Interannual Variability in the North Atlantic Ocean Carbon Sink
Nicolas Gruber,1*
Charles D. Keeling,2
Nicholas R. Bates3
The North Atlantic is believed to represent the largest ocean sink
for atmospheric carbon dioxide in the Northern Hemisphere, yet little
is known about its temporal variability. We report an 18-year time
series of upper-ocean inorganic carbon observations from the
northwestern subtropical North Atlantic near Bermuda that indicates
substantial variability in this sink. We deduce that the carbon
variability at this site is largely driven by variations in winter
mixed-layer depths and by sea surface temperature anomalies. Because
these variations tend to occur in a basinwide coordinated pattern
associated with the North Atlantic Oscillation, it is plausible that
the entire North Atlantic Ocean may vary in concert, resulting in a
variability of the strength of the North Atlantic carbon sink of about
±0.3 petagrams of carbon per year (1 petagram = 1015
grams) or nearly ±50%. This extrapolation is supported by basin-wide estimates from atmospheric carbon dioxide inversions.
1 Institute of Geophysics and Planetary Physics
and Department of Atmospheric Sciences, University of California, Los
Angeles, CA 90095, USA.
2 Scripps Institution of
Oceanography, University of California, San Diego, La Jolla, CA 92093, USA.
3 Bermuda Biological Station for Research,
Inc., Ferry Reach GE01, Bermuda.
*
To whom correspondence should be addressed. E-mail:
ngruber{at}igpp.ucla.edu
