Thermohaline structure, sea ice variability, and circulation in Edisto Inlet, western Ross Sea (Antarctica)

Abstract. The oceanographic characteristics of Edisto Inlet, a fjord located along Victoria Land (north-west Ross Sea, Antarctica), are described in detail for the first time using data acquired in February 2023. The summer thermohaline structure of Edisto Inlet appears to be controlled primarily by salinity (range 34.06–34.73) and, to a lesser extent, by temperature (range −1.91 to −1.10 °C). Strong vertical thermohaline gradients, found in the 150–200 m thick upper layer, are generated by the combined influence of air–sea-ice interaction and highly variable seasonal (and annual) sea-ice coverage. Conversely, relatively uniform conditions are found in the intermediate and deep layers, even on interannual basis. The dominant water masses are Antarctic Surface Water and Modified Shelf Water, while Modified Circumpolar Deep Water (mCDW), whose signal appears in laminated sedimentary records, was not clearly detected inside the inlet at the time of the cruise. However, we do not exclude episodic intrusions of mCDW into the fjord, as its signature has been detected in the upper layers bordering the open sea, about 10–15 km from the inlet mouth. We conclude that the monthly, seasonal, and interannual variability of local water masses, including potential mCDW intrusions, can be attributed to contrasting sea-ice conditions, which can modulate lateral exchanges with the Ross Sea by altering surface momentum transfer, freshwater input, and upper-ocean stratification. Circulation within the stratified fjord results from the combined effects of density gradients and local forcing, and to a lesser extent from local tides, which interact with complex seabed morphology under a strongly baroclinic regime. Edisto Inlet, potentially a representative fjord of Victoria Land, appears to be a highly dynamic environment that links sea-ice variability, shelf circulation, and water-mass transformation.