Earth's Climate Changes in Tune with Eccentric Orbital Rhythms

Scientific American.com ^ | December 22, 2006 | By David Biello

[aculeus]

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 Pälike, 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."

Pälike 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," Pälike 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," Pälike 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," Pälike 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," Pälike 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.

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[Robert A Cook PE]

The pacific floor is dished in, and the mid atlantic ridge pushes the sea floor up; it slopes from the coastlines down to a point that's deepest between the mid atlantic ridge and the coastlines. Wanna bet that sediment drifts slowly towards the deepest parts of these formations? Using core samples of this stuff as measurements of the earths age is just plain silly.
There is no way to predict how much is slides towards these centers a year or how many events have effected it, the rate at which this sediment is produced, that it was always constant, etc etc. What about so called continental drift?

Surely that moved it around a lot in 42 million years. Not to mention that we'd all be dead or very stoned from breathing all that methane gas released from the Methane Hydrate ice formations. There is no way that this stuff can be used to determine what the weather was at any point in history because of these underterminable variables.

Heiko Pälike had better head back to the guessing board if he wants to get more grant money. Surely he could have come up with something more believable than this. It can't be that hard.

Sea floor sediments are actually a pretty way to check.

yes, and no - part of what your saying is right, but the conclusion isn't valid.

Sediment (from erosion and whale poop, and dead plankton, and dead fish poop and plants) drops at a pretty steady rate. The characteristics of that dropped sediment change as the climate changes, which helps.

Yes, the thickness of the seafloor sediment layer is greater at the edges (away from the mid-Atlantic rift for example - where it is zero) compared to the thickness where the seafloor drops into a trench. The rift itself is much higher than the general ocean floor though because of the rising magma pushes up the floor locally.

But, at the trench, the sudden drop-off is so great as the ocean floor goes under a continental plate that the actual ocean depth increases significantly. Much more on the west Pacific than west Atlantic however.

But the sea floor sediment itself is very steady: it doesn't slide or displace sideways as the whole crust moves. A glacier, on the other hand is very unstable and does significantly move its accumulated debris around as it goes down the mountain. The glacier though is moving at ten thousand times the rate.

[Felis_irritable]

"Seriously, I wonder why that stuff isn't being explored as at the very least a very cheap natual gas supply?"

It is. At some point on the cost curve of petroleum (equaling about $5 per gal for gasoline) methane hydrate and methane hydride start to look viable as an alternative fuel. There is a huge quantity available, but the research is not being pursued like E85, fuel cells, etc.

[Nathan Zachary]

That's what I was wondering. "scientists" certainly don't know either. Maybe we should ask Al Gore, He seems to know everything.
You'd think if it just sat there, we'd smell it by now. Pity the first person who gets a wiff of a millions of years old dinosaur fart. "Hog barn days" won't be very pleasant either.
The weather man will have more to do than just guessing at the weather in the future, he'll be guessing at methane gas cloud movements and telling us what the day will smell like.

[HardStarboard]

Al Gore's problem is that his reasoning is circular while his direction is eccentric.

Further complicating things, Gore's rhythm is Koom Bah Yah.

[Prophet in the wilderness]

Is methane a viable energy source ? Either it goes out into space, or it decomposes, can gases decompose ?

[NicknamedBob]

T'weren't the SUVs then, but the Orbital Cycles.

I wonder what kind of mileage you get with them Orbital Cycles. I'd like to visit Mars and stuff.

[RightWhale]

They were rolling along making good progress with orbital eccentricity and then they got carbon in their valves and sputtered to a halt.

[NicknamedBob]

They should have converted that carbon into methane and released it into the atmosphere.

It always makes me feel better.

[NicknamedBob]

Besides, you may think they're "eccentrics," but I say they're a bunch of cranks.

[bert]

Algore has no science. He has only faith.

[Nathan Zachary]

Actually, it isn't very steady. If I could find a better seasat photo you can see just how uneven the floor of the oceans and seas are. You can see just how many catastrophic events have occured and no doubt stirred up this stuff at various times, certainly enough to make it impossible to determine what was were and when.

There are many unaswered questions which make it impossible to determine the age of anything that may be on the floor of the Pacific and Atlantic. For example, the grand Canyon is assumed to have been formed by millions of years of errosion. If that's what formed it, wouldn’t you expect to find a gigantic river delta where the Colorado River enters the Gulf of California? It’s not there. Where did 800 cubic miles of dirt go?
If it's buried under all the magna that sits on top of the actual Pacific floor, which is only assumed to be basalt like the Atlantic ocean floor, (nobody has been able to drill a hole deep enough to find out) it stands to reason anything on the pacific floor would only be as old as the dirt that has piled up from the grand canyon since that event.

Using plate tetonic theory, itself a theory that is in no way free of it's own problems creates even more questions than it answers. Plate tectonics claims a trench forms as a plate dives down into the mantle, a process called subduction. The fact that there is NO distortion as you point out of the horizontal sediment layer in these trenches shows that this can't be what's happening.
If a 30 mile thick plate was sliding into the mantle even only a couple of miles, the friction would be far greater than the rocks strength. We would see much buckling, distortion, breaking and crushing. Yet, there is no horizontal distortion.
Plate tetonic theory suggests earthquakes form where these plates slide under each other , so there would definately be a lot of activty in this area disturbing the sediment greatly. Or, tetonic theory is wrong.
Shallow earthquakes displace the ground horizontally along a fault, and would also cause heat. Since these sediments aren't disturbed or destroyed by heat, these trenches can't be caused a fault line either.
To establish a plausible theory about climate history based on sediments which are impossible to be certain of their age and reliability is a waste of time. certainly not "science" governments enviroment activists should be using to claim the sky is falling, and creating any global warming policy on.

[Nathan Zachary]

Here's where you can get a look at some facinating pics.

SeaSat mission

[NicknamedBob]

"To establish a plausible theory about climate history based on sediments which are impossible to be certain of their age and reliability is a waste of time."

Snowfall occurs in irregular drifts and windrows also, but we can reliably measure the amount we get.

The ocean plain is broad and predominantly featureless. The drifting sediment is little disturbed by currents.

Like tree rings, a certain layering tends to take place, and the proof of it as a reliable gauge is in having similar evaluations from widely scattered locations of ocean floor.

[Paladin2]

"...useless...."? wtf, gratuitous interjection?

[NicknamedBob]

Well, useless to the small animals, which have died. Isn't this the same stuff we use in swimming pool filters, diatomaceous earth?

[Paladin2]

I'm guessing that it's the limestone of the future.

[NicknamedBob]

Good guess.

limestone (lìm´ston´), sedimentary rock composed of calcium carbonate. It is ordinarily white but may be colored brown, yellow, or red by iron oxide and blue, black, or gray by carbon impurities. Most limestones are formed from the skeletons of marine invertebrates; a few are chemically precipitated from solution.

[aculeus]

Are you talkin' to me?

[Paladin2]

No, just an adjective observation from the article.

[NicknamedBob]

"Are you talkin' to me?"

Uh-oh! I'll get out here ...

(Actually, he was responding to David Biello, but I'm going to be busy making popcorn.)