Free Republic
Browse · Search
General/Chat
Topics · Post Article

Skip to comments.

Answer to what ended the last ice age may be blowing in the winds, paper says
The Earth Institute at Columbia University ^ | June 25, 2010 | Unknown

Posted on 06/25/2010 9:47:25 AM PDT by decimon

A chain of past natural events may hold lessons for the future

Scientists still puzzle over how Earth emerged from its last ice age, an event that ushered in a warmer climate and the birth of human civilization. In the geological blink of an eye, ice sheets in the northern hemisphere began to collapse and warming spread quickly to the south. Most scientists say that the trigger, at least initially, was an orbital shift that caused more sunlight to fall across Earth's northern half. But how did the south catch up so fast?

In a review paper published this week in the journal Science, a team of researchers look to a global shift in winds for the answer. They propose a chain of events that began with the melting of the large northern hemisphere ice sheets about 20,000 years ago. The melting ice sheets reconfigured the planet's wind belts, pushing warm air and seawater south, and pulling carbon dioxide from the deep ocean into the atmosphere, allowing the planet to heat even further. Their hypothesis makes use of climate data preserved in cave formations, polar ice cores and deep-sea sediments to describe how Earth finally thawed out.

"This paper pulls together several recent studies to explain how warming triggered in the north moves to the south, ending an ice age," said study co-author Bob Anderson, a geochemist at Columbia University's Lamont-Doherty Earth Observatory. "Finally, we have a clear picture of the global teleconnections in Earth's climate system that are active across many time scales. These same linkages that brought the earth out of the last ice age are active today, and they will almost certainly play a role in future climate change as well."

Earth regularly goes into an ice age every 100,000 years or so, as its orientation toward the sun shifts in what are called Milankovitch cycles. At the peak of the last ice age, about 20,000 years ago, with New York City and large parts of Europe and Asia buried under thick sheets of ice, Earth's orbit shifted. More summer sunlight began falling on the northern hemisphere, melting those massive ice sheets and sending icebergs and fresh water into the North Atlantic Ocean.

It may sound counterintuitive, but the paper says freshening of the North Atlantic triggered a series of cold spells in Greenland and northern Europe by shutting down the Gulf Stream current, which usually carries warm water north from the equator. Sea ice spread across the North Atlantic, bringing bitter cold winters to Europe and profoundly reshaping the planet's wind belts.

With the North Atlantic in a deep freeze, the tropical trade winds shifted south, bringing dry spells across much of Asia and rain to normally arid regions of Brazil. The displaced winds moved not only rain further south, but hot air and warm seawater, heating up the southern hemisphere.

The southern hemisphere westerly winds also shifted south, bringing warm air and seawater to the mid-latitudes. By about 18,000 years ago, mountain glaciers in South America and New Zealand started to melt as the displaced winds blew warm air their way. By 16,000 years ago, the glaciers had beaten a spectacular retreat. This shift in westerly winds would also amplify the warming in both hemispheres by resetting the planet's thermostat, as Anderson has proposed in an earlier study in Science. The displaced westerlies caused heavy mixing in the Southern Ocean around Antarctica, pumping dissolved carbon dioxide from the water into the air. Ice core records show that between 18,000 and 11,000 years ago atmospheric carbon dioxide levels rose from 185 parts per million to 265 parts per million. (Today levels are 393 parts per million, after a sustained rise during the industrial era.) The infusion of carbon dioxide came just as the planet's orientation was shifting, and summer sunlight to the northern hemisphere was declining, at about 11,000 years ago. The boost in carbon dioxide may have prevented Earth from falling into another ice age, the scientists say.

"It's the great global warming of all time," said the study's lead author, George Denton, a glaciologist at the University of Maine, and an adjunct scientist at Lamont. "We're trying to answer the puzzle: why does the Earth, when it appears so firmly in the grip of an ice age, start to warm?"

Scientists have long suspected that carbon dioxide played a major role in the last ice age but have had trouble explaining the early warming in the southern hemisphere, where glaciers in Patagonia and New Zealand were melting before carbon dioxide levels rose significantly. Some scientists suggest that a change in ocean currents, triggered by the freshening of the North Atlantic, caused this early warming. But computer models using ocean circulation to explain the rapid warming in the south have been unable to recreate the large temperature jumps seen in the paleoclimate record. Now, with the evidence for shifting southern hemisphere westerlies, the rapid warming is readily explained.

