Observation and simulation of barrier winds at the western margin of the Greenland ice sheet

• Published in: Quarterly Journal of the Royal Meteorological Society
• Main Authors: Vandenbroeke, MR., Gallee, H.
• Other Authors: UCL
• Format: Article in Journal/Newspaper
• Language: English
• Published: Royal Meteorological Soc 1996
• Subjects: barrier winds; Greenland ice sheet; ice-melting zone; mesoscale modelling; Antarc*; Antarctic; Greenland; Ice Sheet; Tundra
• Online Access: http://hdl.handle.net/2078.1/46950; https://doi.org/10.1002/qj.49712253407

Meteorological observations performed in the melting zone of the Greenland ice sheet during GIMEX-90/91 show the regular occurrence of moderately strong barrier-winds. The barrier wind is a thermally generated jet that develops when the large-scale now advects warm tundra air towards the cold, melting ice sheet, creating a large local horizontal gradient of temperature. As a result, the geostrophic wind in the atmospheric boundary-layer acquires a component perpendicular to the temperature gradient. In the melting zone of the ice sheet, barrier winds interact with persistent surface-based katabatic winds. The forcing mechanisms and detailed two-dimensional structure of the barrier wind have been investigated with a mesoscale meteorological model. The model results confirm the important role of the warm tundra during the development of barrier winds. Barrier winds cause a pronounced rise in temperature and a strong increase of turbulent exchange in the lower melting zone: friction velocity and sensible-heat flux in the melting zone showed peak values of 1.3 m s(-1) and 300 W m(-2) respectively. In combination with large positive net radiation, the daily melt rate increased to 10 cm water equivalent, which is twice the rate in typical katabatic wind conditions. This shows that barrier winds could have a significant impact on the melt regime of areas where the ice sheet ends in the tundra. Although barrier winds in this part of Greenland may occur less frequently than the observations during GIMEX-90 suggest, they are of great importance for the climate of this and of other polar regions, such as the Antarctic, and so merit careful study.