New look at Antarctica's biggest ice shelf shows melting is occurring much faster than we thought

  
Via:  perrie-halpern  •  3 months ago  •  43 comments

New look at Antarctica's biggest ice shelf shows melting is occurring much faster than we thought
The location of the melting coincided with a “pinning point” that lends stability to the entire shelf.

S E E D E D   C O N T E N T


By Denise Chow

Antarctica’s biggest ice shelf may be more vulnerable to climate change than previously thought. A new study of warm seawater seeping into a cavity below the Ross Ice Shelf shows that a key section of the France-size hunk of ice is melting much faster than the rest.

“We’ve identified an especially vulnerable section where the melt rate is 10 times higher than the rest of the ice shelf,” said study co-author Poul Christoffersen, a glaciologist at the University of Cambridge’s Scott Polar Research Institute. The Ross Ice Shelf is considered relatively stable, but Christoffersen said the location of the rapid melting coincided with a “pinning point” — essentially a buttress that holds back flowing ice and lends stability to the entire shelf.

Ice shelves are thick, floating masses of Antarctic ice that form as nearby glaciers flow toward the sea. Previous research showed that warm water from the deep ocean is causing some ice shelves to melt and disintegrate. As that happens, the flow of glaciers into the ocean accelerates, contributing to a gradual rise of sea levels around the world.

A 2017 study by researchers at Cornell University estimated that by the year 2100, 2 billion people across the globe could be displaced by rising seas, which threaten to inundate coastal communities and other low-lying regions. Scientists estimate that seas are currently rising at a rate of roughly 3 millimeters per year, or more than a tenth of an inch.

The new research, which was published online April 29 in the journal Nature Geoscience, shows that a another type of melting — at the water’s surface rather than deep in the ocean — can also affect the stability of ice shelves.

“It’s a new, additional heat source that we point to as being important, certainly with respect to the Ross Ice Shelf which, due to its large size, is of particular concern,” Christoffersen said.

Christoffersen and his colleagues spent four years studying the Ross Ice Shelf and the ocean water underneath it. The scientists drilled an 850-foot-deep hole into the shelf and dropped instruments inside to measure temperature, melting rates and ocean currents within the cavity.

The researchers found that strong offshore winds are blowing sea ice away from the leading edge of the ice shelf, exposing regions of the ocean to the sun’s warmth that previously had been covered by ice. The water’s warmth hastens the melting of the ice.

Laurie Padman, a senior scientist at the Seattle-based Earth & Space Research institute, said the new study provided precise measurements for a phenomenon that has been observed at other ice shelves but which was poorly understood. “For the Ross Ice Shelf, it matters because this melting is occurring in a place where it could change the ability of the ice shelf to buttress the surrounding ice,” he said.

The study doesn’t link the observed melting directly to climate change, but Christoffersen said climate change likely is playing a role. For instance, warmer temperatures could cause the sea ice around ice shelves to thin, making it easier for wind to blow patches away and expose ocean water to sunlight. “We do think melting could become higher due to climate change,” he said.

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Perrie Halpern R.A.
1  seeder  Perrie Halpern R.A.    3 months ago

Well, there is no denying global warming, but is there anything we can do about it?

 
 
 
dave-2693993
1.1  dave-2693993  replied to  Perrie Halpern R.A. @1    3 months ago
but is there anything we can do about it?

Geological evidence says no.

 
 
 
cjcold
1.1.1  cjcold  replied to  dave-2693993 @1.1    3 months ago

Since AGW has never happened before, what geological evidence is there?

Drastically cutting our production of greenhouse gasses would be a good first step.   

 
 
 
dave-2693993
1.1.2  dave-2693993  replied to  cjcold @1.1.1    3 months ago

I think from a general standpoint that is a good strategy.

We certainly are in uncharted waters.

Many claim the 8.200 yr BP cooling event was a result of the thermohaline stopping. This ice sheet just might put us over that edge.

Just a few years ago (2016) we had thought to have crossed a threshold to stop the thermohaline, latest news is, no, it didn't stop.

JMO, I think we are teetering on the edge.

 
 
 
Greg Jones
1.1.3  Greg Jones  replied to  cjcold @1.1.1    3 months ago
Drastically cutting our production of greenhouse gasses would be a good first step

Whose greenhouse gases. Just "ours" here in the US....or should all the countries in the world get involved?

And how would this drastic reduction be accomplished? And what is primary producer or source of these gases?

 
 
 
Ed-NavDoc
1.2  Ed-NavDoc  replied to  Perrie Halpern R.A. @1    3 months ago

This is not something new. When I was at McMurdo Station, Antarctica in late 1987, we had the warmest summer temperature on record which was 58 degrees Farenheit above zero. Positively sweltering by Antarctic standards. They have had routinely warmer temps since then. In talks I had with scientists down there over a four year period, it was widely thought to be man made climate change. To my understanding, that view changed to a routine period of glacial and climactic change that occurs over the millennia. We are warming up subsequent to another ice age sometime in the future. Last one was approximately 10,000 years ago.

 
 
 
tomwcraig
1.2.1  tomwcraig  replied to  Ed-NavDoc @1.2    3 months ago

Ed,

This is something I have been hammering those supporting AGW Theory/Climate Change/Global Warming since 2009 on.  We are still in the cycle of glacials and interglacials, and there is no real sign that the cycle is changing.  As I keep telling people, climate is more of a pendulum style cycle and as you get closer to the midpoint, the acceleration is greatest and we are not at the midpoint yet in this interglacial, but we are getting close.  So, logically, this is when we would see a natural acceleration in actual warming.  Plus, the geological record is clear that the Earth has been much, much warmer than it is currently and we are nowhere near close to those temperatures.

 
 
 
Greg Jones
1.3  Greg Jones  replied to  Perrie Halpern R.A. @1    3 months ago

Slowly rising temps to be sure, but there is no evidence that this will continue. A cooling period or even a new ice age could start at any time.

No direct and scientifically verifiable link has been found between human activities and warming, or the amount it has contributed, if any. As has been stated many times, we have been in an interglacial for the last 12,000 years or so, so much of the observed warming could be natural.

The answer is NO, we really can't do much about it, in spite of all the hopeful and brave talk to the contrary. Reduced use of fossil fuels is not likely to occur worldwide. People these days don't want to freeze to death in the dark or ride horses everywhere.

Since the rate of rise only tenth of an inch a year, people will have time to make changes and move away from the coasts on a gradual basis.

 
 
 
Gordy327
1.3.1  Gordy327  replied to  Greg Jones @1.3    3 months ago
but there is no evidence that this will continue. A cooling period or even a new ice age could start at any time.

I'm sure some people say that every year. And every year, it doesn't happen. Right now, we're doing the opposite of cooling.

No direct and scientifically verifiable link has been found between human activities and warming, or the amount it has contributed, if any.

Yes, there is. Human activity has certainly contributed to climate change.  Or is the billions of tons of CO2 released by human activity every year doing nothing?

