Aller⊘d-Younger Dryas Climatic Inferences from Cirque Glaciers and Vegetational Development in the Nordfjord Area, Western Norway

Abstract

Seventeen cirque basins containing Younger Dryas moraines were investigated at Stad and Vågs⊘y, western Norway. Lithostratigraphic studies, ¹⁴C datings, and pollen analysis of lake sediments just outside one of the moraines show that the glacier developed 50 to 180 yr after the vegetation responded to the climatic deterioration at the Aller⊘d-Younger Dryas transition. At the same transition acidophilous humus plants like Juniperus and Ericales disappeared and the vegetation became dominated by Salix, Artemisia, and Caryophyllaceae. Unusual high pollen influx values during Younger Dryas are interpreted to be the result of high pollen deposition on the glacier subsequently transported into the lake by the meltwater stream. An additional factor was the large amount of Salix growing in the immediate vicinity.

The distribution of cirque moraines and equilibrium-line altitudes suggest that prevailing, snow-bearing winds during Younger Dryas came from southwestern directions. The Younger Dryas equilibrium line was about 700 m below the present. Correlations with marine geological results from adjacent seas indicates that an open North Atlantic and southern Norwegian Sea were the main precipitation sources for Younger Dryas glaciers. It is also suggested that the heaviest precipitation in Norway during Younger Dryas was in the Bergen—Nordfjord region, with increasing continentality both to the north and south.