Phytoplankton spring and fall blooms in the North Atlantic in the 1980s and 2000s

Type Article
Date 2011-11
Language English
Author(s) Martinez Elodie1, Antoine David1, D'Ortenzio Fabrizio1, de Boyer Montegut ClementORCID2
Affiliation(s) 1 : Univ Paris, Lab Oceanog Villefranche, UMR 7093, CNRS,UPMC, F-06230 Villefranche Sur Mer, France.
2 : IFREMER, Ctr Brest, Lab Oceanog Spatiale, F-29280 Plouzane, France.
Source Journal Of Geophysical Research-oceans (0148-0227) (Amer Geophysical Union), 2011-11 , Vol. 116 , N. C11029 , P. 11 p.
DOI 10.1029/2010JC006836
WOS© Times Cited 47
Abstract Phytoplankton chlorophyll-a (Chl) seasonal cycles of the North Atlantic are described using satellite ocean color observations covering the 1980s and the 2000s. The study region is where warmer SST and higher Chl in the 2000s as compared to the 1980s have been reported. It covers latitudes from 30 degrees N-50 degrees N and longitudes from 60 degrees W-0 degrees W, where two phytoplankton blooms take place: a spring bloom that follows stratification of upper layers, and a fall bloom due to nutrient entrainment through deepening of the mixed layer. In the 1980s, spring and fall blooms were of similar amplitude over the entire study region. In the 2000s, the fall bloom was weaker in the eastern Atlantic (east of 40 degrees W), because of a delayed deepening of the mixed layer at the end of summer (mixed layer depth (MLD) determined from in situ data). Conversely, the spring bloom of the eastern Atlantic was stronger in the 2000s than it was in the 1980s, because of a deeper MLD and stronger winds in winter. In the Northwestern Atlantic (northwest of 38 degrees N-40 degrees W), little differences are observed for spring and fall blooms, and for the wintertime MLD. Our results show that the links between upper layer stratification, SST changes, and biological responses are more complex than the simple paradigm that sequentially relates higher stratification with warmer SST and an enhanced (weakened) growth of the phytoplankton population in the subpolar (subtropical) region.
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