Analyzing Factors that Influence the Irreversibility of Ocean Export Production

Ocean export production is the backbone of marine ecosystems, and it is crucial to carefully track their changes under the global warming. This study analyzes the irreversibility of ocean export production and the major factors affecting it by performing CO2 reduction experiments with the LOVECLIM, a medium complexity model. After a 1,500-year spin-up to the present-day CO2 level of 367 ppm, it was increased by 1% per year for 140 years and then decreased again for the same period. The present-day CO2 level was then held for 5,000 years. Ocean export production decreased at low latitudes and increased at mid- and high-latitudes, with the largest changes occurring in the equatorial and Antarctic Circumpolar Current regions. Nutrient concentrations in the euphotic zone decreased as the global ocean circulation weakened and ocean stratification intensified. Nevertheless, ocean export production has increased at high latitudes because of deepen mixed layer depth due to strong westerlies of both hemisphere and the creation of sea ice melting, which has led to the widen euphotic zones, high nutrient concentrations despite decreased nutrient concentrations, and increased ocean temperatures. The irreversibility of ocean export production with CO2 concentration is seen in 84.3% of the world's oceans. It will take more than 1,300 years for global ocean export production to return to its initial concentration after a CO2 reduction experiment, so it will need to be carefully monitored over a long period of time.

 

Acknowledgements: This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Government of Korea (MSIT) (No. 2022R1A2C1008858) and Global - Learning & Academic research institution for Master’s·PhD students, and Postdocs (LAMP) Program of the National Research Foundation of Korea (NRF) grant funded by the Ministry of Education (No. RS-2024-00443714).