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

TL;DR

This paper proposes the thermal acid-calcification hypothesis, suggesting that seasonal ocean temperature changes influence CO2 emissions through calcification, contributing to the Keeling curve's oscillations and indicating ocean warming impacts on atmospheric CO2.

Contribution

It introduces a novel mechanism linking ocean temperature shifts to CO2 emissions via calcification, expanding understanding of seasonal CO2 variations.

Findings

Warming waters promote calcium carbonate formation, increasing CO2 release.

Seasonal pH swings of 0.04 units support the TAC mechanism.

Model predicts a 2 ppmv annual CO2 rise driven by calcification.

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.