Controls of the surface water partial pressure of CO2 in the North Sea

The seasonal variability of the partial pressure
of CO2 (pCO2) has been investigated in the North Sea, a
northwest European shelf sea. Based on a seasonal and high
spatial resolution data set the main controlling factors – biological
processes and temperature - have been identified and
quantified. In the central and northern parts being a CO2-
sink all year round, the biological control dominates the temperature
control. In the southern part, the temperature control
dominates the biological control at an annual scale, since
the shallow water column prevents stronger net-CO2 removal
from the surface layer due to the absence of seasonal stratification.
The consequence is a reversal of the CO2 seato-
air flux during the spring bloom period, the only time,
when CO2 is taken up from the atmosphere in the southern
region. Net community production in the mixed layer
has been estimated to 4mol Cm−2 yr−1 with higher values
(4.3 mol Cm−2 yr−1) in the northern part and lower values
in the southern part (2.6 mol Cm−2 yr−1).