bluuebunny/crossref_metadata_2025_split huggingface dataset:
Snow-Collection Mechanisms and the Capacities of Snow Fences
Authors: Takeuchi Masao 
Published: September 2017

The shapes of equilibrium lee drifts formed by snow fences are scaled in proportion to height of snow fences independent of the snow and weather conditions, even in small-scale models, but those of up-wind drifts are not.Field studies have been made of the snow-collection mechanisms of a snow fence. It has been observed that particles of saltated snow piled up to windward, and that it was the previously suspended particles that were heaped up in the lee drift. It can be shown that the shapes of up-wind drifts vary in different snow and weather conditions because threshold shear stress and drift-snow saltation depend on the physical properties of the surface snow.Equilibrium lee drifts are scaled in proportion to fence height, because snow and weather conditions have less effect on threshold wind speed for suspension, and the sheltering effect of a fence is scaled in proportion to the height of the fence.The dimensions of the equilibrium drifts at snow fences were measured, and maximum snow-retention capacity and lee-drift length presented as a function of fence height, fence density, and depth of snow cover.
Forty Years of Mass-Balance Observations on Glacier de Sarennes, French Alps
Authors: Valla François 
Published: September 2017

Located south of Grenoble, in the French Alps, Glacier de Sarennes is a small cirque glacier whose mass balance has been measured since 1948.Field measurements are made after the accumulation period (from October to May) and during the ablation period (from June to September). The main variables for snow are depth, density, and water equivalent for accumulation, together with ice depth and water equivalent for ablation which are used to calculate mass balance and regime. We present an example of the data collected on the glacier during the 1986–87 season, the evolution of the mass balance during the summer of 1987, and the main variables followed during the 40 years of observation, 1948–88. Mass balance, accumulation, and ablation are directly related to precipitation and temperature. Glacier de Sarennes is a simple glacier which has no tongue and no ice movement, and is like a gigantic rain gauge. The evolution of its mass balance is simply related to the meteorological variables of the year. For more significant and complex glaciers, it is necessary to take account of past as well as present meteorological variables.
Air-Ice-Ocean Feedback Mechanisms and Ice Oscillation on Millennial Time Scales
Authors: Chu P.C. 
Published: September 2017

Air-ice-ocean feedback mechanisms, which are not conventionally incorporated within either climate or glacial models, are investigated to illustrate their potential role in generating ice advance/retreat on the time scale of 103–104 years; i.e. for examining the internal causes for the ice oscillation.Three main feedback loops are found from a coupled air-ice-ocean model developed in this paper: (a) ice advance → lower air temperature → ice freezing → ice advance; and (b) ice advance → higher ocean temperature → ice melting → ice retreat; (c) ice advance/retreat → modification of evaporation rate → change of ice accumulation rate and sea-level height → ice advance/retreat. The relative strength of the three feedback mechanisms determines the characteristics of the modes: growing or decaying, oscillatory or non-oscillatory. The solutions show the generation of growing oscillatory modes with the time scale of 103–104 years in certain parameter ranges.
The Atmosphere’s Response to the Ice Sheets of the Last Glacial Maximum
Authors: Cook Kerry H. 
Published: September 2017

