On which timescales do gas transfer velocities control North Atlantic CO2 flux variability?

Type Article
Date 2016-05
Language English
Author(s) Couldrey Matthew P.1, Oliver Kevin I. C.1, Yool Andrew2, Halloran Paul R.3, Achterberg Eric P.1, 4
Affiliation(s) 1 : Univ Southampton, Natl Oceanog Ctr, Ocean & Earth Sci, Southampton, Hants, England.
2 : Natl Oceanog Ctr, Southampton, Hants, England.
3 : Univ Exeter, Coll Life & Environm Sci, Geog, Exeter, Devon, England.
4 : GEOMAR Helmholtz Zentrum Ozeanforsch, Kiel, Germany.
Source Global Biogeochemical Cycles (0886-6236) (Amer Geophysical Union), 2016-05 , Vol. 30 , N. 5 , P. 787-802
DOI 10.1002/2015GB005267
WOS© Times Cited 12
Keyword(s) carbon flux, gas transfer velocity, carbon cycle, ocean model, climate dynamics, variability
Abstract

The North Atlantic is an important basin for the global ocean's uptake of anthropogenic and natural carbon dioxide (CO2), but the mechanisms controlling this carbon flux are not fully understood. The air-sea flux of CO2, F, is the product of a gas transfer velocity, k, the air-sea CO2 concentration gradient, Delta pCO(2), and the temperature-and salinity-dependent solubility coefficient, alpha, k is difficult to constrain, representing the dominant uncertainty in F on short (instantaneous to interannual) timescales. Previous work shows that in the North Atlantic, Delta pCO(2) and k both contribute significantly to interannual F variability but that k is unimportant for multidecadal variability. On some timescale between interannual and multidecadal, gas transfer velocity variability and its associated uncertainty become negligible. Here we quantify this critical timescale for the first time. Using an ocean model, we determine the importance of k, Delta pCO(2), and.. on a range of timescales. On interannual and shorter timescales, both Delta pCO(2) and k are important controls on F. In contrast, pentadal to multidecadal North Atlantic flux variability is driven almost entirely by Delta pCO(2); k contributes less than 25%. Finally, we explore how accurately one can estimate North Atlantic F without a knowledge of nonseasonal k variability, finding it possible for interannual and longer timescales. These findings suggest that continued efforts to better constrain gas transfer velocities are necessary to quantify interannual variability in the North Atlantic carbon sink. However, uncertainty in k variability is unlikely to limit the accuracy of estimates of longer-term flux variability.

Full Text
File Pages Size Access
Publisher's official version 16 2 MB Open access
Supporting Information S1 7 KB Open access
Figure S1 1 364 KB Open access
Figure S2 25 KB Open access
Top of the page