Richard Alley, a glaciologist at Penn State University who was not involved in the study, called the hypothesis comprehensive and convincing. "This subject has long intrigued policy-makers, and although the issue in no way changes the very strong evidence that adding CO2 to the atmosphere has a warming effect, the inability of the scientific community to provide a complete explanation of the natural CO2 changes across ice-age cycles may have led some people to more broadly question climate science. Testing this hypothesis will be very interesting, to see whether it successfully "predicts" the observed timing of CO2 and temperature changes in the south."

###


TOPICS: History
KEYWORDS: catastrophism; godsgravesglyphs; maunderminimum; milankovitch; milankovitchcycles

1 posted on 06/25/2010 9:47:27 AM PDT by decimon
[ Post Reply | Private Reply | View Replies]

To: SunkenCiv; steelyourfaith

Wafting warm ping.


2 posted on 06/25/2010 9:49:04 AM PDT by decimon
[ Post Reply | Private Reply | To 1 | View Replies]

To: decimon

They still can’t figure out today’s whether and they want to figure out causality 20,000 years ago.


3 posted on 06/25/2010 9:51:06 AM PDT by Mere Survival (Mere Survival: The new American Dream)
[ Post Reply | Private Reply | To 1 | View Replies]

To: decimon

They still can’t figure out today’s whether and they want to figure out causality 20,000 years ago.


4 posted on 06/25/2010 9:51:06 AM PDT by Mere Survival (Mere Survival: The new American Dream)
[ Post Reply | Private Reply | To 1 | View Replies]

To: decimon

They still can’t figure out today’s weather and they want to figure out causality 20,000 years ago.


5 posted on 06/25/2010 9:51:19 AM PDT by Mere Survival (Mere Survival: The new American Dream)
[ Post Reply | Private Reply | To 1 | View Replies]

To: decimon

I’d guess it would have had to turn superwarm to get out of the ice age...after that...it’s back to regular yo yo weather.


6 posted on 06/25/2010 9:59:40 AM PDT by Sacajaweau (What)
[ Post Reply | Private Reply | To 1 | View Replies]

To: decimon; Horusra; Thunder90; Dr. Bogus Pachysandra; Entrepreneur; Darnright; Nipfan; ...
Thanx !

 


Beam me to Planet Gore !

7 posted on 06/25/2010 10:23:16 AM PDT by steelyourfaith (America should take a mulligan on the 2008 presidential election.)
[ Post Reply | Private Reply | To 2 | View Replies]

To: Mere Survival

Ya know,,,, there’s something still messed up with this site’s server! In virtually every thread, there are double and triple posts. I wonder what’s up with that???


8 posted on 06/25/2010 10:32:34 AM PDT by Dr. Bogus Pachysandra ( Ya can't pick up a turd by the clean end!)
[ Post Reply | Private Reply | To 4 | View Replies]

To: Mere Survival

Ya know,,,, there’s something still messed up with this site’s server! In virtually every thread, there are double and triple posts. I wonder what’s up with that???


9 posted on 06/25/2010 10:33:28 AM PDT by Dr. Bogus Pachysandra ( Ya can't pick up a turd by the clean end!)
[ Post Reply | Private Reply | To 4 | View Replies]

To: Mere Survival

Ya know,,,, there’s something still messed up with this site’s server! In virtually every thread, there are double and triple posts. I wonder what’s up with that???


10 posted on 06/25/2010 10:34:16 AM PDT by Dr. Bogus Pachysandra ( Ya can't pick up a turd by the clean end!)
[ Post Reply | Private Reply | To 4 | View Replies]

To: Dr. Bogus Pachysandra

I did the double post because I mispelled weather, hit the back arrow to correct, but it posted the first one anyway.


11 posted on 06/25/2010 10:35:46 AM PDT by Mere Survival (Mere Survival: The new American Dream)
[ Post Reply | Private Reply | To 8 | View Replies]

To: Mere Survival

And I was just “goofin’” with my triple post. However, there have been an extraordinary number of multiple posts since the server went down on Sunday.


