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We present a Simple Lake Ice Model to calculate the growth rate of lake ice in a cold and relatively dry climate. The focus is on Lake St. Moritz, Switzerland, which has an area of 0.78 km2 and is about 45 m deep. In winter the lake is extensively used for recreational purposes, including horse racing with thousands of spectators. Safety on the ice cover is essential, and there is a great need to have a simple tool with which the growth rate of the ice layer can be calculated for given meteorological conditions. The approach is based on a simple formulation of the upper temperature of the ice layer, which depends on air temperature and snow cover. Input data are the date on which the lake freezes over, daily mean air temperatures and snow depth. For the winter 2021/22 calculated ice growth compares well with ice thickness measurements. We demonstrate that grooming of the snow has a significant positive effect on the ice thickening rate. We also evaluate the sensitivity of the simulated ice thickness to increasing mean temperature. [ABSTRACT FROM AUTHOR]

Author(s): Richard Bintanja (corresponding author) [1]; Roderik S.W. van de Wal [1]; Johannes Oerlemans [1] Marine records of sediment oxygen isotope compositions show that the Earth's climate has gone through [...]

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]

A World Without Ice by Henry Pollack Avery: 2009. 304 pp. $26 A World Without Ice opens with a strong foreword from Al Gore: the science has been done--now we [...]

The extensive dataset of Variegated Glacier's 1982/83 surge and antecedent quiescent phase is fragmentary and predominantly of flow line nature. Applying the raw centre line data in a flow line model to conduct research into the mechanism behind Variegated Glacier's surge behaviour inevitably entails problems. In this study, the incomplete dataset is extrapolated into the upper and lower parts of the glacier. Furthermore, the centre line data are adapted to account for differences between width-averaged and centre line surface mass balance and ice thickness change, inflow from tributaries, and changes in surface width over time. The modifications to the dataset are backed-up by observations and clear, plausible physical explanations. Moreover, the revised dataset meets the imposed constraints regarding ice volume flux, specific mass balance and net volume change. Hence, the final dataset is considered a satisfying revision that makes the dataset more valuable for future research. Subsequent application of the revised dataset corroborates the idea that glacier evolution during quiescence is basically the growth back towards steady state after the glacier was brought out of balance by the preceding surge. [ABSTRACT FROM PUBLISHER]

The article discusses a research study on the cyclic behaviour in the Parallel Ice Sheet Model (PISM) through numerical experiments. It describes three sets of experiments including the basal parameter experiments, the climate parameter experiments and the climate feedback experiments for identifying interactions and processes that comprise multiple types of oscillatory flow. Results showed that in the basal parameter experiments, flow enhancement was due to the interplay of water production, sliding and basal shearing with high-frequency oscillations relying on geometric interaction with water redistribution on temperate base. It also notes that the diffusive basal water model is suitable for cyclic behaviour studies.

The oxygen isotope signal in benthic foraminifera from deep-sea cores is mainly determined by deep-ocean temperature and land ice volume. Separating the temperature and ice volume signals is a key step in understanding the evolution of Cenozoic climate. Except for the last few million years, fluctuations in land ice volume were determined mainly by the size of the Antarctic ice sheet. Here a simplified Antarctic ice-sheet model and composite deep-sea oxygen isotope records are used to derive a deep-sea temperature history for the Cenozoic. The ice-sheet model is forced with the oxygen-isotope record, which is instantaneously corrected for the calculated ice volume. Therefore, the resulting deep-sea temperature and Antarctic ice volume curves are mutually consistent.The temperature record of Lear et al. [Science 287 (2000) 269], derived from the Mg/Ca ratio in benthic calcite, is also used to force the ice-sheet model. The resulting ice-volume does not agree well with the ice-volume history inferred by Lear et al. from a comparison of Mg/Ca and δ18O records.The most important points emerging from this study are: [Copyright &y& Elsevier]

In this paper, we propose equations for narrowband-to-broadband (NTB) albedo conversion for glacier ice and snow for four types of satellite sensors: thematic mapper (TM), advanced very high resolution radiometer (AVHRR), moderate resolution imaging spectroradiometer (MODIS), and multi-angle imaging spectroradiometer (MISR). We do this on the basis of spectral albedos and incident spectral irradiances generated with radiative-transfer models of the (sub-)surface (a two-stream model) and the atmosphere, respectively. First, we establish equations for reference values of atmospheric components and the surface elevation. These equations describe measurements with root-mean-square differences of ∼0.016. We then show that the “reference equations” also perform well when total ozone and aerosol optical depth are changed with respect to the reference. The negative effect of humidity and elevation variations on the performance of the equations can be eliminated by adding a correction term. We argue that narrowband albedos are much less sensitive to variations in the incident spectral irradiance than broadband albedos. Hence, our conclusions about the effects of variations in atmospheric composition and elevation are also valid for equations for NTB conversion proposed in other papers. [Copyright &y& Elsevier]

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.

Discusses the use of a Prandtl-type model, which allows eddy diffusivity or conductivity, in studying pure katabatic flow. Background on the katabatic flows; Information on the scale height for eddy diffusivity; Application of the Wentzel-Kramers-Brillouin (WKB) method in developing the theory of pure katabatic flow; Basis for the justification of the WKB method.

Investigates the surface energy balance (SEB) of the Greenland ice sheet for the summer ablation season of 1998. Discussion of the SEB; Factors that influence the SEB and surface mass balance of the ice sheet; Details on a study that examined the sensitivity of the SEB components.

