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The 26 km long tidewater glacier Tunabreen is the most frequently surging glacier in Svalbard, with four documented surges in the past 100 years. We model the evolution of this glacier with a minimal glacier model (MGM), in which ice mechanics, calving, and surging are parameterized. The model geometry consists of a flow band to which three tributaries supply mass. The calving rate is set to the mean observed value for the period 2012–2019 and kept constant. For the past 120 years, a smooth equilibrium line altitude (ELA) history is reconstructed by finding the best possible match between observed and simulated glacier length. There is a modest correlation between this reconstructed ELA history and an ELA history based on meteorological observations from Longyearbyen. Runs with and without surging show that the effect of surging on the long-term glacier evolution is limited. Due to the low surface slope and associated strong height–mass-balance feedback, Tunabreen is very sensitive to changes in the ELA. For a constant future ELA equal to the reconstructed value for 2020, the glacier front will retreat by 8 km during the coming 100 years. For an increase in the ELA of 2 m a -1 , the retreat is projected to be 13 km, and Tunabreen becomes a land-terminating glacier around 2100. The calving parameter is an important quantity: increasing its value by 50 % has about the same effect as a 35 m increase in the ELA, with the corresponding equilibrium glacier length being 17.5 km (as compared to 25.8 km in the reference state). Response times vary from 150 to 400 years, depending on the forcing and on the state of the glacier (tidewater or land-terminating). [ABSTRACT FROM AUTHOR]

The Vadret da Tschierva (Vd Tschierva) is a 4 km long glacier in the Swiss Alps spanning an altitude range of 2400–4049 m a.s.l. Length observations since 1855 show steady retreat interrupted by a period of advance from 1965 until 1985. The total retreat is ~2200 m (period 1855–2018). We have studied the Vd Tschierva with a flowline model, combined with 'buckets' that represent steep hanging glaciers and ice-free rock faces delivering mass to the main stream. The model is calibrated by a control method, in which an ELA history is objectively determined by finding the best match between observed and simulated glacier length. There is a modest correlation between the reconstructed ELA and an ELA record based on meteorological observations at Segl-Maria (only 8 km away from the glacier). It is difficult to reproduce the observed length record when the glacier model is driven by climate model output (Coupled Model Intercomparison Project 5). We have calculated the future evolution of the Vd Tschierva for different rates of ELA rise. For a constant rise of 4 ${\rm m\;}{\rm a}^{ \hbox{-} 1}$ , we predict that the glacier length will change from the current 3.2 km to ~1.7 km in the year 2100. [ABSTRACT FROM AUTHOR]

We present a simple model to calculate the evolution of an ice stupa (artificial ice reservoir). The model is formulated for a cone geometry and driven by energy balance measurements over a glacier surface for a 5-year period. An "exposure factor" is introduced to deal with the fact that an ice stupa has a very rough surface and is more exposed to wind than a flat glacier surface. The exposure factor enhances the turbulent fluxes. For characteristic alpine conditions at 2100 m, an ice stupa may reach a volume of 200 to 400 m 3 in early April. We show sensitivities of ice stupa size to temperature changes and exposure factor. The model may also serve as an educational tool, with which the effects of snow cover, switching off water during daytime, different starting dates, switching off water during high wind speeds, etc. can easily be evaluated. [ABSTRACT FROM AUTHOR]

