Ocean Transport and Eddy Energy

Ocean mesoscale eddies are energetic motions with lateral scales of tens to hundreds of kilometers. These eddies can significantly impact the transport of heat, freshwater, carbon, and nutrients throughout the oceans, and play an essential role in shaping the ocean’s strongest mean currents and their variability. Energy exchanged between the ocean and atmosphere, and across reservoirs and scales in the ocean controls the impact of eddies on the circulation and transport, with most of the ocean kinetic energy contained in the mesoscale range. Mesoscale eddies are, at best, partially resolved in ocean climate models, and most of their momentum and tracer transport must be parameterized. Imperfections in these parameterizations lead to biases in modern climate models, including incorrect rates of exchange of heat and carbon with the atmosphere, errors in the position and strength of the ocean’s strongest current systems, and incorrect stratification at high latitudes, among other things. Extant parameterizations fail to fully account for the exchanges of mesoscale energy with different scales, or conversions between eddy kinetic and potential energy reservoirs. Recent advances from theory, process studies and longer-term observational records of ocean energetics can now be leveraged to improve the current generation of climate models. Our Climate Process Team (CPT) proposes to vet, improve, and unify new advances in energy-, flow- and scale-aware eddy parameterizations in process studies and global models; constrain parameters and parameterized fluxes through a synthesis of up-to-date observations of ocean energetics and transport; and implement and assess schemes within IPCC-class models at NCAR, GFDL, and LANL. Modernized, energetically-consistent mesoscale eddy parameterizations are expected to significantly reduce model biases in ocean currents, stratification, and transport.
Relevance to the CPT call & NOAA: The goals of our project are directly relevant to the CPT call in that they will provide improved representation of the ocean eddies and their role in the ocean energy cycle in climate models by combining recent advances in theory and observations. The CPT will focus on energy-related diagnostics of ocean eddies in order to constrain ocean eddy parameterization. The improvement in ocean and coupled model fidelity via the proper representation of eddy energy cycles is expected to lead to improvement of some of the most stubborn biases in climate models, primarily the strength and position of strong currents, and the ocean’s stratification. Our team includes three leading global coupled modeling centers (including NOAA’s GFDL) and will implement our parameterization within IPCC-class models. Our goals, results and methodology directly align with NOAA’s long-term goals and CPO program mission, which includes improving “understanding […] and prediction of climate and its impacts”.