Joint International Conference on Long-term Experiments ...

OCEAN DYNAMICS: AIR-SEA INTERFACE GASES EXCHANGE 1
Speranta Coldea,
Faculty of Environment Protection, University of Oradea,
Oradea, Str. Gen. Magheru Nr.26, Romania
ABSTRACT
Having known the tracer conservation equation and discussed ocean transport, we will
consider now the processes at the air-sea interface that need to be specified in order to
solve the tracer continuity equation. The most important process that we must consider
here there is the gas exchange. This process has a major impact on the distribution of
gases within both the ocean as well as within the atmosphere. We will introduce an
overview of the major gases in the atmosphere and ocean and some important processes
in which they are involved. Further we will discuss the solubility of gases in seawater
and the processes at the air-sea interface that control the exchange between the
atmosphere and ocean.
Keywords: atmosphere – ocean interaction, gases exchange.
1. INTRODUCTION
The terrestrial atmosphere composition is a unique one in our solar system due to the
influence on long terms of biological processes upon al the basic components, with the
exception of noble gases (see Table.nr.1). The noble gases are near the equilibrium state
between ocean and atmosphere (with the exception of a supersaturation due to air
bubbles solving, bubbles that are injected in ocean by the braking tides, and by the
fluctuations resulted from mixing, heating and from the water-air fluxes). The
distribution of ocean noble gases is determined especially by their solubility. The
equilibrium distribution between the atmosphere and ocean of the basic gases is
determined by the chemical and biological processes that produce the gas consumption
in the ocean. From the eight reactive gases given in the Table nr.1, three of them, e.g.
O2, CO2 and N2O, are produced and consumed in great quantities by the oceanic
processes. The Ocean doesn’t produce methane, but the flux of this gas to the
atmosphere is negligible compared to that from terrestrial sources (∼ 2%). The ocean
produces and consumes also N2, but we don’t know if the ocean is a source or a sink, or
it is neuter for this gas. Some gases have an impact on the thermal state of our planet by
caption of long wave radiation emitted by the Earth, from so called greenhouse effect.
We must observe that CO2 and N2O are in bigger quantities compared with the
beginning of the industrial era and contribute semnificatively to the greenhouse effect.
We will explore partially the vertical and horizontal distribution of the gases, and we
will give a special attention to the concentrations at the ocean surface in contact with the
atmosphere. This distribution has some unusual particularities for O2, CO2, and N2O
that we will introduce in our analysis. The nonquilibrium state between ocean and
atmosphere of CO2 is larger than that of O2. For CO2 the curve seems to begin to be
larger and it is opposite to that of O2. The same biological processes which decay O2 in
the deep waters will enlarge the concentration of the total carbon. This fact explains
why the curve for CO2 at the equator is opposite to that of O2, but doesn’t explain why
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