Effects of surface forcing on interannual variability of the fall phytoplankton bloom in the Gulf of Maine revealed using a process-oriented model

Marine Ecology Progress Series

Changsheng Chen¹  David W. Townsend¹  Song Hu¹  Cabell S. Davis¹  Rubao Ji¹  Rucheng Tian¹  Robert C. Beardsley¹ 

关键词: Fall phytoplankton bloom;    Surface forcing;    Freshening;    Interannual variability;    Gulf of Maine;    Modeling;   

DOI  :  10.3354/meps09043

学科分类：海洋学与技术

来源: Inter-Research

【 摘 要 】

ABSTRACT: SeaWiFS (Sea-viewing Wide Field-of-view Sensor) chlorophyll data revealed strong interannual variability in fall phytoplankton dynamics in the Gulf of Maine, with 3 general features in any one year: (1) rapid chlorophyll increases in response to storm events in fall; (2) gradual chlorophyll increases in response to seasonal wind- and cooling-induced mixing that gradually deepens the mixed layer; and (3) the absence of any observable fall bloom. We applied a mixed-layer box model and a 1-dimensional physical-biological numerical model to examine the influence of physical forcing (surface wind, heat flux, and freshening) on the mixed-layer dynamics and its impact on the entrainment of deep-water nutrients and thus on the appearance of fall bloom. The model results suggest that during early fall, the surface mixed-layer depth is controlled by both wind- and cooling-induced mixing. Strong interannual variability in mixed-layer depth has a direct impact on short- and long-term vertical nutrient fluxes and thus the fall bloom. Phytoplankton concentrations over time are sensitive to initial pre-bloom profiles of nutrients. The strength of the initial stratification can affect the modeled phytoplankton concentration, while the timing of intermittent freshening events is related to the significant interannual variability of fall blooms.

【 授权许可】

Unknown