The Earth once looked like the above picture for a period of time. Incredible how it managed to thaw in the absence of humans burning fossil fuels and the use of hydrocarbons. :p
Posted on 05/26/2011 1:27:37 PM PDT by decimon
Thirty-eight million years ago, tropical jungles thrived in what are now the cornfields of the American Midwest and furry marsupials wandered temperate forests in what is now the frozen Antarctic.
The temperature differences of that era, known as the late Eocene, between the equator and Antarctica were half what they are today.
A debate has been ongoing in the scientific community about what changes in our global climate system led to such a major shift from the more tropical, greenhouse climate of the Eocene to modern and much cooler climates.
New research results published in this week's issue of the journal Science, led by Rensselaer Polytechnic Institute scientist Miriam Katz, are providing some of the strongest evidence to date that the Antarctic Circumpolar Current (ACC) played a key role in the shift.
"What we have found is that the evolution of the Antarctic Circumpolar Current influenced global ocean circulation much earlier than previous studies have shown," said Katz. "This finding is particularly significant because it places the impact of initial shallow ACC circulation in the same interval when the climate began its long-term shift to cooler temperatures."
There has been a debate over the past 40 years on what role the Antarctic Circumpolar Current had in the past cooling trend.
"These climate changes are one of the most significant shifts in Earth's history, from early Cenozoic 'greenhouse' climates to the mid- to late Cenozoic 'icehouse' that saw repeated massive glaciations of the polar regions," said Candace Major, program director in the National Science Foundation's (NSF) Division of Ocean Sciences.
The research was funded by NSF in partnership with the Integrated Ocean Drilling Program, and its predecessor programs, the Ocean Drilling Program and Deep Sea Drilling Project.
"The work by Katz and colleagues is the first to demonstrate that the basic structure of currents associated with modern ocean circulation has existed for the past 33 million years," said Major.
Previous research had placed the development of the deep ACC--greater than 2,000 meters water depth--in the late Oligocene, approximately 23-25 million years ago.
That's well after the global cooling pattern had been established.
Katz and colleagues have placed the global impact of the ACC at approximately 30 million years ago, when it was still just a shallow current.
Oceans and global temperatures are closely linked. Warmer ocean waters result in warmer air temperatures and vice versa.
In the more tropical environs of the Eocene, ocean circulation was weaker and currents more diffuse.
As a result, heat was more evenly distributed around the world. That resulted in fairly mild ocean temperatures worldwide.
Today, ocean temperatures vary considerably and redistribute warm and cold water around the globe.
"As the global ocean currents were formed and strengthened, the redistribution of heat likely played a significant role in the overall cooling of the Earth," Katz said.
No current is more major than the ACC, scientists believe.
Often referred to as the "mixmaster" of the ocean, the ACC thermally isolates Antarctica by preventing the warm surface waters of subtropical gyres from passing through.
The ACC instead redirects some of that warm water back toward the north Atlantic, creating Antarctic Intermediate Water.
This blocking of heat enabled the formation and preservation of the Antarctic ice sheets, according to Katz.
The circumpolar circulation, Katz concludes, was responsible for the development of the modern four-layer ocean current and heat distribution system.
Katz looked at the uptake of several elements' isotopes, or variants, in the fossil skeletons of small planktonic organisms found in ocean sediments.
Using the drillship, the fossil organisms, known as benthic foraminifera, were brought up from beneath the sea-floor in long cores of sediments.
The foraminifera incorporated certain elements and isotopes, reflecting environmental conditions at the time.
By analyzing the ratios of these elements and isotopes, researchers were able to reconstruct past environmental conditions. They looked at isotopes of oxygen and carbon, along with ratios of magnesium versus calcium.
Analysis of these isotopes showed the earliest evidence for Antarctic Intermediate Waters, which circulates as a consequence of the ACC.
This finding is the first evidence of the effects of shallow ACC formation.
The results place the ACC's global impact much closer to the time when Antarctica separated from South America, creating a gateway.
It had previously been thought that currents moving through this gateway could not be strong enough at such shallow depths to affect global ocean circulation.
"By reconstructing the climates of the past, we can explore Earth system responses to current climate change," Katz said.
Katz is joined in the research by Benjamin Cramer of Theiss Research; J.R. Toggweiler of Geophysical Fluid Dynamics Lab/NOAA; Chengjie Liu of Exxon Mobil Exploration Co.; Bridget Wade of University of Leeds; and Gar Esmay, Kenneth Miller, Yair Rosenthal, and James Wright of Rutgers University.
