Peer reviewed study of eastern US coastline from Virginia to Florida finds sea levels more stable than previously reported. Future sea level determinations of US coastline and effects of global ice sheets no longer possible without consideration of Earth's interior, Science Mag., May 16, 2013, Rowley lead

5/16/13, "Dynamic Topography Change of the Eastern United States Since 3 Million Years Ago," ScienceMag.org. "David B. Rowley¹,*,Alessandro M. Forte², Robert Moucha³, Jerry X. Mitrovica⁴, Nathan A. Simmons⁵, Stephen P. Grand<sup>6"

"Abstract"</sup>
"Sedimentary rocks from Virginia through Florida record marine flooding during the mid-Pliocene. Several wave-cut scarps that at the time of deposition would have been horizontal are now draped over a warped surface with a maximum amplitude of 60 m. We modeled dynamic topography using mantle convection simulations that predict the amplitude and broad spatial distribution of this distortion. The results imply that dynamic topography and, to a lesser extent, glacial isostatic adjustment, account for the current architecture of the coastal plain and proximal shelf. This confounds attempts to use regional stratigraphic relations as references for longer-term sea-level determinations. Inferences of Pliocene global sea-level heights or stability of Antarctic ice sheets therefore cannot be deciphered in the absence of an appropriate mantle dynamic reference frame." "Received for publication 22 August 2012. Accepted for publication 30 April 2013."

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More on above Science Magazine study:

5/17/13, "World’s biggest ice sheets likely more stable than previously believed," CIFAR, Canadian Institute for Advanced Research

"Researchers show that high ancient shorelines do not necessarily reflect ice sheet collapse millions of years ago."

"For decades, scientists have used ancient shorelines to predict the stability of today’s largest ice sheets in Greenland and Antarctica. Markings of a high shoreline from three million years ago, for example – when Earth was going through a warm period – were thought to be evidence of a high sea level due to ice sheet collapse at that time. This assumption has led many scientists to think that if the world’s largest ice sheets collapsed in the past, then they may do just the same in our modern, progressively warming world.

However, a new groundbreaking study now challenges this thinking.

Using the east coast of the United States as their laboratory, a research team led by David Rowley, CIFAR Senior Fellow and professor at the University of Chicago, has found that the Earth’s hot mantle pushed up segments of ancient shorelines over millions of years, making them appear higher now than they originally were millions of years ago.

“Our findings suggest that the previous connections scientists made between ancient shoreline height and ice volumes are erroneous and that perhaps our ice sheets were more stable in the past than we originally thought,” says Rowley. “Our study is telling scientists that they can no longer ignore the effect of Earth’s interior dynamics when predicting historic sea levels and ice volumes.”

The study, published online in Science on May 16, was a collaboration that included CIFAR Senior Fellows Alessandro Forte (Université du Québec à Montréal) and Jerry Mitrovica (Harvard), and a former CIFAR-supported post-doctoral fellow Rob Moucha (Syracuse).

“This study was the culmination of years of work and deep collaboration by researchers in CIFAR’s program in Earth System Evolution,” explains Rowley. “For this study, each of us brought our individual expertise to the table: Rob and Alex worked on simulations of Earth’s mantle dynamics, Jerry provided calculations on how glaciers warp Earth’s surface, and I shaped our understanding of the geology of the landscape we were looking at. This study would not have been possible without CIFAR.”

The team studied the coast from Virginia to Florida, which has an ancient scarp tens of metres above present-day sea level. Until now, many research groups have studied this shoreline and 
concluded that during a warm period three million years ago, the Greenland, West Antarctic and a fraction of East Antarctic ice sheets collapsed, raising the sea level at least 35 metres. But the new findings by Rowley and his team suggest that these ice sheets, particularly the East Antarctic Ice Sheet (the world’s largest), were probably more stable.

