Meeting Documents

Role of the Atlantic Meridional Overturning Circulation Variability in North Atlantic Ocean Carbon Storage and its Drivers

Abstract

The Atlantic Meridional Overturning Circulation (AMOC) plays a crucial role in the variability of the ocean carbon sink through physical, biogeochemical, and ecosystem interactions. Ocean circulation influences carbon storage both directly by transporting and mixing Dissolved Inorganic Carbon (DIC) and indirectly through changes in surface temperature, salinity, and alkalinity that affect surface carbon chemistry, as well as nutrient fluxes that influence net biological carbon fixation. Estimates of ocean carbon uptake from global-ocean biogeochemical models and observationally-based products data differ significantly, yet there is relatively good overall agreement among models. However, larger regional differences introduce uncertainty in the ocean’s carbon budget and in identifying the causes of its variability.

We present results from ECCO-Darwin, a data-assimilating ocean biogeochemistry and ecosystem state estimate, that examines the relationship between AMOC and North Atlantic carbon storage and its fluctuations over the past 30 years. The leading mechanisms are identified using budget-based carbon partitioning analyses to mechanistically separate the effects of transport by advection and mixing, solubility, biological activity, and air-sea gas exchange.

Plain-language Summary: The Atlantic Meridional Overturning Circulation (AMOC) is important for how much carbon the North Atlantic, and the Global Ocean, can store. It affects carbon levels in two main ways: directly by moving and mixing carbon in the water, and indirectly by changing temperatures and nutrients that influence how carbon is absorbed by marine life. While global models generally agree on carbon uptake, there are significant regional differences that create uncertainty. This research uses a model that absorbs physical and biogeochemical observations, called ECCO-Darwin, to study the AMOC’s impact on carbon storage over the last 30 years, identifying the main factors that cause changes in carbon levels.