南海东北部夏季叶绿素a浓度垂向变化特征及其对水动力过程的响应  

Vertical variability of chlorophyll a concentration and its responses to hydrodynamic processes in the northeastern South China Sea in summer

作　　者：徐文龙 王桂芬[1,3] 周雯 许占堂[1] 曹文熙[1] XU Wenlong;WANG Guifen;ZHOU Wen;XU Zhantang;CAO Wenxi(State Key Laboratory of Tropical Oceanography(South China Sea Institute of Oceanology,Chinese Academy of Sciences),Guangzhou 510301,China;University of Chinese Academy of Sciences,Beijing 100049,China;College of Oceanography,Hohai University,Nanjing 210098,China)

机构地区：[1]热带海洋环境国家重点实验室(中国科学院南海海洋研究所),广东广州510301 [2]中国科学院大学,北京100049 [3]河海大学海洋学院,江苏南京210098

出　　处：《热带海洋学报》2018年第5期62-73,共12页Journal of Tropical Oceanography

基　　金：国家自然科学基金(41776045;41376042;41576030;41776044);热带海洋环境国家重点实验室自主研究项目(LTOZZ1602)~~

摘　　要：叶绿素a浓度是估算海洋初级生产力的一个重要参数,在海洋中垂向分布极不均匀,其分布特征及影响机制是海洋生态学研究的重要基础问题。利用海洋光学观测的高垂向分辨率剖面数据,系统地研究叶绿素a浓度垂向剖面的时空分布特征及其与海洋动力环境要素的关系,可为揭示南海典型动力过程的生态环境效应提供重要基础。文章基于2015年夏季黑潮调查航次实测生物光学剖面,利用676nm处吸收基线高度(a_(LH)(676))与叶绿素a浓度(Chla)之间的关系,建立了具有较高反演精度的叶绿素a浓度反演算法(Chla=49.96×(a_(LH)(676))^(0.9339),决定系数R^2=0.87和均方根误差RMSE=0.16mg·m^(-3));进一步结合观测期间物理过程,揭示了叶绿素垂向分布对不同水动力过程的响应特征。研究结果表明,近岸区域表层叶绿素a浓度变化范围为0.42~1.57mg·m^(-3),随着水深增加,叶绿素a浓度逐渐降低,在沿岸上升流影响区域,叶绿素a浓度明显增高,垂向上相对趋于均一分布;次表层叶绿素极大值(Subsurface Chlorophyll Maximum,SCM)现象在外海显著存在,受中尺度过程影响明显,SCM深度在34m到100m之间变化,在吕宋岛以西海域,黑潮入侵加速了上层水体的混合,SCM所在水层被显著抬升至34m左右;在冷涡影响区域,次表层叶绿素极大值层被抬升,涡旋中心比涡旋边缘抬升更为显著,同时SCM的厚度增大。Chlorophyll a(Chla)concentration is an important indicator of phytoplankton biomass for estimating primary production,which exhibits inhomogeneous vertical distribution.In this study,optical measurements with high vertical resolution were used for studying the spatio-temporal variability of Chla profiles and its influencing mechanism,providing us much insights for understanding marine environmental dynamics in the South China Sea.In this study,an optical inversion method was proposed to retrieve Chla profiles from in situ measurements with high-spectral absorption/attenuation spectrophotometer in the northeastern South China Sea.Based on the in situ data of the Kuroshio Cruise in summer 2015,an empirical relationship between the absorption line height at 676 nm and Chla was developed for inverting Chla with a high accuracy(Chla=49.96×(aLH(676)(676))0.9339,the coefficient of determination R2=0.87,the root mean square error RMSE=0.16 mg·m-3).Moreover,the response characteristics of Chla profiles to different hydrodynamic processes were studied.Results showed that large spatial differences existed in the vertical distribution of Chla.In the nearshore area,surface Chla varied from 0.42 to 1.57 mg·m-3,which generally followed a decreasing trend with depth.Uniform vertical distribution of Chla in upper ocean was observed in the coastal upwelling region.The Subsurface Chlorophyll Maximum(SCM)layer is nearly ubiquitous in stratified waters of the open ocean,with its vertical structure being influenced by mesoscale processes.The depth of SCM ranged between 34 and 100 m,which showed consistent variability with the isopycnal depth of 1023 kg·m-3.The SCM layer was uplifted to about 34 m due to the mixing effect in the upper ocean caused by Kuroshio intrusion in the western area of Luzon Island.The uplifting and widening of the SCM layer were also observed in the area affected by a cold eddy,with obviously different features in the eddy center from that on the eddy edge.

关 键 词：南海东北部 叶绿素a垂向变化 次表层叶绿素极大值 吸收基线高度 水动力过程 

分 类 号：P733.3[天文地球—物理海洋学] P731.2[天文地球—海洋科学]