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Temporal evolution of near‐surface chlorophyll over cyclonic eddy lifecycles in the southeastern Pacific
Author(s) -
Huang Jie,
Xu Fanghua,
Zhou Kuanbo,
Xiu Peng,
Lin Yanluan
Publication year - 2017
Publication title -
journal of geophysical research: oceans
Language(s) - English
Resource type - Journals
eISSN - 2169-9291
pISSN - 2169-9275
DOI - 10.1002/2017jc012915
Subject(s) - eddy , eddy current , ekman transport , mesoscale meteorology , eddy covariance , atmospheric sciences , climatology , geology , physics , meteorology , oceanography , turbulence , biology , ecology , quantum mechanics , ecosystem , upwelling
Abstract Temporal evolution of near‐surface chlorophyll (CHL) associated with mesoscale eddies over entire eddy lifespan is complicated. Based on satellite measurements and a reanalysis data set, we identify and quantify major temporal and spatial CHL responses in cyclonic eddies in the southeastern Pacific, and explore the associated mechanisms. Only few temporal CHL variations can be directly linked to the four primary mechanisms: “eddy pumping,” “eddy trapping,” “eddy stirring,” and “eddy‐induced Ekman pumping.” About 80% of the temporal CHL variations are too complex to be explained by a single mechanism. Five characteristic CHL responses, including classic dipoles (CD), positive‐dominant dipoles (PD), negative‐dominant dipoles (ND), positive monopoles (PM), and negative monopoles (NM) are identified using the self‐organizing map (SOM). CD, a dominant response induced primarily by “eddy stirring,” has a continued increasing of frequency of occurrence with time, although its contribution to the total CHL variability remains low. As the secondary prominent response, NM has two peaks of frequency of occurrence at eddy formation and maturation stages, mainly accounted by “eddy trapping” after eddy breakup and “eddy‐induced Ekman pumping,” respectively. The sum of frequency of occurrence of PD and PM are comparable to that of NM. The initial positive CHL at eddy formation stage is associated with “eddy trapping.” The significant positive CHL increase from the eddy intensification to early decay stage is mainly attributed to “eddy pumping.” Although the frequency of occurrence of ND is the smallest, its contribution to negative CHL anomalies is unnegligible.