Researchers show that high ancient shorelines do not necessarily reflect ice sheet collapse millions of years ago
From the Canadian Institute for Advanced Research:
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.”
Source: http://www.cifar.ca/ancient-shorelines-ice-sheets-stability
h/t Dennis Wingo
===============================================================
Dynamic Topography Change of the Eastern United States Since 3 Million Years Ago
David B. Rowley, Alessandro M. Forte,Robert Moucha, Jerry X. Mitrovica,
Nathan A. Simmons, Stephen P. Grand
Abstract
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.
Janice Moore says:
May 18, 2013 at 9:38 pm
“I believe the evidence found all over the planet is stronger for a Great Flood than the evidence for its having not occurred.
A skeptical mind is not a closed mind, it is a careful mind, open to whatever the evidence shows.”
This is re marine fossils in the rocks of Everest. Janice, evidence for buckling up of once lower strata caused by the collision of the Indian land mass with the Asian land mass, strange as it may sound, is the reason for the position of these fossils. Indeed, the Himalayas are still rising at 5mm per year. Remember this slow rate geologically is very significant and equals 5m per thousand years and 5km/million years! From Wiki:
http://en.wikipedia.org/wiki/Himalayas#Geology
“During the Upper Cretaceous, about 70 million years ago, the north-moving Indo-Australian Plate was moving at about 15 cm per year. About 50 million years ago, this fast moving Indo-Australian plate had completely closed the Tethys Ocean, the existence of which has been determined by sedimentary rocks settled on the ocean floor, and the volcanoes that fringed its edges. Since both plates were composed of low density continental crust, they were thrust faulted and folded into mountain ranges rather than subducting into the mantle along an oceanic trench.[4] An often-cited fact used to illustrate this process is that the summit of Mount Everest is made of marine limestone from this ancient ocean.[9]
Today, the Indo-Australian plate continues to be driven horizontally below the Tibetan plateau, which forces the plateau to continue to move upwards. The Indo-Australian plate is still moving at 67 mm per year, and over the next 10 million years it will travel about 1,500 km into Asia. About 20 mm per year of the India-Asia convergence is absorbed by thrusting along the Himalaya southern front. This leads to the Himalayas rising by about 5 mm per year, making them geologically active.
grumpyoldmanuk says:
May 18, 2013 at 10:56 pm
“To do their study, the team used computer simulations……. Sorry, lost interest there.
Not so fast grumpyoldmanuk, you should have read down to where there is a 60 metre warp in the old shoreline trace which at the time of formation was horizontal. At least you have to admit that some differential movement must have occurred since – actually 60m is a heck of a warp.
J Martin says: May 19, 2013 at 5:23 am
“…..Found it. ….[….]….
This recent internal PowerPoint presentation (obtained from an insider) from NASA JPL touts the new GRASP (Geodetic Reference Antenna in Space) satellite project….”
Thanks, good stuff, but c’mon mate..gimme a bit of credit . I did provide a link! 🙂
markx says: May 18, 2013 at 9:05 pm
http://ilrs.gsfc.nasa.gov/docs/GRASP_COSPAR_paper.pdf
Speed says:
May 19, 2013 at 3:58 am
“To do their study, the team used computer simulations …
What’s sauce for the goose is sauce for the gander.”
If it were the same sauce I would agree.
grumpyoldman has the same prejudice.
Computational Fluid Dynamics(CFD), used to evaluate and manipulate the Coanda Effect for example, is as complicated as the majority of modeling gets down here amongst the mortals. Adrian Newey excepted.
Most modeling utilized by science is vastly simplistic in comparison.
Modeling climate is a whole other ball-game for the prinincipal reason that CFD is a David compared to the Goliath of Climate System Modeling. Chaos is a manifold problem 😉
“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.”
I assume this warped surface amplitude of 60 meters is the max for the length of the entire eastern U.S. coastal plain. That would equate to a slope of .o4 feet per mile. Am I following this? You wouldn’t notice that much dynamic topography in a bowling alley.
The eastern U.S. coast sits on the more stable portion of the North American plate moving west from the mid-Atlantic ridge. Isostatic rebound from glacial melt would be more pronounced on the northern portion of the plate. Can’t tell from the map, or abstract.
