Variations in the summer oceanic p CO 2 and carbon sink in Prydz Bay using the self-organizing map analysis approach

Abstract. This study applies a neural network technique to produce maps of oceanic surface p CO 2 in Prydz Bay in the Southern Ocean on a weekly 0.1 ∘ longitude  ×  0.1 ∘ latitude grid based on in situ measurements obtained during the 31st CHINARE cruise from February to early March 2015. This study area was divided into three regions, namely, the “open-ocean” region, “sea-ice” region and “shelf” region. The distribution of oceanic p CO 2 was mainly affected by physical processes in the open-ocean region, where mixing and upwelling were the main controls. In the sea-ice region, oceanic p CO 2 changed sharply due to the strong change in seasonal ice. In the shelf region, biological factors were the main control. The weekly oceanic p CO 2 was estimated using a self-organizing map (SOM) with four proxy parameters (sea surface temperature, chlorophyll  a concentration, mixed Layer Depth and sea surface salinity) to overcome the complex relationship between the biogeochemical and physical conditions in the Prydz Bay region. The reconstructed oceanic p CO 2 data coincide well with the in situ p CO 2 data from SOCAT, with a root mean square error of 22.14  µ atm. Prydz Bay was mainly a strong CO 2 sink in February 2015, with a monthly averaged uptake of 23.57±6.36  TgC. The oceanic CO 2 sink is pronounced in the shelf region due to its low oceanic p CO 2 values and peak biological production.