Big whirls have little whirls that feed on their velocity, and little whirls have lesser whirls and so on to viscosity.
Lewis Fry Richardson
For decades, it has been assumed that motions smaller than the mesoscale would decay into turbulence, draining energy from the mean ocean circulation. From limited-area observations and new numerical modelling studies, it is now evident that energy can also transfer to larger scales — the inverse energy cascade —strengthening the circulation and enhancing vertical fluxes, as well as driving mixing.
Four expert teams in physical oceanography, meteorology, biogeochemistry, and biology formed a multidisciplinary synergistic working team to study fine-scale processes across a continuum of scales (1-100 km) and assess their impacts on air-sea exchange, marine biogeochemistry and biodiversity.
Concepts and objectives
The overarching goal of WHIRLS is to improve our understanding of the ocean’s fine-scale dynamics and their role in ocean-atmosphere-biogeochemical interactions.
WHIRLS focuses on the most energetic region of the world ocean, the Agulhas Current System. This system around South Africa is not only unique with respect to its vigorous circulation, intense air-sea heat and carbon uptake and the particularly high-productivity and diversity of the embedded marine ecosystem. It is also an important key region of the global overturning circulation by providing warm and saline Indian Ocean water that passes through the Cape Basin (south-west of Africa) into the Atlantic Meridional Overturning Circulation (AMOC), and thus has an important impact on regional and global climate change.
Researchers are addressing this holistically, via an original and interdisciplinary approach, the continuum of scales, from the submeso- (1–10 km) to the mesoscale (10–100 km), of ocean dynamics and air-sea interactions, as well as their implications for marine biogeochemistry, including the ocean carbon sink, and biodiversity.
There are four working packages: WP1 – Fine-scale processes, WP2 – Climate-critical air-sea fluxes, WP3 – Biogeochemistry and Biome, WP4 – Future ocean and climate models.
WHIRLS is unlocking new knowledge, improving the modeling accounting of these phenomena, and thus augment their predictive skills to:
Observe and model the physical and biogeochemical structure, evolution, and phenomenology of the ocean fine-scale in the upper 1000 m of the water column.
Determine to which degree fine-scale ocean dynamics interact with the atmosphere to drive air-sea exchange of climate-relevant variables, and how they shape ocean productivity and marine ecosystems.
Quantify the role of fine-scale dynamics in the large-scale ocean circulation and the climate-critical cycles of heat, water, and carbon.
Improve future Earth system models by resolving or parameterizing submesoscale dynamics.
Follow live the gliders deployed under the framework of the WP2. Track them on Polar Gliders Obs page.
Principal investigators: Arne Biastoch (Future Ocean and climate models), Sarah Fawcett (Biogeochemistry and biome), Sabrina Speich (Fine-scale processes), Sebastiaan Swart (Climate-critical air-sea fluxes)
Institutes involved in the campaign: Ecole Normale Supérieure, France; GEOMAR, Kiel, Germany; U. Cape Town, South Africa; U. Gothenburg, Sweden
Barabinot, Y., Buckingham, C., Speich, S. and Carton, X., 2026. Analysis of Unforced Symmetric Instability in Mesoscale Eddies Using In Situ Observations. Journal of Physical Oceanography, 56(1), pp.173-190.
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Communications Earth & Environment, 6 (1). Art.Nr. 318 (2025).