Ancient Superflood Brought Climate Chaos

A 'superflood' created by the bursting of a huge lake may have triggered climatic chaos

A catastrophic 'superflood' following the rupture of a massive glacier-dammed lake in Canada at the end of the Ice Age probably plunged the world into centuries of climatic chaos.

That single event was likely responsible for the most dramatic climate change of the last 10,000 years, according to a report by a Canadian team led by Professor Garry Clarke, a geophysicist at the University of British Columbia in Vancouver, which appears today in the journal Science.

The 'superflood' was enough to alter ocean circulation in the Northern Hemisphere: analysis of ice cores taken in Greenland reveal that for the next 200 years or so, the mean temperature dropped by 5°C, snow accumulation decreased sharply and forest fires became more frequent.

Clarke's team found that the water body, known as Lake Agassiz, reached a massive 163,000 cubic km in volume - at least double that of the largest contemporary lake, the Caspian Sea - and that its release was "by far the largest known glacial outburst of the past 100,000 years".

It was formed after the vast Laurentide Ice Sheet, which at its maximum formed a 3-kilometre-thick dome over Hudson Bay, began disintegrating rapidly about 8,500 years ago.

As the ice sheet retreated north, it left behind a large depressed area of land. This sloped towards the former ice dome and gradually filled with meltwater and run-off from precipitation to become Lake Agassiz.

But icebergs and remnants of the ice sheet dammed the lake, which at its maximum elevation had a natural 'spillway' about 230 m above sea level, the researchers said.

"Modern analogues and the known physics of outburst flooding indicate that tunnelling below the ice is the most probable flood release mechanism," Clarke said.

"Because ice floats on water, thinning ice dams are unstable. Initiation of a flood routed beneath the ice therefore pre-empts the possibility of a flood routed across the ice. Once a subglacial path is established, an ice-walled conduit will tend to grow by melting its walls," he added.

As water tunnelled its way through the ice dam, its rupture became unavoidable. The team said that on the basis of radiocarbon dating, a full torrent was finally unleashed about 8,450 years ago. It took less than a year to discharge.

After the lake water gushed into the Hudson Bay, its freshness altered the strength of ocean circulation, which in turn caused the abrupt climate changes in much of the Northern Hemisphere, the team said.

Geological evidence suggests that this first flood was followed by a smaller one from a lower water level of about 125 m, either because the lake was drained by two successive outbursts or because the first flood drained it to sea level or because the ice-dam reformed and allowed it to partly refill before breaking again.

Either way, once the dam had been permanently breached, the discharge that formerly overflowed to the St Lawrence Valley was routed northward to Hudson Bay.

The researchers argue that understanding the mechanisms underlying past climate change events is increasingly important as people grow more concerned about the magnitude and rate of future climate change.

"Changes in the volume and extent of the ice sheets that once covered much of North America directly influenced the freshwater balance of the North Atlantic and are implicated in many abrupt climate events of the past 100,000 years," the researchers wrote.

"During the last Ice Age, when a kilometres-thick ice sheet covered most of Canada and parts of the northern United States, armadas of icebergs were episodically launched into the North Atlantic. The melting of this freshwater ice and the associated freshening of ocean surface waters are believed to have changed the strength of the oceanic thermohaline circulation, thereby causing abrupt climate changes," they said.

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Correct, that's because IMO you are wrong. Consider the Davidson Current, a freshwater current floating on top of and against the California Current that occurs seasonally off the Oregon coast. It moves north at about two knots driven against the wind and the current by coriolis forces. Its displacement moves faster than the current, but not with the speed of wave energy. For the displacement from this event to reach the Mediterranean, it would have had to travel under the entire north polar ice sheet of that time (which was huge and blocked many existing channels between Hudson Bay and the Atlantic). That's one long gravity push around a very tortuous path subject to coriolis centering forces that would tend to pile a freshwater displacement toward the North Pole rather than leak it by gravitational body forces into the Atlantic. The oceans are very lumpy places because coriolis forces are very powerful. Consider that the center of the Pacific is about 12 feet above its "level" at the edges.

In the three major floods at the end of the Ice Age, ocean levels rose worldwide 100 to 200 feet each in a period of two weeks, and that was because it took time for the lake to drain.

The article says the following: "It took less than a year to discharge," a much more believable number.

To assume that these scientists understand all there is to know about modeling worldwide flow for how a glacial lake would drain under breakout conditions the like of which no modern human has EVER witnessed, requires more credulity than is warranted by the data. It is not unusual for all sorts of wild claims to be made in the executive summary of a paper in order for the grantor to be happy. The principal information here is that there is solid evidence there was a lake, a good estimate of its volume, and they may have evidence that it did break out. It MIGHT have taken two weeks for the lake to drain, but I seriously doubt that our knowledge of how fresh water distributes displacement from under a massive ice age cap is so sophisticated. IMHO, they're claiming a whole lot more certainty about events 8,500 years ago than I think our archaeological knowledge can justify.

I would assume a breakout like this might start a chain reaction, lifting vast amounts of sheet ice that would then flow into the oceans to melt. That is a much more likely scenario given the posited impact on global climate.

Let's do a little arithmetic. Lets divide the released volume of the lake, according to the article, by the current surface area of the world's oceans to see how far they would rise as a result of the released water (I know that the ocean surface area was smaller then, but it works for a crude reality check):

(163,000 km³/361,800,000 km²)(1,000 m/km) = 0.45 meters.

Try it yourself.

Think about it. The authors say that this lake is twice the size of the Caspian Sea. Now spread that water over 70% of the Earth's surface and ask yourself if that volume would be large enough to add 100 feet of water. You might also ask if the lake represents sufficient thermal mass to cool the atmosphere by itself. I doubt it. However, the ICE that might have been released into the oceans with the breakout might have sufficient heat of transformation to have such an effect, particularly because the melting fresh water might develop a thermal inversion layer at the surface.

Glacial collapse raised sea levels over 100 feet, not some damned lake. It didn't happen over a matter of days.

I don't think so, the flood in Noah's day was something so profound that when Peter writes of it in the new testament, "For this they are willingly ignorant, the world that was then, standing in the water and out, perished, the world we live in now, is reserved for fire, and the judgement of ungodly men", he makes it clear that we no longer live in anything similar to the pre-flood climate conditions of Noah's day.

For instance according to scriptures, it had never rained on the face of the earth up until the flood of Noah. The earth was watered by a mist rising from the ground. The inhabitants of the earth had no idea what rain was, much less a flood.

While science agrees that at one time the earth was watered by a mist rising from the ground, they maintain that this was billions of years before mankind "evolved". The bible contradicts their findings and places man being alive and well at the time that this climate condition was typical. I know where I'd place my money.

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