What are the differences between 1982 pennies

Glaciers (polar regions)

1 polar regions

Despite their importance to humans, the mountain and valley glaciers of medium latitude and the tropics contain only a small proportion of the glacier ice on earth. About 99% of all freshwater ice is in the large polar and sub-polar ice sheets of Antarctica and Greenland. These continental ice sheets, which are 3 km or more thick, cover much of the polar and sub-polar land masses. Like rivers from a huge lake, numerous glaciers flow from the edge of the ice sheets into the ocean, transporting huge amounts of ice.

The observation and measurement of ice sheets has improved significantly in recent years. In 1992 it was still assumed that the annual mass balance of the Antarctic, for example, was in a range from -600 Gt to +500 Gt. Today the estimates are much more precise. The ice sheets of Greenland and Antarctica are currently losing around 125 gigatons together[1] in mass per year. The loss of Greenland contributes 100 Gt and that of West Antarctica 50 Gt. East Antarctica is gaining about 25 Gt in mass.[2] The improved observations can therefore capture the current situation quite precisely. Nowadays science is particularly troubled by the dynamics in ice sheets and glaciers that are not understood. These make it very difficult to reliably model changes in the future.[3]

1.1 Antarctica

In Antarctica, the mean temperature has increased by an estimated 0.2 ° C since the 19th century.[4] The first complete gravity analysis over the entire Antarctic ice sheet showed that in the observation period between April 2002 and August 2005 the annual loss of ice mass averaged 152 (± 80) km3 scam.[5] There is considerable variability in precipitation, but no clear trend. If the entire continent is considered, there has been no permanent and significant change in snowfall at least since the 1950s. Between 1985 and 1994 the amount of precipitation increased, especially in the interior of the Antarctic, while it had decreased in some areas in the coastal areas. This trend was then practically exactly reversed, so that between 1995 and 2004, apart from three exposed regions, less snow fell almost everywhere, in places up to 25%.[6]

The loss of ice in the Antarctic became particularly dramatic when large parts of the Larsen Ice Shelf broke up. If you look closely, the Larsen Ice Shelf consists of three individual shelves that cover different areas on the coast. These are called Larsen A, Larsen B and Larsen C (from north to south). Larsen A is the smallest and Larsen C is the largest of the shelves. Larsen A disbanded in January 1995, Larsen C is apparently stable at the moment. The dissolution of the Larsen B Shelf was determined between January 31 and March 7, 2002, when it finally broke off with an ice sheet covering an area of ​​3,250 square kilometers. Up until then, the shelf had been stable for over 10,000 years throughout the Holocene. In contrast, the Larsen A Shelf had only existed for 4,000 years.[7]

The Pine Island Glacier in western Antarctica, which flows into the Amundsen Sea, thinned 3.5 ± 0.9 m per year from 1992 to 1996 and has retreated about 5 km over the same period. [8] The neighboring Thwaites Glacier is also losing mass and length.[9] And a decline can also be observed on the Dakshin Gangotri Glacier: Between 1983 and 2002 it retreated by an average of 0.7 m per year. On the Antarctic Peninsula | Antarctic Peninsula, the only part of Antarctica that protrudes beyond the Arctic Circle, there are hundreds of receding glaciers. A study examined 244 glaciers on the peninsula. 212 or 87% of the glaciers receded, averaging a total of 600 m from 1953 to 2003. The Sjogren Glacier has retreated the most with about 13 km since 1953. 32 of the examined glaciers grew. The average growth was 300 m per glacier, which is significantly less than the massive decline observed.[10]

