Considering that glaciers and ice sheets cover about 10% of the Earth's land surface in a world where human civilization is increasingly impacted by the effects of changing glacial activity, Colour Atlas of Glacial Phenomena presents itself as an indispensable guide for students, professionals, and researchers who want to be better informed while studying and tracking the future influences of glaciers and ice sheets on the global environment. While stressing both the beauty and utility of glaciers, the authors cover critical features of glaciers and their landforms and provide useful explanations of the key concepts in glaciology and glacial geology. The authors expand to demonstrate how our lives are influenced by the Cryosphere, a key component of the Earth system and how this heightens the vulnerability of glaciers and ice sheets to deterioration. This illustrated book also helpfully maps out regions of mountain glaciers and ice caps around the world for a practical reference and discusses the products of glacial erosion and deposition integral to understanding rising global sea levels.
An estimation of average mass balance of a high hanging glacier in the Swiss Alps was made by measuring volumes of ice avalanches originating from this glacier. Ice avalanches are this glacier’s predominant form of ablation. Since the volume of the glacier has not noticeably changed over the past few years, the annual ice loss due to ice avalanches can be taken as an indication of average total net acumulation above the ice cliff where the avalanches originate. The mass balance value, as determined by recording ice avalanches, compares well with values obtained by independent methods (measurements of firn stratigraphy in the cliff, direct accumulation measurements in the vicinity). No seasonal variation in the frequency of ice avalanche occurence was detected.
An estimation of average mass balance of a high hanging glacier in the Swiss Alps was made by measuring volumes of ice avalanches originating from this glacier. Ice avalanches are this glacier’s predominant form of ablation. Since the volume of the glacier has not noticeably changed over the past few years, the annual ice loss due to ice avalanches can be taken as an indication of average total net acumulation above the ice cliff where the avalanches originate. The mass balance value, as determined by recording ice avalanches, compares well with values obtained by independent methods (measurements of firn stratigraphy in the cliff, direct accumulation measurements in the vicinity). No seasonal variation in the frequency of ice avalanche occurence was detected.
Assessing risks from potential glacier hazards in relation to safety considerations for settlements and other fixed installations in high mountain areas requires the application of experience gained from previous events, combined with simple rules derived from basic glaciological theory. The general characteristics of steep, and usually unmeasured, glaciers can be estimated on the basis of a rough parameterization scheme. Variations in glacier length, ice avalanches, and glacier floods then have to be considered for time periods ranging from a few years up to a few decades. As a result of such systematic assessments, maps of potentially dangerous zones can be prepared. Although the inhabitants of many Alpine villages have always lived with the risk of glacier hazards, it now appears that modern construction work, especially that connected with the development of tourism, has started to infiltrate previously avoided high-risk zones more and more. In order to plan reasonable safety measures, risks from glacier hazards have to be compared with those from other natural hazards in mountain areas, such as snow avalanches, landslides, rock falls! or storm-induced floods. Decisions about the acceptable level of risk are difficult and subjective; they are also often influenced by political and economical considerations rather than by scientific reasoning.
Glaciers are sometimes called ‘rivers of ice ’. However, this is misleading since glaciers do not normally form from rainfall, but by the transformation of snow to ice. To initiate a glacier, winter snowfall needs to be great enough for some of the snow to last throughout the following summer. This process is then repeated for several years. Finally, under the pressure of its own weight the snow turns into ice. If the ice is thick enough, it flows under the influence of gravity. This transformation of snow to ice is often a long and complex process, since both the nature of the transformation and the time involved depend on temperature and the depth of further, overlying snow. The transformation is most rapid in temperate regions, such as the Alps and the Western Cordillera of North America, where ice can form from snow within five to ten years. In contrast, the transformation in high polar latitudes or at high elevations may take hundreds of years.
Data on temperature and accumulation of high altitude firn in the Alps are compiled and discussed. Firn temperature varies with incoming radiation (slope aspect) at a given altitude. The altitudinal gradient of temperature in highly permeable firn bodies appears to be about twice as high as the mean lapse rate of air temperature. “Cold infiltration” takes place above about 3500 m a.s.l. Firn temperatures on the highest peaks are around -15°C. Accumulation (net balance) also decreases with increasing altitude from about 3m H 2 O at 3500 m a.s.1. to around 0.5 m H 2 O at wind exposed sites between 4300 and 4800 m a.s.l. Probably this is strongly due to wind erosion and topographical effects. However, temperature and accumulation not only appear to be interrelated, but also seem to be positively correlated to the heat applied to the surface. Assuming the observed altitudinal gradients have remained constant in time, it can be estimated that high altitude firn bodies have become considerably warmer since the last century. CO 2 -induced atmospheric warming could lead to a drastic change in (he mass turnover and flow activity of high glaciers, in wind-exposed places where wind erosion of the snowpack becomes a controlling factor of accumulation.
Distributional patterns of glaciological parameters at the Colle Gnifetti core drilling site are described and their interrelationships are brietly discussed. Observations within a stake network established in 1980 furnish information about snow accumulation (short term balance), submergence velocity of ice flow (long term balance), ram hardness (melt layer stratigraphy), and firn temperature. In addition, a numerical model was used to estimate local variations of available radiant energy.
Melt layer formation is considerably more intensive on the south facing parts of the firn saddle where incoming radiation is high. These melt layers seem to effectively protect some of the fallen snow from wind erosion. As a result, balance ist up to one order of magnitude larger on south facing slopes. Heat applied to the surface is therefore positively correlated with balance, whereas the relation between solar radiation and firn temperature is less clear. Distributional patterns of submergence velocity confirm that the observed spatial variability of surface balance is representative for longer time periods and greatly influences the time scale and the stratigraphy of firn and ice cores from Colle Gnifetti.
Assessing risks from potential glacier hazards in relation to safety considerations for settlements and other fixed installations in high mountain areas requires the application of experience gained from previous events, combined with simple rules derived from basic glaciological theory. The general characteristics of steep, and usually unmeasured, glaciers can be estimated on the basis of a rough parameterization scheme. Variations in glacier length, ice avalanches, and glacier floods then have to be considered for time periods ranging from a few years up to a few decades. As a result of such systematic assessments, maps of potentially dangerous zones can be prepared. Although the inhabitants of many Alpine villages have always lived with the risk of glacier hazards, it now appears that modern construction work, especially that connected with the development of tourism, has started to infiltrate previously avoided high-risk zones more and more. In order to plan reasonable safety measures, risks from glacier hazards have to be compared with those from other natural hazards in mountain areas, such as snow avalanches, landslides, rock falls! or storm-induced floods. Decisions about the acceptable level of risk are difficult and subjective; they are also often influenced by political and economical considerations rather than by scientific reasoning.
To many people, the most obvious benefit of glaciers is their landscape value. This is especially true when visiting glacierized areas such as the Alps or Alaska, or glaciated areas like the Scottish Highlands and Yosemite National Park in California. However, we may also pose some questions concerning the wider importance of glaciers in terms of the benefits they provide for human civilization. For example, we may well ask: ‘How much is a glacier worth?’ ‘Would it matter if most glaciers in temperate latitudes melted away?’ ‘How can glaciers, their meltwaters and depositional products be used for our benefit? ’. Therefore, in this chapter we explore not only the benefits of today's glaciers, but also those that have long since disappeared.
