Changes in water mass distribution and horizontal circulation due toseasonal influences on the Ross Sea continental shelf are investigatedusing a circumpolar numerical model. An anticyclonic circulation cellthat extends across the open shelf and into the ice shelf cavity is formedin the model. The increased east-west density gradient caused by the strongbrine release in the Ross Sea polynya in winter results in an intensificationof this anticyclonic cell from 1.5 Sv to 2.5 Sv. This supports the concept ofa thermohaline-driven horizontal circulation on the Ross Sea continental shelf. In addition to a temporal change in the circulation strength, the changes in the density structure lead to complex temporal and spatial variability in the circulation around Ross Island. Due to seasonal variation in circulation strength and water temperatures, the area averaged basal melt rate of 25 cm/a shows a bimodal seasonal cycle ranging from 20-28 cm/a, with maxima in March and August.