The Briksdalsbre Event: A winter precipitation-induced decadal-scale glacial advance in southern Norway in the ad 1990s and its implications

Abstract

In the ad 1990s maritime glaciers in Scandinavia started to advance as a response to positive net mass balance in the preceding years, invoking annual advance rates in the order of ~50–60 m and a total frontal advance of 285 m (at Briksdalsbreen) in less than a decade. Records from six south Norwegian glaciers with continuous, annual front measurements are used to evaluate the magnitude, duration, climatic causes, and frontal time lags involved in this mass balance perturbation and the following frontal response of glaciers in southern Norway. A climate index based on meteorological data from Bergen unequivocally demonstrates that the main cause for the large glacier advances in Scandinavia in the 1990s was high winter precipitation linked to positive NAO index in the winters of 1988/1989, 1989/1990, 1992/1993, 1994/1995, 1997/1998, and 1999/2000. Less positive (or negative) glacier mass balance years were 1990/1991, 1993/1994, 1995/1997, and 1998/1999. Between 1996/1997 and 2009, Briksdalsbreen retreated 486 m (maximum annual retreat of 145 m in 2005/2006). The main cause of the significant glacier retreat in the early twenty-first century was a combined effect of reduced winter precipitation and higher summer temperatures. The glacier advance and following retreat phase back to the pre-advance position was completed in ~20 years, and is here termed the Briksdalsbre Event. This event has relevance for the identification and interpretation of decadal to centennial Holocene glacial events recorded in lacustrine and terrestrial sequences.