The Greenland plateau jet

Greenland with its high ice covered topography represents a significant barrier to atmospheric flow in the North Hemisphere. In recent years, a number of topographically forced jets have been identified around the margins of Greenland. These include westerly and easterly jets that form near Cape Farewell, its southernmost point, as well as barrier flow along its southeastern coast. In all these cases, the jets form as a result of flow distortion resulting from the interaction of extra-tropical cyclones with Greenland's topography. Indeed because of this flow distortion, the Cape Farewell region is the windiest location on the global ocean's surface. In any study of topographically forced flow around Greenland, its high topography renders climatologies that use constant height or pressure suboptimal in regard to their ability to represent the flow. In this presentation we develop a new climatology of wind speed around Greenland that uses the height above the surface as its basis. In the attached figure, we show the winter mean (DJF) wind speed at a height of 500 m above the surface as determined from the ECMWF's Interim Reanalysis. With this new climatology, interesting new information on the vertical structure of the previously identified tip jets and barrier flow can be identified. In addition, hitherto unrecognized wind features over the ice cap are evident. These include a region of high wind speed over the ice cap that we refer to as the Greenland plateau jet, as well as two wind nadirs along the ice cap's eastern and western boundaries. The plateau jet is particularly pronounced during the winter months with mean wind speeds in excess of 12 m/s; 95 percentile wind speeds in excess of 25m/s and a meridional extent of over 1500km. In addition, as a result of a vertical coupling with the upper-level jet associated with the Canadian Circumpolar Trough, the high winds associated with this jet extend from the surface to over 12km. The characteristics of these wind features will be discussed and the dynamics behind them as well as their impact on the weather and climate over the Greenland ice cap.