Uses a 14 year integration with a regional atmospheric model to obtain detailed information on the Antarctic surface mass balance and to understand the mechanisms responsible for the spatial and temporal distribution of the surface mass balance. Sea surface temperature and sea ice extent are prescribed from observations. Generally, good agreement is found between model output and measurements, although in the interior of the ice sheet the temperatures are slightly too high in summer. A statistical relation between precipitation and topographical parameters is derived from model output. Half of the spatial variance in precipitation can be explained by a relation between precipitation and distance to the coast. In the interior of the ice sheet, seasonality of precipitation is mainly determined by temperature, but, near the coast, the dynamics of the flow are important.Year-to-year variations in seasonality of precipitation are large and might affect proxies for meteorological variables in ice cores.

Examines the vertical structure of katabatic flows. Application of varying eddy diffusivities on katabatic floe over glaciers; Association of low level jet with katabatic flows; Employment of the wave-type method in the geophysical boundary layers.

A regional atmospheric climate model with a horizontal grid spacing of 55 km has been used to simulate the Antarctic atmosphere during an austral summer period. ECMWF reanalyses were used to force the atmospheric prognostic variables from the lateral boundaries. Sea surface temperatures and the sea ice mask in the model were prescribed from observations. Parameterizations of the physical processes were taken from the ECHAM4 general circulation model. Before applying the model to Antarctic conditions, several adjustments had been made to the original code. In particular, a better correspondence between model output and measurements was accomplished by 1) the use of a fixed value of 0.8 for the surface albedo rather than applying an albedo that linearly rises with surface temperature and 2) the use of the volumetric heat capacity and the thermal diffusivity of snow rather than employing the values for ice. The model is evaluated for the period 14-19 January 1993 (P1) on the basis of an extensive dataset compiled from measurements made at a site (Svea) in Dronning Maud Land. This dataset contains boundary layer temperature and specific humidity profiles, snow temperatures, and surface heat fluxes. The surface fluxes were obtained from direct measurements combined with an energy balance model. The atmospheric temperature profiles simulated at the grid points corresponding most closely to Svea are in good agreement with the measured profiles, although the model slightly overestimates the vertical temperature gradient. The model probably underestimates the turbulent transport of heat and moisture to atmospheric layers above roughly 200 m. At Svea a cloud cover of less than 0.5 octas was observed during P1. The model overestimates the cloud cover, which results in an underestimation of shortwave and an overestimation of longwave radiative fluxes at the surface. The simulated values for the net radiative fluxes, the heat flux into the snow, and the turbulent.. [ABSTRACT FROM AUTHOR]

Examines repeated advances of the Laurentide ice sheet during episodes of cooler climate as a possible cause of periods of massive iceberg discharge into the North Atlantic ocean during the Pleistocene epoch. Ice-flow model; Mass-balance model; Greenhouse feedback; Size of the Laurentide ice sheet; Orbital parameters; Calving and runoff of melt water; Cooling events.

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.

This article presents albedo measurements of snow and glacier ice at Vatnajo¨kull (Iceland) and the Kangerlussuaq transect (Greenland). Radiative fluxes were measured in the broadband and in four narrowbands, namely, Thematic Mapper (TM) Bands 2 and 4, and Advanced Very High Resolution Radiometer (AVHRR) Bands 1 and 2. The incoming fluxes were measured near the ground and the outgoing fluxes from a helicopter. Extracts of the data collected over snow, ice, supraglacial moraines, supraglacial lakes, and tundra are discussed. Using the data sets from Iceland and Greenland, and data sets with entirely ground-based albedo measurements from the Morteratschgletscher (Switzerland) and Scharffenbergbotnen (Antarctica), new equations for narrowband-to-broadband (NTB) conversion were developed. They have a residual standard deviation of 0.011 for TM and 0.008 for AVHRR and can be applied without having to classify the surface. The helicopter data are also used to develop criteria for distinguishing different types of surfaces, which are needed for the application of Bidirectional Reflectance Distribution Functions (BRDFs). Snow can be distinguished from ice by defining a threshold for a single narrowband albedo. The ratio of the albedos in TM4 and TM2, and to a lesser extent, the ratio of the albedos in AVHRR2 and AVHRR1, may serve as a proxy for the surface characteristics of glacier ice in terms of concentrations of water, debris, and dust. [Copyright &y& Elsevier]

The Antarctic Vostok ice core provided compelling evidence of the nature of climate, and of climate feedbacks, over the past 420,000 years. Marine records suggest that the amplitude of climate variability was smaller before that time, but such records are often poorly resolved. Moreover, it is not possible to infer the abundance of greenhouse gases in the atmosphere from marine records. Here we report the recovery of a deep ice core from Dome C, Antarctica, that provides a climate record for the past 740,000 years. For the four most recent glacial cycles, the data agree well with the record from Vostok. The earlier period, between 740,000 and 430,000 years ago, was characterized by less pronounced warmth in interglacial periods in Antarctica, but a higher proportion of each cycle was spent in the warm mode. The transition from glacial to interglacial conditions about 430,000 years ago (Termination V) resembles the transition into the present interglacial period in terms of the magnitude of change in temperatures and greenhouse gases, but there are significant differences in the patterns of change. The interglacial stage following Termination V was exceptionally long--28,000 years compared to, for example, the 12,000 years recorded so far in the present interglacial period. Given the similarities between this earlier warm period and today, our results may imply that without human intervention, a climate similar to the present one would extend well into the future.