Reduced use of fossil fuels is not likely to occur worldwide.

Until we run out of fossil fuels.

The answer is NO, we really can't do much about it,

Maybe not. But that doesn't mean we shouldn't take steps to try and mitigate the damage caused.

Since the rate of rise only tenth of an inch a year, people will have time to make changes and move away from the coasts on a gradual basis.

Sounds like a slow moving refugee crisis waiting to happen.

 
 
 
Heartland American
1.3.2  Heartland American  replied to  Gordy327 @1.3.1    3 months ago

Well then it’s time to get other humans to make changes since only the USA has significantly reduced its greenhouse gas footprint over recent years.  It’s still much more solar and cyclically related than msn caused.  

 
 
 
Gordy327
1.3.3  Gordy327  replied to  Heartland American @1.3.2    3 months ago
Well then it’s time to get other humans to make changes

Agreed. We can start by making changes ourselves to reduce our carbon footprint and take steps to accept actual science on the matter and combat the lies and misinformation perpetrated by climate change deniers and/or the woefully ignorant. Lead by example.

since only the USA has significantly reduced its greenhouse gas footprint over recent years.

Not exactly. According to the EPA (2016), "In 2014, U.S. greenhouse gas emissions totaled 6,870 million metric tons (15.1 trillion pounds) of carbon dioxide equivalents. This total represents a 7 percent increase since 1990 but a 7 percent decrease since 2005. For the United States, during the period from 1990 to 2014. Emissions of carbon dioxide, the primary greenhouse gas emitted by human activities, increased by 9 percent" (para. 1-2).

While there has been a decline of CO2 emissions from its peak in recent years, we are still at a high level. According to Scientific American (2016), Much of the recent reduction is due to the use of alternative and renewable energy sources and a reduction in fossil fuel use (such as power plants).

It’s still much more solar and cyclically related than msn caused.

That's where you're wrong. While solar activity can affect the climate, it's the current cycle of climate change that is mostly affected by human activity. While we can't affect the sun's effect, we can change our own affect, which only compounds any other factors contributing to climate change. The solar cycle is 11 years. But we still see overall increased warming in between those cycles too. It should be noted that human influenced climate change also affect the sun's effect on Earth.

 
 
 
Bob Nelson
1.4  Bob Nelson  replied to  Perrie Halpern R.A. @1    3 months ago

[Removed

 
 
 
dave-2693993
1.4.1  dave-2693993  replied to  Bob Nelson @1.4    3 months ago
Of course,  one of them is so unglued that he sees Nazi symbolism in antifa's logo

Once again, for the umpteenth time, earth and blood.

As both of our comments should be deleted as off topic, I will take this time to ask why did antifa adopt the well established colors of earth and blood?

 
 
 
Gordy327
1.4.2  Gordy327  replied to  Bob Nelson @1.4    3 months ago
There are lots of people still denying it. Right here in this thread.

Climate change deniers are on the same level as anti-vaccers. The embracing and/or propagation of such ignorance is mind boggling.

 
 
 
dave-2693993
1.4.3  dave-2693993  replied to  Gordy327 @1.4.2    3 months ago
Climate change deniers are on the same level as anti-vaccers. The embracing and/or propagation of such ignorance is mind boggling.

The proof is too positive that climate changes and we are in uncharted waters.

JMO, only something like stopping the thermohaline for an extended period of time will make any measurable change in regaining land.

Unfortunately, that would most likely be disastrous in many ways.

 
 
 
Bob Nelson
1.4.4  Bob Nelson  replied to  dave-2693993 @1.4.1    3 months ago

[Removed

 
 
 
dave-2693993
1.4.5  dave-2693993  replied to  Bob Nelson @1.4.4    3 months ago

[Removed

 
 
 
TᵢG
1.4.6  TᵢG  replied to  dave-2693993 @1.4.3    3 months ago
The proof is too positive that climate changes and we are in uncharted waters.

Of course the climate changes ... and in dramatic fashion that leads to mass extinctions.   The debate is not whether climate changes but rather the current trend, the likely contributing factors and the degree to which human practices are contributing.   Denying anthropogenic factors is what is meant by 'climate change deniers' and that denial disregards solid findings.

In my view there should be no climate deniers - that is irrational.    I fully appreciate those with a skeptical viewpoint who seek further investigation and analysis of the situation so as to produce clear, practical measures we can take.   But to deny we have a problem and not even lift a finger to try to mitigate it (e.g. we can all cut down on CO2 emissions in our daily lives) is irresponsible.   Worse, however, are those who actively try to deny that we even have a problem.   Similar to those who 'scientifically' argued that lead emissions from vehicles was NOT harmful to our health and that cigarette smoking is not really harmful.

 
 
 
dave-2693993
1.4.7  dave-2693993  replied to  TᵢG @1.4.6    3 months ago

I understand your thoughts TiG and agree, but I am a graph guy. Pretty much everything I have ever done has been graphed based, across spectrums most would never imagine.

I look at the graphs and I see the inevitable.

Also, I agree we should do as we can to help preserve our planet for more reasons than just climate. But I look at this and think we are overwhelmed.

What do you think? There was a word in Watership Down that pretty much describes my thoughts. I think it was tharn. Or something like that. It pretty much meant overwhelmed.

 
 
 
Heartland American
1.4.8  Heartland American  replied to  Bob Nelson @1.4.4    3 months ago

Let’s study this to make sure.

JOINT LETTER TO PRESIDENT TRUMP IN SUPPORT OF PROPOSED PRESIDENT'S COMMISSION ON CLIMATE SECURITY

MARCH 18, 2019

Mr. President, you have made a number of comments in recent years expressing doubts about the global warming consensus. Many of the signers of this letter have been similarly skeptical.

Trump-Paris-Rose-Garden.jpg

​Washington, DC
18th March 2019

The Honorable Donald J. Trump
President of the United States
The White House
1600 Pennsylvania Avenue, N. W.
Washington, DC 20500

Via e-mail

Dear President Trump,

The undersigned organizations and individuals write to express our strong support for the proposed President’s Commission on Climate Security. It is our understanding that this commission, which is being planned and would be directed by Dr. William Happer of the National Security Council staff, is currently being considered by your senior White House staff and relevant Cabinet secretaries and agency heads. The commission would consist of a small number of distinguished experts on climate-related science and national security. It would be charged with conducting an independent, high-level review of the Fourth National Climate Assessment and other official reports relating to climate and its implications for national security. Its deliberations would be subject to the transparency requirements of the Federal Advisory Committees Act.

In our view, an independent review of these reports is long overdue. Serious problems and shortcomings have been raised repeatedly in the past by highly-qualified scientists only to be ignored or dismissed by the federal agencies in charge of producing the reports. Among major issues that have been raised and that we hope the commission will scrutinize: the models used have assumed climate sensitivities to CO2 concentrations significantly higher than recent research warrants; the models used have predicted much more warming than has actually occurred; predictions of the negative impacts of global warming have been made based on implausible high-end emissions scenarios; the positive impacts of warming have been ignored or minimized; and surface temperature data sets have been manipulated to show more rapid warming than has actually occurred. An underlying issue that we hope the commission will also address is the fact that so many of the scientific claims made in these reports and by many climate scientists are not falsifiable, that is, they cannot be tested by the scientific method.

