About the objectives of ASGAMAGE
Objectives
1, 2 and 4 can be directly understood from the motives for the project:
-
The importance of the carbon
balance with respect to the global climate, the sizeable share of the
oceans in this balance and the size of the "missing sink", the difference
between the sum of the known sources and sinks that can not be attributed
to a known process or depository.
-
The search for the cause of the order-of-magnitude
discrepancy between the air-sea transfer velocity for CO2
found with chemistry oriented methods (based on e.g. 222Rn,
14C,
deliberate tracers) and with the newly developed micrometeorological techniques,
especially the eddy correlation method.
-
The large uncertainties in the values
for the transfer velocity (even without the micrometeorological results)
in combination with the expectation that there are more geophysical parameters
affecting air-sea gas exchange beside wind speed (the role of which is
generally accepted). Micrometeorological methods, with their measurement
times in the order of half an hour, could be of prime importance for the
study of these other parameters, because their effects are largely averaged
out during the measurement periods of the chemistry oriented methods, which
are in the order of a day or more.
Objective
3 resulted from an earlier experiment, ASGAS-EX, in which strong fluctuations
of the CO2fugacity
with the tide had been found, that could be seen as an indication of vertical
concentration gradients. This was of special importance for the second
objective because in the analysis of the differential tracer method the
assumption is generally made that concentration gradients within the water
column can be neglected and that for air-sea gas transfer processes only
the surface is important.
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