Ice Cores Unlock Climate Secrets

BBC ^ | 6-9-2004 | Julianna Kettlewell

[RightWhale]

I doubt that the air in the bubbles is exactly the same composition as the air of the time it was entrapped. But relative differences between air bubbles of different age might be noted.

[spunkets]

The composition is different. The core is like a pile of bottles, that were closed one each year for the last 0.75M years. The one on the bottom has the oldest air in it.

[VadeRetro]

Analysis of the ice proves our planet has had eight Ice Ages during that period, punctuated by rather brief warm spells - one of which we enjoy today.

Already I don't like this.

[txhurl]

Which reminds me: it's floodin' down in Texas. Is this an el nino or a la nina year, anybody know?

[VadeRetro]

Pretty rainy here in WV. I may have heard it would be a "mild El Nino." Unless that was last year.

[ckilmer]

Extract from "Journey of Human Evolution" [1998] 34, 623-651

The last glacial period was preceded by 1000 years of the coldest temperatures of the Late Pleistocene, apparently caused by the eruption of the Mount Toba volcano. The six year long volcanic winter and 1000-year-long instant Ice Age that followed Mount Toba's eruption may have decimated Modern Man's entire population. Genetic evidence suggests that Human population size fell to about 10,000 adults between 50 and 100 thousand years ago. The survivors from this global catastrophy would have found refuge in isolated tropical pockets, mainly in Equatorial Africa. Populations living in Europe and northern China would have been completely eliminated by the reduction of the summer temperatures by as much as 12 degrees centigrade.

Volcanic winter and instant Ice Age may help resolve the central but unstated paradox of the recent African origin of Humankind: if we are all so recently "Out of Africa", why do we not all look more African?

Because the volcanic winter and instant Ice Age would have reduced populations levels low enough for founder effects, genetic drift and local adaptations to produce rapid changes in the surviving populations, causing the peoples of the world look so different today. In other words, Toba may have caused Modern Races to differentiate abruptly only 70,000 years ago, rather than gradually over 0ne million years.

	Volcanic Winter

The Mount Toba eruption is dated to approximately 71,000 years ago. Volcanic ash from Mount Toba can be traced north-west across India, where a widespread terrestrial marker bed exists of primary and reworked airfall ash, in beds that are commonly 1 to 3, and occasionally 6 meters [18 feet] thick.

Tambora, the largest known historic eruption, displaced 20 cubic kilometres of ash. Mount Toba produced 800 cubic kilometres.* It was therefore forty times larger than the largest eruption of the last two centuries and apparently the second largest known explosive eruption over the last 450 million years.

*Mount St Helens produced a tiny 0.2 cubic kilometres.

	Volcanic Winter, and Differentiation of Modern Humans

Mount Toba's eruption is marked by a 6 year period during which the largest amount of volcanic sulphur was deposited in the past 110,000 years. This dramatic event was followed by 1000 years of the lowest ice core oxygen isotope ratios of the last glacial period. In other words, for 1000 years immediately following the eruption, the earth witnessed temperatures colder than during the Last Glacial Maximum at 18-21,000 years ago.

For the volcanic aerosols to be effectively distributed around the earth, the plume from the volcanic eruptions must reach the stratosphere, a height greater than 17 kilometres. Mount Toba's plume probably reached twice this height. Most solar energy falls at low latitudes between the Tropics of Cancer and Capricorn, so eruptions that happen near the Equator cause much more substantial cooling due to the reflection of solar energy. Toba lies 2 degrees north of the Equator, on the Island Sumatra.

The reduction in atmospheric visibility due to volcanic ash and dust particles is relatively short-lived, about three to six months. Longer-term global climatic cooling is caused by the highly reflective sulphuric acid haze, which stays suspended in the upper atmosphere for several years.

Ice core evidence implicates Mount Toba as the cause of coldest millennium of the late Pleistocene. It shows that this eruption injected more sulphur that remained in the atmosphere fo a longer time [six years] than any other volcanic eruption in the last 110,000 years. This may have caused nearly complete deforestation of southeast Asia, and at the same time to have lowered sea surface temperatures by 3 to 3.5 degrees centigrade for several years.

