Water Mass Characteristics During the ROSSMIZE Cruise (Western Sector of the Ross Sea, November-December 1994)

Abstract

From 14 November to 27 December 1994, the multidisciplinary ROSSMIZE (Ross Sea Marginal Ice Zone Ecology) cruise was carried out in the western sector of the Ross Sea (Antarctica) on board the M/N Italica. This chapter describes the hydrological conditions encountered on the basis of 78 CTD vertical profiles acquired during the cruise. Most of the CTD casts were localized along a transect centred on 175°E, spanning about 520 km from 76°30′S to 71°50′S; casts were generally distanced by 10 nautical miles (18.5 km). At some locations, CTD casts were repeated up to five times during the sampling period. In this area, the period of the cruise corresponded to late austral spring-beginning of summer. Ross Sea polynya was expanding, and a marginal ice zone was encountered on the Pennell Bank. Interestingly, an intense Warm Core (WMCO) was present below it. WMCO occupied also the northern bank crossed by the transect. Lower Circumpolar Deep Water (LCDW) intruding on the continental shelf and its mixing with surface waters in correspondence with the slope front originating WMCO were also noted. Below the LCDW, a bottom boundary layer of Low Salinity Bottom Water (LSBW) was detected; it could have originated from Low Salinity Shelf Water (LSSW) outflowing from the northern end of the Joides Basin. On the two depressions crossed by the transect, both belonging to the Joides Basin, High Salinity Shelf Water (HSSW) formed a dome. HSSW occupied almost the whole water column, with an evident upwelling, in the southern depression, while in the northern one HSSW was present mainly as a bottom layer, with LSSW over it.