Characterization of sea ice kinematics over oceanic eddies

TL;DR

This paper investigates how sea ice floe movements can be used to infer ocean eddy vorticity in the Arctic, combining numerical models and analytical methods to establish a relationship between floe rotation and underlying ocean turbulence.

Contribution

It introduces a novel approach to estimate ocean eddy vorticity from sea ice floe observations using idealized vortex models and turbulence analysis, advancing Arctic oceanography.

Findings

Floe rotation rates relate to ocean vorticity, depending on floe and eddy size.

As floe size exceeds eddy size, the rotation-vorticity relationship deviates from half.

Ice floe thickness, winds, and collisions influence floe rotation dynamics.

Abstract

Eddies within the meso/submeso-scale range are prevalent throughout the Arctic Ocean, playing a pivotal role in regulating freshwater budget, heat transfer, and sea ice transport. While observations have suggested a strong connection between the dynamics of sea ice and the underlying turbulent flows, quantifying this relationship remains an ambitious task due to the challenges of acquiring concurrent sea ice and ocean measurements. Recently, an innovative study using a unique algorithm to track sea ice floes showed that ice floes can be used as vorticity meters of the ocean. Here, we present a numerical and analytical evaluation of this result by estimating the kinematic link between free-drifting ice floes and underlying ocean eddies using idealized vortex models. These analyses are expanded to explore local eddies in quasi-geostrophic turbulence, providing a more realistic representation of eddies in the Arctic Ocean. We find that in both flow fields, the relationship between floe rotation rates and ocean vorticity depends on the relative size of the ice floe to the eddy. As the floe size approaches and exceeds the eddy size, the floe rotation rates depart from half of the ocean vorticity. Finally, the effects of ice floe thickness, atmospheric winds, and floe-floe collisions on floe rotations are investigated. The derived relations and floe statistics set the foundation for leveraging remote sensing observations of floe motions to characterize eddy vorticity at small to moderate scales. This innovative approach opens new possibilities for quantifying Arctic Ocean eddy characteristics, providing valuable inputs for more accurate climate projections.