If Tambora caused the " The year without a summer" in 1816, Mount Toba could have been responsible for six years of relentless volcanic winter, thus causing a massive deforestation, a disastrous famine for all living creatures, and a near extinction of Humankind.

The Volcanic Winter/Weak Garden of Eden model proposed in this paper. Population subdivision due to dispersal within African and other continents during the early Late Pleistocene is followed by bottlenecks caused by volcanic winter, resulting from the eruption of Toba, 71 ka. The bottleneck may have lasted either 1000 years, during the hyper-cold stadial period between Dansgaard-Oeschlger events 19 and 20, or 10ka, during oxygen isotope stage 4. Population bottlenecks and releases are both sychronous. More individuals survived in Africa because tropical refugia were largest there, resulting in greater genetic diversity in Africa.

Bahamas Coral Reef Chart

BLOMBOS CAVE : 77,0000 YEARS OLD

Small and portable, this red ochre stone is engraved with what must be "tally" marks. It is one of two such stones recently found in the Blombos Cave in South Africa and have been dated as being 77,000 years old, making them the oldest form of recorded counting ever found.

The stone is worn which probably indicated that it wasconstantly handled over a period of time, how long is impossible to tell. It looks as though the stone has been reused at least once before as the lighter marks appear to have been erased rather than worn away naturally.

If the dating is accurate this stone was used 5000 years before the Mount Toba eruption of 71,000 years ago. The evidence from the Toba eruption indicates that the world's population of Modern Manwas reduced to a total of around 10,000 adults.

Bradshaw Homepage

[Betis70]

Krakatau erupted in the 1880s. There was a pretty neat show on Discovery Channel about that recently.

[ckilmer]

yeah got it. i was thinking of toba 71,000 years ago, a super volcano. looks like its recorded in soil as well as ice samples.

[shield]

bmp...read later

[Alberta's Child]

Which reminds me: it's floodin' down in Texas. Is this an el nino or a la nina year, anybody know?

Oh, it's even worse than that. It's an El Reno year, which means the summer will be dominated by a large mass of hot air that can cause severe burns among the residents of Waco, Texas.

[squarebarb]

Will your posts be waving in gassy brown and green?

[blam]

"i was thinking of toba 71,000 years ago, a super volcano. looks like its recorded in soil as well as ice samples."

Super Volcano Toba(75,000 Years Ago)

"Their is substantial evidence to show that within the time of the super volcano Toba's eruption in the Indonesian Pacific, the world's population of homo sapiens decreased from over one hundred thousand to less than two thousand, basically because global temperatures dropped five degrees for many years. This was within the current interglacial and at its start. "

I've read that this event can still be seen in the human genetic record.

[bert]

So, the human species is the product of an interglacial..... when the cold resumes, so will the species.

[blam]

Interestingly, recently I read about an ancient human site in Indonesia just above the Toba ash layer.

[Dark Glasses and Corncob Pipe]

Do you stand gaping in awe at a T-Rex skeleton purported to be 100 million years old, or do you gag in astonishment at the fools who believe such nonsense?

[blam]

"Krakatoa was fairly recent. Was heard in London or something."

I've heard it described as the loudest sound ever heard by humans...and, it 'echoed' around the world seven times.

[Kay Ludlow]

I wonder how closely they can narrow down a time period when they are looking back across that many years. Really, the C02 levels that they talking about today as so high represent a few years - 10, 20 or so. Averaged across the last century they likely are still really normal. Can they find a section that correlates to a particular century? I wouldn't think so - I think they'd be lucky to be able to identify particular 1000 year time spans. That means that statistically it's meaningless to compare this years C02 to anything they find in the cores.

That would be like taking the last few letters of a book and comparing them to the entire book - "THE END has a far greater representation the the capital E than the rest of the book, demonstrating a trend toward increasing capitalized vowels". Comparing this year to nearly a million years worth of ice core is just as meaningless.

[txhurl]

It's been so long since her, I'm gonna have to find her html and amend it. You know any CGEB posts from then?

[txhurl]

That's funny. You idiot F Canuck.

Really, I did laugh out loud.

It hurts to laugh, anymore.

[blam]

Frequent identifiable volcano ash layers in the ice core help some with the dating.