The conclusions and predictions made by these reports are the basis for proposed energy policies that could cost trillions of dollars in less than a decade and tens of trillions of dollars over several decades. Given the magnitude of the potential costs involved, we think that taking the insular processes of official, consensus science on trust, as has been the case for the past three decades, is negligent and imprudent. In contrast, major engineering projects are regularly subjected to the most rigorous and exhaustive adversarial review. We suggest that climate science requires at least the same level of scrutiny as the engineering employed in building a bridge or a new airplane.

We note that defenders of the climate consensus have already mounted a public campaign against the proposed commission. We find this opposition curious. If the defenders are confident that the science contained in official reports is robust, then they should welcome a review that would finally put to rest the doubts that have been raised. On the other hand, their opposition could be taken as evidence that the scientific basis of the climate consensus is in fact highly suspect and cannot withstand critical review.

We further note that opponents of the proposed commission have already stooped to making personal attacks on Dr. Happer. Many signers of this letter know Dr. Happer personally and all are familiar with his scientific career. We know him to be a man of high capabilities, high achievements, and the highest integrity.

It has been reported that some officials within your administration have proposed an internal working group as an alternative to an independent commission subject to FACA. Insofar as an internal working group would consist of federal career scientists reviewing their own work, we think this alternative would be worse than doing nothing.

Although an independent commission of distinguished scientists would have high credibility, we do not mean to imply that its report should be the end of the matter. We therefore suggest that the National Academies of Science and Engineering would be appropriate bodies to conduct an initial review of the commission’s report. Mr. President, you have made a number of comments in recent years expressing doubts about the global warming consensus. Many of the signers of this letter have been similarly skeptical. Without prejudging the results, we think that a review of climate science produced by an independent, high-level commission would be a fair test for your views (and ours): either it would provide a sound basis for revising your views or it would confirm your views and confound your critics.

For these reasons, we urge you to create by Executive Order a President’s Commission on Climate Security. Thank you for considering our views.

Sincerely,

Myron Ebell, Director, Center for Energy and Environment
and Marlo Lewis, Senior Fellow
Competitive Enterprise Institute

Tim Huelskamp, Ph. D., President and CEO
and Joseph L. Bast, Founder and Senior Fellow
The Heartland Institute

Adam Brandon, President
FreedomWorks

Tim Chapman, Executive Director
Heritage Action for America

Thomas Pyle, President
American Energy Alliance

Thomas Schatz, President
Citizens Against Government Waste

Craig Rucker, President
and Marc Morano, Publisher, CFACT’s Climate Depot
Committee For A Constructive Tomorrow (CFACT)

Steve Milloy, Publisher
Junk Science

James L. Martin, Founder and Chairman
and Saulius “Saul” Anuzis, President
60 Plus Association

Dr. Thomas P. Sheahen, Chairman
and Kenneth Haapala, President
Science and Environmental Policy Project

Robert L. Bradley, Jr., CEO
Institute for Energy Research

Craig D. Idso, Ph. D., Chairman
Center for the Study of Carbon Dioxide and GlobalChange

Tom Harris, Executive Director
International Climate Science Coalition

Eunie Smith, President
Eagle Forum

Rick Manning, President
Americans for Limited Government

Craig Richardson, President
Energy and Environment Legal Institute

E. Calvin Beisner, Ph. D., Founder and National Spokesman
Cornwall Alliance for the Stewardship of Creation

Phil Kerpen, President
American Commitment

Mario H. Lopez, President
Hispanic Leadership Fund

Al Regnery, Chairman
Conservative Action Project

Bill Walton, Chairman
CNP Action, Inc.

Jennifer Fielder, CEO
American Lands Council

Tom DeWeese, President
American Policy Center

Andrew Langer, President
Institute for Liberty

David T. Stevenson, Policy Director
and Clinton S. Laird, Advisory Council
Caesar Rodney Institute

Rob Roper, President
Ethan Allen Institute

Kory Swanson, President and CEO
John Locke Foundation

Paul Gessing, President
Rio Grande Foundation

Jason Hayes, Director of Environmental Policy
The Mackinac Center for Public Policy

Kathleen Hartnett White, Senior Fellow and Director
Armstrong Center for Energy and the Environment
Life: Powered, a Project of the Texas Public Policy Foundation

Daniel Turner, Founder and Executive Director
Power the Future

John Droz, Jr., Founder
Alliance for Wise Energy Decisions

Alex Epstein, Founder
Center for Industrial Progress

Mark Mathis, President
Clear Energy Alliance

Mandy Gunasekara, Founder
Energy 45 Fund

Peter Ferrara, Chief Consultant
and David Wallace, President and Founder
FAIR Energy Foundation

Mark Anderson, Executive Director
and Karla Davenport, Producer
I Spy Radio

[For a list of the individual signers, please download the PDF of the letter.]. https://www.heartland.org/publications-resources/publications/joint-letter-to-president-trump-in-support-of-proposed-presidents-commission-on-climate-security

 
 
 
Gordy327
1.4.9  Gordy327  replied to  Heartland American @1.4.8    3 months ago
Let’s study this to make sure.

I've studies that e-mail and determined it's climate denier nonsense form obvious biased political groups or businesses with an agenda.  Peddle the climate denier nonsense elsewhere. You're only contributing to the problem.

 
 
 
Greg Jones
1.4.10  Greg Jones  replied to  Gordy327 @1.4.2    3 months ago

Oh, bullcrap...we have looked at the evidence, particularly the lack of it, and are not convinced.

The real problem here is that the liberals somewhere along the line, made this issue totally political and castigated anyone who might not be convinced of the so called science and calls them deniers.  I doubt the poster knows anything much about the actual science of atmospheric physics and just parrots the propaganda spewed by others.

The climate change crowd bitches constantly about the coming catastrophe, yet can offer no viable and affordable solutions, other than name calling and fear mongering. The masses are not buying the hype and hysteria of the chicken little climate change crowd.

 
 
 
Bob Nelson
1.4.11  Bob Nelson  replied to  Heartland American @1.4.8    3 months ago

So you have a letter signed by a Who's Who of climate denial. Is it supposed to convince anyone?

 
 
 
Gordy327
1.4.12  Gordy327  replied to  Greg Jones @1.4.10    3 months ago
Oh, bullcrap...we have looked at the evidence, particularly the lack of it, and are not convinced.

It's obvious you didn't look at my links then. There's plenty of information at NASA, the National Academy of Sciences, and other scientifically reputable sources. Denying the science doesn't mean it's not there. 

The real problem here is that the liberals somewhere along the line,

When you have to make this a political us vs them, then it's clear you have nothing of substance to offer to the actual discussion and lack any credibility.

