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Sea Level & Risk of Flooding Rising Rapidly in Mid-Atlantic

During the 20th century, sea levels along the highly populated U.S. Mid-Atlantic coastline between New York and Virginia rose faster than in any other century during the past 4,300 years, according to a new study. And as those sea levels continue to increase as a result of global warming and local land elevation changes, the risks of coastal flooding will dramatically escalate.

The study, by geoscientists at Rutgers and Tufts Universities and published in the new journal “Earth’s Future,” took a comprehensive look at the history of sea level in the Mid-Atlantic, combining sediment records of prehistoric sea level with modern data, which includes readings from tide gauges and satellite instruments. The result is one of the most in-depth examinations of past, present, and future sea level rise of any region in the U.S.

The amusement pier in Seaside Heights, N.J., was heavily damaged by Hurricane Sandy.
Credit: Master Sgt. Mark C. Olsen, New Jersey Air National Guard.

The study warns that regional planners will need to factor local rates of sea level rise when making decisions on building any long-lasting infrastructure, from water treatment facilities to Manhattan skyscrapers and Atlantic City casinos.

For example, the study estimated that the New Jersey shore will likely see a sea level rise of about 1.5 feet by 2050, and about 3.5 feet by 2100, at least a foot higher than the average global sea level rise over the rest of the century. Using a middle-range scenario for future sea level rise, the study found that by 2050, flooding caused by a 10-year storm, which has a 10 percent probability of occurring each year, would exceed all historic storms in Atlantic City.

According to the study, relative sea levels in the Mid-Atlantic region rose at about 0.10 inches per year during the 19th century, and that rate accelerated to 0.15 inches per year during the 20th century. That may not sound like much, but it is already enough to make a major difference when storms strike.

The impact from Hurricane Sandy clearly illustrates that. The study found that a 7.87-inch global sea level rise during the 20th century, which was largely driven by manmade global warming, caused Hurricane Sandy to flood an additional 27 square miles compared to what it would have if the storm had struck in 1880 when sea levels were lower. Using figures from Climate Central’s sea level rise database, the researchers (who were not affiliated with Climate Central) found that sea level rise exposed an additional 83,000 people to coastal flooding, with about 45,000 in New York City and the rest in New Jersey.

While two factors largely control global average sea level — temperature and variations in the volume of the Earth’s ice sheets and mountain glaciers — local rates of relative sea level rise are more complicated.

While the U.N. Intergovernmental Panel on Climate Change (IPCC) projected that global mean sea level rise for 2081-2100 will likely be between 10-to-32 inches, those numbers mean little to local policymakers, who must make decisions based on local sea level rise rates that often differ from the global average. Those differences are the result of several factors, including ocean currents that can cause faster or slower rates of sea level rise in some areas, groundwater depletion, which can result in sinking land, and gradual post-ice age adjustments of the land.

In the Mid-Atlantic region, it turns out, all three of these factors are conspiring to accelerate sea level rise. Every part of the region saw the level rise at a faster rate than the global trend, the study found. In fact, that rate since the early 1900s was nearly double the global average.

Locations that sit atop a coastal plain, such as the Jersey Shore, are seeing the fastest rates of sea level rise compared to those Mid-Atlantic coastal locations that are built on top of bedrock, such as New York City, since the geology of the coastal plain features more settling of the land from groundwater depletion and long-term sediment compaction. Other studies have also identified the Mid-Atlantic as a so-called “hot spot” of sea level rise, but the new research provides more statistical proof that modern sea level rise in this region is outpacing even periods from several thousand years ago. 

“The study highlights the importance of geological data when making predictions for coastal inundation during the 21st century and that it is important to take a regional approach,” Simon Engelhardt, a professor at the University of Rhode Island who was not involved in the new study, said in an email.

Comparison of tide gauges along the coast with the Battery in Manhattan, showing sea levels are rising slightly faster along the coastal plain than in Manhattan. (The tide-gauge records are referenced to a synthetic 1900–1920 datum.) 
Click image to enlarge. Credit: Miller et al. 2013.

To put recent rates of sea level rise into historical perspective, the study found there is at least a 95 percent probability that the rate of sea level rise in the Mid-Atlantic during the 20th century was faster than any century in the past 4,300 years, and a 67 percent probability that it was faster than any century in more than 6,600 years.

“The sea level rise that we’re seeing now is very significant,” including in a “prehistoric context,” said study co-author Ben Horton of Rutgers University, in an interview.

The study projects that lower Manhattan will see about 8.6 inches of sea level rise by 2030, 15.7 inches by 2050, and 38 inches, or just more than 3 feet, by 2100. The 15.7 inches of sea level rise by 2050 would be sufficient to transform what would be considered a moderate 10-year storm today to reach the same flood level as a 100-year storm would. The higher-end scenario considered in the study would bring 5.5 feet of sea level rise to Lower Manhattan by 2100. That would cause a 10-year storm event to bring flooding comparable to Hurricane Sandy, which brought the highest storm tide on record to Lower Manhattan. Every subway tunnel connecting Manhattan with Brooklyn and Queens flooded, along with transit stations in adjacent areas of New Jersey and all three of the city's major airport hubs.