Wonder if they checked any marine seismic profiles on both the western portion of Europe and eastern U.S. to determine if the onlap sedimentary sequences matched. If a match, it’s all eustatic sea level change by glacial melting. Oh, excuse me, “glacial collapse.”
Really? Does this mean that the seashells and swamp fern fossils imbedded in the mountains around Wallowa County are there because of uplift and not because of ancient sea levels being that high? Oh my gosh! I did not know that! Tectonic uplift! Quick! Give the man a Nobel Prize for a new discovery! Rewrite all the grade school science books to include this new information!
Oh…wait…
pfft. they used models. thats not real data
Steven Mosher says:
May 19, 2013 at 8:21 am
”
pfft. they used models. thats not real data”
I refer the Right Honourable Gentleman(‘s sniping) to my previous reply:
http://wattsupwiththat.com/2013/05/18/good-news-worlds-biggest-ice-sheets-likely-more-stable-than-previously-believed-upsets-previous-estimates-of-melting-and-sea-level/#comment-1309813
One of the, at first confusing concepts in the Physics study of “Dynamics”, is the concept of “Reference Plane”, that systems involving motion will vary, depending on the location of the observer. The reason i mentioned the 1980’s implementation of the GPS system, is that this was the ONLY method of detecting this vertical, Earth tide, land mass movement. All geology research that i have reviewed since that time has been in reference to that correct Earth model.
The second point involving Plate Tectonics relates to the previously unexplained “westward” movement of the plates in my 3:02 am post. Without proof of Earth tide, it could only be assumed that tectonics was a random motion. Once Earth tide was accepted, this Lunar force was obvious. Some further explanation may be beneficial. On one side of a paper, draw a large circle, place a “N” in the center and an arrow at the perimeter indicating a anti-clockwise rotation. Now on the other side of the paper draw a smaller circle and place a “M” in the center. You are now looking down on the Earth from the north pole. As the Earth spins, the rotational motion, prior to passing the Earth-Moon axis line, is in the direction of the Moon’s gravity, thereby reducing the gravitational effect. Once the Earth’s surface passes the axis line, the Moons gravity is combining with the Earths rotation to pull the crust to the west with a STRONGER force than the pre-axis transit force.
False paradigms are built on false reference planes. As the reference plane changes, the basis for the false reality is undermined and will fail. If this basic Earth science is not taught in elementary school at present, then it SHOULD be. We are capable of understanding far more than our blinkered government, education, media and entertainment thought police allow. As more of the false reference planes in science and history are corrected, the overlying and overbearing current false social structure paradigm will also fail. Every epiphany is permanent, find and share Truth.
“Lesson: Don’t put your faith in mortals. Not even kings.”
Or in immortals, since they don’t exist.
“””””….. The Indo-Australian plate is still moving at 67 mm per year, and over the next 10 million years it will travel about 1,500 km into Asia…….”””””
Crikey ! the whole bloody plate is moving much faster than the sea level is rising.
I think we should be focusing on unauthorized Australian invasion of India, and forget about sea level rise.
Paul Marko says:
May 19, 2013 at 8:00 am
“I assume this warped surface amplitude of 60 meters is the max for the length of the entire eastern U.S. coastal plain. That would equate to a slope of .o4 feet per mile. Am I following this? You wouldn’t notice that much dynamic topography in a bowling alley.”
First, Paul, a 60m difference in sea level is half the total swing between Ice Age and interglacial so it is a mammoth variation – any estimates made of Pliocene sea levels from it and the amount of ice they erroneously thought melted would certainly depend where your university is located along this scarp. Secondly, welcome to the world of annual small changes. The Himalayas are rising approximately 5mm a year. Geologically this is enormous: 5 metres in a thousand years, 5 kilometres in a million years! A warp of 60 metres in a relatively quiet stable part of the earth’s crust over 3 million years is significant.
“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.”
I hope their geology is better than their English, or has it become normal to predict the past?
Steven Mosher says:
” May 19, 2013 at 8:21 am
pfft. they used models. thats not real data”
Glad to see Mosher doesn’t believe in models :-). Now can we just call off this CO2 is evil meme and get back to cheap and abundant energy and prosperity?
