Carbon Sinks and Variations of p CO 2 in the Southern Ocean From 1998 to 2018 Based on a Deep Learning Approach

• Published in: IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing
• Main Authors: Yanjun Wang, Xiaofeng Li, Jinming Song, Xuegang Li, Guorong Zhong, Bin Zhang
• Format: Article in Journal/Newspaper
• Language: English
• Published: IEEE 2021
• Subjects: Carbon sink; feedforward neural network (FFNN); machine learning; <named-content xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:ali="http://www.niso.org/schemas/ali/1.0/" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" content-type="math" xlink:type="simple"> $p\text{CO}_2$ </named-content>; Southern Ocean; Ocean engineering; TC1501-1800; Geophysics. Cosmic physics; QC801-809
• Online Access: https://doi.org/10.1109/JSTARS.2021.3066552; https://doaj.org/article/dd59d4e24ee04f87b6b70d1238266dbd

The Southern Ocean comprises 25&#x0025; of the global ocean surface area, accounts for nearly half of the total carbon sink of the global oceans, and is a place that significantly reduces the impacts of anthropogenic CO 2 emissions. Due to the sparsity of observational data, the changes in Southern Ocean carbon sinks over time remain uncertain. In this study, we integrated correlation analysis and a feedforward neural network to improve the accuracy of carbon flux estimations in the Southern Ocean. Based on observation data from 1998&#x2013;2018, we reconstructed the Southern Ocean&#x0027;s pCO 2 grid data during this period. The root-mean-square error obtained by fitting the observation data was 8.86 &#x03BC;atm, indicating that the results were better than those of the two primary statistically based models in the Surface Ocean p CO 2 mapping intercomparison. The results also showed that the Southern Ocean&#x0027;s capacity to act as a carbon sink has gradually increased since 2000; it reduced during 2010&#x2013;2013 but increased significantly after that. The Southern Ocean&#x0027;s seasonality is characterized by minimum carbon uptake in winter due to increased upwelling; this is followed by a rapid increase toward maximum uptake in summer, which is mainly biologically driven. There is an apparent double-ring structure in the Southern Ocean, as noted in other studies. This study confirms that the inner ring (50&#x2013;70&#x00B0;S) is a carbon source area gradually transforming into a carbon sink, while the outer ring (35&#x2013;50&#x00B0;S) continues to serve as a carbon sink.