Spinning ice floes reveal intensification of mesoscale eddies in the western Arctic Ocean

Abstract

Under-ice eddies are prevalent in the major circulation system in the western Arctic Ocean, the Beaufort Gyre. Theoretical studies hypothesize that the eddy-driven overturning and the ice-ocean drag are crucial mechanisms of the gyre equilibration in response to atmospheric winds. However, due to severe weather conditions and limitations of remote sensing instruments, there are only sparse eddy observations in the ice-covered Arctic Ocean. Hence, the evolution of the under-ice eddy field, its impact on the gyre variability, and their mutual response to the ongoing Arctic warming remain uncertain. Here, we infer the characteristics of the under-ice eddy field by establishing its tight connection to the angular velocities of isolated spinning sea ice floes in marginal ice zones. Using over two decades of satellite observations of marginal ice zones in the western Arctic Ocean, we identified and tracked thousands of floes and used idealized eddy modeling to infer the interannual evolution of the eddy energetics underneath the ice. We find that the eddy field is strongly correlated to the strength of the Beaufort Gyre on interannual timescales, which provides the major observational evidence consistent with the hypothesis of the gyre equilibration by eddies. The inferred trends over the past two decades signify that the gyre and its eddy field have been intensifying as the sea ice cover has been declining. Our results imply that with continuing sea ice decline, the eddy field and the Beaufort Gyre will keep intensifying and leading to enhanced transport of freshwater and biogeochemical tracers.

Bridging Gaps in the Climate Observation Network: A Physics-based Nonlinear Dynamical Interpolation of Lagrangian Ice Floe Measurements via Data-Driven Stochastic Models

“…The dynamics of a single ice floe is described as follows [21,44]. Let X ice = (x ice , y ice ) be the centroid of the floe and Ω its the angular displacement about the centroid.…”

“…This data set was the first of its kind in that it provides not only the Lagrangian trajectories but also the floe sizes and geometries together with the angular displacements of floes in the MIZ extending throughout the 21 st century. Given the demonstrated link between floe rotation rates and the characteristics of the underlying small-scale ocean eddies in the Beaufort Gyre MIZ, these sea ice floe observations have proved to be essential for recovering the state of the underlying turbulent ocean field, providing a unique insight into the multi-scale nature of the ocean [21].…”

“…See Figure 1 for an example. A commonly used approach to filling these gaps is to interpolate between the available observations through linear interpolation [21]. Such an approach ignores the MIZ dynamics, leading to trajectories lacking many physical properties.…”

Bridging Gaps in the Climate Observation Network: A Physics‐Based Nonlinear Dynamical Interpolation of Lagrangian Ice Floe Measurements via Data‐Driven Stochastic Models

“…This data set was the first of its kind in that it provides not only the Lagrangian trajectories but also the floe sizes and geometries together with the angular displacements of floes in the MIZ extending throughout the 21st century. Given the demonstrated link between floe rotation rates and the characteristics of the underlying small‐scale ocean eddies in the Beaufort Gyre MIZ, these sea ice floe observations have proved to be essential for recovering the state of the underlying turbulent ocean field, providing a unique insight into the multi‐scale nature of the ocean (Manucharyan et al., 2022).…”

“…See Figure 1 for an example. A commonly used approach to filling these gaps is to interpolate between the available observations through linear interpolation (Manucharyan et al., 2022). These trajectories (and their curvature) are used to characterize ocean circulation/eddy behavior.…”