Posts Tagged ‘Greenland Ice Core’

If I could live during the Pleistocene (Part one)

September 9, 2010

For many years now I’ve often fantasized what I would see, if I could really travel in time back to the Pleistocene.  A quick trip of a few hours wouldn’t give me enough time to study the plants, animals, and climate of that time.  Instead, it would be necessary to spend many years there.  In fact I would like to spend a lifetime living in that long gone unspoiled wilderness.  Nevertheless, I’m not a big fan of roughing it, and I don’t want to give up the creature comforts of modern civilization.  I just don’t want to live without such things as college football, good books and movies, the internet, certain foods, and modern dental care.  So let’s suppose there’s a kind of time portal or wormhole that connects the modern world in 2010 with a time period, say about 38,000 radiocarbon (or about 41,000 calender) years before present.  I would live in a dwelling that I would construct 41,000 BP, but for example if I get a painful cavity, I would travel through the wormhole to the dentist’s office.  Moreover, I’d have wires running through the wormhole so I could communicate with the present.  I could sit in my 41,000 year BP home and watch modern television and communicate through phone lines and the internet with the modern world of 2010.

Why I would choose 41,000 BP

I would choose a place in what’s now Georgia before people lived in the region.  I don’t fear the megafauna–I can avoid rampaging mammoths and packs of dire wolves–but primitive men do worry me.  They could be cannibalistic or maybe they’d choose to kill me just for the hell of it–who knows what a primitive man’s motivation might be?  Besides, I want to study the ecology before humans had any impact on it at all.  Therefore, 41,000 years ago is probably a safe bet for avoiding humans in southeastern North America.  According to archaeologists, concrete evidence of humans in the region prior to 14,000 calender years ago is scarce.  Before 19,000 calender years ago, it’s nonexistent.   If there were people on the continent 41,000 years ago, which is highly doubtful, they were so few in number I’d doubt we’d cross paths.

Another reason why I’d choose 41,000 calender years ago is climate.  This time period was an interstadial–a somewhat warmer and rainier phase of the Wisconsinian Ice Age than a stadial or glacial phase.  Though temperatures are still cooler than those of today, for about 2,000 years they were warmer than the coldest time of the Ice Age.  When I originally conceived of this fantasy, I thought I might like to live during the last Interglacial, about 120,000 years ago.  However, the heat of the current summers in Georgia are uncomfortable enough, and the Sangamonian interglacial was even warmer.  I decided I’d rather live during a time when Georgia summers were much cooler than those of today.  The following is a link with a graph depicting climate change over the past 40,000 radiocarbon years.  Scientists are able to estimate past average temperatures based on the gas content found in air bubbles encased in a glacier in Greenland.  Scientists take cores of this 100,000 year old glacier and can count the years which correspond to the rings in the ice created by melting in summer and addition of ice in the winter, much like a tree’s age can be calculated by counting the number of rings in the trunk.  The ratio of heavy to light oxygen isotopes correlates to exact average temperatures.  Using this method, scientists know what temperatures were thousands of years ago.  Analysis of carbon dioxide and the amount of dust particles also give evidence of past climate.  Here’s the link:

See the first upward spike in this graph.  That’s the time I would choose to live.  Note the precipitous drop in temperatures after the interstadial ended.  Average annual temperatures must have dropped drastically within a few decades.  Note also how steady average annual temperatures have been over the last 11,000 years (the Holocene) compared to the Pleistocene.  These sudden changes in climate from moderate and rainy to cold and dry must have had a profound effect on the composition of plant species and the distribution of animal species.  In recorded history climate fluctuations that are merely a blip compared to the huge shifts during the Pleistocene have had devastating effects on agriculture.  A period known as the little Ice Age lasted from 1320-1870.  Cold rainy summers ruined crops and caused mass starvation.  Imagine what would happen to modern agriculture, if average temperatures suddenly dropped by more than ten degrees F as happened frequently during the Pleistocene. 

Fluctuations in Pleistocene temperatures correlate with the waxing and waning of the Laurentide glacier which covered most of Canada throughout the last Ice Age.  Interstadials resulted from when warm temps melted the glacier which put more moisture in the atmosphere; stadials occurred when this melting ice caused massive amounts of cold fresh water and icebergs to flood the north Atlantic which shut down the gulf stream, causing a sudden reversal in climate.  More moisture became locked in ice and the atmosphere became more arid and sea level dropped.

Georgia’s summer temperatures were much cooler and more comfortable during the interstadial than thay are in the present, but winter temperatures in the southeast were probably only a little cooler than they are today, thanks to the gulf stream off the Atlantic coast, which scientist believe created a warm thermal enclave in the region, especially near the coast.

During the interstadial I’d expect to find a mix of 75% forest and 25% meadow or small prairie in what’s now east central Georgia.  I’ll have more on the  ecology and landscapes of my chosen place of habitation next week along with a discussion of the geographical location of my Pleistocene homestead, and the adobe house I would build.