Changing Climate Report of the Carbon Dioxide Assessment Committee (1983) / Chapter Skim
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PROBABLE FUTURE CHANGES IN SEA LEVEL RESULTING FROM INCREASED ATMOSPHERIC CARBON DIOXIDE
PROBABLE FUTURE CHANGES IN SEA LEVEL RESULTING FROM INCREASED ATMOSPHERIC CARBON DIOXIDE
Pages 433-448
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From page 433... ...
They include local or regional uplift or subsidence of the land; changes of atmospheric pressure, winds, or ocean currents; changes in the volume of the ocean basins owing to volcanic activity, marine sediment deposition, isostatic adjustment of the Earth's crust under the sea or changes in the rate of seafloor spreading; changes in the mass of ocean water brought about by melting or accumulation of ice in ice sheets and alpine glaciers; and thermal expansion or contraction of ocean waters when these become warmer or colder. Only the last two processes are of primary interest in considering worldwide changes in sea level resulting from climatic change, such as the warming that may be induced by increasing atmospheric carbon dioxide.
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From page 434... ...
To obtain some semblance of a global average, Barnett divided the stations, using empirical orthogonal function analysis (Barnett, l978) , into six oceanic regions in which there was strong coherence among different stations.
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From page 435... ...
Barnett tentatively inferred that perhaps three fourths of the rise represents water added to the ocean from ablation or melting of the Greenland and Antarctic ice caps and alpine glaciers. Observed changes in the length of the day since l900 and a displacement by 730 cm toward 70° W in the position of Earth's mean pole of rotation are consistent with this explanation, which would mean that between 30,000 and 40,000 km3 of ice (less than 0.2% of the land-ice volume)
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From page 436... ...
Of even greater uncertainty is the potential disintegration of the West Antarctic Ice Sheet, most of which now rests on bedrock below sea level. This could cause a further sea-level rise of 5 to 6 m in the next several hundred years.
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From page 437... ...
Unfortunately, there is no good understanding of what happens in the deeper layer; major ongoing research efforts such as the projected World Ocean Circulation Experiment of the World Climate Research Program are directed at remedying this unsatisfactory situation. The evidence points toward the importance of heat transport along isopycnal (quasihorizontal constant-density)
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From page 438... ...
for the middle of the twenty-first century, assuming a doubling of atmospheric carbon dioxide and the probable increase in other greenhouse gases during the next 70-80 years.* Cess and Goldenberg show that a time delay of at least 20 years can be expected before the upper ocean waters come near to equilibrium with these projected values.
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From page 439... ...
between zero and l000 m for each l0° latitude band was multiplied by the percentage of ocean area in that band. We thus arrive at a rise in sea level about l00 years from now of at least 30 cm, resulting from ocean warming.
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From page 440... ...
Adding this estimate for ocean warming to our estimates for melting in Greenland and Antarctica and in alpine glaciers, we arrive at a probable rise in sea level during the next l00 years of about 70 cm. But a much larger rate of rise is not unlikely during the following several centuries because of events in Antarctica.
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From page 441... ...
A collapse of the West Antarctic Ice Sheet would release about 2 million knr of ice before the remaining half of the ice sheet began 90- W -90-E \ AMUNDSEN SEA \ EDGE Of FLOATiNG iCE GROUNDiNG LiNE^X • MOUNTAINS ^™ -^ •'/Mti BEDROCK ABOVE SEA iKX//. LEVEL SUPPORTING ICE • BEDROCK MORE THAN ONE KILOMETER ~ANTAnrVTr~riHcCE BELOW SEA LEVEL SUPPORTiNG ICE ISOFIGURE 8.4 The West Antarctic Ice Sheet (WAIS)
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From page 442... ...
Evidence from radar soundings of flow lines extending across the Ross ice shelf indicates that the remaining West Antarctic Ice Sheet has been relatively stable for the last l000-2000 years. Indeed, various lines of evidence suggest that the mass balance of the entire Antarctic Ice Sheet may be positive -- i.e., ice may be accumulating.
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From page 444... ...
During this period the Ross and Filchner-Ronne ice shelves could have disappeared, and all the ice could be discharged within 500 years. If the time required for the ice shelves to disappear is l00 years, Bentley's analysis would not be incompatible with a minimum time of 300 years for disintegration of the West Antarctic Ice Sheet.
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From page 446... ...
. Among these, five problems deserve special emphasis: possible change in the mass balance of the Antarctic Ice Sheet; interaction between the Ross and Filchner-Ronne ice shelves and adjacent ocean waters; ice stream velocities and mass transport into the Amundsen Sea from Pine Island and Thwaites Glaciers; modeling of the ice sheet response to C02-induced climate change; and deep coring of the ice sheet to learn whether it in fact disappeared l25,000 years ago.
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From page 447... ...
. The West Antarctic Ice Sheet: diagnosis and prognosis.
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From page 448... ...
. West Antarctic Ice Sheet and CO2 greenhouse effect: a threat of disaster.
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