Ocean energetics in an ocean reanalysis

The near-surface circulation of the Arctic Ocean (AO) affects freshwater flux, ocean mixing, nutrient transport, and equator-to-pole energy exchange. In the Arctic, climate change impacts the near-surface fluid dynamics across scales, with notable effects like sea ice loss, thinning, and changes to the weather, such as changes to the strength and frequency of cyclones. However, a clear understanding of climate change on ice-covered Arctic circulation remains limited. Eddy kinetic energy (EKE) is a key indicator of AO variability. In this talk, we present the first long-term assessment of seasonal and regional EKE patterns using version 4 of Estimating the Circulation and Climate of the Ocean (ECCOv4r4). ECCOv4r4 is a dynamically consistent ocean state estimate synthesizing a vast number of oceanographic observations using the MITgcm model at coarse but eddy-permitting resolution. Results show strong upper-ocean EKE in the Eurasian Basin and Nordic Seas during winter (Dec-Feb), decreasing with summer melt (Jul-Sep). Freshwater flux reduces summer stratification in the Beaufort and Kara Seas, while winter ice retreat alters it. Preliminary findings indicate increased ocean energetics across the Arctic. Moving forward, we will examine how modeled ice drift speed biases influence the representation of upper-ocean air-ice momentum transfer.