Transport and storage of anthropogenic C in the North Atlantic Subpolar Ocean
<p>The North Atlantic Ocean is a major sink region for atmospheric CO<sub>2</sub> and contributes to the storage of anthropogenic carbon (Cant). While there is general agreement that the intensity of the meridional overturning circulation (MOC) modulates uptake, transport and st...
| Main Authors: | , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2018-07-01
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| Series: | Biogeosciences |
| Online Access: | https://www.biogeosciences.net/15/4661/2018/bg-15-4661-2018.pdf |
| Summary: | <p>The North Atlantic Ocean is a major sink region for atmospheric
CO<sub>2</sub> and contributes to the storage of anthropogenic carbon (Cant).
While there is general agreement that the intensity of the meridional
overturning circulation (MOC) modulates uptake, transport and storage of Cant
in the North Atlantic Subpolar Ocean, processes controlling their recent
variability and evolution over the 21st century remain uncertain. This
study investigates the relationship between transport, air–sea flux and
storage rate of Cant in the North Atlantic Subpolar Ocean over the past 53
years. Its relies on the combined analysis of a multiannual in situ data
set and outputs from a global biogeochemical ocean general circulation model
(NEMO–PISCES) at 1∕2° spatial resolution forced by an atmospheric
reanalysis. Despite an underestimation of Cant transport and an
overestimation of anthropogenic air–sea CO<sub>2</sub> flux in the model, the
interannual variability of the regional Cant storage rate and its driving
processes were well simulated by the model. Analysis of the multi-decadal
simulation revealed that the MOC intensity variability was the major driver
of the Cant transport variability at 25 and 36° N, but not at OVIDE.
At the subpolar OVIDE section, the interannual variability of Cant transport
was controlled by the accumulation of Cant in the MOC upper limb. At
multi-decadal timescales, long-term changes in the North Atlantic storage
rate of Cant were driven by the increase in air–sea fluxes of anthropogenic
CO<sub>2</sub>. North Atlantic Central Water played a key role for storing Cant
in the upper layer of the subtropical region and for supplying Cant to
Intermediate Water and North Atlantic Deep Water. The transfer of Cant from
surface to deep waters occurred mainly north of the OVIDE section. Most of
the Cant transferred to the deep ocean was stored in the subpolar region, while the
remainder was exported to the subtropical gyre within the lower MOC.</p> |
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| ISSN: | 1726-4170 1726-4189 |