Basic HTML Version
International Journal of Marine Science 2014, Vol.4, No.72, 1-7
http://ijms.biopublisher.ca
3
k
= 0.0283
3
10
660 /
Sc
(5)
Moreover, recent investigation evaluating the transfer
velocity-wind speed relationship using a long-term
series of direct eddy correlation CO
2
flux
measurements from the Baltic Sea suggests a
combination of quadratic and linear wind speed
dependence (Weiss et al., 2007; Rutgersson et al., 2008).
k
= (0.365
2
10
+ 0.46
2
10
)
660 /
Sc
(6)
A positive flux (
fCO
2
) value represents a net CO
2
exchange from sea to the atmosphere and a negative
flux value refers to the net CO
2
exchange from the
atmosphere to the sea. For the purposes of this
research, 8-day averages of air-sea
p
CO
2
difference
(Δ
p
CO
2
), SST, wind speed at 10 m height, and mixed
layer depth are produced, and calculations of 8-day CO
2
flux densities,
f
, were performed using equation (4).
2 Results and discussion
2.1
Seasonal to monthly pCO
2
net flux in North
Atlantic NW / NE basins
The emerging trend of the seasonal
p
CO
2
cycle at the
PAP observatory site indicates high
p
CO
2
difference
between the seawater relative to atmospheric
p
CO
2
,
showing a persistent undersaturation of surface waters
by Δ
p
CO
2
of about 70 µatm in summer of 2004
(Figure 2). This predicts an influx of CO
2
from the
atmosphere into the ocean, and the trend notably
followed an increasing seawater surface temperature
(warming). Winter deep convection has been
established as a mechanistic process of exposing
CO
2
-enriched subsurface water to the seawater surface
(McKinley et al., 2004b). This mechanism is markedly
observed during the winter months (Figure 2) where
relatively low or damped Δ
p
CO
2
were obtained.
Figure 2 Monthly Δ
p
CO
2
between July 2003 – March 2005 plotted as a function of SST at the PAP observatory
In other words, the time-trend Δ
p
CO
2
flux
variability indicates relatively damped Δ
p
CO
2
during wintertime and enhanced Δ
p
CO
2
in
summertime. Also, uptake of anthropogenic CO
2
from the atmosphere increases during wintertime
resulting in relatively low Δ
p
CO
2
. However, a
positive Δ
p
CO
2
was observed in early summer of
2003 (August 2003) resulting in a possible efflux of
CO
2
into the atmosphere leading to a decrease in net
ocean CO
2
uptake during the summertime. This
could be attributed to a dominant DIC-driven
p
CO
2
.
Considering the average monthly CO
2
flux variability
at the NW K1 Central Labrador Sea, a relatively high
sea-air Δ
p
CO
2
of about 60 µatm was recorded in
September 2004 as a negative CO
2
flux (Figure 3).
However, decreasing CO
2
sink of the time series
location is observed following seasonal change from
summertime of 2004 to wintertime. Uptake of CO
2
by
the ocean almost equilibrated with the atmospheric
p
CO
2
during the peak period of the winter months,
thereby creating a near saturated condition with
relatively low sea surface temperature. Evidently,