A thermal acid calcification cause for seasonal oscillations in the increasing Keeling curve

Abstract

Why do atmospheric carbon dioxide levels rise and fall seasonally measured on Mauna Loa? This study explores the thermal acid-calcification (TAC) hypothesis, suggesting that seasonal temperature shifts in surface seawater trigger acid pH-driven CO2 emissions caused by calcification. Using oceanographic data, we modeled how temperature affects dissolved inorganic carbon including CO2, bicarbonate, and carbonate. Our findings reveal that warming waters absorb atmospheric CO2 by promoting calcium carbonate formation, acidifying seawater and boosting CO2 release to the atmosphere in late autumn and winter, when atmospheric CO2 becomes highest. The model predicts a net annual CO2 rise of 2 ppmv, driven by calcification rather than land-based processes. Seasonal pH swings of 0.04 units corroborate this mechanism. The TAC hypothesis indicates that continued ocean warming, not just fossil fuels, contribute to rising CO2 levels, calling for deeper investigation into marine carbon dynamics.