Low Coastlines Under Watery Siege
Part 1
Aitutaki in the Cook Islands. Photo Courtesy NASA
Low-lying islands and coastlines around the world face a “perfect storm” of warming atmosphere and rising seas (Hansen et al., 2006; Hearty, 2011). If, as scientists predict, the oceans rise 1m or more before 2100 (United Nations’ Intergovernmental Panel on Climate Change; IPCC, 2007), waters will inundate significant areas of low-lying islands and coastlines, causing widespread damage to public and private property, roads, communications, power installations, sewage facilities and airports. Flooding and other extreme weather events will likewise threaten human life.
Lower panel: Ice core record of atmospheric CO2 over the past 400,000 years (Petit et al., 1999) together with historical trends of CO2 (Keeling curve) and sea-level change (inset). Upper panel: Geological record of sea-level highstands (Hearty and Kaufman, 2000), showing broad correspondence with ice core CO2 record over the same interval. Red circles identify two past warm interglacials that reveal geological evidence of rapid ice sheet melting or collapse. [Graph sources: assembled by Hearty; data from cited authors
Loss of ice shelves may lead to destabilization of adjacent ice streams ultimately leading to higher sea level. Image Creative Commons
And further, many experts believe that thermal expansion of the oceans due to global warming is not our only worry. Thermally expanding seas will be augmented by an enormous volume of fresh water released by melting mountain glaciers and collapsing ice shelves and ice sheets, discharging huge masses of icebergs into the ocean. Melting polar ice might perhaps double the magnitude of sea-level rise, potentially disrupting global oceanic thermohaline circulation, wreaking havoc on developed countries at higher latitudes, such as the United Kingdom and Europe.
Island Nations Under Threat
Coral atoll in the South Pacific Ocean. Low-lying islands such as this will ultimately disappear beneath the sea in the coming decades due to sea-level rise. Image Courtesy USFW
Island nations under threat include Bermuda and the Bahamas in the Atlantic, the Pacific Islands of Palmerston, Tuvalu, Kiribati, Vanuatu, Marshall Islands, Cook Islands, Fiji, Solomon Islands, and the Maldives in the Indian Ocean. However, in terms of numbers of persons impacted, the oceanic islands pale in comparison with the slow-motion disasters that will occur in densely populated, low-lying coastal cities like New Orleans, New York, Los Angeles, Tokyo, Amsterdam, Mumbai, Shanghai, Singapore, Jakarta and Dhaka. Huge populations of several Asian countries will be forced to retreat from coasts, creating generations of “Greenhouse Refugees.” In the Western World, Greater Miami and the southeast Florida coastline has the dubious distinction of being among the most defenseless regions of high population density. A rise of 1.5 m would sever the Miami megapolis from the mainland and flood much of the Florida peninsula. Imagine, a century or two from now, a 100 km-long offshore “artificial reef” composed of crumbling high-rise apartments and freeway overpasses.
Our warming planet
Climate and sea-level scientists were not surprised when the National Atmospheric and Oceanic Administration (NOAA) issued a review in 2010 stating the last decade (2000-2009) was the warmest on record. More than 300 scientists in 48 countries contributed to a series of reports that conclude the Earth has been getting warmer for the past 50 years and that the sea level is rising as a consequence. These conclusions are based on millions of separate and independent studies and data bits using satellite telemetry, weather balloons, weather stations, ship buoys and field surveys.
NOAA reports that atmospheric and oceanic temperatures are rising, glaciers and polar ice sheets are flowing faster, melting, or simply disappearing–all without historic precedent. Floating ice shelves buttressing ice sheets in Antarctica are breaking up, like the Larsen ice shelf in 2002 – not directly elevating sea level but initiating the destabilization and surging of the ice streams they support. These events are clearly increasing in frequency, and will ultimately lead to greater ocean volume, as documented from past warm periods (Hearty et al., 2007).
