Considerations on the Origin of the Quaternary Ice Sheet of North America
Loewe F. 1971. Considerations on the Origin of the Quaternary Ice Sheet of North America. Arctic and Alpine Research. 3(4):331-344
It is generally agreed that the Quaternary ice sheets of the Northern Hemisphere were brought about by a cooling of the atmosphere. A temperature decrease tends to reduce water vapor in the air and thus the precipitation. Ahlmann's curve connecting summer temperature and apparent accumulation at the glaciation limit is probably not applicable to the start of the Labrador-Ungava ice sheet which could have been initiated with smaller accumulation than the curve indicates. However, a cooling of 6°C with the present precipitation hardly seems sufficient. It is unlikely that "glacial ice" of high density could have started an ice sheet itself. Even if the possibility of a growth of the Keewatin ice sheet from "valley ice" is accepted, a cooling of only 6°C would not be enough. The region would then have had the climate of unglacierized northern Siberia today. The start of the North American ice sheet would have required an initial cooling considerably greater than 6°C, or a decrease of 6°C with precipitation somewhat higher than the present. The conditions which brought about the synoptic and climatic changes which started the Quaternary ice sheet of North America are still not established.