This paper discusses some modeling results that indicate how the atmospheric response to the topography of the continental ice of the Last Glacial Maximum (LGM) may be related to the cold North Atlantic Ocean of that time. Broccoli and Manabe (1987) used a three-dimensional general circulation model (GCM) of the atmosphere coupled with a fixed-depth, static ocean mixed-layer model with ice-age boundary conditions to investigate the individual influences of the CLIMAP ice sheets, snow-free land albedos, and reduced atmospheric CO2 concentrations. They found that the ice sheets are the most influential of the ice-age boundary conditions in modifying the northern hemisphere climate, and that the presence of continental ice sheets alone leads to cooling over the North Atlantic Ocean.One approach for extending these GCM results is to consider the stationary waves generated by the ice sheets. Cook and Held (1988) showed that a linearized, steady-state, primitive equation model can give a reasonable simulation of the GCM’s stationary waves forced by the Laurentide ice sheet. The linear model analysis suggests that the mechanical effect of the changed slope of the surface, and not changes in the diabatic heating (e.g. the high surface albedos) or time-dependent transports that necessarily accompany the ice sheet in the GCM, is largely responsible for the ice sheet’s influence. To obtain the ice-age stationary-wave simulation, the linear model must be linearized about the zonal mean fields from the GCM’s ice-age climate. This is the case because the proximity of the cold polar air to the region of adiabatic heating on the downslope of the Laurentide ice sheet is an important factor in determining the stationary waves. During the ice age, cold air can be transported southward to balance this downslope heating by small perturbations in the meridional wind, consistent with linear theory. Since the meridional temperature gradient is more closely related to the surface albedo (ice extent) than to the ice volume, this suggests a mechanism by which changes in the stationary waves and, therefore, their cooling influence at low levels over the North Atlantic Ocean, can occur on time scales faster than those associated with large changes in continental ice volume.
Air Temperature and Precipitation at Wolverine Glacier, Alaska; Glacier Growth in a Warmer, Wetter Climate
Authors: Mayo L.R. , March R.S. 
Published: September 2017

Measurements at Wolverine Glacier, Alaska, from 1968 to 1988 indicate unsteady increases of air temperature and precipitation since the early 1970s. These increases were due almost entirely to changes in winter. Variations in annual temperature and precipitation at Wolverine Glacier and at Seward, a nearby climatological station at sea level, correlate positively with global temperature variations and are in general agreement with the changes at high latitudes predicted by five recent general atmospheric circulation models forced by anticipated rises of CO2.A consequence of the air temperature and precipitation increases at Wolverine Glacier was a change to a generally positive mass balance after 1976. Although these observations in the coastal maritime climate of Alaska run against the common, oversimplified notion that in a warming climate glaciers will melt, causing sea level to rise, they are logical and easily understood when the sensitivity of the glacier to the seasonal distribution of the changes is considered. The observed seasonal changes at Wolverine Glacier also are in agreement with global climate models. Snow precipitation and glacier accumulation increased, but at the same time warming affected only these those temperatures below about −5°C, and melting was not altered. The extent of this response is not well known, but the process may be taking place in other important glacierized regions.
Climate Sensitivity and Equilibrium Climate States Of A Two-Dimensional Energy Balance Model
Authors: Huang Jin , Bowman Kenneth P. 
Published: September 2017

A two-dimensional energy balance model (EBM) with a seasonal cycle and a realistic land–ocean distribution is used to study climate sensitivity and the properties of equilibrium climate states. The land–ocean distribution is represented by the heat capacity of the surface. The horizontal heat flux is parameterized by diffusion. Nonlinearity is introduced into the model by the albedo–temperature feedback. A multi-grid finite difference method is used to solve the model equation. This method shows great advantages compared to other numerical methods.The sensitivity of snow cover to changes in the solar constant is examined. It is found that the climate is more sensitive in summer due to a more effective albedo–temperature feedback. The local annual mean temperature and the amplitude of the seasonal cycle depend on the land–ocean distribution. Because Eurasia has the largest annual cycle of temperature and is the coldest in winter, winter snow appears first in Eurasia as the solar constant is reduced. Wintertime snow appears next in Greenland because of its low annual mean temperature and last in North America. Perennial snow cover appears first in Greenland because of the low annual mean temperature and the small annual cycle, and next appears in North America. Perennial snow in Eurasia appears only when the solar constant is reduced to a very low value, since the Eurasian land mass is too hot in summer for perennial snow cover. The sensitivity of the model climate to changes in the orbital parameters is also investigated and discussed.Small polar ice caps in one-dimensional mean-annual EBMs are unstable to small perturbations. The ice caps either vanish or grow to a stable finite size. This phenomenon, referred to as the small ice-cap instability (SICI), is a consequence of the multiple stable equilibrium states in one-dimensional models. The SICI may be related to glacial–interglacial transitions. However, numerical results with the two-dimensional EBM demonstrate that the existence of the SICI depends on the land–ocean distribution. The SICI exists in the southern hemisphere, but not in the northern hemisphere. This casts doubt on the role of the SICI in northern hemisphere glaciations. Experiments with a one-dimensional seasonal EBM with simplified geography have been made to analyze the two-dimensional results. Mechanisms for the existence of the SICI in seasonal EBMs are discussed.
Climatic Warming, Glaciers and Sea Level
Authors: Koerner R.M , Fisher D.A. 
Published: September 2017

