20579,42306006&41876004)。

摘　　要：Oceanic submesoscales can significantly influence phytoplankton production and export owing to their similar timescales of days.Based on two-year Biogeochemical Argo(BGC-Argo) observations,this study investigated the development of submesoscale instabilities,particularly symmetric and mixed-layer baroclinic instabilities,and their impacts on biological production and export in the oligotrophic South China Sea basin.In the northern basin,near-surface winter blooms consistently cooccurred with seasonally deepened mixed layers.However,significantly stronger and weaker winter blooms were observed over two consecutive winters within the BGC-Argo observation period.During the first winter,symmetric-instability-induced upward nutrient entrainment played a crucial role in initiating the strong winter bloom in early December,when the mixed layer was approximately 20–30 m shallower than the nutricline.This bloom occurred approximately 20–30 days earlier than that anticipated owing to the contact between the seasonally deepened mixed layer and mesoscale-cyclone-induced uplifted nutricline.The symmetric instability also facilitated the export of fixed phytoplankton carbon from the surface to deeper layers.Conversely,during the second winter,remarkably intense mixed-layer baroclinic instability associated with an intense mesoscale anticyclone led to more significant shoaling of the mixed layer compared to the nutricline,thus increasing the vertical distance between the two layers.Under this condition,upward nutrient injection,phytoplankton bloom,and carbon export were suppressed.In contrast,the BGC-Argo float in the central basin revealed significantly inhibited seasonality of phytoplankton biomass and submesoscale instabilities compared to those in the northern basin,primarily owing to the significantly shallower winter mixed layer.

关 键 词：Submesoscale instability PHYTOPLANKTON Nutrient transport BGC-Argo South China Sea 

分 类 号：P734.44[天文地球—海洋化学] Q948.8[天文地球—海洋科学]