To date, ocean eddies have been difficult to research due to their small size of a few kilometers and the limited availability of proper satellite data. A new study, led by Nathan Beech of the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI), shows how eddies could develop in the 21st century. For this, the researchers carried out simulations at AWI for the international climate model comparison project CMIP6, which the Intergovernmental Panel on Climate Change (IPCC) also uses for its reports. CMIP6 data enable forecasts of how climate changes, for example higher global temperatures due to the increase in greenhouse gases, will develop in the future.
In order to simulate how ocean eddies might evolve in a world that is becoming warmer due to anthropogenic climate change, the research team used a novel approach developed at AWI: In eddy-rich regions, AWI's CMIP6 model uses a comparatively high spatial resolution for a climate model, while retaining coarser resolution in other regions. This novel approach allowed researchers to analyze how the relatively small eddies – the ocean's weather – will evolve over the 21st century in a warming world. “Certainly, this is the first such assessment with a dataset so comprehensive,” notes Nathan Beech. “The intensity and clarity of the projected changes in eddy activity were remarkable.”
The model simulations reveal pronounced long-term alterations to ocean eddy activity, including a poleward shift that follows the movement of ocean currents. “We project eddy activity in the Kuroshio Current, Brazil and Malvinas Currents, and Antarctic Circumpolar Current to increase significantly, and in the Gulf Stream, we project a strong decline,” says Prof. Dr. Thomas Jung, head of the Climate Dynamics section and Vice Director of AWI. The decline of Gulf Stream eddy activity reflects an anticipated decline in Atlantic meridional overturning circulation, which significantly contributes to the flow of warm saltwater from the Tropical Atlantic towards Northern Europe. The changes illustrated by the study demonstrate that anthropogenic impacts on climate go well beyond temperature rise and can alter diverse ocean properties.
Nathan Beech, Thomas Rackow, Tido Semmler, Sergey Danilov, Qiang Wang, und Thomas Jung. Long-term Evolution of Ocean Eddy Activity in a Warming World (2022). DOI: https://doi.org/10.1038/s41558-022-01478-3.
Semmler, T., Danilov, S., Gierz, P., Goessling, H. F., Hegewald, J., Hinrichs, C., Koldunov, N., Khosravi, N., Mu, L., Rackow, T., Sein, D.V., Sidorenko, D., Wang, Q., und Jung, T. (2020). Simulations for CMIP6 With the AWI Climate Model AWI-CM-1-1. Journal of Advances in Modeling Earth Systems, 12, e2019MS002009. https://doi.org/10.1029/2019MS002009