20 January 2026 / Kiel. The renewal of deep waters in the North Atlantic has slowed markedly over the past three decades. This is shown by a new study from the GEOMAR Helmholtz Centre for Ocean Research Kiel, now published in the scientific journal Nature Communications. The study demonstrates that the “age” of water masses in the North Atlantic has been increasing continuously since the 1990s – an indication of a weakening of the Atlantic circulation system. The results suggest that this trend cannot be explained by natural variability alone, but instead represents a signal of anthropogenic climate change. A slowdown in ocean circulation has far-reaching consequences for climate regulation as well as for the ocean’s oxygen supply and its uptake of carbon.