Abstract
It has been speculated that the partial pressure of carbon dioxide (pCO2) in shelf waters may lag the rise in atmospheric CO2. Here, we show that this is the case across many shelf regions, implying a tendency for enhanced shelf uptake of atmospheric CO2. This result is based on analysis of long-term trends in the air–sea pCO2 gradient (ΔpCO2) using a global surface ocean pCO2 database spanning a period of up to 35 years. Using wintertime data only, we find that ΔpCO2 increased in 653 of the 825 0.5° cells for which a trend could be calculated, with 325 of these cells showing a significant increase in excess of +0.5 μatm yr−1 (p < 0.05). Although noisier, the deseasonalized annual data suggest similar results. If this were a global trend, it would support the idea that shelves might have switched from a source to a sink of CO2 during the last century.
Highlights
It has been speculated that the partial pressure of carbon dioxide in shelf waters may lag the rise in atmospheric CO2
The recent development of the communitydriven global ocean pCO2 data product SOCAT offers a complementary approach to assess whether continental shelves show a change in the air–sea pCO2 gradient (ΔpCO2 = pCO2,air−pCO2) over time
The data coverage remains sparse within SOCAT, it allows reconstructing the evolution in ΔpCO2 for 15 regions across the global shelves with a time span of at least a decade
Summary
It has been speculated that the partial pressure of carbon dioxide (pCO2) in shelf waters may lag the rise in atmospheric CO2. Our analysis employing a narrow definition of the continental shelf corresponding to the 200 m isobaths and winter-only data provides decadal trends in ΔpCO2, i.e., dΔpCO2/dt values, for 825 cells with an average length of our time series of 18 years.
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