The climate change crowd bitches constantly about the coming catastrophe, yet can offer no viable and affordable solutions, other than name calling and fear mongering.

No one is saying there's a catastrophe-yet. Only that climate change can lead to one. But I suppose climate deniers will only be convinced if a catastrophe does occur. And even then I wonder if they'll be convinced.

 
 
 
Dignitatem Societatis
1.4.13  Dignitatem Societatis  replied to  dave-2693993 @1.4.1    3 months ago
why did antifa adopt the well established colors of earth and blood?

If you mean black and red, those colors are for anarchism and labor. The combo is most often used for anarcho syndicalism or libertarian socialism. I suppose Antifa uses them because they're made up of people from both red flag and black flag tendencies, both of which are anti-fascist.

It is not an allusion to the German Black, White and Red flag created under Bismark and later reused and modified by the Nazis.

 
 
 
dave-2693993
1.4.14  dave-2693993  replied to  Dignitatem Societatis @1.4.13    3 months ago

Thank you for that good comment.

But when looking at the antifa symbols, it is often black, white and red. I know I didn't mention the white before, but that is what it is.

I can't describe how much I hate the earth and blood symbolism. Hate is not an easy word to use, but I will for them.

I believe it was originally called blood and soil. Today, earth and blood.

Also today in many representations it is strictly black and red, all far right wing.

Thank you again.

 
 
 
Greg Jones
1.4.15  Greg Jones  replied to  Gordy327 @1.4.12    3 months ago
No one is saying there's a catastrophe-yet. Only that climate change can lead to one.

And once again, where is the scientific evidence of that?

Is Earth to become another Venus with the greenhouse effect on steroids?

 
 
 
Gordy327
1.4.16  Gordy327  replied to  Greg Jones @1.4.15    3 months ago
And once again, where is the scientific evidence of that?

For one, We observe the polar ice caps and mountain snow covers melting and the oceans warming. Do you understand how that will affect the planet's climate and various ecosystems? Not to mention effects on weather patterns. Like I said, you don't bother with cited links and probably won't even admit to a catastrophe until one actually happens, if ever. By then, it might very well be too late. But there is plenty of evidence if you bother to look and understand, rather than outright dismiss.

Is Earth to become another Venus with the greenhouse effect on steroids?

If enough greenhouse gasses buildup, then it can. Venus is an example of the greenhouse effect to its extreme. But we can observe and measure the same process happening on Earth.

 
 
 
Vic Eldred
1.5  Vic Eldred  replied to  Perrie Halpern R.A. @1    3 months ago

I think the US has done all it can at home. Now the trick is to get all the rest of the world involved.

 
 
 
dave-2693993
2  dave-2693993    3 months ago

Not surprised Perrie.

Is this the one that stops the thermohaline circulation?

 
 
 
Bob Nelson
3  Bob Nelson    3 months ago

Global warming is a conspiracy among scientists in order to get more grant money.

Well, okay... Global warming is real, but we don't know how bad it is.

Well, okay... It's bad, but we don't know humanity's role.

Well, okay... It's anthropogenic, but we don't know how bad it may get.

Well, okay... It's going to destroy the planet, but it's too expensive to stop.

These assholes are killing our grandchildren, and we can do little. We're not even allowed to label them as what they prove themselves to be, every day.

 
 
 
Greg Jones
3.1  Greg Jones  replied to  Bob Nelson @3    3 months ago

and we can do little.

At least ya got that right. 

What assholes are you referring to...

the Russians?

the Chinese?

the countries of Eastern Europe?

the countries of Southeast Asia

the rain forest burning people in South America......or

just those nasty mean old capitalists here in the good old USA....

where the air quality has improved markedly in the last few decades????  jrSmiley_26_smiley_image.gif

 
 
 
Heartland American
3.1.1  Heartland American  replied to  Greg Jones @3.1    3 months ago

Americans have reduced our greenhouse gas footprint 👣 in addition to cleaning our water 💦 and air.  Now that we have made so much progress the tree 🌲 huggers and earth first! types have to create a scare beyond normal solar and cyclical changes in order to win control over our economy and individual choices that they could not win when they were pure socialists.  They have melded a green veneer on their social and economic red.  

 
 
 
dave-2693993
4  dave-2693993    3 months ago

I would say, save the histrionics for NASA and NOAA.

I will repeat that, NASA and NOAA.

Those horrible conspiracy sites.

For the "eleventy hundredth" time I will post this information from those two horrible conspiracy sites. Must I put this /s?

Now, please, anyone, tell me which cold or even ICE AGE EVENT turned around or even stopped the sea level rise? Which one?

https://www.giss.nasa.gov/research/briefs/gornitz_09/

slr_s.jpg

Generalized curve of sea level rise since the last ice age. Abbreviations: MWP = meltwater pulse. MWP-1A0, c. 19,000 years ago, MWP-1A, 14,600 to 13,500 years ago, MWP-1B, 11,500-11,000 years ago, MWP-1C, ~8,200-7,600 years ago.

Sea Level Rise, After the Ice Melted and Today

By Vivien Gornitz — January 2007

Climate warming is expected to result in rising sea level. Should this occur, coastal cities, ports, and wetlands would be threatened with more frequent flooding, increased beach erosion, and saltwater encroachment into coastal streams and aquifers. Global sea level has fluctuated widely in the recent geologic past. It stood 4-6 meters above the present during the last interglacial period, 125,000 years ago, but was 120 m lower at the peak of the last ice age, around 20,000 years ago. A study of past sea level fluctuations provides a longer-term geologic context, which can help us better anticipate future trends.

Massive ice sheets covered parts of North America, northern Europe, and several other regions during the last ice age. This huge volume of ice lowered global sea level by around 120 meters as compared to today. After the ice sheets began to melt and retreat, sea level rose rapidly, with several periods of even faster spurts. The first such spurt may have started about 19,000 years ago, at which time ocean levels rose 10-15 m in less than 500 years. However, this event is not seen in all past sea level records and new evidence suggests that ice melting may have begun much earlier. A more clearly-defined accelerated phase of sea level rise occurred between 14,600 to 13,500 years before present (termed "meltwater pulse 1A" or "MWP-1A" by Fairbanks in 1989), when sea level increased by some 16 to 24 m (see Figure 1). Although the meltwater was previously believed to have come chiefly from Antarctica, a recent reconstruction by Tarasov and Peltier of ice sheet retreat using a glacial model calibrated by a variety of data points instead to a largely North American source. Furthermore, diatom fossils in sediments from fjords in East Antarctica show that ice melting there began perhaps 3000 years later, thus ruling out Antarctica as a likely source.

