Global high-resolution monthly p CO 2 climatology for the coastal ocean derived from neural network interpolation

In spite of the recent strong increase in the number of measurements of the partial pressure of CO 2 in the surface ocean ( p CO 2 ), the air–sea CO 2 balance of the continental shelf seas remains poorly quantified. This is a consequence of these regions remaining strongly under-sampled in both time...

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Bibliographic Details
Published in:Biogeosciences
Main Authors: G. G. Laruelle, P. Landschützer, N. Gruber, J.-L. Tison, B. Delille, P. Regnier
Format: Article in Journal/Newspaper
Language:English
Published: Copernicus Publications 2017
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Online Access:https://doi.org/10.5194/bg-14-4545-2017
https://doaj.org/article/bcea6ade62ba42298ed14f7a1a34f40e
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Summary:In spite of the recent strong increase in the number of measurements of the partial pressure of CO 2 in the surface ocean ( p CO 2 ), the air–sea CO 2 balance of the continental shelf seas remains poorly quantified. This is a consequence of these regions remaining strongly under-sampled in both time and space and of surface p CO 2 exhibiting much higher temporal and spatial variability in these regions compared to the open ocean. Here, we use a modified version of a two-step artificial neural network method (SOM-FFN; Landschützer et al., 2013) to interpolate the p CO 2 data along the continental margins with a spatial resolution of 0.25° and with monthly resolution from 1998 to 2015. The most important modifications compared to the original SOM-FFN method are (i) the much higher spatial resolution and (ii) the inclusion of sea ice and wind speed as predictors of p CO 2 . The SOM-FFN is first trained with p CO 2 measurements extracted from the SOCATv4 database. Then, the validity of our interpolation, in both space and time, is assessed by comparing the generated p CO 2 field with independent data extracted from the LDVEO2015 database. The new coastal p CO 2 product confirms a previously suggested general meridional trend of the annual mean p CO 2 in all the continental shelves with high values in the tropics and dropping to values beneath those of the atmosphere at higher latitudes. The monthly resolution of our data product permits us to reveal significant differences in the seasonality of p CO 2 across the ocean basins. The shelves of the western and northern Pacific, as well as the shelves in the temperate northern Atlantic, display particularly pronounced seasonal variations in p CO 2, while the shelves in the southeastern Atlantic and in the southern Pacific reveal a much smaller seasonality. The calculation of temperature normalized p CO 2 for several latitudes in different oceanic basins confirms that the seasonality in shelf p CO 2 cannot solely be explained by temperature-induced changes in solubility ...