The oceanic environment beneath the northwest Ronne Ice Shelf, Antarctica

Oceanographic data have been obtained from beneath the Ronne Ice Shelf at a site on the southeastern side of a sea-floor trough, the Ronne Depression. The data consist of 5 d of conductivity temperature depth (CTD) profiling and a long-term temperature record from a thermistor cable. The water column was found to be composed of two layers: a cold buoyant layer of lce Shelf Water (ISW) overlying a layer of unmodified Western Shelf Water (WSW). A change in the water column was observed on the last day of profiling, the WSW layer thinning, a cold intrusion appearing directly above the WSW and the ISW becoming colder. In addition, on three profiles the ISW cooled further and increased in salinity, becoming apparently statically unstable. The temperature record from the thermistor cable confirms that the ISW layer occasionally becomes colder. with greater variation in temperature than seen on the CTD profiles. These low temperatures and high salinities arc interpreted as indicating that water containing ice crystals in suspension has been advected beneath the site.