CIRCULATION VARIABILITY AND PHYSICAL FORCING IN EDISTO INLET (FJORD), ANTARCTICA
Edisto Inlet is a narrow, NNE–SSW elongated fjord (16 km long, 4 km wide) on the northern Victoria Land coast, western Ross Sea, Antarctica. Glacially carved, it deepens landward in a step-like profile to about 670 m, while a 400-m-deep sill separates it from the Ross Sea. It preserves a Holocene sedimentary record shaped by bottom currents and sea-ice processes, yet its present-day circulation has not been characterized through continuous observations. This study analyzes the mechanisms driving circulation and thermohaline variability using mooring data collected between 2022 and 2025 within the LASAGNE project, funded by the Italian National Antarctic Research Program (PNRA) and managed by the Istituto Nazionale di Oceanografia e di Geofisica Sperimentale (OGS) and the Istituto di Scienze Polari (CNR-ISP), Italy. Observations are interpreted alongside atmospheric reanalysis and regional tidal-model output. The mooring, deployed in approximately 460 m of water, resolved currents in the upper ~200 m, vertical thermal structure across the lower ~200 m, and hydrographic variability at mid-depth (233 m).
The record-mean current is weak (approximately 0.019 m s⁻¹) relative to instantaneous currents, which occasionally exceed 0.30 m s⁻¹, and has limited persistence. The mean vector points consistently northeastward and remains vertically coherent throughout the upper layer. The dominant velocity variance follows a near-meridional, bidirectional axis aligned with the basin orientation, consistent with bathymetric steering. The flow is influenced by predominantly diurnal astronomical tides and is not vertically uniform: its intensity and variability decrease downward, indicating that the response is not purely barotropic.
In austral summer, atmospheric warming and reduced sea-ice cover coincide with renewed stratification and intensified upper-layer diurnal energy; at 233 m, salinity reaches a maximum after increasing for several months. In autumn, the response remains high, while salinity and density at 233 m decrease and dissolved oxygen increases, consistent with episodic renewal or ventilation during sea-ice formation. In winter, the air cools, landfast ice covers the surface, and the kinetic response declines markedly without disappearing, while the harmonic pressure tide remains present. Seasonality affects the velocity response rather than the astronomical forcing. This low-variability interval coincides with a homogeneous water column, gradual salinity increase, oxygen decline, and near-freezing conditions at 233 m, consistent with prolonged retention. The salinity increase continues through spring into the following summer.
The two annual cycles show similar salinity increases, but their fitted maxima differ by more than two months and the periods of gradual increase differ in duration: what repeats is the magnitude, not the timing or duration. The fjord alternates between prolonged salinification and oxygen decline and shorter freshening and reoxygenation events, whose timing is associated with surface and sea-ice conditions rather than a fixed calendar date. Although geographically limited, Antarctic fjords are localized environments where the ocean, sea ice, and marine-terminating glaciers interact, and their sills can modulate exchange with the adjacent ocean. Understanding their circulation is important for interpreting sedimentary records and responses to environmental change.