Monacobreen is a 40 km long surge-type tidewater glacier in northern Spitsbergen. During 1991-1997 Monacobreen surged and advanced by about 2 km, but the front did not reach the maximum Little Ice Age (LIA) stand. Since 1997 the glacier front is retreating at a fast rate (~ 125ma-1). The questions addressed in this study are as follows: (1) Can the late Holocene behaviour of Monacobreen be understood in terms of climatic forcing?, and (2) What will be the likely evolution of this glacier for different scenarios of future climate change? Monacobreen is modelled with a minimal glacier model, including a parameterization of the calving process as well as the effect of surges. The model is driven by an equilibriumline altitude (ELA) history derived from lake sediments of a nearby glacier catchment in combination with meteorological data from 1899 onwards. The simulated glacier length is in good agreement with the observations: the maximum LIA stand, the front position at the end of the surge, and the 2.5 km retreat after the surge (1997-2016) are well reproduced (the mean difference between observed and simulated glacier length being 6% when scaled with the total retreat during 1900-2016). The effect of surging is limited. Directly after a surge the initiated mass balance perturbation due to a lower mean surface elevation is about -0.13mw.e. a-1, which only has a small effect on the longterm evolution of the glacier. The simulation suggests that the major growth of Monacobreen after the Holocene climatic optimum started around 1500 BCE. Monacobreen became a tidewater glacier around 500 BCE and reached a size comparable to the present state around 500 CE. For the mid-B2 scenario (IPCC, 2013), which corresponds to a ~ 2ma-1 rise of the ELA, the model predicts a volume loss of 20%to 30%by the year 2100 (relative to the 2017 volume). For a ~ 4ma-1 rise in the ELA this is 30% to 40 %. However, much of the response to 21st century warming will still come after 2100. [ABSTRACT FROM AUTHOR]

Many large valley glaciers in the world are retreating at historically unprecedented rates. Also in the Alps, where warming over the past decades has been more than twice as large as the global mean, all major glaciers have retreated over distances of several kilometers over the past hundred years. The Morteratsch Glacier, Pontresina, Switzerland, is a major touristic attraction. Due to strong retreat, the lowest part of the glacier is getting out of sight from the gravel road that provided direct access to the glacier front. The Community of Pontresina has commissioned a preparatory study to find out if it is possible to slow down the retreat of the Morteratsch Glacier in an environmentally friendly way. In this article, we report on the outcome of such a study, based on a modeling approach. Our analysis is based on a 20-year weather station record from the lower part of the glacier, combined with calculations with a calibrated ice-flow model. We arrive at the conclusion that producing summer snow in the ablation zone over a larger area (typically 0.5 to 1 km) may have a significant effect on the rate of retreat on a timescale of decades. We consider various scenarios of climate change: (i) no change, (ii) a rise of the equilibrium-line altitude (ELA) by 1, 2, and 4 m/yr. Projections of glacier length are calculated until the year 2100. It takes about 10 years before snow deposition in the higher ablation zone starts to affect the position of the glacier snout. For the case of modest warming, the difference in glacier length between the snow and no-snow experiments becomes 400 to 500 m within two decades. [ABSTRACT FROM AUTHOR]

Glaciers in northern and southern Norway are subject to different daily and seasonal cycles of incoming solar radiation, which is presumably reflected in the importance of net solar radiation in their surface energy balance. We present a 3 year continuous record from an automatic weather station in the ablation zone of the ice cap Langfjordjøkelen, one of the most northerly glaciers of mainland Norway. Despite its location at 70°N, Langfjordjøkelen was found to have a maritime climate, with an annual mean air temperature of -1.0°C, frequent cloud cover and end-of-winter snow depths over 3m in all three years. The main melt season was May-October, but occasional melt events occurred on warm, cloudy winter days. Net solar and longwave radiation together accounted for 58% of the melt energy, with a positive contribution by net longwave radiation (7%). The sensible and latent heat fluxes supplied the remainder of the melt energy. Cloud optical thickness over Langfjordjøkelen was larger than on two glaciers in southern Norway, especially in the summer months. This resulted in a smaller contribution of net solar radiation to surface melt on Langfjordjøkelen; the effect of the higher latitude on net solar radiation was found to be small. [ABSTRACT FROM AUTHOR]

Marine records of sediment oxygen isotope compositions show that the Earth's climate has gone through a succession of glacial and interglacial periods during the past million years. But the interpretation of the oxygen isotope records is complicated because both isotope storage in ice sheets and deep-water temperature affect the recorded isotopic composition. Separating these two effects would require long records of either sea level or deep-ocean temperature, which are currently not available. Here we use a coupled model of the Northern Hemisphere ice sheets and ocean temperatures, forced to match an oxygen isotope record for the past million years compiled from 57 globally distributed sediment cores, to quantify both contributions simultaneously. We find that the ice-sheet contribution to the variability in oxygen isotope composition varied from ten per cent in the beginning of glacial periods to sixty per cent at glacial maxima, suggesting that strong ocean cooling preceded slow ice-sheet build-up. The model yields mutually consistent time series of continental mean surface temperatures between 40 and 80° N, ice volume and global sea level. We find that during extreme glacial stages, air temperatures were 17 ± 1.8 °C lower than present, with a 120 ± 10 m sea level equivalent of continental ice present. [ABSTRACT FROM AUTHOR]

