Sea Level Rise – or Land Subsidence?
Alarmist claims about rising seas inundating coastal areas blame the wrong culprit.
In his 2006 Inconvenient Truth mockumentary, Al Gore infamously predicted melting ice caps would cause oceans to rise “up to 20 feet” (6.1 meters) “in the near future.” Kevin Costner’s 1995 “action thriller” Water World presumed totally melting planetary ice would almost submerge the continents.
However, the Intergovernmental Panel on Climate Change estimated in 2007 that seas might rise up to only 2 feet by 2107. By comparison, oceans have risen nearly 400 feet since the last ice age ended, reflecting how much water was trapped in mile-thick glaciers that buried much of North America, Europe and Asia. In recent decades, though, global sea level rise has averaged just 7 inches per century – which may explain why Mr. Gore bought an $8.5-million mansion on the California coast in 2010.
And yet “rising seas due to dangerous manmade climate change” remains a contentious issue, with profound land use, wildlife, economic, insurance and policy implications – especially for certain regions, like the Atlantic Coast’s Chesapeake Bay region. Some say “seas could rise” 2.5 to 7 feet (2.1 meters) or more by the end of the century around Norfolk, Virginia, a huge population and agricultural center and home to America’s largest Navy base. Even if that happens, the prediction combines multiple causes.
Saltwater intrusion clearly has been an increasing problem across much of this region for several decades, and storms have sent tides and waves further inland than in the past, flooding and battering homes, croplands and wildlife habitats. Climate alarmists attribute this danger to human fossil fuel use.
As a new report by Dr. Bezdek explains, reality is much different. (His report awaits publication in a scientific journal.) At least for the Chesapeake region, Houston-Galveston, Texas area, Santa Clara Valley, California and other places around the globe, the primary cause of seawater intrusions is not rising oceans – but land subsidence due to groundwater withdrawal from subsurface shale and sandstone formations, and to “glacial isostatic adjustments” that have been ongoing since the last glaciers melted.
The solution therefore is not to continue trying to control Earth’s climate – an impossible, economy-busting task that would further impede fossil fuel use, economic development, job creation, and human health and welfare. The solution requires reducing groundwater removal in these coastal areas.
Ice age glaciers buried continental land masses under trillions of tons of ice. Land under the ice was pushed downward, while areas somewhat beyond the glaciers were forced up. Once the ice was gone, the compressed areas began to rise, while lands that had bulged upward began to sink. Isostatic subsidence is still occurring, at about 1 millimeter a year (4.4 inches per century) in the Chesapeake region.
While Chesapeake farms and cities have been utilizing groundwater for centuries, withdrawal rates from Virginia Coastal Plain aquifers skyrocketed between 1950 and 1970, as modern pumps took over. The rates have remained high ever since, causing significant land subsidence.
The aquifer systems involve layers of porous sandstone with water in the interstices between sand grains. These layers are sandwiched between layers (lenses) of impermeable but wet shale and clay. As water is pumped from the sandy layers, the shale-clay layers are squeezed like a sponge by hundreds of feet of overlying rock and sediment, forcing their water into less compressible sands, and then into pumps.
The amount of water in a system, its recharge rates (from rain, snowmelt and other sources), and the degree of compaction depend on how much water is being withdrawn, the thickness of sand and clay layers, and how compressible the layers are. Most of the pumped water ultimately comes from the clays, as they are squeezed dry. Analysts have estimated that 95% of water removed from Virginia Coastal Plain aquifers between 1891 and 1980 came from their clay layers, which have steadily compressed as a result.
Compression means subsidence, at 1.1-4.8 mm/yr – for an average rate of 11 inches per century, on top of the 4.4 in. per century in isostatic subsidence, and compared to the average sea level rise of 7 in. a century.
The net effect in Virginia’s Coastal Plain can thus be nearly 2 feet of subsidence per century. The impacts on land, habitat and property loss, saltwater intrusions, inland storm surges, farming, homes and other buildings, regional economics, wharves, piers and naval bases, and insurance rates is easy to discern.
Confusion arises because discussions often involve “relative sea level rise” – which combines glacial isostatic and groundwater subsidence, along with actual sea level rise – just as we just did with our 2 feet per century total. However, the term obscures what is really going on and lends itself to climate alarmism, by leaving the false impression that the entire problem is melting icecaps and rising seas.
It clearly is not. Focusing attention on alleged “manmade climate cataclysms,” supposedly driven by carbon dioxide and other greenhouse gas emissions, will result in our spending hundreds of billions of dollars to replace oil, gas and coal with expensive, subsidized, land-intensive renewable energy systems – while foregoing hundreds of billions of dollars in jobs and economic growth. Meanwhile, China, India, Indonesia and other developing nations will continue doing what they must to lift billions out of abject poverty and disease: burn more fossil fuels, thereby emitting more CO2.
Those nations are not about to succumb to the Obama EPA “social cost of carbon” con game. This is the fraudulent scheme under which bureaucrats blame US oil, gas and coal for every climate and weather event, habitat and species loss, and other problem that they can possibly conjure up anywhere in the world – while completely ignoring the phenomenal and undeniable benefits of using those fuels, and the equally important benefits of having more plant-fertilizing carbon dioxide in our atmosphere.
President-Elect Trump’s nomination of Oklahoma Attorney General Scott Pruitt to head the EPA underscores his intent to end climate-obsessed government by junk science and Executive Branch decree.
What can be done about the real-world problems of “relative sea level rise”? Sea levels will continue to rise (or fall) in response to ice growth and melting, caused by powerful natural forces over which humans have no control. Glacial isostatic subsidence will continue – albeit at a glacial or geologic pace – unless another ice age buries continents under more miles of ice, again lowering sea levels hundreds of feet, and wiping out arable land, growing seasons and agricultural productivity.
Moreover, once water has been squeezed out of the clay and shale, it cannot easily be replenished. That means the subsidence process cannot be reversed. However, we can nevertheless reduce or even halt subsidence due to groundwater extraction.
Rates and locations of land subsidence and relative sea level rise change over time. Accurate predictive tools and measurements are thus needed to improve our understanding of subsidence in particular areas. Although subsidence rates are not as high on the Atlantic Coast as they have been in the Houston-Galveston area or Santa Clara Valley, the problem is nonetheless serious because of the southern Chesapeake Bay region’s low-lying topography and consequent susceptibility to ocean water intrusion.
In the Houston-Galveston area and Santa Clara Valley, resource managers have moved groundwater pumping away from the coast, reduced groundwater withdrawal rates, increased aquifer recharge and substituted surface water for groundwater supplies. These actions have successfully stopped subsidence in the Santa Clara Valley and slowed the process in the Houston-Galveston area.
Similar steps could be taken in Virginia’s Tidewater or Coastal Plain region. In addition, pipelines could bring fresh water from nearby lakes and rivers, replacing at least some of what is now provided by wells. Yet another option might be to construct one or more desalination plants (in California and Texas, as well), utilizing nuclear or natural gas power to operate facilities that utilize new Israeli technologies that employ a chemical-free reverse osmosis process that converts seawater into freshwater for pennies per gallon.
The new Congress and Executive Branch need to focus our limited money and resources on real problems and viable solutions – not on their false, politically correct, anti-development alter egos.