A separate study published in 2012 found that similar increases in storm surge risk would occur at many other coastal locations in the U.S.

Assuming continued groundwater extraction rates at coastal plain locations, those areas would see a greater amount of sea level rise, the study found. The study projected that those areas could be in for a rise of 9.8 inches by 2030, 1.5 feet by 2050, and about 3.5 feet, by 2100.

While the study shows that the main component of future sea level rise will be from global sea level rise, local land elevation changes should be factored into development decisions, since they will influence the rate and extent of relative sea level rise at the local level. The study noted that there are currently limited tools for policymakers to use to factor in sea level rise to the planning process.

Even the Federal Emergency Management Agency’s newest flood elevation data, released this year and used to help determine federal flood insurance requirements, failed to include sea level rise projections. “They are accordingly relevant to insuring against current risks but do not provide appropriate guidance for long-term planning,” the study said.

Related Content
Climate Projections More Confident, Dire from IPCC
Risks of Hurricane Sandy-Like Surges Rising
Zeroing in on IPCC's Sea Level Rise and Warming 'Hiatus'
The 5 Most Sobering Charts From the IPCC Report
Surging Seas: Sea Level Rise Analysis by Climate Central
Warming Has Doubled Risk of Katrina-like Storm Surges
Global Warming May Bring More 'Black Swan' Storm Surges
Ongoing Coverage of Historic Hurricane Sandy
Sea Level Rising Faster Than Average in Northeast U.S.
Hurricane Isaac Spurs Design of Storm Surge Warnings
New York Launches $19.5 Billion Climate Resiliency Plan

Comments

By Pee Dee
on December 14th, 2013

If you carefully read the article, it says that Atlantic sea level rise is primarily to due groundwater extraction (e.g. land settlement) and NOT to ‘sea level rise’, except where meandering Gulf Stream and easterly winds pile up seich waves, and oh, let’s not forget tectonic rebound from the Ice Age, and torrential rains in the Australian desert!

That makes the misleading headline, and the banner placement of that headline on the green aggregator press, a quasi-political, quasi-religious straw dog.

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By Bill B (22302)
on December 15th, 2013

From the study: “These records reflect global rise (∼1.7±0.2 mm/yr since 1880 CE) and subsidence from
glacio-isostatic adjustment (∼1.3±0.4 mm/yr) at bedrock locations (e.g., New York City). At coastal plain
locations, the rate of rise is 0.3–1.3 mm/yr higher due to groundwater withdrawal and compaction.” So, the primary cause is sea level rise (global rise), followed by subsidence. You can add on 0.3-1.3 mm/yr. at coastal plain locations due to groundwater withdrawal and compaction.

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By galivantstom (Michigan)
on December 23rd, 2013

From what I’ve seen, I thought the study concluded that rising waters were a result of global warming which was exacerbated by ground water extraction. Whether one or the other is the overall cause. Since we can’t stop extracting ground water for things like food,  therefore, the land masses sinking, the water levels are not increasing because the liquids (oil, natural gas. water) that hold lands up are being remove. . Regardless of the causes, the oceanic water levels are rising relative to the land masses and the arctic and its glaciers are melting.Either way, the end result is the same.

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By Steven Blaisdell
on December 15th, 2013

No. This comment is a series of blatantly false statements with concomitantly false conclusions ad hominem, and should be removed by the moderators.

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By Steven Blaisdell
on December 15th, 2013

I’m wondering if NYC has plans for dikes across the Verrazano Narrows, and between Staten Island and New Jersey. Or - do the plans exist, awaiting the next disaster so as to motivate political will?
Google - of course. Asked and answered:
http://www.csmonitor.com/USA/2012/1113/How-will-New-York-keep-out-a-rising-sea-Dikes-huge-sea-wall-oyster-beds

Reply to this comment

By Sue (NY)
on December 15th, 2013

Pee Dee, if you carefully read the article it states that climate-induced sea level rise is exacerbated in certain regions, such as the mid-Atlantic states, by local factors like groundwater extraction, which also need to be taken into account - the headline is appropriate and not misleading..

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By Jason McCullough (PIttsburgh, PA USA)
on December 17th, 2013

FLORIDA
The US Army Corps is currently using 5 feet of sea level rise by 2100 for their estimates. Some recent data indicates it may be between 6-9 feet, conservative estimates at 3 feet. So, likely sometime between 2050 and 2100 most of Florida will be gone. However, just one foot more (there have been 8 inches due to human-induced global warming already) and many cities will have unsolvable problems, as the sea level rise increases the salinity of the groundwater. Also, most of Florida is limestone which is very porous - so it will do no good at all to try to build walls to stop this.

Your best bet is to get out now. If you wait, you will find that mortgage and insurance companies will no longer choose to be involved - so you won’t be able to sell to anyone that needs a mortgage to buy. At that point (this will likely be by 2020), your market for selling a home will be reduced to climate deniers with a lot of cash.

