The World in 2050_ Four Forces Shaping Civilization's Northern Future - Laurence C. Smith [176]
498 The story begins with W. S. Broecker, D. M. Peteet, D. Rind, “Does the Ocean-Atmosphere System Have More than One Stable Mode of Operation?” Nature 315 (1985): 21-26. A recent development is Z. Liu et al., “Transient Simulation of Last Deglaciation with a New Mechanism for Bølling-Allerød Warming,” Science 325 (2009): 310-314.
499 A. K. Rennermalm et al., “Relative Sensitivity of the Atlantic Meridional Overturning Circulation to River Discharge into Hudson Bay and the Arctic Ocean,” Journal of Geophysical Research 112 (2007), G04S48, DOI:10.1029/2006JG000330. The IPCC AR4 (2007) gave >90% chance the thermohaline conveyor will remain functioning for the next century.
500 Even at the lowest carbon dioxide scenarios, with stabilization at 450 ppm, this critical threshold is eventually crossed in thirty-four out of thirty-five stabilization scenarios. J. M. Gregory et al., “Climatology: Threatened Loss of the Greenland Ice-Sheet,” Nature 428 (April 8, 2004): 616, DOI:10.1038/428616a.
501 Table 1, G. A. Milne et al., “Identifying the Causes of Sea-Level Change,” Nature Geoscience 2 (June 14, 2009): 471-478, DOI:10.1038/ngeo544. However, keep in mind the Earth had 70% more ice then than it does today, so a four-meters-per-century sea-level rise is not likely to be repeated.
502 Ibid., 496.
503 Ice sheets help to preserve their own existence by creating an elevated surface at high, cold altitudes and by reflecting back much of the sun’s energy. If Greenland’s ice sheet were removed, temperatures over its low, dark bedrock surface would be much warmer than today and the ice sheet unlikely to form again.
504 Especially Shanghai, Osaka-Kobe, Lagos, and Manila. Also affected will be Buenos Aires, Chennai, Dhaka, Guangzhou, Istanbul, Jakarta, Karachi, Kolkata, Los Angeles, Mumbai, New York, Rio de Janeiro, Shenzhen, and Tokyo.
505 Geological data suggests the WAIS collapsed 400,000 years ago, and perhaps even 14,500 years ago. P. U. Clark et al., “The Last Glacial Maximum,” Science 325, no. 5941 (August 7, 2009): 710-714, DOI:10.1126/science.1172873. It is also clear the WAIS is currently losing mass, and there is evidence this has been happening for the past 15,000 years in response to rising sea levels initiated by deglaciation in the northern hemisphere. Thus, even limiting greenhouse warming may not lead to the desired stabilization of the ice sheet. J. Oerlemans, “Freezes, Floes, and the Future, Nature 462 (2009): 572-573, DOI:10.1038/462572a.
506 Sea levels are not the same everywhere but vary owing to water pile-up from currents, gravitational attraction, water temperature, crustal rebound, and other factors. The above-average sea-level rise along the U.S. coastline is shown by J. X. Mitrovica et al., “The Sea-Level Fingerprint of West Antarctic Collapse,” Science 323, no. 5915 (February 6, 2009): 753, DOI:10.1126/science.1166510; and J. L. Bamber et al., “Reassessment of the Potential Sea-Level Rise from a Collapse of the West Antarctic Ice Sheet,” Science 324, no. 5929 (May 15, 2009): 901-903, DOI:10.1126/science.1169335. The latter study also suggests a global average sea-level increase of 3.2 meters for a WAIS collapse, lower than the five-meter estimate by the IPCC AR4.
507 For more, see D. G. Vaughan, R. Arthern, “Why Is It Hard to Predict the Future of Ice Sheets?” Science 315, no. 5818 (2007): 1503-1504, DOI:10.1126/science.1141111; and R. B. Alley et al., “Understanding Glacier Flow in Changing Times,” Science 322 (2008): 1061-1062.
508 S. A. Zimov et al., “Permafrost and the Global Carbon Budget,” Science 312, no. 5780 (2006): 1612-1613, DOI:10.1126/science.1128908; E. A. G. Schuur et al., “Vulnerability of Permafrost Carbon to Climate Change: Implications for the Global Carbon Cycle,” Bioscience 58, no. 8 (2008): 701-714; C. Tarnocai