essay on ice in kannada
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Glaciers and ice caps are among the most fascinating elements of nature, an important freshwater resource but also a potential cause of serious natural hazards. Because they are close to the melting point and react strongly to climatic change, glaciers are important indicators of global climate.
Glaciers reached their Holocene (the past 10000 years) maximum extent towards the end of the Little Ice Age (the Little Ice Age extended from the early 14th to mid-19th century.) Since then, glaciers around the globe have been shrinking dramatically, with increasing rates of ice loss since the mid-1980s.
Glaciers and ice caps formed around the world where snow deposited during the cold/humid season does not entirely melt during warm/dry times. This seasonal snow gradually becomes denser and transforms into perennial firm (rounded, well-bonded snow that is older than one year) and finally, after the air passages connecting the grains are closed off, it is converted to ice. The ice from such accumulation areas then flows under the influence of its own weight and the local slopes down to lower altitudes, where it melts again (ablation areas).
Accumulation and ablation areas are separated by an equilibrium line, where the balance between gain and loss in the ice mass is exactly zero. Where glaciers formed depends not only on air temperature and precipitation, but also on the terrain, which determines how much solar radiation the glacier will receive and where ice and snow will accumulate.
In humid-maritime climates the equilibrium line is at a relatively low altitude because, for ablation to take place, warm temperatures and long melting seasons are needed to melt the thick layers of snow that accumulate each year. These landscapes are thus dominated by ‘temperate’ glaciers with firn and ice at melting temperatures.
The response of a glacier to climatic change involves a complex chain of processes. Changes in atmospheric conditions (such as solar radiation, air temperature, precipitation, wind and cloudiness) influence the mass and energy balance at the glacier surface.
The total increase of global mean air temperature of about 0.75°C since 1850 is clearly manifested in the shrinking of glaciers and ice caps worldwide. The sensitivity of glaciers in humid-maritime areas to this warming trend has been found to be much higher than that of glaciers in dry-continental areas.
According to climate scenarios for the end of the 21st century, changes in global temperature and precipitation ranges between +1.1 and +6.4°C and -30 and +30 per cent, respectively. Such an increase in mean air temperature will continue the already dramatic glacier changes.
Changes in glaciers may well lead to hazardous conditions, particularly in the form of avalanches and floods, and thus have dramatic impacts on human populations and activities located in glacierized mountain regions. The majority of glacier hazards affect only a limited area—often only a few square kilometres—and mostly pose a danger to densely populated mountain regions such as the European Alps. In some cases, however, glacier hazards have far-reaching effects over tens or even hundreds of kilometres and thus also affect less densely populated and developed mountain regions.
The long-term average annual economic loss from glacier disasters or related mitigations costs are estimated to be in the order of several hundred million U.S. dollars. The largest disasters have killed more than 20,000 people, for instance the Huascaran rock-ice avalanches in Peru in 1970 or the Nevado del Ruiz lahars (rapidly flowing volcanic debris flows) in Colombia in 1985.
Landscapes around many high-mountain regions also in vast lowlands were moulded and sculpted by large ice bodies during the most recent part of Earth’s history—the Ice Ages—over the last few million years. The detection, in the first half of the 19th century, of corresponding traces from glacier erosion and of erratic boulders far from mountain chains led to the formulation of the Ice Age theory by Louis Agassiz and colleagues.
It was soon understood that large ice sheets had formed over North America and even entirely covered Scandinavia, lowering global sea level by more than 100 m, greatly modifying coastlines of all continents and dramatically affecting the courses of large rivers and the global ocean circulation.