Barrier winds and air-sea interaction off South-East Greenland
Supervisers – Ian Renfrew and Nina Petersen

            When stably stratified atmospheric flow encounters a relatively large and high barrier, such as Greenland, much of the flow is forced along-the-barrier, setting up what is known as a barrier wind. Barrier winds are confined to below the height of the mountain range and generally exist as a balance between the topographic pressure-gradient force and the Coriolis force. They have been noted along the coastal mountains of western North America, the Antarctic Peninsula, and more recently along the coast of SE Greenland. The climatological location of the “Icelandic low” means that barrier flows are common off SE Greenland. Although observations of such barrier flows are relatively rare and it is only with the advent of satellite-derived ocean wind fields that the frequent occurrence of these events has been discovered.

            During the recent Greenland Flow Distortion experiment several cases of barrier winds were observed by instrumented aircraft. Preliminary results show that as well as the basic barrier flow mechanism, a “gap flow” in the Denmark Strait between Iceland and Greenland, downslope “katabatic flows” off the Greenland ice sheet, and boundary-layer “ice-front jets” also appear to be important in this area.

The high winds and cold-air outbreaks associated with barrier flows leads to elevated air-sea heat fluxes out of the ocean, especially at the edge of the seasonal sea-ice pack. It has been hypothesised that these elevated heat fluxes play an important role in the dynamics of a recently discovered oceanic “spill jet” which flushes water off the continental shelf and it part of the East Greenland Current – a key part of the ocean’s thermohaline circulation.  

            This project will carry out idealised and case study numerical modelling of barrier flows, and related phenomena, off SE Greenland. In addition, a climatology of barrier flows and their associated air-sea heat fluxes will be compiled. The student will need to become familiar with the UK Met Office’s “Unified Model”, so a willingness to learn computing skills is important. There may be the opportunity to collaborate with research groups in the UK, Canada, USA and Europe and make use of superb data sets recently assembled as part of field programmes such as GFDex. The project will start during the International Polar Year, when much attention is being focused on this key region of the climate system. 

References

http://lgmacweb.env.uea.ac.uk/e046/research/gfdex/
Moore, G. W. K. and I. A. Renfrew, 2005: Tip jets and barrier winds: A QuikSCAT climatology of high wind speed events around Greenland, J. Climate, 18, 3713-3725.
Pickart, R. S, D. J. Torres, and P.S. Fratantoni, 2005: The East Greenland spill jet, J. Phys. Oceanog., 35, 1037-1053.
Renfrew et al. 2008: The Greenland Flow Distortion experiment, submitted to Bulletin of the American Meteorological Society.