When Florida is abandoned, 10s of millions of jobs will end up being lost. Compare that to the 40,000 coal miners of today.

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By Terry Cook (Findlay, Ohio 45840)
on December 21st, 2013

www.thetopcatplan,com is the only plan to launch the hydrogen economy and the hemp industry in fifty states.  People have told me, stop using fossil fuel will cause loss of jobs.  I say, for ever one job lost, We’ll have 9 jobs in the green industry.  Kill fracking NOW!!!!  People still believe we must have it.  So much so, 465 billion tax payer’s money went to, as a gift to big oil, to find it and keep the price down, and we don’t care if you trash the world doing it.  140 years of living in a modern day dark age ruled by the greedy cronies is finally coming to an end.  Hemp will be legal to grow and the hydrogen economy will serve to do many positive things for every one.  Hemp char-coal will replace fossil coal completely.  There are 20 million good jobs coming in 17 divisions of the original and only Brothers Chopper in every state and 7 provinces.  Any questions?  Top Cat II

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By Frank Leslie (Palm Bay FL 32905)
on January 10th, 2014

“most of Florida will be gone”? I live on the mainland in from the beach at 26 ft above mean sea level. The beach is about 15 ft msl. SO if the ocean rises 3 ft, that margin will be gone, but the mainland won’t be underwater and “gone”.

The central Florida ridge is about 137 ft msl. We could divide 137 ft by 3 ft in decades to get about 44 decades. That’s really rough, but it takes a long time for Florida to be “gone”.

Frank

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By Phil McKrakin (New York New York 22121)
on December 20th, 2013

Did anyone ever think that maybe the ground is sinking ??  The water is of course going to rise !!

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By AlecB (Carmel/CA/93921)
on December 22nd, 2013

The graph shows uniform sea level rise of 3 mm/year during the last 113 years.

It shows no acceleration whatsoever for the last 40 years of high emissions, so since the slope is the same now as a hundred years ago, it must be natural.

As the slope has remained the same, and no new dramatic mechanism is proposed for its change in the immediate future, the sea level rise according to that graph will likely be 7 in by 2050 and 10 in by 2100.

Of course, sinking due to phreatic water use needs to be added to this.

The difference between 10 in and 5 ft must be due to reasons unknown, or to a 500% safety margin.

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By Conodo Mose (Trenton NJ 08603)
on December 27th, 2013

The only reason for rising risk is ongoing increase of construction on barrier islands and coastlines naturally pre-disposed to storm events. In other words people purposely expose themselves to flooding by intentionally locating in high risk areas. In other words “stop complaining” or move to the mountains.

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By harry presley (chattanooga tn)
on December 30th, 2013

Florida gone by 2020? That’s 6 years from now. Does anyone on here know what a mm is?  It will be 500 years before anyone can tell a difference in sea level, and by then it just might recede.  The Antarctic ice shelf is larger than at any time in recorded history. The sky is not falling, nor the ocean rising.

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By William Hughes-Games (Waipara New Zealand)
on January 2nd, 2014

A great deal of sea level rise on the Eastern Seaboard of the US of A is just what we need.  America is the country most responsible for this rise in sea level and her policy makers are concentrated on the East coast.  Perhaps having Washington DC flooded once or twice will wake them up and induce them to cut loose from the fossil fuel industry.

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By craig gosling (Indianapolis, IN 46256)
on January 8th, 2014

Great discussion! Question: At what point will climate change deniers admit that man influenced climate change is happening and will cause great human dislocation and habitat change? Answer: Never. If people still disbelieve in evolution, why would they ever admit to climate change.

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By TJ Stewart (Claysville, Pa. 15323)
on January 15th, 2014

Good grief! All here seem to site man as the great driver of “climate change”. I was taught that glaciers at one point covered the North American continent as far south as the Alabama - Mississippi area. The climate changed. Greenland (much more recently) was so named because it was fertile farm lands discovered by the Vikings. Since that time it has turned colder and has been covered by glaciers. While the sinking of the coastal plain, and other places, can certainly be attributed to the actions of man. I am not convinced that the current “climate change” can be attributed to man. Especially when some people are so quick to jump on the actions of a hurricane as “proof” of climate change yet cold fronts and blizzards that break 100+ year records are merely “weather”. Also I was taught that the drought in the heartland of the US in the 1930’s would likely be repeated as such “weather changes” are cyclical. And the “shifting sands” of the Sahara had been repeated through out recorded history. I believe that much of the “data” being used in the AGW “movement” is being cherry picked to advance a theory or position. Call me when Greenland is a great agricultural center again.

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By LPetersen (Black Mountain)
on January 21st, 2014

I am sure the insurance companies will settle the matter.  They deal in odds.  And our children will bear no great love for fools who keep doing the same and getting worse results.

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By Jan Freed (los angeles/ca/90041)
on March 19th, 2014

Those communities that take AGW into account (such as MD) will be far better off than those who think they can out think every national academy of science worldwide and dozens of Nobel Laureates.  I refer to NC.  You may proceed, contrarians.

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