Transports of Total Inorganic Carbon (TIC), Total Alkalinity (TA) and
Anthropogenic Carbon (CANT) are calculated across a densely sampled World Ocean
Circulation Experiment (WOCE) section at the southern boundary of the subpolar North
Atlantic (WOCE A25, 4x cruise). The circulation pattern was approximated using an
inverse model constrained with measured mass transports at specific sites, while
conserving the mass and salt transports, and forcing the silicate flux to equal the river
input north of the section. The mass and chemical fluxes are decomposed into their
barotropic, baroclinic and horizontal components. The TA transport is negligible
(transport ± maximum estimate of uncertainty, 135 ± 507 kmol s 1), while TIC is
transported southwards ( 1015 ± 490 kmol s 1) and CANT northwards (116 ± 125 kmol
s 1). Combining our results with those from Roso´n et al. [2002] across 24.5 N (WOCE
A5) we examine the contemporary and preindustrial TIC budgets in the subpolar and
temperate North Atlantic based on two different approximations for the budget
definitions. Initially, river input, biological production of TIC, along with sedimentation
of calcium carbonate are ignored. Then, extended contemporary and preindustrial TIC
budgets are discussed including rough estimates of the former processes, mainly based on
values from the literature. Our findings point to the North Atlantic Ocean north of 24.5 N
as a strong sink for atmospheric CO2 both today (2932 ± 2057 kmol s 1) and
preindustrially (2439 ± 1721 kmol s 1). Only 17% of the contemporary CO2 air-sea
uptake corresponds to CANT, which is mainly taken up in the temperate North Atlantic
(between the 4x and 24.5 N sections). North of 24.5 N the Atlantic Ocean stores CANT at
a rate of 1123 ± 200 kmol s 1. This CANT is mainly advected into the area in the upper
limb of the overturning circulation, while 44% is directly introduced by air-sea
uptake.
Peer reviewed