Natural ocean alkalinization through erosion of glacial till and weathering at the seafloor

[Geoengineering News]

https://www.nature.com/articles/s43247-025-03009-2

Authors: Florian Scholz, Janine Börker, Christoph Vogt, Jens Hartmann & Klaus Wallmann 

26 November 2025

Abstract

The ocean absorbs about 25% of anthropogenic carbon dioxide emissions, with this uptake regulated by acid-neutralizing anions collectively termed alkalinity. Most seawater alkalinity originates from the weathering of aluminosilicate and carbonate minerals on land, whose dissolved products are transported to the ocean by rivers, a slow process that causes carbon dioxide removal to lag behind emissions. Here we present geochemical evidence showing that fine-grained glacial sediments mobilized by coastal erosion undergo rapid seafloor weathering. While aluminosilicate weathering is largely balanced by secondary clay formation (reverse weathering), carbonate dissolution yields a significant net release of alkalinity to coastal waters. Because more than two-thirds of the global coastline was formerly glaciated, ongoing deglaciation and erosion may enhance alkalinity fluxes, providing a previously unrecognized shortcut in the global carbon cycle. As this enhanced flux is ultimately driven by climate warming, it may act as a negative feedback that helps moderate future increases in atmospheric carbon dioxide.

Source: Communications Earth & Environment