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Sea-Level Change (1990) / Chapter Skim
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10 Role of Land Ice in Present and Future Sea-Level Change
Pages 171-184

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From page 171...
... Calculation of future changes of the Greenland Ice Sheet, the Arctic ice caps, and the marginal areas in Antarctica requires study of the complex fluid mechanics/thermodynamics of subfreezing snow and firn subjected to water percolation. Determination of changes in iceberg calving is difficult because little is known about the rate-controlling processes: in addition, changes in the geometry of a glacier or ice stream cause changes in the rate of basal sliding, a process that is still imperfectly understood.
From page 172...
... Much of this chapter is derived from the results of a 1984 Workshop on Glaciers, Ice Sheets, and Sea Level: Effects of a CO2-Induced Climatic Change (Committee on Glaciology, 1985) , to which the reader is referred for more detail on the current state of knowledge.
From page 173...
... Greenland and Antarctic Ice Sheets These two large ice masses gain material mainly through the accumulation of snow, and lose material through several processes that include surface melt and the runoff of meltwater, calving (discharge) of icebergs, melting of the underside of floating ice shelves, evaporation of snow, and erosion and transport of surface snow to the sea by wind.
From page 174...
... Melting of the underside of ice shelves has no effect on sea level, but it does control the speed of discharge of landbased ice from Antarctica and is important for predicting the behavior of that ice sheet in the next century. The difficulty of estimating the surface mass balance of the Greenland Ice Sheet can be illustrated by reference to the concept of snow facies (Benson, 1962; Muller, 1962)
From page 175...
... Increased air temperature and/or meltwater production may also cause some outlet glaciers and ice streams to flow faster, transferring land-based ice to the ocean and causing a further rise in 175 sea level. On the other hand, a rise in CO2 concentration may, in some regions, lead to increased snow precipitation on glaciers and ice sheets, which will have the opposite effect on sea level.
From page 176...
... The mass balance of the Greenland Ice Sheet can be analyzed by considering the attitudinal gradient as primary, although the latitude and distance from the sea are also important (Ambach, 19851. Such an approach is less useful in Ant arctica, where iceberg discharge and subshelf melting are the dominant processes causing ice loss to the sea.
From page 177...
... The Warming of Cold Snow and Firn Figure 10.3 illustrates the fact that most of the Antarctic Ice Sheet and much of the Greenland Ice Sheet are not likely to be affected by small rises in air temperature, such sit t4 111 ~ 2 ~ _ ILL / 6 O / it 0 20 · . ~ glacier area 1 1 1 1 40 60 80 1 00 TIME (a)
From page 178...
... warned that a climatic change due to increased CO2 in the atmosphere could lead to disintegration of the West Antarctic Ice Sheet, causing a 5-m rise in global sea level. The discharge of ice from this ice sheet is mainly through rapidly moving ice streams, which flow into floating ice shelves (Figure 10.8~.
From page 179...
... were assumed. Assuming that the model results from Ice Stream E are representative of the whole West Antarctic Ice Sheet, Lingle (1985)
From page 180...
... . Ice streams A and E in West Antarctica are shown; floating ice shelves are stippled.
From page 181...
... ) TABLE 10.3 Estimates of the Contribution to Sea Level Rise by Ice Wastage in a CO2-Enhanced Environ ment (from Committee on Glaciology, 1985)
From page 182...
... Kuhn (1985~. The shift of equilibrium-line altitude on the Greenland Ice Sheet following climatic changes, in Glaciers, Ice Sheets, and Sea Level: Effects of a CO2 lnduced Climatic Change, Committee on Glaciology, National Academy Press, Washington, D.C., pp.
From page 183...
... (1985~. A model of a polar ice stream, and future sealevel rise due to possible drastic retreat of the West Antarctic Ice Sheet, in Glaciers, Ice Sheets, and Sea Level: Effects of a CO2-Induced Climatic Change, Committee on Glaciology, National Academy Press, Washington, D.C., pp.
From page 184...
... (19851. Iceberg discharge and the mass balance of Antarctica, in Glaciers, Ice Sheets, and Sea Level: Elects of a CO2-Induced Climatic Change, Committee on Glaciology, National Academy Press, Washington, D.C., pp.


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