Biological and Physical Controls on North Atlantic Carbon Sink Variability
Galen
A
McKinley, University of Wisconsin - Madison, galen@aos.wisc.edu
(Presenting)
Val
Bennington, University of Wisconsin - Madison, benesh@wisc.edu
David
Ullman, University of Wisconsin - Madison, ullman@wisc.edu
Stephanie
Dutkiewicz, Massachusetts Institute of Technology, stephd@ocean.mit.edu
We investigate biological and physical controls on the carbon sink in the North Atlantic using ocean color data and a physical-biogeochemical model. We find that biological production is significant to the mean carbon sink in the subpolar gyre and dominates the seasonal cycle of pCO2, but that variations in annual CO2 flux and export variability are not significantly correlated. This occurs because the large year-to-year variability in pCO2 during the bloom is due to bloom timing, not integrated bloom strength and associated carbon uptake and export. The small variation of modeled annual integrated chlorophyll is consistent in magnitude with SeaWiFS (1998-2006) data. Thus, we conclude that biological variability is not a first-order control of subpolar CO2 flux variability on interannual timescales. In contrast, we find that physical variability is the dominant control on flux variability and trends across the North Atlantic. Spatio-temporal variability in the carbon sink since 1992 is due largely to decadal trends in the strength of gyre circulations (Hakkinen and Rhines, 2004). These results suggest that changes in the carbon cycle due to horizontal advection have first-order impacts on decadal variability in surface ocean pCO2 (Shuster and Watson, 2007), and thus on the spatial distribution of the North Atlantic carbon sink.
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