The modern concensus outside of the glaciological community is that “greenhouse” gases, released by human activity, will cause an unprecedented temperature rise over the next 100 years and thereby cause a socially-threatening rise of sea level. With respect to ice the concept is simple: warmer means less. The relationship between glaciers and climate is much more complex than this. Warmer also means more vapour transport and there is ample evidence from both theory and ice-core data that snow accumulation rates in both Greenland and Antarctica were lower during the last glacial period. The problem is whether the increased accumulation rates will be exceeded by increased melting of ice in the ablation areas. Antarctica could play a dominant role because of its size and very low temperatures. Only a small percent of Antarctica will increase its meltwater run-off into the ocean. Furthermore, its dynamic response time is so large that the calving rate will not change over a 200-year period. Most of the increased melt will be absorbed in the firn and the question is how much the snow accumulation rate will increase over the major part of the continent.In the northern hemisphere one has to consider the way in which the warming will manifest itself seasonally. Most of the “forecasts” indicate that most of the warming will occur in the winter rather than the summer. In this case one has to consider the balance between greatly increased winter snowfall rates and only slightly increased summer melt rates. In this respect a review of the snow accumulation and ice melt rates from different glaciers and ice caps in the Canadian Arctic Islands is pertinent. Over the past 20 to 30 years we see no sign of a trend of either side of the balance equation (accumulation, melt). Is this the effect of high noise levels or is there simply no trend?Finally, we review the ground-ice potential in terms of sea-level change. Ground ice may not form a large part of the world's ice reserves but it covers a large area. Both increased snowfall rates in winter, and summer warming will move to increase the thickness of the active layer. This will result in run-off to the oceans.Global circulation models might be modified to determine a “best guess” of future sea-level change. To do this they must incorporate all of the parameters considered in this paper.
Climate Sensitivity: The Significance of the Altitude-mass-balance Feedback on Glaciers and Ice Sheets
Authors: Letréguilly Anne , Oerlemans Johannes 
Published: September 2017

An ice mass increasing its extent will generally also increase its mean surface elevation (anything else being unchanged). Since temperature drops rapidly with height this often implies a more positive mass balance and thus further growth. This powerful feedback loop is at least as important as the temperature-albedo feedback. In this work, we present a general study of the nature of the altitude-mass-balance feedback, with special attention for the role of differences in the bedrock geometry. One- and two-dimensional experiments on various bedrock topographies are run, using a numerical ice-sheet model based on plane shear flow of ice. Different climates are simulated by lowering or raising uniformly the mass-balance distribution over the ice sheet.These studies were first done on steady state ice sheets. They show that some geometries can largely enhance this altitude mass-balance feedback. On an island, for instance, it is possible to have two different stable steady states under the same climatic environment: no ice sheet, or a large one over the whole island. When the geometry of the island becomes more complex, for instance with two hills of unequal heights, four different equilibria can be found for the same climatic conditions: no ice sheet, one small one, two small ones or a very large one. Which will develop depends entirely on the history of the mass-balance fluctuations.
Effects Of Eurasian Snow Cover On Atmospheric Circulation In The Northern Hemisphere
Authors: Morinaga Yuki , Yasunari Tetuzo 
Published: September 2017