On glacial time scales, the waxing and waning of the Eurasian and North American ice sheets depend largely on variations in atmospheric temperature. As global sea level is primarily determined by the volume of these ice sheets, there is a direct (yet complex) relation between global sea level and the northern hemispheric (NH) temperature. This relation is essentially represented by a model of the NH ice sheets. We use a thermomechanical ice-sheet-ice shelf-bedrock model in conjunction with an inverse method to deduce a time series of NH temperature (from 120 kyr BP until present) that is consistent with the observed global sea level record. The advantage of this method is that it provides the annual mean surface air temperature averaged over the NH continents north of 40°N. The results reveal that ice age temperatures were 4-10°C lower than today, which agrees with other temperature reconstructions. However, reconstructed temperatures are comparitively low during the early stages of the glacial, a feature that is consistent with the rapid growth of the ice sheets. The sensitivity of the results for uncertainties in precipitation rate, in observed sea level and in some other model parameters is examined to quantify the error in reconstructed temperature. During the glacial period (120-15 kyr BP), surface air temperatures in the NH (north of 40°N) were 7.2±1.5°C lower than today’s (interglacial) temperatures. [ABSTRACT FROM AUTHOR]

Presents a study that investigated the data from several automatic weather stations concerning katabatic flow over glaciers. Background on the glacier winds; Information on the wind maximum and vertical temperature of glaciers; Discussion on the Prandtl model used in the estimation of heat flux associated with the glacier wind.

Part I. Describes a three-dimensional dynamic downscaling model of the Greenland atmospheric boundary layer, (GABLM) and applied it to the Greenland ice sheet for the 1998 ablation season. Discussion on the GABLM; Determinants of the surface mass balance of ice sheets and glaciers; Information on the meteorological variables of temperature.

Reports on a workshop held during the Climate Conference in August 2001 at Utrecht University in the Netherlands regarding the katabatic flows over glaciers and ice sheets. Effects of turbulence on the glacier surface and atmosphere; Reasons behind the existence of katabatic flows; Discussion on the spatial scale of glaciers.

Abstract: Fluctuations in the length of 72 glaciers in the Northern and Southern Patagonia Icefield (NPI and SPI, respectively) and the Cordillera Darwin Icefield (CDI) were estimated between 1945 and 2005. The information obtained from historical maps based on 1945 aerial photographs was compared to ASTER and Landsat satellite images and to information found in the literature. The majority of glaciers have retreated considerably, with maximum values of 12.2km for Marinelli Glacier in the CDI, 11.6km for O''Higgins Glacier in the SPI and 5.7km for San Rafael Glacier in the NPI. Among the 20 glaciers that have retreated the most relative to their size, small (less than 50km²) and medium (between 50 and 200km²) glaciers are the most affected. However, no direct relation between glacier retreat and size was found for the 72 glaciers studied. The highest percentage retreat in the CDI was by the CDI-03 Glacier (37.9%) and Marinelli Glacier (37.6%). In the SPI, relative retreats were heterogeneous and fluctuated between 27.2% (Amelia Glacier) and 0.4% (Viedma Glacier). In the NPI, relative retreat was very high for Strindberg and Cachet glaciers (35.9% and 27.6%, respectively) but for the remaining glaciers in this icefield it ranged between 11.8% (Piscis Glacier) and 3.6% (San Quintín Glacier). In addition to surface area, the surface slope (calculated on the basis of the DEM SRTM) was also related to the relative retreat and no straightforward relation was found. From a global point of view, we suggest that glacier retreat in the region is controlled firstly by atmospheric warming, as it has been reported in this area. Besides the general increase in temperature observed, no signal of a geographical pattern for the fluctuations in glacier length was found. Consequently, glaciers appear to initially react to local conditions most probably induced by their exposition, geometry and hypsometry. The heterogeneity of rates of retreat suggests that differences in basin geometry, glacier dynamics and response time are key features to explain fluctuations of each glacier. [Copyright &y& Elsevier]