Oceanography

Global warming

Geology

Climate change

Sea ice

Arctic sea ice decline

Arctic geoengineering

Arctic ice pack

Antarctic sea ice

Organic chemistry

Chemistry

Ecology

Seawater

Ocean acidification

Mineralogy

Aragonite

Calcite

Canada Basin

Environmental science

Alkalinity

Climatology

Arctic

Carbon dioxide

Biology

Effects of global warming on oceans

Science

The Arctic Ocean has experienced rapid warming and sea ice loss in recent decades, becoming the first open-ocean basin to experience widespread aragonite undersaturation [saturation state of aragonite (Ωarag) < 1]. However, its trend toward long-term ocean acidification and the underlying mechanisms remain undocumented. Here, we report rapid acidification there, with rates three to four times higher than in other ocean basins, and attribute it to changing sea ice coverage on a decadal time scale. Sea ice melt exposes seawater to the atmosphere and promotes rapid uptake of atmospheric carbon dioxide, lowering its alkalinity and buffer capacity and thus leading to sharp declines in pH and Ωarag. We predict a further decrease in pH, particularly at higher latitudes where sea ice retreat is active, whereas Arctic warming may counteract decreases in Ωarag in the future.

Climate change drives rapid decadal acidification in the Arctic Ocean from 1994 to 2020