Wednesday, August 17, 2016

Ground Zero for Sea-Level Rise: South Florida

Discussions of global warming and its effects are usually posed in terms of what awaits us in the future.  However, for some places the future has already arrived.  In The Siege of Miami, Elizabeth Kolbert provides an excellent account of the impact of rising sea levels as they are now being experienced in South Florida. The article appeared in The New Yorker.

Many predictions of sea-level rise by the end of this century fall in the range of several feet.  However, these predictions are highly uncertain and others believe the rise could be much greater, including one of Kolbert’s hosts in the Miami area: Hal Wanless, the chairman of the University of Miami’s geological-sciences department.

“Wanless, who is seventy-three, has spent nearly half a century studying how South Florida came into being. From this, he’s concluded that much of the region may have less than half a century more to go.”

“’Many geologists, we’re looking at the possibility of a ten-to-thirty-foot range by the end of the century,’ he [Wanless] told me.”

These estimates of much higher sea levels are not unreasonable given that the Greenland icepack alone holds enough water to raise sea levels by twenty feet.

Kolbert provides perspective on what havoc a few feet of sea-level rise can cause.

“Many of the world’s largest cities sit along a coast, and all of them are, to one degree or another, threatened by rising seas. Entire countries are endangered—the Maldives, for instance, and the Marshall Islands. Globally, it’s estimated that a hundred million people live within three feet of mean high tide and another hundred million or so live within six feet of it. Hundreds of millions more live in areas likely to be affected by increasingly destructive storm surges.”

“Against this backdrop, South Florida still stands out. The region has been called ‘ground zero when it comes to sea-level rise.’ It has also been described as ‘the poster child for the impacts of climate change,’ the ‘epicenter for studying the effects of sea-level rise,’ a ‘disaster scenario,’ and ‘the New Atlantis.’ Of all the world’s cities, Miami ranks second in terms of assets vulnerable to rising seas—No. 1 is Guangzhou—and in terms of population it ranks fourth, after Guangzhou, Mumbai, and Shanghai.”

South Florida has characteristics that make it particularly vulnerable, like its topography.

“In Miami-Dade County, the average elevation is just six feet above sea level. The county’s highest point, aside from man-made structures, is only about twenty-five feet, and no one seems entirely sure where it is….Broward County, which includes Fort Lauderdale, is equally flat and low, and Monroe County, which includes the Florida Keys, is even more so.”

The land consists of porous limestone which is easily penetrated by water.  In its natural state there was plenty of freshwater flow on the surface to keep salty sea water from penetrating too far inland.  With development, the region had to be dried out and water flow controlled.  Water level in a system of canals was kept at an elevated value in order to perform this same function.  But as sea level rises the system is no longer able to control what is referred to as the “saltwater front.”  The water table also rises diminishing the capacity of the land to absorb water from storms.

“Researchers at Florida Atlantic University have found that with just six more inches of sea-level rise the district will lose almost half its flood-control capacity. Meanwhile, what’s known as the saltwater front is advancing. One city—Hallandale Beach, just north of Miami—has already had to close most of its drinking wells, because the water is too salty. Many other cities are worried that they will have to do the same.”

In some places threatened by encroaching seas it is possible to consider building some sort of barrier to hold the rising water out.  Not so in South Florida where its limestone structure would allow the water to seep under any structure and equalize the levels on each side.

And it gets worse.  It seems the sea level in South Florida is rising much faster than for the world as a whole.

“For the past several years, the daily high-water mark in the Miami area has been racing up at the rate of almost an inch a year, nearly ten times the rate of average global sea-level rise. It’s unclear exactly why this is happening, but it’s been speculated that it has to do with changes in ocean currents which are causing water to pile up along the coast.”

Kolbert spent much of her Florida time in Miami Beach, a city on a small island off the coast.  Flooding is common there as high tides regularly cause sea water to flow up through the storm drains.

“The city of Miami Beach floods on such a predictable basis that if, out of curiosity or sheer perversity, a person wants to she can plan a visit to coincide with an inundation.”

Real estate developers seem to have gone about their business oblivious to any flooding concerns.  Kolbert relates what she encountered on a short drive with the geologist Wanless.

“Wanless turned onto a side street, and soon we were confronting a pond-sized puddle. Water gushed down the road and into an underground garage. We stopped in front of a four-story apartment building, which was surrounded by a groomed lawn. Water seemed to be bubbling out of the turf.”

“We’d come to a neighborhood of multimillion-dollar homes where the water was creeping under the security gates and up the driveways. Porsches and Mercedeses sat flooded up to their chassis.”

“’This is today, you know,’ Wanless said. ‘This isn’t with two feet of sea-level rise’.”

The people of Miami Beach know they have a problem.  The mayor seems to have a plan.

“He described the steps his administration was taking to combat the effects of rising seas. These include installing enormous underground pumps that will suck water off the streets and dump it into Biscayne Bay.  Six pumps have been completed, and fifty-four more are planned.”

When asked if all this effort constituted a “solution” the mayor stated his belief that technology would come to the rescue.

“Thirty or forty years from now, he said, ‘We’re going to have innovative solutions to fight back against sea-level rise that we cannot even imagine today’.”

Others, including the geologist Wanless, are doubtful that Miami Beach has a long-term future.

“To cope with its recurrent flooding, Miami Beach has already spent something like a hundred million dollars. It is planning on spending several hundred million more. Such efforts are, in Wanless’s view, so much money down the drain. Sooner or later—and probably sooner—the city will have too much water to deal with. Even before that happens, Wanless believes, insurers will stop selling policies on the luxury condos that line Biscayne Bay. Banks will stop writing mortgages.”

Kolbert and Wanless leave us with this image of what the future will bring.

“’If we don’t plan for this,’ he told me, once we were in the car again, driving toward the Fontainebleau hotel, ‘these are the new Okies.’ I tried to imagine Ma and Pa Joad heading north, their golf bags and espresso machine strapped to the Range Rover.”

The interested reader might find these articles informative:

Putting Climate Change in Perspective

Climate Change: Global Warming and Global Dimming

Geoengineering, Volcanoes, and Climate Change Experiments

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