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International Journal of Marine Science 2014, Vol.4, No.72, 1-7
http://ijms.biopublisher.ca
1
Research Article Open Access
Observed trends of
p
CO
2
and air-sea CO
2
fluxes in the North Atlantic Ocean
Nsikak U. Benson
1,
, Oladele O. Osibanjo
2
, Francis E. Asuquo
3
, Winifred U. Anake
1
1. Environmental Chemistry Unit, Department of Chemistry, School of Natural and Applied Sciences, Covenant University, Ota, Nigeria
2. Department of Chemistry, University of Ibadan, Ibadan, Nigeria
3. Institute of Oceanography, Marine Chemistry Unit, University of Calabar, Nigeria
Corresponding author email
International Journal of Marine Science, 2014, Vol.4, No.72 doi: 10.5376/ijms.2014.04.0072
Received: 22 Sep., 2014
Accepted: 20 Oct., 2014
Published: 10 Dec., 2014
Copyright
©
2014
Benson et al., This is an open access article published under the terms of the Creative Commons Attribution License, which permits unrestricted
use, distribution, and reproduction in any medium, provided the original work is properly cited.
Preferred citation for this article:
Benson et al., 2014, Observed trends of
p
CO
2
and air-sea CO
2
fluxes in the North Atlantic Ocean, International Journal of Marine Science, Vol.4, No.72 1
-
7
(doi
Abstract
Observed partial pressure of carbon dioxide (
p
CO
2
) and temperature data in surface and mixed layer seawater of the
Northeast (49
o
N, 16.5
o
W) and Northwest (56.5
o
N, 52.6
o
W) Atlantic Ocean time series sites have been analyzed for seasonal
variability and air-sea CO
2
fluxes. The NE PAP data showed an annual mean
p
CO
2
of 335.9
89.6
atm (2003), 286.7
103.5
atm
(2004), and 335.9
89.6
atm (2005). The annual data for NW KI deployments indicated annual
p
CO
2
average of 336.6
14.3 and
359.1
25.3
atm for 2004 and 2005 respectively. The oceanic
p
CO
2
distribution across the spatial gradients over a seasonal
timescale is relatively homogeneous with marked seasonal variability. These data indicated consistently the undersaturation of
oceanic surface water at the sites and thus a perennial carbon sink. Sea surface
p
CO
2
trend is marked by summertime minimum and
wintertime maximum, while depicting anti-phase patterns with the observed temperature signals. Seasonal to annual CO
2
fluxes
indicated a year-round CO
2
invasion of the NE and NW basins. Estimated net basin-scale CO
2
uptake fluxes of 2.96 ±1.73 and 1.84
±1.3 mol m
-2
CO
2
a
-1
were obtained for NE PAP (2nd - 4th) and NW K1 deployments, respectively.
Keywords
p
CO
2
; air-sea CO
2
fluxes; seasonal variability; temperature trends; North Atlantic Ocean
Introduction
The North Atlantic Ocean is regarded as the largest
ocean sink for atmospheric carbon dioxide (CO
2
),
based both on observational estimates (Schneider et al.,
1992; Kuss et al., 2006; Takahashi et al., 2002; 2009),
and forward and inverse modeling results (Gloor et al.,
2003; McKinley et al., 2004; 2008). The strong CO
2
sink capacity of the North Atlantic Ocean is largely
attributed to two principal factors vis-a-vis the
counteractive effect of vertical circulation in which
large volumes of surface water driven poleward by
strong currents, cools and absorbs huge quantities of
atmospheric CO
2
before getting sunk to mixed layer
depth during the wintertime, and also to the effective
and sustained carbon and nutrients (phosphorus, silica
and iron) uptake (Takahashi et al., 2002, 2009;
Schuster and Watson, 2007; Körtzinger et al., 2008a).
However, observations have indicated substantial
variability in the uptake of CO
2
spatially (Watson et
al
.,
1991) and temporally (Gruber et al., 2002).
The exchange of CO
2
between the ocean and the
atmosphere is a major biogeochemical process that
regulates the fate and rate of increase of anthropogenic
CO
2
, which will in turn determine the rate of likely
climate change. This biogeochemical process is
significantly controlled by prevailing
p
CO
2
existing
between the atmosphere and surface of the ocean. Sea
surface
p
CO
2
is governed by physical and biological
factors such as change of sea surface temperature (SST)
(Schuster et al., 2009), deep convective mixing,
re-stratification (Straneo, 2006), entrainment of CO
2
enriched deeper water (Avsic et al., 2006; Körtzinger et
al
.
, 2008b), salinity (Dickson et al
.
, 2002), phase of the
North Atlantic Oscillation (Thomas et al., 2008),
consumption by marine biota linked to the availability of
surface nutrients (productivity / respiration) (Behrenfeld
et al., 2006). The net CO
2
transfer is a function of the
difference in the
p
CO
2
at the air-sea interface, and of
the exchange processes in the atmosphere and the
ocean (Takahashi et al., 2009; Omstedt et al
.,
2009).
There is a growing understanding that adequate
parameterization of CO
2
flux is a significant factor in
the quantification of spatially resolved air-sea CO
2
exchange (Rutgersson et al., 2008; Takahashi et al.,
2009). The assessment is crucial for climate modeling