According to researchers in the United States, the melting of the Greenland icecap may have caused a rise in the sea level during the last interglacial period around 125,000 years ago. At that time the sea level was about five metres higher than present levels. The origins of the water are, however, unclear. Because of its situation partly below sea level and also its ability to melt rapidly, the West Antarctic ice sheet was the main suspect. However, an analysis of oxygen isotopes by Kurt Cuffey of the University of California at Berkeley and Shawn Marshall at the University of Calgary shows Greenland was up to 8