The useless shells of tiny ocean animals--foraminifera--drift silently down through the depths of the equatorial Pacific Ocean, coming to rest more than three miles (five kilometers) below the surface. Slowly, over time, this coating of microscopic shells and other detritus builds up. "In the central Pacific, the sedimentation rate adds between one and two centimeters every 1,000 years," explains Heiko P¿like, a geologist at the National Oceanography Center in Southampton, England. "If you go down in the sediment one inch, you go back in time 2,500 years."

P¿like and his colleagues went considerably further than that, pulling a sediment core from the depths of the Pacific that stretched back 42 million years. Limiting their analysis to the Oligocene--a glacial time period that lasted between roughly 34 million and 23 million years ago--the researchers found that global climate responds to slight changes in the amount of sunlight hitting Earth during shifts in its orbit between elliptical and circular. "Of all the records so far, this is both the longest and, also, the clearest that most of the climatic variations between glacial and interglacial at that time [were] most likely related to orbital cycles," P¿like says.

The researchers pulled specific foraminifera samples from the core and then dissolved the shells in acid. They pumped the resultant carbon dioxide gas into a mass spectrometer and determined exactly what elements comprised the shells. This allowed them to distinguish between shells composed of the relatively lightweight isotopes of carbon and oxygen versus those made with a higher proportion of heavier isotopes.

The isotopes, in turn, reveal a picture of the climate eons ago. Oxygen (O) with an atomic weight of 16 evaporates more readily than its heavier counterpart ¹⁸O. Thus, when ice caps form, ocean water bears a higher ratio of the heavier isotope. Because the tiny creatures build their shells from materials in seawater, their calcium carbonate homes reflect the ratio of the two isotopes in the seas of that time. "They are a recorder of how much ice is present on the earth at any given time," P¿like notes.

The same is true for the various isotopes of carbon, ¹²C and ¹³C. Because plants preferentially use the lighter isotope, its scarcity is a record of how much life the oceans supported. By matching these isotope ratios to the astronomical cycle--Earth's orbit oscillates between an elliptical and circular path on a roughly 400,000-year cycle--the researchers found that patterns of glaciation and ice retreat followed the eccentricity of our planet's orbitthey report in the December 22 Science.

But the eccentricity of Earth's orbit does not cause that much of a flux in the amount of sunlight the planet receives; that energy budget is much more strongly impacted by variances in the degree ofEarth's tilt toward or away from the sun, which would lead one to expect glaciation to occur on a shorter cycle. Instead, the long times required to move carbon through the oceans apparently acts as a buffer. "Each carbon atom that you put in the ocean stays there for about 100,000 years," P¿like explains. "The climate system accentuates very long periodic variations and dampens shorter term variations."

Earth is currently nearly circular in its orbit and, if this Oligocene pattern were to be followed, would next be headed into another ice age in about 50,000 years. But the amount of carbon dioxide in the atmosphere has reached levels not seen for millions of years prior to the Oligocene. Thus, to get an accurate picture of what the climate might be like in coming years, scientists will have to continue back even farther in history to a period known as the Eocene.

It is already clear, however, that the effects of the carbon released now will affect the oceans for years to come. "Another effect of this residence time of carbon in the ocean is that it takes a long time to flush the system out," P¿like says. "It will take a very long time to go back to the level that existed before a large excursion of CO₂. It's not going to be doomsday, end of the world, but a rise in sea level would affect a very large percentage of humankind." Not to mention the shells laid down today on the deep ocean floor of the Pacific.

1 Comments

1. 1. BlueHue 12:25 PM 1/15/09

   MILANKOVITCH CYCLEs
   I am afraid to tell that I am rusty on this I only heard that the Author used incomplete material and on top of that employed a generic arythmatic.
   
   What I am most intrested in is the Following:
   
   Dr Velikovsky( as a PHD in Geology )has discovered that there is 500 non existing Years in Egyptian Chronology, but he was demonised for that.
   
   BUT
   he also postulated that the end orf the ICE Age was not in 10.000 bc
   but in :2.000 bc
   
   ALSO
   that the Quartenary LAKE Burst as a result of the END of that ICE age was not in 8.000 bc but in 800 bc.
   
   THUS
   the Neolythic ICE- age Man of MAGDALIEN did not live in 8.000 but 800 bc.
   
   THIS
   means that while the Egypttians enyoyed the 18--th Dynasty already,
   the Europeans still lived in the late Stone-age.
   
   Isn't that an idea to ponder upon ?
   
   Lately a German Professor:" Von PROTSCH" from the Univ. of MANNHEIM invented a Heidelberg Mensch or Neanderthaler-Skeleton-Find of 35.000 years ago as the oldest Neanderthaler skeleton in Germany, but it was a HOAX and he was fired.
   
   Still nobody believed Dr Velikovsky's postulated Date for the End of the ICE- Age at 2.000 bc instead of 10.000 bc. Sincerely BlueHue muster@online.nl
   

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