Last year's El Nino resulted in unprecedented erosion of the Pacific coastline: study

Last year’s El Nino resulted in unprecedented erosion of the Pacific coastline: study
Waves during the 2015-16 El Niño “were exceptional and among the largest ever recorded.” Credit: David Hubbard

Last winter's El Niño might have felt weak to residents of Southern California, but it was in fact one of the most powerful climate events of the past 145 years.

If such severe El Niño events become more common in the future as some studies suggest they might, the California coast—home to more than 25 million people—may become increasingly vulnerable to coastal hazards. And that's independent of projected sea level rise.

New research conducted by U.S. Geological Survey (USGS) scientists and their colleagues at UC Santa Barbara and six other institutions found that during the 2015-16 El Niño winter beach erosion on the Pacific coast was 76 percent above normal, and that most beaches in California eroded beyond historical extremes. The results appear in the journal Nature Communications.

"This study illustrates the value of broad regional collaboration using long-term data for understanding coastal ecosystem responses to changing climate," said ecologist David Hubbard, an associate specialist at UCSB's Marine Science Institute. "We really need this scale of data on coastal process to understand what's going on with the ecology of the coast."

The research team assessed seasonal beach behavior for 29 beaches along more than 1,200 miles of the Pacific coast. The investigators' efforts included making 3-D surface maps and cross-shore profiles using aerial LiDAR (Light Detection and Ranging), GPS topographic surveys and direct measurements of sand quantities. They then combined that with wave and water level data from each beach between 1997 and 2016. Winter beach erosion—the removal and loss of sand from the beach—is a normal seasonal process, but during El Niño events the extent of erosion can be more severe.

"Wave conditions and coastal response were unprecedented for many locations during the winter of 2015-16," said lead author Patrick Barnard, a geologist with the USGS. "The winter wave energy equaled or exceeded measured historical maximums along the West Coast, corresponding to extreme beach erosion across the region."

The 2015-16 El Niño was one of the three strongest events ever recorded, along with the El Niño winters of 1982-83 and 1997-98. From a water resources perspective though, the most recent El Niño was largely considered a dud due to the unusually low rainfall, particularly in Southern California, which received 70 percent less rain than during the past two big El Niño events.

"However, the waves that attacked our coast, generated from storms across the North Pacific, were exceptional and among the largest ever recorded," Barnard said. "Further, the lack of rainfall means the coastal rivers produced very little sand to fill in what was lost from the beaches, so recovery has been slow." Rivers remain the primary source of sand for California beaches, despite long-term reductions in the 20th century due to extensive dam construction.

While most beaches in the survey eroded beyond historical extremes, some fared better than others. The condition of the beach before the winter of 2015 strongly influenced the severity of erosion and the ability of the beach to recover afterward through natural replenishment processes.

Unlike California, many Pacific Northwest beaches have gained sediment in the years leading up to the 2015-16 El Niño. That's due—at least in part—to more production of sand from local watersheds, dune growth and a series of mild winter storm seasons. Mild wave activity in the Pacific Northwest and artificial augmentation of beaches (adding sand) in Southern California prior to the winter of 2015-16 prevented some areas from eroding beyond historical landward extremes.

"It looks like climate change will bring us more El Niño events, possibly twice as many, at twice the frequency as in the past," Hubbard said. "So this is a taste of what's coming.

"First we need to understand the challenges, and those include the rising sea level and the fact that most of the problems occur during these peak El Niño events," he added. "Then we need to restore or manage our coasts in ways that will enable us to deal with these events and conserve beach ecosystems. I think that's the challenge that we as a society have to address."

"Infrequent and extreme events can be extremely damaging to coastal marine habitats and communities," said David Garrison, a program director in the National Science Foundation's (NSF) Division of Ocean Sciences, which funded the research. "While this paper stresses the effect of waves and sediment transport on beach structure, organisms living on and in the sediment will also be profoundly affected."


