Environment Counts | Glaciers, ice sheets, sea ice and the environment
Author: Rick Higgins – Published At: 2013-09-18 22:41 – (1145 Reads)
|
There is mounting evidence that climate change is contributing to a shrinking and thinning of many glaciers around the world, according to the UN Environment Program (UNEP). Glaciers, sea ice and the World’s two continental ice sheets (which together compose the largest part of the earth’s cryosphere) have a major impact on the global environment. The water supply of hundreds of millions of people is at risk as glaciers continue to shrink and disappear. Continuing rise in the global sea level is determined largely by melting of the two continental ice sheets with smaller rises from melting glaciers. Sea ice is a significant contributor to the conveyor-belt of ocean circulation. Ice covers approximately 16 million sq km of the world’s land surface with an estimated volume of 28 to 30 million cu km. Around 70% of the entire freshwater resources of the World is in the form ice. This article is a high level summary of the world’s ice; its magnitude, geographic distribution and importance in the environment. It may be used to provide a global context to other articles on this site which cover more scientific and regional aspects of ice and the environment. UNEP 2008 Global Glacier Changes
|
Glaciers and the environment
The two continental ice sheets (in Antarctica and Greenland)
along with glaciers and ice along with glaciers and ice cover some 10 per cent of the earth’s land surface and contain around 70 per cent of the entire freshwater resources of the Earth. Changes in glaciers provide some of the clearest evidence of climate change, and as such they constitute key variables for early detection strategies in global climate-related observations. Changes in this land ice have impacts on global sea level fluctuations, regional and local natural hazard situations, and on societies dependent on glacier melt water. Sea ice (primarily in the Arctic and Antarctic regions) is a significant factor in ocean circulation, sea and animal life and shipping.
Ice sheets
- The World’s two (so called continental) ice sheets of Antarctica and Greenland together contain more than 99 per cent of the World’s freshwater ice. In turn this represents approximately 70 per cent of the entire freshwater resources of the Earth. In turn this represents approximately 70 per cent of the entire freshwater resources of the Earth.
- The Antarctic ice sheet covers an area of some 13.6 million sq km; larger than the area of the USA and Mexico combined. The Antarctic ice sheet contains around 28 – 30 million cu km of ice.
- The Greenland ice sheet covers an area of some 1.7 million sq km and it contains around 2.8 million cu kms of ice.
- If the Antarctic ice sheet melted the sea level would rise by about 60 m (200 ft).
- If the Greenland ice sheet melted the sea level would rise by about 6 m (20 ft).
Source: National Snow and Ice Data Center (NSIDC).
Glaciers
- In proportion to Antarctica and Greenland the world’s
glaciers outside these two ice sheets cover much smaller areas. - Glaciers on the Canadian arctic islands cover an area of some 150,000 sq kms.
- Glaciers in Asia (including the Himalaya, Karakoram and Tien Shan) cover around 120,000 sq kms.
- All other glaciated areas of the World are relatively smaller than these.
- The IPCC estimates (2007) the total area of land ice (ie glaciers and ice caps, but excluding the two continental ice sheets) at around 540,000 sq kms. The corresponding potential sea level rise from the melting of these glaciers and ice caps is estimated at between
150 and 370 mm. - If the trend continues it is possible that glaciers may completely disappear from many mountain ranges in the 21st century.
- There is mounting evidence that climate change is triggering a shrinking and thinning of many glaciers world-wide which may eventually put at risk water supplies for hundreds of millions of people. If the trend continues it is possible that glaciers may completely disappear from many mountain ranges in the 21st century.
Sea ice
Sea ice is (which occurs mainly in the Polar Regions) has a significant influence on the global climate. Its bright surface reflects sunlight so those areas don’t absorb as much solar energy and temperatures remain relatively cool. Melting of sea ice over time results in less reflected sunlight which in turn leads to more solar energy being absorbed and temperature rises. The cycle is temporarily
halted during the polar winters to restart in the spring. However, even a small temperature increase can lead to more warming over time and this makes the Polar Regions among the most sensitive areas on Earth to climate change.
- Sea ice, and its impact on salinity, is a significant contributor to the global “conveyor-belt” of ocean circulation.
- Too much or too little sea ice can be a problem for wildlife and people who hunt and travel in Polar Regions.
- In the Arctic, sea ice can be an obstacle to normal shipping routes through the Northern Sea route and Northwest Passage.
- Mean Antarctic sea ice cover over 1979 – 2000 was 18.7 million sq km in September vs 2.9 million sq km in February. Source: http://earthobservatory.nasa.gov/Features/WorldOfChange/sea_ice_south.php
- Arctic sea ice cover was approximately 15 million sq km in March 2013 and 3.4 million sq km in September 2012. The following link provides access to an interesting interactive graph on Arctic sea ice variations from 1979 to 2013. Arctic sea ice variations interactive graph – NSDIC
- In recent years the annual Arctic sea ice cover has been declining, whereas the annual Antarctic sea ice cover is showing small increases.
The Cryosphere
Glaciers, ice sheets and sea ice compose
the largest part of the earth’s cryosphere. Other components include frozen ground/permafrost, snow cover and river and lake ice. The cryosphere (the frozen part of the earth’s surface) is a major influence on the global climate through its influence on temperature, energy, ocean currents and salinity, and gas flux (eg methane from permafrost melt). The adjacent diagram provides and indicative overview of the time scale of each component of the cryosphere.
Sources:
UNEP 2008 Global Glacier Changes
Arctic sea ice concentrations: interactive graph. NSDIC
Environment Counts article: The water cycle – a summary
NASA Earth Observatory: Sea ice concentration
The Cryosphere: An Interactive Open Access Journal of the European Geosciences Union
