995 / 2024-09-20 00:29:02

Seasonal Variability of Eddy Kinetic Energy at the Eastern Boundary of the Weddell Gyre

Eddy Kinetic Energy,Weddell Gyre,Enderby Plain,EKE Diagnosis

Currents at the northeastern Weddell Gyre (WG) are perturbed and steered southward by the Southwest Indian Ridge (SWIR), forming the eastern boundary of the WG (WGeb) with active eddies. The seasonal variability of the eddy kinetic energy (EKE) at the WGeb is investigated using the altimeter data and data-assimilating model outputs. The EKE is derived from the current velocity perturbation deviating from the climatological monthly mean, and the energy equation is diagnosed to determine the dominant mechanism for the seasonal EKE variation. The eddy-rich WGeb occupies the southern Enderby Plain (sEP) and causes the local high EKE, where the EKE intensity is closely correlated with the seasonal expansion of the WG. From summer to autumn, the WGeb extends eastward and the associated EKE is high, while from winter to spring, the WGeb retreats westward and the associated EKE is suppressed. The EKE diagnosis performed below the surface water layer reveals three dominant processes contributing to the long-term EKE balance: the production of EKE by baroclinic conversion, the consumption of EKE by inverse barotropic conversion and the divergence of the EKE flux induced by pressure work. The seasonal variability of EKE is modulated by the relative changes of these three processes, which are further related to the background WG field. The density and mean flow fields at WGeb change with the seasonal expansion of the gyre, thus influencing the modulations of the above processes on the local EKE field. The findings herein are helpful to deepen our understanding of the current structure at the WGeb, which plays a critical role in connecting the Antarctic open ocean with the coastal region.