Posted on 09/26/2007 11:09:22 AM PDT by Red Badger
A close up of one of the stalagmites analyzed in the study. Credit: Jud Partin
When Georgia Tech Assistant Professor Kim Cobb and graduate student Jud Partin wanted to understand the mechanisms that drove the abrupt climate change events that occurred thousands of years ago, they didn't drill for ice cores from the glaciers of Greenland or the icy plains of Antarctica, as is customary for paleoclimatolgists. Instead, they went underground.
Growing inside the caves of the tropical Pacific island of Borneo are some of the keys to understanding how the Earth's climate suddenly changed - several times - over the last 25,000 years. By analyzing stalagmites, the pilar-like rock formations that stem from the ground in caves, they were able to produce a high-resolution and continuous record of the climate over this equatorial rainforest.
"These stalagmites are, in essence, tropical ice cores forming over thousands of years," said Partin. "Each layer of the rock contains important chemical traces that help us determine what was going on in the climate thousands of years ago, much like the ice cores drilled from Greenland or Antarctica."
The tropical Pacific currently plays a powerful role in shaping year-to-year climate variations around the globe (as evidenced by the number of weather patterns influenced by the Pacific's El Nino), but its role in past climate change is less understood. Partin and Cobb's results suggest that the tropical Pacific played a much more active role in some of the abrupt climate change events of Earth's past than was once thought and may even have played a leading role in some of these changes.
Polar ice cores reveal that the Northern Hemisphere and the Southern Hemisphere each have their own distinct patterns of abrupt climate change; the tropical Pacific may provide the mechanistic link between the two systems. Understanding how the climate changes occurred and what they looked like is important to helping scientists put into context the current trends in today's climate. They published their findings in the Sept 27, 2007, issue of the journal Nature.
The research team collected stalagmites from the Gunung Buda cave system in Borneo in 2003, 2005 and 2006. Analyzing three stalagmites from two separate caves allowed the pair to create a near-continuous record of the climate from 25,000 years ago to the present. While this study is not the first to use stalagmites to examine climate over this time period, it is the first to do so in the tropical Pacific. Typically, in these types of studies, only one stalagmite is analyzed, but Partin and Cobb compared their three stalagmite records to isolate shared climate-related signals.
Stalagmites are formed as rain water, mixed with calcium carbonate and other elements, makes its way through the ground and onto the cave floor. As this solution drips over time, it hardens in layers, creating a column of rock.
Partin and Cobb cut open each stalagmite and took 1,300 measurements of their chemical content to determine the relative moisture of the climate at various periods in history starting from the oldest layers at the bottom to the present at the top. They dated the rocks by analyzing the radioactive decay of uranium and thorium, and determined the amount of precipitation at given times by measuring the ratio of oxygen isotopes.
"Our records contain signatures of both Northern and Southern Hemisphere climate influences as the Earth emerged from the last ice age, which makes sense given its equatorial location,” said Cobb. “However, tropical Pacific climate was not a simple linear combination of high-latitude climate events. It reflects the complexity of mechanisms linking high and low latitude climate.”
For example, Partin and Cobb's records suggest that the tropical Pacific began drying about 20,000 years ago and that this trend may have pre-conditioned the North Atlantic for an abrupt climate change event that occurred about 16,500 years ago, known as the Heinrich 1 event.
"In addition, the Borneo records indicate that the tropical Pacific began to get wetter before the North Atlantic recovered from the Heinrich 1 event 14,000 years ago. Perhaps the tropical Pacific is again driving that trend," said Partin.
"Currently our knowledge of how these dramatic climate changes occurred comes from just a few sites," said Cobb. "As more studies are done from caves around the world, hopefully we'll be able to piece together a more complete picture of these changes. Understanding how the dominoes fell is very important to our understanding of our current warming trend."
No, I havn’t seen either one of them. I have read some extensive comments on a cave forum. It sounds like they are worth watching at least once. I’m not much of a movie watcher. I usually see a movie after it’s been out for a few years.
Plot (for both!):
Group goes down in cave and can't get back out.
They get attacked by strange creatures.
Some in the group get eaten by creatures (fun to try and pick who)
Some make it back to surface.
The end............
Hah! The plot as you describe is exactly what I’ve heard.
Eeeeghhhhhhhh Thanks pal. You just ruined my vision of cave people looking like Barbara Bach in a fur bikini.
uh, dude...cavers rescue Spelunkers...
hey - did I see you at OTR?
......hey - did I see you at OTR?....
No, fraid not. My current caving activity is remembering. I haven’t been undergroung in a long time.
The laast trip I got lerft behind and found passages once easily negotiated a bit tight around my belly.
This topic was posted , thanks Red Badger.
from deep in the archives:Caves reveal clues to UK weatherAt Pooles Cavern in Derbyshire, it was discovered that the stalagmites grow faster in the winter months when it rains more. Alan Walker, who guides visitors through the caves, says the changes in rainfall are recorded in the stalactites and stalagmites like the growth rings in trees. Stalagmites from a number of caves have now been analysed by Dr Andy Baker at Newcastle University. After splitting and polishing the rock, he can measure its growth precisely and has built up a precipitation history going back thousands of years. His study suggests this autumn's rainfall is not at all unusual when looked at over such a timescale but is well within historic variations. He believes politicians find it expedient to blame a man-made change in our weather rather than addressing the complex scientific picture.
by Tom Heap
I like that closing sentence -- "future decision-making could be made based on scientific data and not on political expediency". I wouldn't count on it, but that would be great.
Is anyone watching Ben, at SO on YouTube?
(Suspicious Observers)
https://www.youtube.com/watch?v=pPwFwiV7Jso&list=PLHSoxioQtwZf1-8QeggXIVdZ-abyJXaO1&index=2&t=2s
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.
