Climate change has continuously moved to the top ranks of the political agenda. However, a number of critical processes driving climate change are poorly understood. A Danish research project now aims to elucidate these key processes for climate regulation in the North Atlantic and Arctic Ocean by refining existing climate models.
Our ability to predict climate changes is limited by our inadequate understanding of how ocean waters circulate and mix, e.g. in the North Atlantic and Arctic Ocean. Despite the importance of these areas for the climate system (see Text Box), they are poorly monitored. A recently launched Danish research project termed “North Atlantic - Arctic coupling in a changing climate: impacts on ocean circulation, carbon cycling and sea-ice (NAACOS)” addresses these existing climate model uncertainties. Fieldwork on research cruises to the Arctic will be complemented by earth observation and modelling on a variety of scales, from process-focused high resolution modelling to global climate modelling.
Fig. 1: The Faroe Bank Channel is one of the few gaps in the Greenland-Scotland Ridge, a major barrier for deep water transport stretching from East Greenland to Iceland and the Faroe Islands, and across to Scotland. (Copyright: E. Paul Oberlander, Woods Hole Oceanographic Institution).
DHI contributes to the project with a study on the mixing and entrainment processes of the dense water transport through the Faroe Bank Channel, a deep trench separating the Faroe Islands from Northern Scotland. “From the project, we expect an improved understanding and quantification of the mixing processes, resulting in a better parameterization of overflow processes in the recognized global climate model, EC-Earth. DHI`s work is supported by the focused development of the MIKE 3 FM-software for modeling deep water plumes and deep sea oceanographic processes at high resolution, and the integration of the results with the large measurement data set available in the Faroe Islands " says Dr. Jacob Tornfeldt Sørensen, DHI's project manager in NAACOS.
“The integration of a small-scale phenomenon into climate models is very challenging. We need research to address the known present gaps of knowledge and uncertainties in existing climate models. Continually, the improved understanding of selected key processes revealed in this project will enter the global climate change community and debate and will result in improved process descriptions and increased reliability of global climate models”, explains Dr. Andre Visser from DTU Aqua, who is the overall coordinating manager of the 4-year project supported by Danish Strategic Research Council.
The Arctic Ocean and the North Atlantic are key areas for understanding the climate on Earth. The northern North Atlantic is one of the few places on Earth where relatively cold, salty waters sink to the abyss, forming the so-called North Atlantic Deep Water and propelling a system of global ocean circulation called the Ocean Conveyor. This conveyor is closely linked to the strength of the Gulf Stream. Changes in this strategic region can lead to widespread abrupt climate changes.
The Faroe Bank Channel is a bottleneck for the flux of dense water from the Arctic into the North Atlantic and a region of strong mixing with fresher seawater from above. Moreover, ocean circulation impacts marine biological productivity mainly by phytoplankton, which determines the oceans` capacity to take up atmospheric CO2 as well as the whole marine food chain and ultimately fishery revenues.
Fig. 2: The North Atlantic off Norway and the Faroe Islands (Credit: NASA image courtesy Jeff Schmaltz, MODIS Land Rapid Response Team at NASA GSFC).