1.2 Iceland

The 8,100 km² Vatnajökull Ice Cap lies on Iceland. Breiðamerkurjökull Glacier, one of the glaciers in the Vatnajökull Ice Cap, shortened by 2 km between 1973 and 2004. At the beginning of the 20th century, the glacier extended up to 250 m into the ocean. By 2004, the end of the glacier had retreated three kilometers inland. As a result, a rapidly growing lagoon has formed, in which there are icebergs that break off the glacier (“calve”). The lagoon is around 110 m deep and almost doubled in size between 1994 and 2004. Since 2000, all but one of the 40 glaciers in the Vatnajökull Ice Cap have gone back.[11] In Iceland, of the 34 glaciers examined, the majority receded between 1995 and 2000 (28), four were stable and two were growing.[12]

1.3 Canadian Arctic Archipelago

There are a number of sizeable ice caps in the Canadian Arctic archipelago. These include the Penny and Barneseis caps on Baffin Island (the fifth largest island in the world with 507,451 km²), the Bylotei Cap on Bylot Island (11,067 km²) and the Devonian Cap on Devon Island (55,247 km²). These ice caps are thinning and slowly retreating. Between 1995 and 2000, the Penny and Barneseis caps thinned by more than 1 m each year at lower altitudes (below 1,600 m). In total, the ice caps of the Canadian Arctic lost 25 km³ of ice annually between 1995 and 2000.[13] Between 1960 and 1999 the Devonian Ice Cap lost 67 ± 12 km³ of ice, mainly through dilution. The main glaciers that extend from the edge of the eastern Devonian Ice Cap have retreated 1–3 km since 1960.[14] The Simmon Ice Cap on the Hazen Highlands on Ellesmere Island has lost 47% of its area since 1959.[15] If the current conditions persist, the remaining glacial ice on the Hazen Highlands will have disappeared by 2050.

1.4 Spitsbergen

To the north of Norway is the island of Spitzbergen in the Svalbard Archipelago between the North Atlantic and the Arctic Ocean, which is covered by many glaciers. The Hansbreen glacier on Spitzbergen z. B. withdrew 1.4 km between 1936 and 1982. It lost another 400 m in length between 1982 and 1998.[16] The Blomstrandbreen has also been shortened: in the past 80 years, the length of the glacier has decreased by around 2 km. Since 1960 it has retreated an average of 35 m per year, with the speed increasing since 1995.[17] The Midre Lovenbreen Glacier lost 200 m in length between 1997 and 1995.[18]

1.5 Greenland

The temperatures in the south of the largest island in the world have risen particularly sharply since the middle of the 20th century, namely by 2.5 ° C. As a result, there were rapid changes in the dynamics of the Greenland | Greenland glaciers. In a comparison of measurements from 2002 to 2004, glacier melt doubled between 2004 and 2006, i.e. in just two years. According to various measurements, the mass loss in Greenland is between 239 ± 23 km3 and 224 ± 41 km3 per year.[19] This loss became particularly evident in 2005 when a new island called Uunartoq Qeqertoq (in English Warming Island) has been discovered. After a large amount of mainland ice had melted, it was found that Uunartoq Qeqertoq was not a peninsula connected to the mainland as had previously been assumed.

The dynamism of individual glaciers in Greenland is surprising. Two of the largest glaciers on the island, the Kangerdlugssuaq and the Helheim, which together contributed 35% to the mass loss of East Greenland in recent years, were examined in more detail by a team led by glaciologist Ian Howat. It turned out that the melting rate of the two glaciers had doubled between 2004 and 2005. By 2006, the mass loss had dropped back to the value of 2004.[20] Such behavior was previously unknown for glaciers, and it illustrates the uncertainty at what speed the Greenland ice sheet will continue to thaw over the next few decades.

