THE GREENLAND GlLACIAL ANTICYCLONE

Abstract

The material contained in this paper is a description of the weather conditions over Greenland based on observations taken by exploring expeditions. It can be summarized as follows: Greenland is overlaid by a fixed glacial anticyclone of great vigor which spreads beyond its borders. Within a central cold region of Greenland is a core of descending air currents from levels above 4000 meters. The central region is sharply delimited on all its margins, which are marked by an abrupt rise of air temperature and by a fall of daily temperature range. The zone surrounding the cold central area of Greenland and extending beyond the glacial margin has at all times outblowing winds supplied from the central area. The winds centrifugal to Greenland vary in force from near-calms to surges with velocities of 100 and more miles per hour. Variations of wind velocity occur with little change in wind direction. For every point on the glacier's surface there is a wind direction which deviates from the downslope direction only as determined by earth rotation. The cold interior area is one of frequent and heavy snow precipitation, and this snow is swept out to the borders of the glacier by the surges of the anticyclone. Beyond the glacier's borders wherever there is land the finer meltwater deposits of the short summer are in the succeeding colder months lifted by the surges of the anticyclone and carried far out beyond the glacier margin to be deposited there as a peripheral zone of loess surrounding the outwash deposits. The Greenland Glacial Anticyclone is the unique all-season northern wind pole of our planet, where high-level high-latitude air currents of equatorial origin descend and return to lower latitudes. Glacial anticyclones such as those of Greenland and the Antarctic have existed on the earth only during its relatively brief glacial periods, and they appear to be responsible for its climatic zones; for, as is shown by the past distribution of plants and animals, at all other times relative uniformity, subtropical mildness, and comparatively equable, highly humid climate has prevailed over the greater part of the earth and extended beyond the polar circles. During the latest or Pleistocene glacial period, when great continental glaciers have lain over northern North America, and over northern Europe, they have been similarly covered by glacial anticyclones, as is proven by the widely distributed ventifacts and by the surrounding zone of loess deposits. Cyclones which arrive from the west athwart the Greenland glacial anticyclone are diverted northward and forced to skirt its borders. During the brief summer season they may invade for a short distance its western periglacial portions, but in the colder months not at all.