Are Rising Seas a Risk to U.S. Naval Bases?
The Union of Concerned Scientists, a not-for-profit advocacy group based in Cambridge, MA, recently issued a report that drew immediate responses from news outlets. They predict 17 U.S. military facilities, including the Norfolk Naval Yard, will deal with flooding events from rising seas by the year 2050, and also assert some bases may be awash by 2100. Such dire predictions are based on climate models suggesting future atmospheric temperature rise of two degrees or more accompanied by melting of the massive glaciers that cover Greenland and Antarctica. But the climate models, which have yet to be validated, come under criticism because of poor correlation between increasing CO2 and global temperatures — temperatures that have not risen at the pace models predict, while CO2 emissions have risen significantly. Without meaningful temperature increases, little melting of either polar icecap would occur.
The Union of Concerned Scientists, a not-for-profit advocacy group based in Cambridge, MA, recently issued a report that drew immediate responses from news outlets. They predict 17 U.S. military facilities, including the Norfolk Naval Yard, will deal with flooding events from rising seas by the year 2050, and also assert some bases may be awash by 2100.
Such dire predictions are based on climate models suggesting future atmospheric temperature rise of two degrees or more accompanied by melting of the massive glaciers that cover Greenland and Antarctica.
But the climate models, which have yet to be validated, come under criticism because of poor correlation between increasing CO2 and global temperatures — temperatures that have not risen at the pace models predict, while CO2 emissions have risen significantly.
Without meaningful temperature increases, little melting of either polar icecap would occur.
Warming ocean water contributes to rising sea level. Ocean volume expands as upper layers warm. Sea level is expected to rise in conformity with the historic 6-7 inch per century observed since the end of the Little Ice Age two centuries ago from a combination of both effects. No more, no less.
Reports of accelerating sea level rise (SLR) during the 20th century have been proven incorrect.
Shifting of persistent weather patterns and periodic changes in ocean-atmospheric circulations such the dominant El Nino Southern Oscillation (ENSO) of the equatorial Pacific are largely responsible for temporary changes.
But a sea level rise of five inches projected from historic trends out to 2100 (again, the same rate since the Little Ice Age) would be manageable for the Department of Defense. The Dutch have battled a rising North Sea for centuries.
UCS’s report does not mention time-averaged water level measured by tidal gauges known as Relative Sea Level (RSL). RSL combines average sea level of the neighboring open ocean and the elevation of the shore measured against a permanent stationary structure usually located in a harbor.
Relative Sea Level Rise (RSLR) is the increase resulting from a combination of a rising ocean and sinking land surface where sea level appears to rise if either or both the ocean rises or the land settles. The latter process is called “subsidence.”
To determine what actually causes an observed change requires detailed analysis of coastal features aided with satellite altimetry. But RSLR determines the degree of risk from potential flooding during spring tides and less frequently from massive surges accompanying hurricanes or tsunami.
The Norfolk Naval Yard is located near the mouth of the Chesapeake Bay, an embayment encompassing the drowned river valleys of the James and Potomac rivers (and their tributaries). The embayment comprises a major part of the Mid-Atlantic coastline of the United States. It is an example of land undergoing subsidence (sinking).
Subsidence along the bay’s circumference is proceeding at a rate of from a half inch to as much as nearly two inches per decade. Research at Virginia Institute of Marine Science concluded somewhat more than half the RSLR observed there from 1976 to 2007 resulted from subsidence.
Increases of sea level rise stated by UCS would depend on an acceleration in the rate of melting of polar ice and thermal expansion of the oceans that has not yet been observed in the 21st century.
Projections of global temperature rise based on EPA climate models have disappointed expectations. Inherent uncertainties in model inputs used to predict polar ice melt relegate the enterprise to a level of speculation not science.
Many climate experts had predicted sea ice in the Arctic Ocean would be completely melted by 2008. Yet the extent of ice remaining in late summer has stabilized over the past decade and does not show indications of disappearing this summer. The Arctic Ocean refreezes each winter.
Sea ice surrounding Antarctica has expanded for nearly two decades despite predictions to the contrary. Warnings the ice shelf was on the verge of imminent collapse proved wrong. Localized melting results from a volcano beneath the glacier. The polar floe ice, although it does not affect sea levels, is considered a barometer of future melting of landed ice of the two icecaps.
For rising oceans to pose significant threats to U.S. bases, global warming would need to proceed at an increasing rate, without reversals, before 2050.
With prospects for CO2 sensitivity being revised down to a modest 1 degree Celsius for a doubling of CO2 there is serious doubt warming this century would support sufficient melting or induce enough thermal expansion to reach UCS’s projections.
But subsidence poses problems wherever coastal land is sinking, whether in Norfolk, New Orleans or Venice, and will proceed independently of any effects of CO2-induced global warming from the combustion of fossil fuels. DOD is well advised to plan accordingly.
William D. Balgord, Ph.D. (geochemistry) heads Environmental & Resources Technology, Inc. in Ft. Pierce, FL and Middleton, WI. He is a Contributing Writer for the Cornwall Alliance for the Stewardship of Creation.