Effects of Eurasian snow cover were first noted by Blanford (1884) who found an inverse relationship between summer monsoon rainfall over India and winter snow cover over the Himalayas. Hahn and Shukla (1976) confirmed it by using satellite-derived data and their work stimulated succeeding studies on the interaction between large-scale snow cover and atmosphere. Matson and Wiesnet (1981) showed that interannual variation of northern hemisphere snow cover is dominated by Eurasian snow cover, both showing similar trends and fluctuations during 1967–79. Recent studies (Barnett, 1988) also noted that Eurasian snow cover has a greater feedback potential than that of North America on hemispheric-scale climatic anomalies.Though the importance has been thus recognized, not many studies have been done on the interaction between Eurasian snow cover and large-scale atmospheric circulation anomalies. Morinaga and Yasunari (1987) studied lag correlations between satellite-derived snow-cover extent over central Asia and the 500 mb-geopotential height field in the Northern Hemisphere (1967–84), and indicated that so-called Eurasian pattern (Wallace and Gutzler, 1981) in December brings large snow-cover extent in February; in turn, February snow cover has a considerable lingering effect on the atmosphere in April.This study present further results on the time-lag teleconnections of the atmosphere associated with Eurasian snow-cover anomalies and their physical implications including the evaluation of snow-hydrological process.
Parameterization Of Boundary Conditions Between The Atmosphere and Cryosphere
Authors: Morris E.M. , Harding R.J. 
Published: September 2017

Parameterization of the boundary conditions between the atmosphere and cryosphere is an important part of the general problem of modelling climatic change. It is necessary to define the mass, momentum and energy exchanges at the ice/atmosphere interface in order (i) to use atmospheric global circulation models (AGCMs) to predict future climate and (ii) to use snow, glacier or ice-sheet models to predict the corresponding response of the cryosphere. The physics of the boundary processes are fairly well known; the difficulty lies in choosing the appropriate space and time scales for modelling and in understanding the changes in the effective values of the model parameters which may be produced by spatial and temporal averaging.Sensible heat, water vapour and momentum are tranferred vertically in the boundary layer of the atmosphere by turbulent motion. Equations for these fluxes contain parameters, the so-called scaling lengths zH, ZE and z0. Net radiation input to snow or ice is controlled by the albedo of the surface, α These four parameters play a major role in defining the boundary conditions between the atmosphere and cryosphere. It is normally assumed that their values are constants, determined by the characteristics of the snow or ice surface alone. For example, climate models may set zH = Ze = z0 = 0.1 mm and α = 0.9 for smooth, fresh snow. However, in modelling practice it is often found that the effective values of the parameters, i.e. those values that give the best simulations, are also influenced by the level of variability in the meteorological conditions.The authors have made intensive micro-meteorological studies in the firn area of the Hintereisferner, Ötztal Alpen (Austria), on a frozen lake near Finse, Hardangervidda (Norway), and in the south-west coastal region of Greenland. Data from these field sites will be used to investigate the sensitivity of effective values of the boundary condition parameters to the choice of time scale using the Institute of Hydrology Distributed Model (IHDM).
Nitrate In Coastal Antarctic Shallow Firn Cores: Comparison Of Seasonal Pattern and Of Total Flux
Authors: Moser K. , Wagenbach D. , Münnich K.O 
Published: September 2017

