Katabatic wind forcing of the Terra Nova Bay polynya

The Terra Nova Bay polynya is a perennial winter feature in the western Ross Sea, Antarctica, which occupies roughly 1000 km2, it is formed and maintained by the combined influence of persistent katabatic winds, which advect newly formed bay ice eastward, and the Drygalski Ice Tongue, which prevents northward drifting pack ice from entering Terra Nova Bay. Existence of anomalously strong katabatic drainage along this coast is predicted by Parish's (1982) simulation of wintertime airflow which reveals a pronounced confluence of surface winds upslope from the Reeves Glacier where the winds are further focused by local topography. The simulation is strongly supported by regional sastrugi orientations. Average wintertime atmospheric conditions and ice sheet topography which control surface air drainage are stable on a climatic time scale; therefore, persistent wintertime katabatic winds should be an annual phenomenon. Further evidence comes from multi-year Landsat images which consistently show windswept, snowfree areas on the Reeves Glacier. In marked contrast to typical Antarctic katabatic winds, strong persistent winter winds are observed at sea level ∼25 km beyond the coastal slope break. Air probably descends as bora-type winds and is likely to be significantly denser than the air at sea level; conditions are not favorable for hydraulic jumps apparently typical of other katabatic regimes. The horizontal density difference is maintained during airflow across the Nansen Ice Sheet because relatively little air mass modification occurs there in contrast to situations where air moves over an ice-laden ocean. Observations thus suggest that katabatic winds maintain their identity for some distance seaward of the coast; qualitative trajectory calculations indicate that for representative geostrophic conditions this distance is on the order of the observed polynya width. Estimated ice freezing rates are ∼20 cm day−1, but wind-generated waves and currents prevent ice from consolidating. The blocking effect of the Drygalski Ice Tongue is a consequence of its orientation with regard to western Ross Sea ice drift patterns; ice tongue length controls polynya width. Absence of such blocking along other coasts experiencing strong katabatic outflow partly explains why similar polynyas do not form there.

[1]  R. Richards.  Work and Adventures of the Northern Party of Captain Scott's Antarctic Expedition, 1910-1913 , 1914 .

[2]  British Antarctic Expedition,et al.  Glaciology, physiography, stratigraphy, and tectonic geology of South Victoria Land , 1916 .

[3]  R. Brown,et al.  The Home of the Blizzard , 1915 .

[4]  The Ross Sea Drift of the "Aurora" in 1915-1916 , 1921 .

[5]  R. Scorer.  Mountain‐gap winds; a study of surface wind at Gibraltar , 1952 .

[6]  F. Ball.  The theory of strong katabatic winds , 1956 .

[7]  F. Ball.  The Katabatic Winds of Adélie Land and King George V Land , 1957 .

[8]  Glaciological Work of the 1959–60 U.S. Victoria Land Traverse , 1961 .

[9]  K. B. Mather.  Further observations on sastrugi, snow dunes and the pattern of surface winds in Antarctica , 1962, Polar Record.

[10]  T. Foster.  Haline convection induced by the freezing of sea water , 1968 .

[11]  G. Weller.  A meridional surface wind speed profile in MacRobertson Land, Antarctica , 1969 .

[12]  H. Loon,et al.  Climate of the Upper Air: Southern Hemisphere: Volume 1: Temperatures, Dew Points, and Heights at Selected Pressure Levels , 1969 .

[13]  K. B. Mather.  The pattern of surface wind flow in Antarctica , 1969 .

[14]  J. Zillman,et al.  The surface temperature inversion over the Antarctic Continent , 1970 .

[15]  S. Jacobs,et al.  Ross sea oceanography and antarctic bottom water formation , 1970 .

[16]  K. Countryman.  An explanation of supercooled waters in the Ross Sea , 1970 .

[17]  E. Lewis,et al.  The water structure under a growing sea ice sheet , 1970 .

[18]  A. H. Gordon,et al.  Computations of surface layer air parcel trajectories, and weather, in the oceanic tropics , 1975 .

[19]  R. K. Reed,et al.  On estimation of net long-wave radiation from the oceans , 1976 .

[20]  O. Watanabe.  Distribution of Surface Features of Snow Cover in Mizuho Plateau , 1978 .

[21]  Further Calculations of Sea Level Air Trajectories over the Equatorial Indian Ocean , 1978 .

[22]  W. Liu,et al.  Bulk Parameterization of Air-Sea Exchanges of Heat and Water Vapor Including the Molecular Constraints at the Interface , 1979 .

[23]  Meteorological data at Mizuho Station, Antarctica in 1980(Meteorology 10) , 1979 .

[24]  W. Schwerdtfeger.  Meteorological aspects of the drift of ice from the Weddell Sea toward the mid-latitude westerlies , 1979 .

[25]  METEOROLOGICAL DATA AT MIZUHO STATION, ANTARCTICA IN 1979 , 1979 .

[26]  S Martin,et al.  Frazil Ice in Rivers and Oceans , 1981 .

[27]  Arnold L. Gordon,et al.  Seasonality of Southern Ocean sea ice , 1981 .

[28]  T. Parish.  The katabatic winds of Cape Denison and Port Martin , 1981, Polar Record.

[29]  Jeff Dozier,et al.  Effect of grain size and snowpack water equivalence on visible and near‐infrared satellite observations of snow , 1981 .

[30]  A Field and Laboratory Study of Wave Damping by Grease Ice , 1981 .

[31]  Thomas R. Parish,et al.  Surface Airflow Over East Antarctica , 1982 .

[32]  J. Gosink,et al.  Measurements of katabatic winds between Dome C and Dumont d'Urville , 1982 .

[33]  D. Bromwich,et al.  Experiences of Scott's Northern Party: evidence for a relationship between winter katabatic winds and the Terra Nova Bay polynya , 1982, Polar Record.

[34]  S. Larsen,et al.  Small scale drainage front , 1982 .

[35]  David H. Bromwich,et al.  Satellite Observed Behavior of the Terra Nova Bay Polynya , 1983 .

[36]  R. M. Reynolds,et al.  A model of the atmospheric boundary layer over the marginal ice zone , 1983 .

[37]  T. Parish.  The influence of the Antarctic Peninsula on the wind field over the western Weddell Sea , 1983 .

[38]  J. G. Ferrigno,et al.  Blue ice, meteorites and satellite imagery in Antarctica , 1983, Polar Record.

[39]  J. Jouzel,et al.  Climatic information over the last century deduced from a detailed isotopic record in the south pole snow , 1983 .