Warmer waters in the Southern Ocean have led to the loss of Antarctic ice during past interglacial times. The shells of foraminifera are preserved in Ross Sea sediment, which is collected in cores. Benthic species from Site U1523 inform us about changing water masses and current activity, including incursions of Circumpolar Deep Water. Warm water planktic species were found in sediment samples from four intervals within 3.72–1.82 million years ago, indicating warmer than present conditions.