Accession Number : AD0664816

Title :   RADIOCARBON ISOCHRONES OF THE RETREAT OF THE LAURENTIDE ICE SHEET.

Descriptive Note : Technical rept.,

Corporate Author : WISCONSIN UNIV MADISON DEPT OF METEOROLOGY

Personal Author(s) : Bryson,Reid A. ; Wendland,Wayne M.

Report Date : DEC 1967

Pagination or Media Count : 34

Abstract : A Map of northern North America is presented which shows isochrones of the outer limit of the Laurentide ice sheet from about 13,000 years ago until the present. The data points are radiocarbon dates of moraines, basal peat, and lacustrine deposits which represent the dates of deglaciation. The chronology of the ice sheet shows that the ice front retreated northward from the Great Lakes to south of James Bay by about 8,000 years ago. By about 7,500 yrs BP, the continental ice sheet was split by an open Hudson Bay, with one center of ice over northern Keewatin and Baffin Island, and another about 400 km south of Ungava. By 7,000 yrs BP, the ice over Baffin Island had separated from the mass of ice to the west. The Baffin Island ice remained after that time, and apparently is found today as the Barnes Ice Cap and the Penny Glacier. The ice retreated faster over the Prairie Provinces than over the Labrador-Quebec area, suggesting that snowfall and/or cloud cover inhibited the retreat in the more maritime area. A glacial energy balance is presented which compares a glacial net radiation regime to that of a non-glacial time. The effect of variations in mean cloud cover and snowfall upon the ablation rate are investigated. It is suggested that cloud cover is the important determining factor for glacial net budget at lower latitudes, and that snowfall is more important at higher latitudes. (Author)

Descriptors :   (*GEOLOGIC AGE DETERMINATION, ICE), (*GLACIERS, NORTH AMERICA), DEPOSITS, PERIODIC VARIATIONS, CLOUD COVER, SNOW, ENERGY, HEAT TRANSFER, GREAT LAKES, HISTORY, ARCTIC REGIONS, ARCTIC OCEAN ISLANDS, MAPS, MASS TRANSFER

Subject Categories : Geology, Geochemistry and Mineralogy
      Snow, Ice and Permafrost

Distribution Statement : APPROVED FOR PUBLIC RELEASE