Modelling annual mass balances of eight Scandinavian glaciers using statistical models

M Trachsel,A Nesje

doi:10.5194/tc-9-1401-2015

Abstract

Abstract. Mass balances of Scandinavian glaciers are mainly influenced by winter precipitation and summer temperature. We used simple statistical models to assess the relative importance of summer temperature and winter precipitation for annual balances of eight glaciers in Scandinavia. Winter precipitation was more important for maritime glaciers, whereas summer temperature was more important for annual balances of continental glaciers. Most importantly relative importances of summer temperature and winter precipitation were not stable in time. For instance, winter precipitation was more important than summer temperature for all glaciers in the 25-year period 1972–1996, whereas the relative importance of summer temperature was increasing towards the present. Between 1963 and 1996 the Atlantic Multidecadal Oscillation (AMO) index was consistently negative and the North Atlantic Oscillation (NAO) Index was consistently positive between 1987 and 1995, both being favourable for glacier growth. Winter precipitation was more important than summer temperature for annual balances when only considering subsets of years with high NAO-index and negative AMO-index, respectively, whereas the importance of summer temperature was increased analysing subsets of years with low NAO-index and positive AMO-index, respectively. Hence, the relative importance of precipitation and temperature for mass balances was probably influenced by the state of the AMO and the NAO, as these two indexes are associated with changes in summer temperature (AMO) and winter precipitation (NAO).

Highlights

Glaciers respond to climate change because their mass balance and extent are mainly a result of variations in winter accumulation and summer ablation
As demonstrated in other studies (Andreassen and Oerlemans, 2009; Giesen and Oerlemans, 2010; Laumann and Nesje, 2009a, b, 2014; Oerlemans, 1992), that the annual glacier mass balance on near coastal, maritime glaciers was mainly controlled by winter precipitation and that the annual mass balance on the inland, continental glaciers was mainly controlled by summer temperature (Andreassen et al, 2005; Nesje et al, 1995)
Looking at the 25year windows centred between 1978 and 1984, we found that winter precipitation was more important than summer temperature for all glaciers including the continental glaciers in southern Norway, the differences were not significant for the continental Gråsubreen

Summary

Introduction

Glaciers respond to climate change because their mass balance and extent are mainly a result of variations in winter accumulation and summer ablation. Andreassen et al, 2006; Andreassen and Oerlemans, 2009; Engelhardt et al, 2013; Giesen and Oerlemans, 2010; Hock et al, 2007; Laumann and Nesje, 2009a, b, 2014; Oerlemans, 1992, 1997; Rasmussen and Conway, 2005; Rasmussen et al, 2007; Schuler et al, 2005) Most of these studies have focused on estimating sensitivities of winter balances, summer balances and annual balances to changes in temperature and precipitation.

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