The rate of sea level rise slowed between 14,000 and 12,000 years ago during the Younger Dryas cold period and was succeeded by another surge, "meltwater pulse 1B", 11,500-11,000 years ago, when sea level may have jumped by 28 m according to Fairbanks, although subsequent studies indicate it may have been much less. Meltwater from glacial Lake Agassiz (southwest of Hudson Bay) draining catastrophically into the North Atlantic via Lake Superior and the St. Laurence seaway was once thought to have initiated ocean circulation changes leading to the Younger Dryas cold period. Regional removal of ice sheets, however, occurred nearly 1000 years later, and hence draining of Lake Agassiz could not likely have caused the Younger Dryas cold reversal. This cold spell may have instead been triggered by increased outflow into the Arctic Ocean, the Fram Strait east of Greenland, and ultimately the eastern North Atlantic, between 12,900 and 12,800 years before present, as suggested by the glacial model of Tarasov and Peltier. On the other hand, Leventer et al. indicate that the timing of deglaciation in eastern Antarctica roughly coincides with the onset of meltwater pulse 1B.

A fourth interval of rapid sea level rise 8200-7600 years ago was first identified by a hiatus in coral growth in the Caribbean about 7600 years ago. Although less firmly established than the other such intervals, it is supported by stratigraphic data from elsewhere including Chesapeake Bay; the Mississippi River delta; the Yellow River in China; coastal Lancashire, England; and Limfjord, northwestern Denmark. This spurt has been linked to a cold event 8200 year ago, which apparently resulted from the catastrophic drainage of glacial Lakes Agassiz and Ojibway around 8400 yrs ago, releasing a volume of about 105 cubic kilometers within a few years or even less. But it only produced about 1 meter of global sea level rise, assuming an even spread of this volume spread across the world's oceans. Yet even this minor increase in sea level left an imprint in the stratigraphic record.

By the mid-Holocene period, 6000-5000 years ago, glacial melting had essentially ceased, while ongoing adjustments of Earth's lithosphere due to removal of the ice sheets gradually decreased over time. Thus, sea level continued to drop in formerly glaciated regions and rise in areas peripheral to the former ice sheets. At many low-latitude ocean islands and coastal sites distant from the effects of glaciation, sea level stood several meters higher than present during the mid-Holocene and has been falling ever since. This phenomenon is due to lithospheric responses to changes in ice and water loading. Water is "siphoned" away from the central equatorial ocean basins into depressed areas peripheral to long-gone ice sheets. Loading by meltwater that has been added to the oceans also depresses far-field continental shelves, tilting the shoreline upward and thus lowering local sea level. Over the past few thousand years, the rate of sea level rise remained fairly low, probably not exceeding a few tenths of a millimeter per year.

Twentieth century sea level trends, however, are substantially higher that those of the last few thousand years. The current phase of accelerated sea level rise appears to have begun in the mid/late 19th century to early 20th century, based on coastal sediments from a number of localities. Twentieth century global sea level, as determined from tide gauges in coastal harbors, has been increasing by 1.7-1.8 mm/yr, apparently related to the recent climatic warming trend. Most of this rise comes from warming of the world's oceans and melting of mountain glaciers, which have receded dramatically in many places especially during the last few decades. Since 1993, an even higher sea level trend of about 2.8 mm/yr has been measured from the TOPEX/POSEIDON satellite altimeter. Analysis of longer tide-gauge records (1870-2004) also suggests a possible late 20th century acceleration in global sea level.

Recent observations of Greenland and the West Antarctic Ice Sheet raise concerns for the future. Satellites detect a thinning of parts of the Greenland Ice Sheet at lower elevations, and glaciers are disgorging ice into the ocean more rapidly, adding 0.23 to 0.57 mm/yr to the sea within the last decade. The West Antarctic Ice Sheet is also showing some signs of thinning. Either ice sheet, if melted completely, contains enough ice to raise sea level by 5-7 m. A global temperature rise of 2-5°C might destabilize Greenland irreversibly. Such a temperature rise lies within the range of several future climate projections for the 21st century. However, any significant meltdown would take many centuries. Furthermore, even with possible future accelerated discharge from the West Antarctic Ice Sheet, it highly unlikely that annual rates of sea level rise would exceed those of the major post-glacial meltwater pulses.

Related Links

+ News: NASA Looks at Sea Level Rise, Hurricane Risks to New York City

Reference

Fairbanks, R.G. 1989. 17,000-year glacio-eustatic sea level record: influence of glacial melting rates on the Younger Dryas event and deep-ocean circulation. Nature, 342, 637-642.

Gornitz, V., 2007. Sea level change, post-glacial. In Encyclopedia of Paleoclimatology and Ancient Environments (V. Gornitz, Ed.). Springer. (in preparation).

Leventer, A., et al. 2006. Marine sediment record from the East Antarctic margin reveals dynamics of ice sheet recession. GSA Today 16, no. 12, 4-10.

Tarasov, L., and W.R. Peltier 2005. Arctic freshwater forcing of the Younger Dryas cold reversal. Nature 435, 662-665.

Additional references may be found in Gornitz (2007).

Contact

Please address all inquiries about this research to Dr. Vivien Gornitz.

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Then of course NOAA has this to say Those rat bastard conspiracy theorists.  ooops, forgot /s.

Here is a temperature graph that teis in very well with the graph and article above. PLEASE NOTE, We are NOWHERE NEAR OUR MAX TEMPERATURES already experienced during our current interglacial, regardless of greenhouse gasses being absolutely off the charts at never before seen levels.

https://www.climate.gov/news-features/features/day-yesterday-when-abrupt-climate-change-came-chesapeake-bay

The day before yesterday: when abrupt climate change came to the Chesapeake Bay

Author: 
March 7, 2014

A version of this article was originally published in Chesapeake Quarterly, the magazine of Maryland SeaGrant.

Thomas Cronin, a research geologist, collaborated with colleagues at the U.S. Geological Survey, who analyzed sediment cores from the Chesapeake Bay and found evidence of abrupt climate change during the early evolution of the estuary. Credit: Michael W. Fincham

IN OCTOBER 2003, A LITTLE-KNOWN THINK TANK in the Department of Defense quietly released a report warning that climate change could happen suddenly—so suddenly it could pose a major threat to our country's national security.

The title of the Pentagon report was a mouthful: An Abrupt Climate Change Scenario and its Implications for United States National Security. Those implications included rising seas, flooded coastal cities, at least one drowned country, droughts, food shortages, failed states, and fortress states. The report was never designed as a scientific prediction. It was a speculative effort by defense strategists to dramatize all the security threats the country would face if the climate suddenly shifted.

Why was the Pentagon suddenly worried about abrupt climate change? Because there was new evidence it had happened before.

historictemperaturerecord_greenland_610.

Ice core indicators show that the Holocene, our current interglacial epoch, began some 11,000 years ago and brought a time of stable temperatures, interrupted by a cool-down 8,200 years ago and later by the Medieval Warm Period and the Little Ice Age. Graph adapted from Richard B. Alley, The Two-Mile Time Machine.

On June 2, 2003, a French vessel designed for deep-ocean research entered the Chesapeake Bay, an estuary noted for its shallow waters. On board were a dozen American scientists, most of them geologists or geophysicists who were hoping to punch coring tubes down into the bottom of the Bay and bring up sediments buried there before the estuary formed.

