Response of the ice cap Hardangerjøkulen in southern Norway to the 20th and 21st century climates

R H Giesen,J Oerlemans

doi:10.5194/tc-4-191-2010

Abstract

Abstract. Glaciers respond to mass balance changes by adjusting their surface elevation and area. These properties in their turn affect the local and area-averaged mass balance. To incorporate this interdependence in the response of glaciers to climate change, models should include an interactive scheme coupling mass balance and ice dynamics. In this study, a spatially distributed mass balance model, comprising surface energy balance calculations, was coupled to a vertically integrated ice-flow model based on the shallow ice approximation. The coupled model was applied to the ice cap Hardangerjøkulen in southern Norway. The available glacio-meteorological records, mass balance and glacier length change measurements were utilized for model calibration and validation. Forced with meteorological data from nearby synoptic weather stations, the coupled model realistically simulated the observed mass balance and glacier length changes during the 20th century. The mean climate for the period 1961–1990, computed from local meteorological data, was used as a basis to prescribe climate projections for the 21st century at Hardangerjøkulen. For a linear temperature increase of 3 °C from 1961–1990 to 2071–2100, the modelled net mass balance soon becomes negative at all altitudes and Hardangerjøkulen disappears around the year 2100. The projected changes in the other meteorological variables could at most partly compensate for the effect of the projected warming.

Highlights

Glacier volume projections are required to assess the rate of sea level rise expected from ice wastage in a warmer future climate (e.g., IPCC, 2007; Meier et al, 2007; Bahr et al, 2009)
Ice dynamical effects are excluded in these model runs by keeping the surface topography fixed at the 1995 digital elevation model (DEM)
The parameterizations for the surface energy fluxes were calibrated with the AWS1 measurements, but this calibration was performed with the meteorological records from AWS1, while the energy fluxes shown in Fig. 4a were calculated with local meteorological data

Summary

Introduction

Glacier volume projections are required to assess the rate of sea level rise expected from ice wastage in a warmer future climate (e.g., IPCC, 2007; Meier et al, 2007; Bahr et al, 2009). In contrast to other regions in Scandinavia and the global trend, the maritime glaciers in mainland Norway advanced in the late 20th century, following a series of wet winters around 1990 (Andreassen et al, 2005). Since the year 2000, all monitored glaciers in Norway had a net mass deficit and retreated (Kjøllmoen et al, 2008). On the maritime Norwegian glaciers, the interannual variability in the net mass balance is dominated by variations in the winter balance, while summer balance fluctuations are more important on the glaciers further inland (Andreassen et al, 2005). The high dependence on winter precipitation suggests that the future of the maritime Norwegian glaciers is determined by the degree of warming, and by the accompanying change in precipitation

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Conclusion