Gary Pearse says:
May 19, 2013 at 10:02 am
“a 60m difference in sea level is half the total swing between Ice Age and interglacial so it is a mammoth variation”
The 60m they refer to is the variation in the topography (elevation) of the stranded shoreline horizon, not the variance in sea level between glacial cycles. No?
If the 60 meters is related to techtonic warp, not Glacial rebound on one end, what caused the vaiance on a relatively stable continental plate?
“The paper is important because it shows that no prediction of ancient ice volumes can ever again ignore the Earth’s interior dynamics,”
So the climate scientists were told that a quarter of a century ago but used their influence to prevent studies like this being funded in favour of AGW ones. Perhaps we will see the one that says that the climate changes are to do with a cyclic disturbance originating in the north west passage area which affects the ocean current flow getting some funding.
As someone else noted, the top of mount Everest is sedimentary rock from an ocean bottom. Just about 6 million years ago, the land making the mountains where the Grand Canyon is now, was on the bottom of a shallow inland sea. It’s now a few thousand feet in the air.
The California coastline rises a few feet at a time, some times (during large quakes). The entire coast range has ongoing uplift (that is why we have those dramatic high cliffs that occasionally fall into the ocean, taking $Million houses with them).
The notion that the land is static is a silly one. It’s always either rising, or eroding away, and does so by thousands of feet…
In High School we took a geology field trip up into the Sierra Nevada mountains… to collect Sharks Teeth… from when THEY were ocean bottom… (For most of the history of the Earth, there was no life with teeth… they are a recent invention in geologic / evolutionary time scales).
The earth moves, sometimes quite fast. During the Indonesia quake / tsunami the bottom of the ocean moved up 9 feet in one giant rumble. There’s a big rift zone in east Africa where far too soon it will become a new inland sea. At one point Madagascar was part of Africa and was rifted off. That rift is still active, but more inland now, slicing off a new chunk of Africa… While Africa is slamming into Europe and pushing up the Alps. (And, eventually, will close the Strait of Gibraltar and then the Mediterranean Sea will evaporate… as it has done in the past…)
Oh, and don’t forget that just about 12,000 years ago Canada was an Ice Sheet up to a couple of miles thick. It will be again in some thousands of years more. ALL of the wildlife and forests of Canada are going away, to be scraped off and frozen under mile high ice. Think that will “leave a mark”? The notion we can freeze time in a bottle and somehow keep Canada like it is at present is the completely broken notion. Life flows and changes with the geologic times. Nothing is static or stable.
THE best thing we can do for Canada is haul out all the coal and tar sands and oil we can, and burn it, then pray to God that there really is a CO2 warming effect; since if there isn’t Canada is doomed. Similarly Norway, Scotland, Sweden, Finland, Russia / Siberia, etc. etc. (Oh, and both Chile and Argentina too…)
There are ancient coral fossil shelves in the Caribbean that form solid strata bands and show that those coral formed over 1000 years approx where there were no hurricanes at all in that time ( ie 1000 of constant coral fourishes without destruction ). There is absolutely no explanation for this and scientists who discovered it were amazed. One was quoted as saying : “We know virtually nothing about the geological past in anywhere near enough detail. Everyday a general assumption is challenged” Another said : “Who turned off the Hurricanes for a 1000 years in this part of the world ?” . I think it may finally be dawning on those many scientists who jumped on the catastrophy bandwagon too soon that they forgot the cornerstones of science…. Experiment, deduce, challenge [ then repeat ].
Those cores of the ongoing variable continental ice coverage will likely not melt until we break out of the Quaternary. What, maybe 10M years from now if we are lucky?
Funny. I was skimming through the latest issue of Pop Sci ($6 for a year subscriptions, but you get what you pay for) last night and there was an article about how sea level rise of +/- 25 feet would be plausible over the next century based on Greenland and Antarctic ice sheet melting driven by global warming. Not surprisingly, the study the article referenced uses the same elevated prehistoric shorelines as the study in this article. All with nice graphics of the NY Metro area and Los Angeles underwater. Might be nice if these scientists spoke to one another on occasion.
Thank god for scientists and computer modelling, without whom this study would not exist.
The KISS version: climatologists were (eagerly) suckered by mis-attribution of the lifting of old shorelines above current sea level.