Development of ECCO-downscaled Amundsen-Bellingshausen Sea regional simulation using MITgcm(66j)

Abstract. The Amundsen and Bellingshausen Seas are among the most rapidly changing regions of the Southern Ocean, playing a pivotal role in Antarctic ice‐shelf mass loss and global sea‐level rise. Several ocean models have been developed to investigate these changes, revealing complex interactions among the atmosphere, ocean, sea ice, and ice shelves. However, the diversity of model configurations, parameter choices, and model versions often hampers user-friendliness, limits meaningful intercomparison, and constrains broader multidisciplinary use. Here, we present a regional ocean model configuration of the Amundsen and Bellingshausen Seas with a horizontal resolution of 2.2–3.9 km based on MITgcm, downscaled from the global ECCO-LLC270 ocean state estimate, and further optimized using regional observations. We conduct extensive model evaluation and demonstrate its applications through multiple examples and previously published analyses, with the goal of providing model configuration and their outputs – achieving good model-data agreement – to the broad scientific community. The model reproduces key hydrographic features of the region, including realistic temperature and salinity profiles and water mass distributions that closely align with local CTD and mooring observations. Simulated sea-ice concentration and extent are consistent with satellite observations, capturing the observed seasonal cycle and spatial variability. Ice-shelf basal melt rates fall within the range of available satellite and in situ estimates. The configuration also includes passive tracers for surface water, ice-shelf meltwater, and Circumpolar Deep Water, as well as Lagrangian particle-tracking capabilities that facilitate studies of water-mass transformation and tracer pathways. By providing open access to the model code, configuration, diagnostics, tracer outputs, and sensitivity experiments, we aim to support data interpretation, hypothesis testing, and observational planning across the broad scientific community.