Glacier mass-balance and length variation in Norway

We explore the climatic information contained in the record of length fluctuations of Glaciar Frías, in the north Patagonian Andes of Argentina. This record is one of the longest and most detailed glacier records in southern South America, starting in 1639. In order to interpret the length variations of Glaciar Frías since the maximum Little Ice Age extent, we use a combination of a simplified surface energy-balance model to calculate the glacier mass balance, and a flowline model to account for the dynamical response of the glacier to changes in the climatic forcing. The overall retreat of the glacier observed over 1639–2009 is best explained by an annual mean temperature increase of 1.2 °C or a decrease in annual precipitation of 34%, most of which would have occurred during the 20th century. The glacier model is also forced with two independent tree-ring and multi-proxy reconstructions of precipitation and temperature. The uncertainties in these reconstructions are rather large, leading to a wide range in the modelled glacier length that includes most of the observations. However, in both reconstructions, the mid-17th century seems to be too cold and the early 19th century too warm to explain the observed glacier lengths with the glacier model forced with the reconstructions. Forcing with reconstructed precipitation and temperature separately shows that the influence of historical variations in precipitation on the glacier fluctuations of Glaciar Frías is smaller than that of the temperature fluctuations. This suggests that the observed 1639–2009 retreat could be best explained by a warming close to 1.2 °C

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“…This is in line with mass balance profiles observed elsewhere (e.g. Andreassen et al, 2005). The calculated mass balance gradient of 0.012 m w.e.…”

Section: Model Calibration and Validationsupporting

confidence: 75%

Modelling and climatic interpretation of the length fluctuations of Glaciar Frías (north Patagonian Andes, Argentina) 1639–2009 AD

et al. 2012

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“…The terminus change from 1988 to 2000 for Rembesdalskåka was +147 m and for Midtdalsbreen +46 m. By 2013, Rembesdalskåka and Midtdalsbreen had retreated 332 and 164 m, respectively, from their positions in 2000 (Andreassen et al, 2005, Kjøllmoen et al, 2011, Cryoclim.net, 2014.…”

Section: Outlet Glacier Changes Since the Little Ice Agementioning

confidence: 99%

Simulating the evolution of Hardangerjøkulen ice cap in southern Norway since the mid-Holocene and its sensitivity to climate change

et al. 2017

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Abstract. Understanding of long-term dynamics of glaciers and ice caps is vital to assess their recent and future changes, yet few long-term reconstructions using ice flow models exist. Here we present simulations of the maritime Hardangerjøkulen ice cap in Norway from the mid-Holocene through the Little Ice Age (LIA) to the present day, using a numerical ice flow model combined with glacier and climate reconstructions.In our simulation, under a linear climate forcing, we find that Hardangerjøkulen grows from ice-free conditions in the mid-Holocene to its maximum extent during the LIA in a nonlinear, spatially asynchronous fashion. During its fastest stage of growth (2300-1300 BP), the ice cap triples its volume in less than 1000 years. The modeled ice cap extent and outlet glacier length changes from the LIA until today agree well with available observations. Volume and area for Hardangerjøkulen and several of its outlet glaciers vary out-of-phase for several centuries during the Holocene. This volume-area disequilibrium varies in time and from one outlet glacier to the next, illustrating that linear relations between ice extent, volume and glacier proxy records, as generally used in paleoclimatic reconstructions, have only limited validity.We also show that the present-day ice cap is highly sensitive to surface mass balance changes and that the effect of the ice cap hypsometry on the mass balancealtitude feedback is essential to this sensitivity. A mass balance shift by +0.5 m w.e. relative to the mass balance from the last decades almost doubles ice volume, while a decrease of 0.2 m w.e. or more induces a strong mass balance-altitude feedback and makes Hardangerjøkulen disappear entirely. Furthermore, once disappeared, an additional +0.1 m w.e. relative to the present mass balance is needed to regrow the ice cap to its present-day extent. We expect that other ice caps with comparable geometry in, for example, Norway, Iceland, Patagonia and peripheral Greenland may behave similarly, making them particularly vulnerable to climate change.

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“…1) where both seasonal mass-balance and discharge measurements are available. The glacier coverage in each catchment is > 50 % (Table 1) and at each glacier, seasonal mass balance measurements have been carried out for more than 50 yr (Andreassen et al, 2005) following the traditional stratigraphic method (Østrem and Brugman, 1991). The catchments of Ålfotbreen and Storbreen are similar in size, covering about 8 km 2 , whereas the catchment of Nigardsbreen is about eight times as large.…”

Section: Study Sites and Input Datamentioning

confidence: 99%

Contribution of snow and glacier melt to discharge for highly glacierised catchments in Norway

Engelhardt

Schuler

Andreassen

2014

Hydrol. Earth Syst. Sci.

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Abstract. Glacierised catchments show a discharge regime that is strongly influenced by snow and glacier meltwaters. In this study, we modelled the mass balance and discharge rates for three highly glacierised catchments (> 50 % glacier cover) in western Norway over the period 1961-2012. The spatial pattern of the catchments follows a gradient in climate continentality from west to east. The model input were gridded temperature and precipitation values from seNorge (http://senorge.no) which are available at daily resolution. The model accounted for accumulation of snow, transformation of snow to firn and ice, evaporation and melt. Calibration and validation were performed for each catchment based on measurements of seasonal glacier mass balances and daily discharge rates, as additional validation data served daily melt rates from sonic rangers located in the ablation zones of two of the glaciers. The discharge sources snowmelt, glacier melt and rain were analysed with respect to spatial variations and temporal evolution. Model simulations reveal an increase in the relative contribution from glacier melt to total discharge for the three catchments from less than 10 % in the early 1990s to 15-30 % in the late 2000s. The decline in precipitation by 10-20 % in the same period was therefore overcompensated, resulting in an increase in annual discharge by 5-20 %. Annual discharge sums and annual glacier melt are most strongly correlated with annual and winter precipitation at the most maritime glacier and, with increased climate continentality, variations in both glacier melt contribution and annual discharge are becoming more strongly correlated with variations in summer temperatures. Therefore, glaciers in more continental climates are especially vulnerable to decrease in both annual and summer discharge with continued rise in summer temperatures and subsequent decrease in glacier extent. This may lead to significant changes to the discharge regime, with increase during spring but decline later in the year, especially for catchments in less maritime climate conditions.

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Glacier mass-balance and length variation in Norway

Cited by 146 publications

References 18 publications

Modelling and climatic interpretation of the length fluctuations of Glaciar Frías (north Patagonian Andes, Argentina) 1639–2009 AD

Modelling and climatic interpretation of the length fluctuations of Glaciar Frías (north Patagonian Andes, Argentina) 1639–2009 AD

Simulating the evolution of Hardangerjøkulen ice cap in southern Norway since the mid-Holocene and its sensitivity to climate change

Contribution of snow and glacier melt to discharge for highly glacierised catchments in Norway

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