12 posted on 06/25/2010 10:42:14 AM PDT by Dr. Bogus Pachysandra ( Ya can't pick up a turd by the clean end!)
[ Post Reply | Private Reply | To 11 | View Replies]


The Cycle of Cosmic Catastrophes: Flood, Fire, and Famine in the History of Civilization The Cycle of Cosmic Catastrophes:
Flood, Fire, and Famine
in the History of Civilization

by Richard Firestone,
Allen West, and
Simon Warwick-Smith


13 posted on 06/25/2010 6:15:29 PM PDT by SunkenCiv ("Fools learn from experience. I prefer to learn from the experience of others." -- Otto von Bismarck)
[ Post Reply | Private Reply | View Replies]

To: 75thOVI; aimhigh; Alice in Wonderland; AndrewC; aragorn; aristotleman; Avoiding_Sulla; BBell; ...
Thanks decimon!
 
Catastrophism
 
· join · view topics · view or post blog · bookmark · post new topic · subscribe ·
 

14 posted on 06/25/2010 6:15:54 PM PDT by SunkenCiv ("Fools learn from experience. I prefer to learn from the experience of others." -- Otto von Bismarck)
[ Post Reply | Private Reply | View Replies]

To: decimon; StayAt HomeMother; Ernest_at_the_Beach; 1ofmanyfree; 21twelve; 240B; 24Karet; ...

· join list or digest · view topics · view or post blog · bookmark · post a topic · subscribe ·

 
Gods
Graves
Glyphs
Thanks decimon.

To all -- please ping me to other topics which are appropriate for the GGG list.
GGG managers are SunkenCiv, StayAt HomeMother, and Ernest_at_the_Beach
 

·Dogpile · Archaeologica · Mirabilis.ca · LiveScience · Biblical Archaeology Society ·
· Discover · Nat Geographic · Texas AM Anthro News · Yahoo Anthro & Archaeo · Google ·
· Archaeology · The Archaeology Channel · Excerpt, or Link only? · cgk's list of ping lists ·


15 posted on 06/25/2010 6:16:08 PM PDT by SunkenCiv ("Fools learn from experience. I prefer to learn from the experience of others." -- Otto von Bismarck)
[ Post Reply | Private Reply | View Replies]

To: steelyourfaith

16 posted on 06/25/2010 6:26:04 PM PDT by BenLurkin
[ Post Reply | Private Reply | To 7 | View Replies]

To: BenLurkin
LOL that's so funny!!!
(although surface water back then may have had more organic impurities than today's municipal water supplies...)
17 posted on 06/25/2010 6:32:04 PM PDT by steelyourfaith (America should take a mulligan on the 2008 presidential election.)
[ Post Reply | Private Reply | To 16 | View Replies]

To: steelyourfaith

Seeing as how in some places folks still aint figured it out, I bet it took a long while before many people discovered the value of peeing and pooping downstream from the drinking area.


18 posted on 06/26/2010 1:07:18 AM PDT by Grimmy (equivocation is but the first step along the road to capitulation)
[ Post Reply | Private Reply | To 17 | View Replies]

To: Grimmy

Now if we could just get the fish, other animals and microbes in compliance ...


19 posted on 06/26/2010 6:00:14 AM PDT by steelyourfaith (America should take a mulligan on the 2008 presidential election.)
[ Post Reply | Private Reply | To 18 | View Replies]

To: Dr. Bogus Pachysandra
And I was just “goofin’” with my triple post. However, there have been an extraordinary number of multiple posts since the server went down on Sunday.

Sometimes it takes so long for "post" to activate that one forgets whether one has hit the post button.

And do it again.

And again.

20 posted on 06/26/2010 2:01:47 PM PDT by Ole Okie
[ Post Reply | Private Reply | To 12 | View Replies]

To: SunkenCiv
They are desperate to attribute the glacial cycle to CO2, even though it's a lagging indicator. My prediction is their next move will be to “reexamine” the ice cores to suddenly discover CO2 isn't a lagging indicator after all, but the leading indicator of temperature change.
21 posted on 06/28/2010 11:27:11 AM PDT by colorado tanker
[ Post Reply | Private Reply | To 15 | View Replies]

Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.

Free Republic
Browse · Search
General/Chat
Topics · Post Article

FreeRepublic, LLC, PO BOX 9771, FRESNO, CA 93794
FreeRepublic.com is powered by software copyright 2000-2008 John Robinson