Observation system simulation experiments in the Atlantic Ocean for enhanced surface ocean pCO(2) reconstructions

• Published in: Ocean Science
• Main Authors: Denvil-sommer, Anna, Gehlen, Marion, Vrac, Mathieu
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Gesellschaft Mbh 2021
• Subjects: Southern Ocean
• Online Access: https://archimer.ifremer.fr/doc/00755/86724/92197.pdf; https://archimer.ifremer.fr/doc/00755/86724/92198.pdf; https://archimer.ifremer.fr/doc/00755/86724/92199.pdf; https://archimer.ifremer.fr/doc/00755/86724/92200.pdf; https://doi.org/10.5194/os-17-1011-2021; https://archimer.ifremer.fr/doc/00755/86724/

To derive an optimal observation system for surface ocean pCO(2) in the Atlantic Ocean and the Atlantic sector of the Southern Ocean, 11 observation system simulation experiments (OSSEs) were completed. Each OSSE is a feedforward neural network (FFNN) that is based on a different data distribution and provides ocean surface pCO(2) for the period 2008-2010 with a 5d time interval. Based on the geographical and time positions from three observational platforms, volunteering observing ships, Argo floats and OceanSITES moorings, pseudo-observations were constructed using the outputs from an online-coupled physical-biogeochemical global ocean model with 0.25 degrees nominal resolution. The aim of this work was to find an optimal spatial distribution of observations to supplement the widely used Surface Ocean CO2 Atlas (SOCAT) and to improve the accuracy of ocean surface pCO(2) reconstructions. OSSEs showed that the additional data from mooring stations and an improved coverage of the Southern Hemisphere with biogeochemical ARGO floats corresponding to least 25% of the density of active floats (2008-2010) (OSSE 10) would significantly improve the pCO(2) reconstruction and reduce the bias of derived estimates of sea-air CO2 fluxes by 74% compared to ocean model outputs.