<jats:p>Changes in water mass distribution and horizontal circulation due to seasonal influences on the Ross Sea continental shelf are investigated using a circumpolar numerical model. An anticyclonic circulation cell that extends across the open shelf and into the ice shelf cavity is formed in the model. The increased east–west density gradient caused by the strong brine release in the Ross Sea polynya in winter results in an intensification of this anticyclonic cell from 1.5 Sv to 2.5 Sv. This supports the concept of a 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<jats:sup>−1</jats:sup> shows a bimodal seasonal cycle ranging from 20–28 cm a<jats:sup>−1</jats:sup>, with maxima in March and August.</jats:p>