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Control of phytoplankton bloom inception in the Ross Sea, Antarctica, by Ekman restratification
Author(s) -
Long Matthew C.,
Thomas Leif N.,
Dunbar Robert B.
Publication year - 2012
Publication title -
global biogeochemical cycles
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.512
H-Index - 187
eISSN - 1944-9224
pISSN - 0886-6236
DOI - 10.1029/2010gb003982
Subject(s) - oceanography , stratification (seeds) , advection , ekman transport , ekman layer , mixed layer , geology , phytoplankton , ocean dynamics , bloom , spring bloom , ocean current , environmental science , upwelling , boundary layer , ecology , seed dormancy , botany , germination , physics , dormancy , nutrient , biology , thermodynamics
Observations from November 2006 in the southwestern Ross Sea indicate that stratification developed in a localized fashion, proximal to upper ocean fronts. These regions were hotspots for biological productivity, exhibiting greater drawdown of CO 2 and accumulation of oxygen, indicative of enhanced photosynthesis and air‐sea gas exchange. While the effect of stratification is clear, the reasons for its development was not; air temperatures were unseasonably cold, sea‐ice melt and sea surface warming were not significant. By comparing a one‐dimensional mixed layer model with two‐dimensional numerical simulations that include horizontal density gradients characteristic of the region, it is shown that Ekman advection is critical to structuring early season stratification. Where fronts are forced by winds that oppose the surface frontal current, Ekman advection displaces lighter water over dense. As biological productivity is light limited in the Ross Sea, and thus sensitive to the depth of the mixed layer, Ekman restratification plays an important role in determining the spatial distribution and development of the annual phytoplankton bloom in the region. The presence of fronts is therefore of first‐order importance to the restratification and bloom dynamics of the Ross Sea in the early spring.