Explore further

El Nino and La Nina will exacerbate coastal hazards across entire Pacific

More information: Patrick L. Barnard et al, Extreme oceanographic forcing and coastal response due to the 2015–2016 El Niño, Nature Communications (2017). nature.com/articles/doi:10.1038/NCOMMS14365
Journal information: Nature Communications

Provided by University of California - Santa Barbara
Citation: Last year's El Nino resulted in unprecedented erosion of the Pacific coastline: study (2017, February 14) retrieved 19 October 2019 from https://phys.org/news/2017-02-el-nino-gobbled-california-beaches.html
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Feb 14, 2017
California often shows us what is ahead. In this case, most Californians already understand Global Warming is real, so they don't need yet another lesson by damaging their beaches. Unfortunately, they are going to continue to receive these lessons until the problem is corrected.

Looking into my crystal ball, by the 2030s sea ice will be gone from the Arctic in the summer, Glacier National Park won't have a single glacier left, and the pounding we will be taking from Global Warming will be more than convincing for the vast majority of us..

We should hold the Republican Party accountable for decades of lying about this and doing everything they can to profit their big donors like Big Oil and Big Coal and the expense of the country and the world.


Feb 14, 2017
Looking into my crystal ball, by the 2030s sea ice will be gone from the Arctic in the summer, Glacier National Park won't have a single glacier left, and the pounding we will be taking from Global Warming will be more than convincing for the vast majority of us..

LOL.
Tell us the truth. You were looking up at your crystal balls and up into to your rectum when you saw all that doom and gloom.

Feb 15, 2017
....Looking into my crystal ball, by the 2030s sea ice will be gone from the Arctic ...


Yes, whatever you call it: crystal ball, climate model, they are all the same. Religious artifacts from an AGW cult. They are about as accurate as my big toe in predicting the future.

Feb 15, 2017
Ok. @antigoracle and @FactsReallyMatter will not answer this; What proof is there if an "AGW cult"? I know for certain there is not. So basically they are liars, and I challenge them to prove otherwise. So are you dim bulbs up to the challenge and show that you are not a stack of lying poo

Having an Ice free Arctic really will change climate in large scale ways. Don't expect the nice northern cool breezes. Summer will be known as the fire season. Eventually as the Arctic ocean warms, we can expect the ocean currents to be altered. That may not be kind to the planet. Overall, @Mr Thomas sounds reasonable.


Feb 16, 2017
Having an Ice free Arctic really will change climate in large scale ways.


Therein is your proof. Despite all evidence that the arctic will not go ice free any time soon you persist in believing that it will.

https://wattsupwi...ce-page/

That my friend is faith, and due to your inability to see the world in any other way and dying devotion to it makes it a cult.

Feb 16, 2017
Despite all evidence that the arctic will not go ice free any time soon you persist in believing that it will.

https://wattsupwi...ce-page/


No evidence on your linked page just graphs showing a decline in arctic ice.

Tell me, when you checked those graphs did you see this one?

http://psc.apl.uw...V2.1.png

From the same site as this graph you can find this one

http://psc.apl.uw...rent.png

So why do you think that September sea ice volume will not decrease to zero?

Don't come back with a knee jerk cant reply or some cultist conspiracy theory where everybody is lying to you, give it some thought. Facts really DO matter.

Feb 16, 2017
That my friend is faith, and due to your inability to see the world in any other way and dying devotion to it makes it a cult.


This is the first time you made me laugh out loud. So funny.

I like your link, it shows sea ice declining scary quick.

Feb 16, 2017
Arctic ice showed a large decline in 2012, but then a strong recovery following 2 years. Now it declines again.

More than temp drives the ice growth and decline. Plus there is a lot of uncertainty, just look at the error bars.

We've only got coverage for 40 years - once again I ask the question, is this trend climate or is this weather?? Is this regional or is this global, cause I get varying answers depending on the topic at hand.

Feb 17, 2017
Plus there is a lot of uncertainty, just look at the error bars.


-3.2 plus or minus 1 1000km3 per decade. Even at the lower rate of -2.2 the current trend will result in an ice free September within 25 years. So why do you think the current trend will not continue?

http://psc.apl.uw...rent.png

We've only got coverage for 40 years


http://arctic.atm.../SEAICE/

Northern Hemisphere 1870-2011

Despite all evidence that the arctic will not go ice free any time soon you persist in believing that it will.


What evidence? You haven't shown any yet. To believe without evidence, that my friend is faith.

Give it some thought and remember, facts really DO matter.

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