It is an empirical fact that CO2 air-sea flux measurements from either eddy covariance or differences in their respective partial pressures with turbulence etc are much greater than the surface water biological driven net CO2 uptake i.e. the balance between CO2 fixation and community respiration. This is also after accounting for advective CO2 fluxes. NEP is often correlated with air-sea flux as the driver. For terrestrial ecosystems, this is not the case, air fluxes and NEP seems to be equivalent. I have heard an argument that says "Oh it's just a matter of time for NEP depletion of DIC to reequilibrate with the atmosphere" However I don't see this and it is a statement that sounds reasonable at first thought but the fact that the earth atmospheric ocean system is not a equilibrium. Furthermore, at scale the NEP such as in the whole of Chesapeake Bay, averaged over a year across different zones and the Atmospheric flux correlated well and was is still around 5 times less (Atmospheric flux is 5 x more). Is one reason that CO2 sources for the biological pump do not depend only on atmospheric flux? i.e. remineralization and advective supply?
Air-sea fluxes of CO2 are much greater than surface water net ecosystem production because they include the transfer of CO2 between the atmosphere and the ocean. The atmosphere has a much larger reservoir of CO2 than the ocean, so air-sea fluxes are an important way for CO2 to move between these two reservoirs. In addition, the ocean is a dynamic environment, with currents and mixing processes that transport CO2 from the surface to the deep ocean, where it can be stored for longer periods of time. These processes contribute to the overall air-sea flux of CO2.
Thank you Peter. However, even in situations where there are no advective fluxes or situations in which measurements are rapid relative to water residence times the air-sea flux must be different to the NEP. In other words, the NEP is a function of the change in DIC minus the flux CO2 from the air. DIC change comes from the air and from the water. In which that DIC from a past legacy biological processes of fixation and respiration, independent of the immediate Air sea flux. It seems that global climate models use the air-sea flux and biology only explains the additional drawdown and the correlation. For forest systems this is not a problem it seems as a gas exchange from the forest to the atmosphere is direct. Submersion, however, seems to complicate the matter in which temp salinity and wind speed also determine the pCO2 and the rate of exchange. I THINK? As a consequence, unlike export to soils in forests, the export of algae that survives decomposition to the sediments or the deep sea cannot be a measure of atmospheric sequestration? even though it is often considered as equivalent.
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