At the XMAS-IV meeting in 2019, I presented early results from a pioneering global kilometer-scale simulation carried out by the Estimating the Circulation and Climate of the Ocean (ECCO) consortium and based on a 1/48° configuration of the Massachusetts Institute of Technology general circulation model (MITgcm)—the ECCO LLC4320. A key characteristic of LLC4320 is the inclusion of tidal forcing, which enables the generation of internal tides and the admission of an internal gravity wave spectrum. This simulation has supported over 240 publications on topics including air-sea interactions, surface gravity waves, internal waves, ocean mesoscale and submesoscale variability, vertical transports, sea-ice, bathymetry-steered currents, biological dispersion, machine learning, and satellite mission design.

Today, eight years later, I will introduce two new km-scale simulations that address several shortcomings of the classic LLC4320 simulation and are optimized for global modeling during the Surface Water and Ocean Topography (SWOT) era. First, the ECCO LLC4320v2 simulation is a 1/48° global-ocean-ice-river-tides simulation integrated during the active SWOT period. It features 173 vertical levels (instead of 90) and uses an updated bathymetry (GEBCO 2025) that incorporates SWOT observations. It also includes ice shelf cavities, hourly ERA5 atmospheric forcing, daily river discharge and temperature forcing, and much more accurate tidal forcing that includes online computation of self-attraction and loading.

Second, I will highlight a 14-month coupled atmosphere-ocean simulation that couples a 7-km cloud-admitting NASA Goddard Earth Observing System (GEOS) atmospheric configuration with a 2–4-km ECCO ocean configuration—the GEOS/ECCO C1440-LLC2160 simulation. This coupled simulation enables a more realistic representation of air-sea interactions than is possible with forced ocean simulations. Together, these two turnkey simulations lower community barriers, driving synergistic analysis with SWOT observations, oceanographic field campaigns, geostationary satellites, machine learning parameterizations, and studies of vertical transports, mixing, and air-sea exchange processes.