The American scientists had questions about past climate changes and the sediments might hold answers–or at least clues. “We were trying to learn more about the long-term history of the Chesapeake Bay,” says Debra Willard of the U.S Geological Service. Sediments, if you know how to read them, have a story to tell: they catch and hold the remnants of whatever washed into the Bay once upon a time, or blew into the Bay, or lived and died in these waters. One question the scientists were asking: How has climate change shaped the evolution of this estuary?

To answer their questions, the American scientists had chartered the R/V Marion Dufresne for 48 hours of round-the-clock coring work. The ship was big, 395 feet long, and it offered five-course French cuisine complete with waiters, wine, cheese plates, and pastries. It also carried the gear and staff that could take very deep core samples. Managed by the Institute Polaire Paul Emile Victor (IPEV), the ship had two key missions: carrying supplies to French research stations near Antarctica and mounting expeditions around the world to uncover evidence of climate change.

“It was the only ship that had the capability to get long continuous cores,” says Willard. A research geologist with expertise in buried pollen, she coordinated the expedition for the cadre of American scientists, most of them from the U.S. Geological Survey and the Naval Research Laboratory. The R/V Marion Dufresne came equipped with science laboratories, high-end computer workstations, and huge cranes, but its secret weapon was the Calypso corer, one of the longest, heaviest coring samplers in the world.

With all that gear, the Americans planned to capture the deepest sediment samples ever taken in the history of Chesapeake Bay science, evidence that could hold clues about earlier climate change in the Chesapeake.

Ten years ago the specter of abrupt climate change seemed to invade the American mindset rather abruptly. Perhaps it was a reflection of post-9/11 fears about how fast the future could turn grim, but a lot of serious people were suddenly talking about it.

The Pentagon report on “An Abrupt Climate Change Scenario” was commissioned by Andrew Marshall, long-time director of a think tank called the Office of Net Assessment. Press reports usually called Marshall the “Yoda” of the Pentagon, and Foreign Policy magazine in 2012 called him one of the world’s top global thinkers. Now 92 years old, Marshall is still on the job, and a big part of his job is still the same: thinking about the unthinkable and reporting his thoughts directly to his boss, the Secretary of Defense. In 2003, one of his thoughts was that the country should now take seriously the possibility of abrupt climate change.

He had this thought because he knew that many scientists were finding new evidence it could happen. In 1997, Richard B. Alley, a Penn State geologist, had found evidence in Greenland ice cores that a sudden and mysterious cooling hit the Northern Hemisphere thousands of years ago during an era of global warming.  In 2002, the National Research Council had released a study warning that climate change could occur quickly, within decades, especially if something happened to slow down or shut down the Atlantic Meridional Overturning Circulation, a branch of the ocean conveyor belt that, among other missions, carries heat from the tropics up into the North Atlantic. After Marshall read the scientific study, he commissioned his own study and hired Peter Schwartz and Doug Randall, two self-described futurists, to work out a geopolitical scenario.

Hollywood producers were also skimming those science reports, skipping any inconvenient details about the speed of climate change. In 2004 they created their own vivid version of abrupt climate change by releasing a 125-million-dollar movie, The Day After Tomorrow. For geologists, abrupt change usually took several decades, for filmmakers it only took several days. Unleashing the power of digital special effects, they showed New York City succumbing to a new ice age in the space of three weeks, a climate change so abrupt and so devastating it sent the U.S. government decamping to Mexico.

What was the scientific evidence for “abrupt climate change” in the past? The Pentagon modeled its nightmare scenario on a specific episode that struck the planet some 8,200 years ago. The earth was well into our current interglacial era, an age of warming oceans and melting ice sheets, when a major cooldown suddenly arrived. It’s called the 8.2 kiloyear event–or the "8.2 ka" event in scientific shorthand. Evidence for the event came from those ice cores in Greenland: these early estimates suggested that temperatures dropped between 7 and 14 degrees Fahrenheit in less than 20 years. And that drop altered ocean currents, atmospheric circulation, and weather patterns around most of the planet. In geological time scales, that's abrupt.

The first evidence for the 8.2 kiloyear cooling was found in ice cores in Greenland, but on board the Marion DuFresne Tom Cronin and Debra Willard suspected there might also be evidence of the event buried in sediments below Chesapeake Bay.

As the French ship dropped anchors for its first coring site, Cronin found a spot along the high walkways that hang above the stern deck so he could watch the work crew below prepare the sampling gear. Tall and fit with graying hair and strong opinions, Cronin is a research geologist who joined the USGS in 1978 and has been publishing prolifically ever since on ancient episodes of climate change, sea level rise and estuary formation, and ocean circulation. Gathered to watch with him along the walkways were most of the American scientists.  Each "core drop" from this kind of ship represented a rare opportunity for gathering deeper sediments and deeper insights into the evolution of the estuary.

The heavy lifting on this ship was handled not by the American or the French scientists, but by a crew of 20 Malagasians recruited from the island of Madagascar, a former French colony. Working the deck in hard hats, they hooked together several pipes into one extended tube, craned it up to the coring platform, and dangled it over the side like a long ice pick. There they could top load the ice pick with weight, up to 10 tons of weight if needed. On deep ocean drops, all that weight has driven long tubes 230 feet beneath the ocean floor.

Their hopes took a hit at the first coring site. The coring drove into the bottom and smacked against a barrier of hard sand. When the Malagasian crew winched it back up and laid it on deck, the American geologists found a badly bent core pipe, holding only a short stub of sand. That hurt. Willard and Cronin hoped an ice pick in that spot would jab all the way down into sediments buried during the last ice age.

Deep cores, however, are hard to come by in Chesapeake Bay. To drive very far into bottom sediments, a coring tube needs a lot of deep water. And that’s the problem: a shallow-water estuary calls for shorter coring tubes and shorter drops. On this trip, three more core pipes would come up holding short stubs with 2.7 feet, 2.9 feet, and 8.1 feet of sediment.

“Coring the Bay is very much like fishing,” said Peter Vogt, a marine geophysicist with the Naval Research Laboratory who helped pick out coring spots. The Marion Dufresne kept fishing, casting 10 coring pipes in all into Chesapeake waters, and the crew eventually landed some big catches: a 42-foot core along the eastern side of the lower Bay, then a 52-footer nearby, a 55-footer off the Patuxent River, two 60 footers off the mouth of the Potomac, and along Kent Island, they raised an 80-foot sediment core, the longest sediment core ever landed in Chesapeake Bay.

For Cronin, the third core drop was the charm. In the blue twilight of an overcast evening the ship dropped anchor along the eastern side of the lower Bay, and at 10:05 p.m., the core pipe splashed down into dark waters. This would not prove the longest core drop at 52.5 feet, but it hauled up strong evidence that the 8.2 kiloyear cooling once came to the Chesapeake.

