New CO2 Data Reflects Ice Cap Formation

Of course the hidden assumption is that dropping CO2 led to a growth of the South Polar Ice Cap. What if dropping temperatures caused a sharp drop in atmospheric CO2 instead? Which is most realistic?

Right now a whole range of questions are wide open. Was there a Northern Cap or did we in fact have to wait for the creation of the blockage at Panama around a million years ago? If not, why not?

Polar glaciation forming an Ice cap is dependent on the presence of a continental land mass within fifteen degrees of the pole. It will force the ice further away but that is the minimum need. Antarctica today is perfectly positioned to produce a maximal ice cap. It is also ringed by open ocean sealing it off from much external weather. It is optimized to be our climate refrigerator and is also well balanced so as not to place stress on the crust.

In fact we know from the polar ice record that a warming climate leads production of CO2. Thus what evidence is now available suggests that our present assumptions are exactly backward.

An obvious conjecture is that a simple lack of polar lands led to tropical conditions on a global basis. I am sure that every winter, the oceans froze over and that a good yard or so of sea ice was produced. Yet with the spring, this all broke up and was quickly dispersed and the full blast of twenty four hour sunlight reasserted itself.

This sort of assertive material finds its way into text books and whole generations grow up believing this as correct. Except both interpretations have merit, yet the latter one today has the weight of present evidence however scant.

New CO2 Data Helps Unlock The Secrets Of Antarctic Formation

by Staff Writers
Cardiff, UK (SPX) Sep 15, 2009

http://www.terradaily.com/reports/New_CO2_Data_Helps_Unlock_The_Secrets_Of_Antarctic_Formation_999.html

The link between declining CO2 levels in the earth's atmosphere and the formation of the Antarctic ice caps some 34 million years ago has been confirmed for the first time in a major research study.

A team of scientists from Cardiff, Bristol and Texas A and M universities braved the lions and hyenas of a small East African village to extract microfossils in samples of rocks which show the level of CO2 in the Earth's atmosphere at the time of the formation of the ice-cap.

Geologists have long speculated that the formation of the Antarctic ice-cap was caused by a gradually diminishing natural greenhouse effect.

The study's findings, published in Nature online, confirm that atmospheric CO2 declined during the Eocene - Oligocene climate transition and that the Antarctic ice sheet began to form when CO2 in the atmosphere reached a tipping point of around 760 parts per million (by volume).

Professor Paul Pearson from Cardiff University's School of Earth and Ocean Sciences, who led the mission to the remote East Africa village of Stakishari said: "About 34 million years ago the Earth experienced a mysterious cooling trend. Glaciers and small ice sheets developed in Antarctica, sea levels fell and temperate forests began to displace tropical-type vegetation in many areas.

"The period, known to geologists as the Eocene - Oligocene transition, culminated in the rapid development of a continental-scale ice sheet on Antarctica, which has been there ever since.

"We therefore set out to establish whether there was a substantial decline in atmospheric carbon dioxide levels as the Antarctic ice sheet began to grow."

The team mapped large expanses of bush and wilderness and pieced together the underlying local rock formations using occasional outcrops of rocks and stream beds.

Eventually they discovered sediments of the right age near a traditional African village called Stakishari. By assembling a drilling rig and extracting hundreds of meters of samples from under the ground they were able to obtain exactly the piece of Earth's history they had been searching for.

Co-author Dr Gavin Foster from the University of Bristol Earth Sciences Department said: "By using the rather unique set of samples from Tanzania and a new analytical technique that I developed, we have, for the first time, been able to reconstruct the concentration of CO2 across the Eocene-Oligocene boundary - the time period about 34 million years ago when ice sheets first started to grow on Eastern Antarctica. "
The new findings offer important lessons for the future and will add to the debate around rising CO2 levels in the earth's atmosphere as the world's attention turns to on UN Climate Conference, which opens in Copenhagen later this year.

Co-author Dr Bridget Wade from Texas A and M University Department of Geology and Geophysics added: "This was the biggest climate switch since the extinction of the dinosaurs 65 million years ago.

"Our study is the first to provide a direct link between the establishment of an ice sheet on Antarctica and atmospheric carbon dioxide levels and therefore confirms the relationship between carbon dioxide levels in the atmosphere and global climate."