2 individual proofs

  1. ↑ One gigatonne equals one billion (109) Tons or a trillion (1012) Kilogram.
  2. ^ Shepherd, Andrew and Duncan Wingham (2007): Recent Sea-Level Contributions of the Antarctic and Greenland Ice Sheets, in: Science, Vol. 315, No. 5818, pp. 1529-1532
  3. ^ Vaughan, David G. and Robert Arther (2007): Why Is It Hard to Predict the Future of Ice Sheets? In: Science, Vol. 315, No. 5818, pp. 1503-1504
  4. ↑ Schneider, D. P., E. J. Steig, T. D. van Ommen, D. A. Dixon, P. A. Mayewski, J. M. Jones, and C. M. Bitz (2006): Antarctic temperatures over the past two centuries from ice cores, in: Geophysical Research Letters, 33, L16707
  5. ↑ Velicogna, Isabella and John Wahr (2006): Measurements of Time-Variable Gravity Show Mass Loss in Antarctica, in: Science, Vol. 311, No. 5768, pp. 1754-1756
  6. ↑ Monaghan, Andrew J., David H. Bromwich, Ryan L. Fogt et al. (2006): Insignificant Change in Antarctic Snowfall Since the International Geophysical Year, in: Science, Vol. 313, No. 5788, pp. 827-831 (PDF)
  7. ↑ E. Domack, D. Duran, A. Leventer, S. Ishman, S. Doane, S. McCallum, D. Amblas, J. Ring, R. Gilbert, M. Prentice (2005): Stability of the Larsen B ice shelf on the Antarctic Peninsula during the Holocene epoch, in: Nature, Vol. 436, pp. 681-685, June 7, online
  8. ↑ E.J. Rignot (1998): Fast Recession of a West Antarctic Glacier, in: Science, Vol. 281, pp. 549-551, July 24, online
  9. ↑ E.J. Rignot (2001): Evidence for rapid retreat and mass loss of Thwaites Glacier, West Antarctica, in: Journal of Glaciology, Vol. 47, pp. 213-222, March, online
  10. ↑ A.J. Cook, A.J. Fox, D.G. Vaughan, J.G. Ferrigno (2005): Retreating Glacier Fronts on the Antarctic Peninsula over the Past Half-Century, in: Science, Vol. 308., pp. 541-544, April 22, online
  11. ↑ Dorothy Hall (2006): Receding Glacier in Iceland, Earth Observatory Newsroom: New Images, Feb. 18, online
  12. ↑ World Glacier Monitoring Service (2005): Glacier mass balance data 2004 , online
  13. ↑ Abdalati, W., W. Krabill, E. Frederick, S. Manizade, C. Martin, J. Sonntag, R. Swift, R. Thomas, J. Yungel, and R. Koerner (2004): Elevation changes of ice caps in the Canadian Arctic Archipelago, in: J. Geophys. Res., 109, November 20, online
  14. ↑ David O. Burgess and Martin J. Sharpa (2003): Recent Changes in Areal Extent of the Devon Ice Cap, Nunavut, Canada, in: BioOne, Volume 36, pp. 261-271, online
  15. ↑ Carsten Braun, D. R. Hardy, R. S. Bradley (2004): Mass balance and area changes of four High Arctic plateau ice caps, 1959–2002, in: Geografiska Annaler, V. 86, online (PDF)
  16. ^ Glowacki, Piotr: Glaciology and environmental monitoring, Research in Hornsund, online
  17. ↑ Greenpeace (2002): Arctic environment melts before our eyes., August 7th, online
  18. ↑ David Rippin, Ian Willis, Neil Arnold, Andrew Hodson, John Moore, Jack Kohler and Helgi Bjornsson (2003): Changes in Geometry and Subglacial Drainage of Midre Lovenbreen, Svalbard, Determined from Digital Elevation Models, in: Earth Surface Processes and Landforms, Vol. 28, pp. 273–298, online (PDF)
  19. ↑ Chen, J. L., C. R. Wilson and B. D. Tapley (2006): Satellite Gravity Measurements Confirm Accelerated Melting of Greenland Ice Sheet, in: Science, published online Aug 10, 10, Science
  20. ^ Howat, Ian M., Ian Joughin and Ted A. Scambos (2007): Rapid Changes in Ice Discharge from Greenland Outlet Glaciers, in: Science, March 16, Vol. 315., No. 5818, pp. 1559-1561

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