With this core, Cronin and his co-authors would insert a new chapter into the oft-told story about the origins of Chesapeake Bay. According to the accepted account, the Bay was coming to life as the last glacier era was dying out. When the great ice sheets began melting some 19,000 years ago, sea levels began rising, creeping across the continental shelf, steadily drowning the lower river valley of the ancient Susquehanna River. Roughly 10,000 years ago, the ocean reached the area we now call Norfolk, and pushing north, the seawater began turning the lower river into a brackish water estuary.  By 3,000 years ago, the estuary reached 190 miles north to Havre de Grace, Maryland.

The new chapter in this story is the 8.2 ka cooling. Evidence of its abrupt arrival can be seen in the ups and downs of marsh growth in the evolving estuary.  As brackish waters began pushing north, marshes were accreting steadily along the borders of the new estuary, keeping pace with rising sea levels. Around 9,000 years ago, however, sea level rise accelerated, and many marshes, unable to keep up, began drowning.  It would take the abrupt onset of the 8.2 ka cooling to slow the rate of sea level rise and revive marsh growth. Marsh accretion could once again keep pace with the rising water.

That’s the story Cronin and Willard and their colleagues were able to extract from the sediments in core MD03-2656. They carbon-dated key sections of the core and probed its mud for evidence of plants and “bugs”—the nickname scientists use for tiny crustaceans and protozoa that live on or in aquatic mud. They were looking for large groupings and large gaps in population numbers, evidence that would tell them when certain plants and sediment-loving bugs flourished and when they faded. Willard focused on pollen, Cronin on bugs. Knowing the salinities and temperature ranges for their plants and bugs, they could use these groupings as indicators for changes in rainfall, salinities, temperatures, and sea level rise.

When saltwater bugs suddenly flourished, for example, and certain sedge grasses suddenly faded, they could say sea level was rising fast and marshes were disappearing. When the signs reversed—when protozoa numbers dropped and sedge grasses reappeared— “we interpret that as a slowdown in the rate of sea level rise, allowing marshes to grow,” says Cronin. And the cause for the slowdown: the big cooling, the 8.2 kiloyear event.

___________________________________

What could bring on such an abrupt climate change? It’s easy to see how the sudden onset of the 8.2 ka cooling could lead to the Pentagon’s nightmare scenario. It could also, perhaps, inspire yet another Hollywood film, let’s call it The Day Before Yesterday. It would open with an aerial shot gliding over a huge lake that once covered a small part of America’s Great Plains and a large swath of Canada.

Some 9,000 years ago, Lake Agassiz was sitting in a depression left behind by the retreat of the Laurentide Ice Sheet that once stood two miles high, mashing down parts of the U.S. and all of Canada. That depression was now brimming with meltwater from the retreating ice field. It eventually held a small ocean of fresh water, but rimming the lake on the north and east were the ramparts of the retreating Laurentide. They stood like a great white dam, holding back all that fresh water.

In a still-warming world, that dam had to burst. And sometime just before 8,200 years ago, it did, probably several times and in several places. That dam break kicks off Act II in our movie: Icy water rushes through the breaches, huge amounts of water, something like 50 Amazon Rivers, according to Cronin. It’s probably headed out through Hudson Bay and the Hudson Strait. 

Scientists call this a “catastrophic release.” When this huge flood of fresh water hit the saltwater oceans of the North Atlantic, it caused a catastrophe: it slowed the Atlantic Meridional Overturning Circulation (AMOC), part of the great conveyor belt that carries warm and cold water around the globe. The Atlantic branch of the conveyor usually pumps warm, salty waters out of the tropics into northern regions where the water cools off, increases in density, and sinks. The conveyor then manages a U-turn, carrying cold water southwards in deep underwater currents. This "overturning" system not only circulates heat around the globe, it also drives atmospheric circulation that largely drives weather patterns.

What happens to this conveyor when a tsunami of meltwater arrives? “You are flowing a lot of warm water up north,” says Cronin, “and all of a sudden you throw this fresh water on top and you lower the salinity and the density.” Water that is less salty gains buoyancy and loses density. It doesn't sink as easily. In effect, it turns down one of the heat pumps for the planet.

The result: less Gulf Stream heat reached the high latitudes, atmospheric circulation altered, sea level rise slowed down, and effects were felt around much of the globe. For the movie, it’s the perfect Act III plot reversal: The warming of the planet unleashes a widespread cooling.

And there were more plot twists on the way. The glacier lakes finally drained out, the Atlantic Meridional Overturning Circulation (AMOC) recovered and stabilized, heat flowed again to the Northern Hemisphere, the big 8.2 ka cooling began to wane, and sea levels began to rise again. In the Chesapeake, marshes began drowning for a second time.

There was a happy ending, of sorts, and not just for marsh lovers. Sea level rise began to slow down and stabilize around 7,000 years ago, enabling marsh growth to flourish again in the Chesapeake and setting the stage for a major transition in human history. According to scientists like John Day of Louisiana State University, the rise of urban, state-governed societies began in coastal villages and cities that located alongside estuaries and the lower flood plains of major rivers. Think the Tigris-Euphrates in Iraq, the Nile in Egypt, the Yellow River in China. The rich biological productivity of newly stable coastal areas, says Day, helped unleash the social productivity behind the emergence of early civilization.

What Caused Abrupt Climate Change?

 IceCapMelting_610.jpg The great ocean conveyor belt is driven by density differences created by temperature and salinity. Warm, salty waters flow out of the tropics along the surface, pumping heat into the atmosphere in northern latitudes. As the surface waters cool, density increases, and these waters sink into bottom currents that move south towards Antarctica. That conveyor belt seems to have slowed several times in the past, as North Atlantic waters were suddenly flooded with fresh, low-salt, low-density meltwater that was too buoyant to sink. The water came from great inland glacial lakes like Lake Agassiz that probably released meltwater through Hudson Bay, the Saint Lawrence River, the Mississippi River, and the MacKenzie Straits. Map illustrations: Global Ocean Conveyor Belt, Smithsonian Institution; Lake Agassiz, courtesy of Michael Lewis and John Shaw, Geological Survey of Canada Atlantic, Dartmouth NS, Canada.

What would be the fate of our current version of civilization if a climate change as abrupt as the 8.2 kiloyear cooling arrived sometime soon? The question was hard to answer 10 years ago when Andrew Marshall commissioned his Pentagon scenario. In 2002 the National Research Council said there was virtually no research on the economic and ecological impacts of abrupt climate change. A year later a report published by the Royal Society of London came to the same conclusion.

The authors of the Pentagon report were, in effect, “first in the field” to consider the social and political impacts of sudden climate change. But they were offering informed speculation rather than scientific research. Their goal was to create a geopolitical scenario chock full of what-if speculations–all designed to spur new thinking about threats to American society and security.