With the intention of contributing to a better understanding of snow depth profiles used in reconstructing the southern hemisphere nitrate background we have measured C1−, , and in firn cores from two coastal Antarctic locations (GvN = Ekströmisen 70°S, 8°W, and Filchner = Filchner-Ronne Ice Shelf 79°S, 57°W). The depth resolution chosen is 2 cm per sample (i.e. 36 and 14 samples per year, respectively).The isotopie composition of the firn cores was concurrently measured, with equally high resolution (deuterium and 18O data, W. Graf, private communication). The GvN core yields an average accumulation rate of 35 cm H2O per year during the period 1979–86, while the Filchner core gives 14 cm H2O per year during the period 1955-80. The net snow accumulation being relatively high allows precise determination of the year to year boundaries, as well as the relative contribution of individual seasons to the total net accumulation. This was achieved by combining the stable isotope data with the chemical tracers nss-sulfate (high concentration in summer) and sea salt (high C1− in autumn and winter). For the two individual locations this procedure allowed assessment of the glacial nitrate concentration seasonality as well as comparing the yearly nitrate deposition.The Filchner location shows a distinct seasonality with maximum concentrations in summer. For nearly half of the years covered we also find higher concentrations in winter. This higher nitrate in winter is always accompanied by high sea salt concentrations. We suggest therefore a mechanism making sea salt aerosol an additional deposition pathway for nitrate in winter. This means that we are not able to link the enhanced winter nitrate deposition to stratospheric denitrification directly. The GvN core does not show significant seasonality. This is presumably due to frequent snow drift events preventing signal conservation.Although the individual accumulation rates differ by a factor of 2.5 the yearly nitrate deposition is in the same range (4-11 kg (km-2 a-1) at both sites. This is caused by the different seasonal modulation of the net snow accumulation. At GvN low nitrate autumn precipitation prevails and keeps the yearly nitrate level constantly low (18-22 ppb). At Filchner, however, a high contribution of summer snow brings the yearly concentration average up to about 30–70 pbb.
Some Possible Causes For Recent Variations Of Patagonian Glaciers
Authors: Naruse Renji , Aniya Masamu 
Published: September 2017

The Patagonian glaciers located in the southern part of the Andes between 46°30′S and 51°30′S are characterized by typical temperate conditions of heavy precipitation, rapid ice flows and high melting rates. During the austral summers of 1983–84 and 1985–86, field studies were made of the ice flow, heat balance and morphology of several glaciers in Patagonia. Coupled with aerial photographic surveys, these revealed that most glaciers had retreated extensively in the recent years, a maximum being 200 m a-1 at San Rafael Glacier from 1974 to 1986. The lower part of Soler Glacier had thinned by a rate of 5.2 m a-1 from 1983 to 1985.This paper presents three possible mechanisms to explain the large variation of temperate glaciers during the last decade, based on analyses of mass balance and dynamics of Patagonian glaciers:(1) The annual melting rate was estimated at about 10–15 m a-1 in water equivalent over the ablation area (from 350 to 1350 m a.s.l.) of Soler Glacier. Monthly mean air temperature in the coldest season (June through August) was estimated at about 0°–4°C near the termini of most glaciers in Patagonia. That temperature coincides with an air temperature which is critical for solid or liquid precipitation. The difference in the surface albedo, that is, 0.7–0.8 for new snow and 0.4–0.55 for bare ice (0.1–0.2 for debris-covered ice), results in different melting rates. Hence, a slight change in air temperature should cause an enhanced change in ice thickness by a positive feedback mechanism.(2) The flow velocity was measured or estimated and was found to change daily and seasonally by factors of 3 to 5 at Soler Glacier. The large flow velocity variation was attributed to difference in the basal sliding velocity. Consequently, a change in the amount of subglacial water or the structure of the basal water system should cause a large change in the ice flow, which in turn results in a retreat or an advance of the glacier-like “mini-surge”.(3) Frequent fluctuations of calving glaciers (e.g. San Rafael and Pio XI glaciers) have been much reported; however, information on the position of the grounding lines is very scarce. The advance or retreat of the glacier front may possibly have been affected by that of the floating terminus. The rate of calving from the ice tongue or spreading of ice shelves should mainly be controlled by the melting rate of ice in the water and by the mechanical properties of ice, and these factors are not directly related to climatic change or the surge phenomenon.