Assessment of requirements for cirque formation in northern Sweden

Abstract

AbstractCirques in the Rassepautasjtjåkka massif currently lack glaciers and the geomorphology indicates that no glaciers occupied the cirques during the Holocene. The current climatic conditions in the cirques can be assessed using available climatic data; air temperature at Rassepautasjtjåkka, summer and winter balances of adjacent glaciers, and general precipitation patterns in northern Sweden. The data suggest that either a significant change in precipitation and wind regime or a moderate change in temperature is required to initiate a cirque glacier in the massif. Formation of a wet-based erosive glacier requires warmer winters with higher accumulation rates, equivalent to a more maritime influence in the area. Studies of current atmospheric circulation suggest that strong west- east circulation, associated with a northerly position of the polar front, is favourable for increased accumulation. Using typical erosion rates from present glaciers, we see that ~ 10% of the last 3 Myr may be required for forming the Rassepautasjtjåkka cirques. This is a significant portion of time since most of the glacial cycles are spent in states of interglacials, maximum glaciation or mountain-based glaciation. Marine sediments from the Norwegian Sea provide indications of minor glaciations back to ~12.6 Myr and, hence, cirque-formation periods are not restricted to Quaternary. Thus, it is possible that many cirque forms have a much longer history than previously recognized.