-NSF-
Media Contacts Cheryl Dybas, NSF (703) 292-7734 cdybas@nsf.gov Gabrielle DeMarco, RPI (518) 276-6542 demarg@rpi.edu Kris Ludwig, Consortium for Ocean Leadership-IODP (202) 448-1254 kludwig@oceanleadership.org
Related Websites Integrated Ocean Drilling Program: http://www.iodp.org Ocean Drilling Program: http://www-odp.tamu.edu/sched.html Deep Sea Drilling Project: http://www.deepseadrilling.org/i_reports.htm
The National Science Foundation (NSF) is an independent federal agency that supports fundamental research and education across all fields of science and engineering. In fiscal year (FY) 2010, its budget is about $6.9 billion. NSF funds reach all 50 states through grants to nearly 2,000 universities and institutions. Each year, NSF receives over 45,000 competitive requests for funding, and makes over 11,500 new funding awards. NSF also awards over $400 million in professional and service contracts yearly.
Separate from equal ping.
i do like the expanding earth theory...
but we all know this is man’s fault.
teeman
But where was the obligatory conclusion of how AGW will slow the Antarctic Circumpolar Current once again flooding half of Florida and parts of Missouri?
http://newsdesk.org/2010/09/scientists-unmask-ghost-mountains-of-antarctica-at-last/ Earlier and Related to this story. The date was given as anywhere from 34 million years ago to 500 million years ago. The point is part of Antarctica was already REALLY COLD ~ opening up the channel between Antarctica and South America allowed these mountains’ glaciers to flow out into the ocean and form ice shelves. Before they’d just melted. The 500 million year date takes this back to the SNOWBALL EARTH era.
The leaking radiation into the Pacific Ocean from Japan and the toxic dumps of sludge into the Atlantic are responsible for the state of the oceans of the world.
Global warming and climate change have nothing to do with the current state of the oceans of the world.
Some years are worse than others when it comes to hurricanes, floods, erupting volcanoes, forest fires, torrential rains, tornadoes and earthquakes.
But these things are natural phenomena.
And the best thing that we who live in areas that see these various natural phenomena is to prepare as best as we can.
These things mean upgrading the infrastructure and when it comes to building structures to go far beyond building code requirements in these areas.
The Earth once looked like the above picture for a period of time. Incredible how it managed to thaw in the absence of humans burning fossil fuels and the use of hydrocarbons. :p
Poor arrogant man...Trying to solve something that has too many variables and not enough data aka “CLOSE enough for government work”.....AND MORE GRANT MONEY!! 6.9 BIL IN 2010!!!!!
When you don't have any SUVs around, volcanoes [lots and lots of them] can be really helpful!
Report from the Free Republic Institute of Science: “Sh*t Happens.”
It’s got just as much insight and accuracy as the article cited - or from virtually anywhere else; now write me a grant for fifteen million bucks.
I thought that weaker currents moved energy slower, resulting in greater temperature differentials?
It is confusing and I don’t think they can adequately cover it in a press release.
I think it all depends on what point in time you begin the discussion. For this they start at a time of relatively warm temperatures, worldwide.
My puny speculation is that there may have been times when the planet as a whole was warmer or cooler but probably more times when global temperatures were distributed more and less evenly.
They mention less ocean circulation. From that I imagine colder waters more staying deep and warmer waters more staying on the surface. If that imagining should be correct then the entire surface of the planet would have been warmer.
And there you have some speculation from a rank amateur. :-)
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I can’t remember where I read that as long as our continents are where they are in the Northern Hemisphere, all crowded around the north pole, we are stuck in cycles of glaciation. The continents keep the water from easily circumnavigating the globe.
I’m not an expert, and I don’t play one on TV.
I’m not an expert, and I don’t play one on TV.
I'm not an expert and my VCR blinks. ;-)
Some time ago I posted a speculation that we wouldn't have another ice age because we now have a Bering Strait to allow some circulation. Looks like the same general idea.
Well, I can’t even get my satellite dish box to turn on, so you are doing better than me right now.
I don’t think the Bering Straight is big enough. My recollection was about the time of Pangea, when all of the continents were clustered together around the equator, the water moved freely around.
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