Diatom Diversity

Diatom diversity maximized during a period of hothouse conditions on earth. This suggests a maximizing of its habitat rather than anything else. Again warm conditions would have released more CO2 into the atmosphere during this period, much of that because of a warmer ocean. The warmer ocean encourages a rapid expansion of the diatom population as they took advantage of the higher energy environment.

It sounds very much like the polar ice caps disappeared 30 million years ago for a while. This also sounds like it is happening on the time scales associated with plate movement. If Antarctica moved thirty degree north we would swiftly add a couple of hundred feet of sea level and the earth would be a hothouse about ten degrees warmer.

This also a reminder that the short term climate variations we have uncovered as part of the history of the past one million years would be submerged into the background noise after that. Earth’s climate could as volatile as could be and we would never know it from the data available.

Now if there were some way to improve the resolution of the diatom record, the climate record could be modestly refined and perhaps mapped for many millions of years.

http://www.news.cornell.edu/stories/Jan09/diatom.evolution.hp.html

http://www.news.cornell.edu/stories/Jan09/diatoms_noaa.jpg

Jan. 7, 2009

Decline of carbon dioxide-gobbling plankton coincided with ancient global cooling

By Hugh Powell

The evolutionary history of diatoms -- abundant oceanic plankton that remove billions of tons of carbon dioxide from the air each year -- needs to be rewritten, according to a new Cornell study. The findings suggest that after a sudden rise in species numbers, diatoms abruptly declined about 33 million years ago -- trends that coincided with severe global cooling.

The study is published in the Jan. 8 issue of the journal Nature.

The research casts doubt on the long-held theory that diatoms' success was tied to an influx of nutrients into the oceans from the rise of grasslands about 18 million years ago. New evidence from a study led by graduate student Dan Rabosky of Cornell's Department of Ecology and Evolutionary Biology and the Cornell Laboratory of Ornithology takes into account a widespread problem in paleontology: that younger fossils are easier to find than older ones.

"We just tried to address the simple fact that the number of available fossils is colossally greater from recent time periods than from earlier time periods," Rabosky said. "It's a pretty standard correction in some fields, but it hasn't been applied to planktonic paleontology up till now."

More than 90 percent of known diatom fossils are younger than 18 million years. So an unadjusted survey of diatom fossils suggests that more diatom species were alive in the recent past than 18 million years ago.

The dearth of early fossils is understandable. Sampling for diatom fossils requires immense drill ships to bore into seafloor sediment. To find an ancient fossil, scientists first have to find ancient sediment -- and that's no easy task because plate tectonics constantly shift the ocean floor, fossils and all. Much of the seafloor is simply too young to sample.

So Rabosky and co-author Ulf Sorhannus of Edinboro University of Pennsylvania controlled for how many samples had been taken from each million-year period of the Earth's history, going back 40 million years. After reanalysis, the long-accepted boom in diatoms over the last 18 million years disappeared. In its place was a slow recent rise, with a much more dramatic increase and decline at the end of the Eocene epoch, about 33 million years ago.

With the new timeline, diatoms achieved their peak diversity at least 10 million years before grasslands became commonplace.

"If there was a truly significant change in diatom diversity at all, it happened 30 million years ago," Rabosky said. "The shallow, gradual increase we see is totally different from the kind of exponential increase you would expect if grasslands were the cause."

As an example of that kind of increase, Rabosky turned to another fossil record: horse teeth. Before grasslands, horses had small teeth suited for chewing soft leaves. But as grasslands appeared, much hardier teeth appeared adapted to a lifetime of chewing tough, silica-studded grass leaves. Diatoms ought to show a similar evolutionary response to the sudden availability of silica, Rabosky said, but they don't.

Although the new results don't explain the current prevalence of diatoms in the ocean, Rabosky said that whatever led to diatoms' rise at the end of the Eocene, the tiny organisms may have contributed to the global cooling that followed.

"Why diatom diversity peaked for 4 to 5 million years and then dropped is a big mystery," Rabosky said. "But it corresponds with a period when the global climate swung from hothouse to icehouse. It's tempting to speculate that these tiny plankton, by taking carbon dioxide out of the air, might have helped trigger the most severe global cooling event in the past 100 million years."

The research was supported in part by the National Science Foundation.