| Summary: | NOTE: Text or symbols not renderable in plain ASCII are indicated by [.]. Abstract is included in .pdf document. The Greenland ice sheet is treated as a monomineralic rock formation, primarily metamorphic, but with a sedimentary veneer of snow and firn. This sedimentary member is perennial above the firn line, and the classical methods of stratigraphy and sedimentation can be profitably applied to it. During a 4-year period 146 pit studies and 288 supplementary Rammsonde profiles were made along 1100 miles of over-snow traverse (Fig.1). Temperature, density, ram hardness, and grain size were measured in the strata exposed in each pit. Stratification of snow results from variations in the conditions of deposition and is emphasized by subsequent diagenesis. Summer layers are coarser-grained and have generally lower density and hardness values than winter layers; they may also show evidence of surface melt. The onset of fall is usually identified by an abrupt increase in density and hardness accompanied by a decrease in grain size. This stratigraphic discontinuity is used as the annual reference plane. Strata in the upper 10 to 20 meters compose a succession of annual sequences which are preserved in recognizable form for at least several decades. Correlation of annual layers between pits, spaced 10 to 25 miles apart along the traverse of Figure 1, gives a picture of annual accumulation during the past 5 to 20 years for western Greenland between 69 and 77°N. The control established by these data, together with information from earlier expeditions (primarily those of Koch-Wegener and DeQuervain) and from permanent coastal meteorological stations, have been used to make a map showing the distribution of gross annual accumulation, essentially the equivalent of annual precipitation, for the entire ice sheet (Fig. 30). In general, the accumulation contours follow the north-south trend of the coast lines, with extremes of less than 10 cm H2O in the northeast and more than 90 cm H2O per year in the south; the average for ...
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