Studies of internal gravity waves at Halley Base, Antarctica, using wind observations

At Halley Base, which is situated on the Brunt Ice Shelf in Antarctica, internal gravity waves are frequently observed in the stably stratified atmospheric boundary layer. In this paper, time series of wind speed and direction at a height of 8 m, observed from three meteorological masts, are used to determine some of the physical properties of the waves, such as their wavelengths, phase speeds and directions of propagation. The relationship of the results to various theories of the generation of internal gravity waves is considered. It is shown that the waves do not usually propagate in the direction of the surface wind; typically the direction of propagation is rotated about 45° clockwise from the wind vector. The waves most frequently propagate from a direction of about 135°, which is perpendicular both to the Hinge Line (line where the ice shelf meets the land) and to the ridges in the ice shelf, suggesting a topographic influence. It is shown that the waves obey a dispersion relation similar to that for neutral, trapped internal gravity waves.