To do their study, the team used computer simulations to follow the movement of mantle and tectonic plates that occurred over time. Their prediction of how the ancient shoreline would have developed over millions of years matched what geologists mapping this ancient coast have observed. The next steps for the team are to try to make accurate predictions in other locations around the world.

“The paper is important because it shows that no prediction of ancient ice volumes can ever again ignore the Earth's interior dynamics,” explains Rowley. “It also provides a novel bridge between two disciplines in Earth science that rarely intersect: mantle dynamics and long-term climate. It is the kind of study that changes how people think about our past climate and what our future holds."" via Free Republic
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Definitions:
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Pliocene was 1.8-5.3 million years ago. Changes in land masses at that time caused changes in climate:
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"Tectonics during the Pliocene," paleobiology.si.edu, Smithsonian
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"The Pliocene began with the catastrophic origin of the Mediterranean Sea. The Mediterranean Basin had been dry since the Miocene, replaced by grasslands. However, at the beginning of the building was also taking place in Europe, including the Alps. All these orogenies affected global climate and worked with astronomically controlled climate cycles to create cooler and more unstable conditions relative to the Miocene."
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"All these orogenies affected global climate cycles:" Ongoing changes in earth's crust cause climate changes:
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Definition of Orogeny: "The process of mountain formation, especially by folding and faulting of the Earth's crust and by plastic folding, metamorphism, and the intrusion of magmas in the lower parts of the lithosphere. Unlike epeirogeny , orogeny usually affects smaller regions and is associated with evidence of folding and faulting. The long chains of mountains often seen on the edges of continents form through orogeny."

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5/20/13, "Last time CO2 was this high, the world was underwater? NO, actually Ice sheets DIDN'T melt 3 million years B.C., say boffins," UK Register, Lewis Page

"OK, so levels of atmospheric CO₂ are rising through 0.0004 (or 400 parts per million) at the moment. Disaster, right? The last time the world saw carbon levels like this, some three million years ago, the mighty ice sheets of Greenland and the Antarctic had melted from the heat and the seas were 35 metres higher than they are today. Anybody who doesn't live up a mountain will soon find themselves underwater. Aaargh!

Not so much, according to new research.

The idea that the seas were 35 metres higher 3 million years back comes mainly from scientists examining ancient high-tide marks found along coastal cliffs and scarps - particularly some often-used ones on the US eastern seaboard. By determining the ages of the rocks and marks, scientists have come to the conclusion that the seas were much, much higher then - and thus, that the Greenland ice and large parts of the Antarctic ice as well must have been melted at the time.

According to a crew of top boffins led by Professor David Rowley of Chicago uni, the problem with this is that over these sorts of timescales, areas of the Earth's crust rise and fall as much as the sea does. And nobody thus far has taken account of that - it has just been assumed that the rocky coasts have remained fixed with respect to the centre of the Earth, which means that the studies thus far have been - basically - wrong.

"No prediction of ancient ice volumes can ever again ignore the Earth's interior dynamics,” says Rowley.

The prof and his colleagues' new investigation has sought to reconstruct the behaviour of the crust along the oft-studied scarp running up the US coast from Florida to Vermont. And it turns out that over the past three million years, interactions in the Earth's mantle have lifted the entire coastline and the ancient tidemarks with it - giving a false impression of much higher sea levels.

Using the corrected, much lower sea levels, Rowley's team say that in fact the world's ice sheets didn't melt nearly as much back in the old days of 400+ ppm CO₂ as people think. According to a statement highlighting the new research:

"Until now, many research groups have studied this shoreline and concluded that during a warm period three million years ago, the Greenland, West Antarctic and a fraction of East Antarctic ice sheets collapsed, raising the sea level at least 35 metres. But the new findings by Rowley and his team suggest that these ice sheets, particularly the East Antarctic Ice Sheet (the world’s largest), were probably more stable."
 
The new paper has just been published in hefty boffinry mag Science.

"It is the kind of study that changes how people think about our past climate and what our future holds," comments Rowley, bluntly. ®" via Climate Depot




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