# Warm rings in mesoscale eddies in a cold straining ocean

## TL;DR

Ocean eddies in the Lofoten Basin transport heat upward, creating warm rings and contributing to heat loss from Atlantic Water.

## Contribution

The study identifies submesoscale ageostrophic motions at eddy edges as a key mechanism for vertical heat transport in the Lofoten Basin.

## Key findings

- Submesoscale motions along mesoscale eddy edges transport heat upward, increasing sea surface temperature by ~0.4 °C.
- These motions form 'warm ring' structures in both cyclones and anticyclones.
- Submesoscale heat transport is a primary mechanism for heat loss from Atlantic Water in the Lofoten Basin.

## Abstract

The warm and saline Atlantic Water has long been recognized as being subjected to substantial heat loss during its transit towards the polar regions. In particular, the Lofoten Basin, a subpolar sea with energetic eddy activity and strong air-sea interactions, plays a crucial role in the transformation of Atlantic Water. Vertical heat transport at submesoscales (0.1-10 km) in the Lofoten Basin is potentially a key link in the heat transfer to the atmosphere. Here, based on multi-year Seaglider observations augmented by satellite altimeters, radiometers, and high-resolution numerical model results, we evaluate the oceanic vertical heat transport in the Lofoten Basin and demonstrate how geostrophic strain enhances heat transport. The enhancement is found to be associated with submesoscale ageostrophic motions along the mesoscale eddy edges, occurring on spatial scales smaller than 10 km and below the mixed layer depth. These strain-induced submesoscale vertical motions transport heat from the ocean interior to the surface, leading to a 0.4 °C increase in sea surface temperature and the formation of “warm ring” structures in both cyclones and anticyclones. The dominant role of submesoscale heat transport likely represents the primary mechanism for substantial heat loss from Atlantic Water in the Lofoten Basin.

The authors use data from underwater gliders, satellites and numerical simulations and show that submesoscale motions at ocean eddy edges pump heat upward, forming “warm rings” and a ~ 0.4 °C warming in the Lofoten Basin—a key pathway for Atlantic water heat loss.