Long-term evolution of eddying oceans in a warming world

Abstract

<p>Mesoscale ocean eddies impact atmosphere-ocean gas exchange, carbon sequestration, and nutrient transport. Studies have attempted to identify trends in eddy activity using satellite altimetry; however, it is difficult to distinguish between robust trends and natural variability within the short observational record. Using a novel climate model that exploits the variable-resolution capabilities of unstructured meshes in the ocean component to concentrate computational resources in eddy-rich regions, we assess global mesoscale eddies and their long-term response to climate change at an unprecedented scale. The modeled results challenge the significance of some trends identified by observational studies, as well as the effectiveness of linear trends in assessing eddy kinetic energy (EKE) change. Some anticipated changes to ocean circulation, such as a poleward shift of major ocean currents and eddy saturation in the Southern Ocean, are reinforced by the modeled EKE changes. Several novel insights regarding the evolution of EKE in a warming world are also proposed, such as a decrease of EKE along the Gulf Stream in unison with weakening Atlantic meridional overturning circulation (AMOC); increasing Agulhas leakage; and accelerating, non-linear increases of EKE in the basins of the Kuroshio Current, Brazil and Malvinas Currents, and the Antarctic Circumpolar Current (ACC).</p>

The multi-scale response of the eddy kinetic energy and transport to strengthened westerlies in an idealized Antarctic Circumpolar Current

“…Focusing on the strengthened winds, both satellite observations and eddy-resolving models indicated a positive trend in Southern Ocean eddy kinetic energy (EKE) under the historical strengthening of the westerly winds (Morrow et al, 2010;Patara et al, 2016). A similar trend is evident even in global warming simulations (Beech et al, 2022).…”

Characteristics and Trends of the Campbell Plateau Meander in the Southern Ocean: 1993-2020

“…The section upstream from and around the Campbell Plateau is strongly constrained by the local topography, with a low eddy kinetic energy regime (Daniault & Ménard, 1985;Gille et al, 2000;Morrow et al, 2010), making it a true standing meander, however, the section downstream from the Plateau is not constrained by topographic features, and is in a highly dynamical area of the Southern Ocean, with high eddy kinetic energy activity (Gille et al, 2000;Morrow et al, 2010;Y. Zhang et al, 2021;Beech et al, 2022).…”

“…Region, which is one of the eddy kinetic energy hotspots in the Southern Ocean (Morrow et al, 2010;Y. Zhang et al, 2021;Beech et al, 2022). It is also worth noting that the increased speed or shear in the front that forms the meander could be either local impacts or global impacts manifesting locally, but it is difficult to disentangle those two mechanisms.…”

Recent Developments in Oxygen Minimum Zones Biogeochemistry

“…Finally, changes that affect O 2 gradients without changing the regional O 2 inventory can also lead to changes in the volume and intensity of the Arabian Sea OMZ. For instance, a change in mixing driven by changes in eddy activity (e.g., Beech et al, 2022) in the region could alter the intensity of the OMZ Levy et al, 2022). Furthermore, changes in the remineralization depth associated with changes in the particle sinking speed or remineralization rate (for instance due to warming or changes in the community composition) can also affect the depth and intensity of the Arabian Sea OMZ as has been demonstrated by previous studies (e.g., Al Azhar et al, 2016) (Table 1).…”