The 2009 North Water anomaly

Abstract

The North Water (NOW) polynya is an area of ocean between Greenland and Ellesmere Island that does not freeze completely during the winter months. The northern border of the polynya is typically demarked by an ice arch that forms across the narrow head of Smith Sound during winter. Once the ice arch consolidates, winds and current advect ice to the south, allowing the formation of new ice. The ice arch generally breaks down in late spring, at which point floes enter the region from the Arctic Ocean via Nares Strait. In 2009, the Smith Sound ice arch did not consolidate, but another ice arch formed 500 km to the north at the junction of Nares Strait and the Arctic Ocean. This northern ice arch prevented floes from reaching the NOW until 23 July and led to decadal low ice coverage for the region. In July, satellite-derived sea surface temperatures (SSTs) reached 8–10°C, which is approximately 5°C above typical seasonal values. With the introduction of floes into the NOW after 23 July, SSTs began to moderate.