What if, for example, the ocean conveyor belt were to slow suddenly in the near future as it did in the not-too-distant past? The climate effects, they speculated, could include temperature drops in North America, Europe, and Asia, coupled with some temperature rises in Australia, South America and South Africa.  Europe could become like Siberia. Coastal cities like The Hague could be flooded out, and countries like Bangladesh could become uninhabitable. China could have less predictable monsoon cycles, colder winters, hotter summers, and food shortages leading to famine. The U.S. could face shorter, less-productive growing seasons and suffer larger floods, especially in mountain regions, and more intense forest fires. Southern countries could suffer less. Australia, for example, could remain a major food exporter. *

The geopolitical upheavals would include food and water shortages, mass emigrations, wars for resources, and realignments among have and have-not nations. Would Australia and the U.S. become “fortress nations?” Would the U.S and Canada eventually morph into one nation to better control their borders?

The main point of all these speculations was a "shock and awe" attack on the "gradual change view," the belief that climate change would necessarily come slowly. That nations could adapt. That they would have time to increase food production. That they would find technological solutions for water shortages.

Some of their speculations seem less plausible now, but it's clear that the “abrupt change view” has been drawing more attention from the American scientific community during the last 10 years. The 2002 report by the National Research Council (NRC) was followed by a 2008 report by the U.S. Climate Change Science Program, and most recently the NRC weighed in again with a new study released in December 2013. The new study goes by the title, "Abrupt Impacts of Climate Change: Anticipating Surprises," and it calls for the U.S. government to create an early warning system that would carefully monitor key earth systems for subtle signs they may be approaching "tipping points" that could unleash sudden climate changes.

This latest NRC report claims to be the first to examine the research on human, social and economic impacts. The study was developed in collaboration with the U.S. intelligence community and it concurs with many of the non-scientific speculations in the earlier Pentagon report.  Food scarcity and famines, epidemics and pandemics, mass migrations, political instability and wars could all ensue in the aftermath of a sudden climate shift. The national security challenges would be daunting, and the NRC recommended the "excellent discussion” of those challenges found in the Defense Department report ordered up a decade earlier by a “Yoda of the Pentagon“ who wanted to spark new thinking.  

___________________________________

What were the lessons of the long cores that came out of the bottom of the Bay?

In 2003 the Marion Dufresne ended its Chesapeake cruise at a dock in Baltimore where  the French staff threw a wine and cheese party for the American scientists. The next day the Malagasian crew lifted dozens of core samples out of the ship’s hold and loaded them on trucks destined for the Reston laboratories of the U.S. Geological Survey.

Out of those cores is coming a revised account of the evolution of the estuary, one that includes better dating of key events, more details, and a new chapter on the arrival of the 8.2 kiloyear cooling in the Chesapeake. With their pollen studies, Willard and her colleagues outlined the shifts in forest communities that came with earlier shifts in temperatures and sea levels. They also identified five major droughts, each lasting several centuries, that struck the region over the last 8,200 years.

Findings like these also undercut the gradual change view that seemed to underlie earlier stories about the Bay’s evolution. As the Bay formed, it experienced episodes of climate variability kicked off not by humans, but by natural forces, by interlocking shifts in ocean dynamics and atmospheric circulations and solar inputs. “The rate of sea level rise in the Chesapeake was not constant as the bay was flooding," says Cronin."It was kind of staccato” with several “oscillations and hiccups."   Some of those oscillations—the Younger Dryas and the Little Ice Age—arrived gradually. The 8.2 kiloyear cooling, the big hiccup, arrived abruptly.

The evidence of climate change in the Chesapeake and in other parts of the planet are sketching a dicey picture of our current geological era. “The Holocene,” says Cronin, “the interglacial that we live in, that we perturb with CO2,wasn’t nearly as stable as some people used to think.” And the odds are the future may not be so stable either.

The good news is that the latest NRC report downgraded the odds that the ocean conveyor belt would stop anytime soon. The worrisome news is that they elevated the chances of that other abrupt changes could be in the works. The Laurentide Ice Sheet may be gone, but the glaciers in Greenland and the ice sheets in Antarctica are still here, and they are huge, and they are melting.

They hold enough meltwater to unleash the greatest hiccup since the 8.2 kiloyear event suddenly cooled off a gradually warming world.

*The Pentagon report’s thought-provoking speculations were based in science, but were still just that: speculations. And some speculations are less plausible than others. According to paleoclimatologist Carrie Morrill, reviewer for this article, the temperature drops and chillier winters that occurred in parts of the Northern Hemisphere during the AMOC slowdown 8,200 years ago are unlikely to be repeated in a modern-day scenario. With global warming due to rising greenhouse gas concentrations, what’s more plausible is less warming in affected areas—but not actual cooling.

Links

An Abrupt Climate Change Scenario and its Implications for United States National Security. 2003. Schwartz, P. & D. Randall. Jet Propulsion Laboratory Pasadena, CA.

Abrupt Climate Change. 2008. U.S. Climate Change Science Program and the Subcommittee on Global Change Research.

Abrupt Impacts of Climate Change: Anticipating Surprises. 2013. Committee on Understanding and Monitoring Abrupt Climate Change and Its Impacts.

The Bays Beneath the Bay. Chesapeake Quarterly issue on geology and the building of the Chesapeake Bay bridge.

 
 
 
Greg Jones
5  Greg Jones    3 months ago

With global warming due to rising greenhouse gas concentrations, what’s more plausible is less warming in affected areas—but not actual cooling.

It seems there hasn't been much warming in the last several years, so actually cooling could occur.

 
 
 
Gordy327
5.1  Gordy327  replied to  Greg Jones @5    3 months ago
It seems there hasn't been much warming in the last several years, so actually cooling could occur.

Not according to NASA. There might be periods of cooling, but the overall trend is warming.

 
 
 
devangelical
6  devangelical    3 months ago

according to a professional life science acquaintance of mine, the melting ice caps are in the big 3 as a most probable cause of future human extinction events. potentially frozen inside those mega ice walls are a layer of antique microbes that could mutate thru the food chain and humans will have no immunity.   

 
 
 
Greg Jones
6.1  Greg Jones  replied to  devangelical @6    3 months ago

Oh, like in "The Last Ship"?

 
 
 
charger 383
7  charger 383    3 months ago

Overpopulation is the problem

 
 
 
Dignitatem Societatis
7.1  Dignitatem Societatis  replied to  charger 383 @7    3 months ago
Overpopulation is the problem

Along with CO2. Double whammy.

 
 
 
Greg Jones
7.1.1  Greg Jones  replied to  Dignitatem Societatis @7.1    3 months ago

Quit screwin' and breathing...that should solve the problem!

 
 
 
Heartland American
7.2  Heartland American  replied to  charger 383 @7    3 months ago

Over population is a problem that is decelerating as even in the poorest third world nations population increases are slowing and in first world affluent nations native populations are declining outright in some and maintained only by immigration in others. One poorer 2nd world economy nation (Russia) is also seriously losing population. 

 
 
 
Gordy327
7.2.1  Gordy327  replied to  Heartland American @7.2    3 months ago

And yet, the global population is over 7 billion and climbing. That's a problem. 

 
 
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