The Antarctic Peninsula has warmed more over the past 50 years than nearly any other location on earth. Warmer air and ocean currents accelerate ice melting and sea-level rise. Photo Courtesy Jim Yungel/NASA
The extraordinary warming of 2.5°C (4.5°F) over the past 50 years on the Antarctic Peninsula is both the world’s greatest temperature change and least opportune venue for warming on the planet. Warmer air and currents penetrating deep into West Antarctica could initiate collapse of the marine based West Antarctic Ice Sheet ice sheet (Joughin and Alley, 2011), rapidly elevating global seas by as much as 3-6 meters.
Other predicted harbingers of change include record-breaking snow and rainfall, catastrophic wildfires and devastating deluge, droughts, and heat waves, more frequent and intense storms, all now matter of fact in 2011! Arizona, Colorado, Louisiana, New Mexico, Oklahoma and Texas reported the hottest August on record in 2011.
There is little doubt that the human-generated increase in CO2 over the past two centuries is leading to warming atmosphere, oceans, and climate. Gas micro-samples embedded in ice cores dating back 800,000 years from the central Antarctic ice sheet clearly display the natural relationship between the increases in greenhouse gasses and warmer climate. Climate and sea-level changes are highly correlated with insolation cycles created by imperfections in the earth-moon orbits around the sun and the changing abundance of Greenhouse gasses (see Köhler et al., 2010). The documented 30 percent increase in atmospheric CO2 over the past 200 years to 400 ppm is unequaled over the past 3 million years of the geologic record (Raymo et al., 2011), and humanity can expect to see a near-future response in the form of changing ice volume and ocean level.
Although there are many ways in which low-lying islanders could become more green – their carbon footprints are miniscule compared to those of the behemoths of CO2 production such as the US, China, and India. The very existence of such small and relatively blameless island nations is thus being threatened by runaway consumption of fossil fuels by the industrialized nations. Ignoring this global problem will not make it go away. The greatest defense against a changing planet is to have a plan of action that includes weaning humanity from fossil fuels. Political rhetoric and seawalls will do little to hold back warming seas and rising tides.
Paul J. Hearty, Ph.D.
Ecology Global Network, Earth Science Advisor
References:
Hansen, J., M. Sato, R. Ruedy, K. Lo, Lea, D.W., Medina-Elizade, M., 2006. Global temperature change. Proceedings of the National Academy of Sciences, 103, 14288-14293.
Hearty, P.J., 2011. The above story was modified and adapted from “Global Warming and Rising Ocean Waters”. The Bahamas Handbook 2011, Etienne Dupuch Jr Publications Ltd., Nassau, Bahamas, pp. 100-111.
Hearty, P.J., and Kaufman, D.S., 2000. Whole-Rock Aminostratigraphy and Quaternary Sea-Level History of the Bahamas Quaternary Research, 54, 163-173.
Hearty, P.J., J.T. Hollin, A.C. Neumann, M.J. O’Leary, M. McCulloch, 2007: Global sea-level fluctuations during the last interglaciation (Mis 5e), Quaternary Science Reviews, 26, 2090-2112.
IPCC, 2007. Intergovernmental Panel on Climate Change, fourth assessment report, available at: http://www.ipcc.ch/ipccreports/ar4-syr.htm.
Joughin, I., and Alley, R.B., 2011. Stability of the West Antarctic ice sheet in a warming world. Nature Geoscience 4, 506–513, doi:10.1038/ngeo1194.
Köhler, P., Bintanja, R., Fischer, H., Joos, F., Knutti, R., Lohmann, G., Masson-Delmotte, V., 2010. What caused Earth’s temperature variations during the last 800,000 years? Data-based evidence on radiative forcing and constraints on climate sensitivity. Quaternary Science Reviews 29, 129-145.
Petit J.R., et al., 1999. Climate and Atmospheric History of the Past 420,000 years from the Vostok Ice Core, Antarctica, Nature 399, 429-436.
Raymo, M.E., Mitrovica, J.X., O’Leary, M.J., DeConto, R. M., and Hearty, P.J., 2011. Departures from eustasy in Pliocene sea-level records. Nature Geoscience. 17 April 2011, DOI: 10.1038/NGEO1118.
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