DR
Wallace Broecker was a detective in every sense of the word. Like a modern day Sherlock Holmes, he solved deep mysteries with surprising twists and unpredictable results, using careful analysis and logical inference. But unlike the great fictional detective, DR Broecker's investigative tools included a prospecting hammer and an ice drill, his garb was a white lab-coat or a parka, his victim was the planet earth; the MO was death by freezing. And while he solved one of the biggest crimes in nature, the serial killer he revealed was never apprehended. The ruthless perpetrator remains at large. Now there is chilling evidence the killer has once again emerged from a secret hideaway, encouraged by accomplices, to claim more victims. And in only a few years, you and I may witness the corpses pile up as the ancient culprit begins once again to feeds its grisly habit: To the bitter end of civilization.
For want of a nail the horse-shoe was lost. For want of a shoe the horse was lost. For want of a horse the rider was lost. For want of a rider the battle was lost. For want of a battle the kingdom was lost: For want of a nail the kingdom fell.
The Butterfly Effect is a shorthand way to refer to a complex phenomena: Tiny changes in the initial conditions of certain kinds of complicated interacting systems, such as lacking a single horseshoe nail in the hoof of one battle horse, can produce enormous changes down the road. As the study of Chaos Theory progressed in the 60s and 70s, the term was adopted to encapsulate the sobering realization that a single butterfly flapping its wings could alter weather patterns over decades, change global circulation over centuries, affect the dynamics of tidal momentum transfer between the earth and the moon over millions of years, and tweak the orbital dynamics of the solar system itself! In the end, a billion years later, it's scientifically and mathematically plausible that that butterfly's effect would cause the earth to be on the other side of the sun from where our planet would have been had the butterfly not flapped its wings. And if a lone butterfly can have that effect over eons, perhaps a larger, yet relatively subtle change could explain a mysterious, dramatic drop in temperature 12,000 years ago?
For decades climatologists and geologists believed that ice ages were relatively lethargic events. The fossil record in the last few million years spoke of periodic glaciation; sheets of ice marching south from the North pole and holding the shivering land in their icy grip for hundreds of thousands or millions of years. Thus it was inferred that the advance was gradual and that therefore the onset was slow as measured by our mayfly lives. But Wally--as he insisted I call him some years ago--was presented with evidence along the shore of Nova Scotia, Greenland, and Scotland of a sudden onset of glacial periods and rapid pulses of extreme temperature swings.
On the left an ice-core and on the right a varve-core that's been cross sectioned. Careful microscopic analysis of annual ice/snow deposits and seasonal mud layers provides climatic details on a year by year basis
The geo-fossil evidence in Greenland, Scotland, and Nova Scotia bounced from moderate to arctic over a period of a few years as the seas receded exactly as glacial models predicted they would during ice ages! In particular there was one burst of winter like conditions christened the Big Freeze (AKA The Younger Dryas) lasting for a millennia circa 11,000-12,000 years ago, but after the great Pleistocene ice sheets had retreated globally. How to explain it?
Over a period of many years, Broecker worked out the flow of deep ocean currents which circulate from the temperate and tropical zones to the poles. With the aid of radiocarbon dating of seawater, and using residue from atom bomb tests, he came to understand a critical portion of the great exchange mechanism at work on our planet.
Picture courtesy Jeff Masters at the Weather Undergound
Our detective Broecker felt this mysterious cold snap had to have something to do with what became known as the Atlantic Conveyor or AC. The AC is but one portion of a great oceanic circulation that spans the globe. The Atlantic component of this marine heat engine is a great river of water in the ocean itself, which carries warm water from the tropics to the North polar region on the surface of the ocean and returns cold water to the tropics crawling along the bottom. This current is what keeps Great Britain and the rest of Western Europe much warmer year round than Upstate New York and Toronto, even though the populous parts of Europe are farther north than the population centers in Canada and Northeast America. Turning off the AC would explain the great climatic flip-flop Wally Broecker was seeing in the geologic record. But how in the heck could a current which dwarfs the flow of the Amazon River be turned off in a few short years?
Well, these grand currents are salt water of course. And salt water is heavier than fresh water. In fact the formation of ice near the poles and harsh winds create water that is both salty and cold; a double heavy layer of water which sinks rapidly and which is key to the return leg of the AC. So a massive injection of cold fresh water into the northern Atlantic Ocean might shut the conveyor down temporarily. The cargo of heat would be delivered much earlier on its journey to the Northeast--into the mid-Atlantic rather than the shores of Western Europe and the arctic. Like a heater turned off on a wet, freezing cold day, that would allow the ice sheets to make a comeback into the temperate zones and fast. DR Broekcer had the MO of the Ice Box Killer identified. Now all he needed was a mechanism. A source of fresh water entering the Atlantic: Lots of it and all at once, to pin down the Killer.
One explanation was the collapse of a gigantic ice dam plugging a valley east of Michigan. It's plausible based on geologic data that twelve-thousand years ago, most of the land in states around present day Michigan were at the bottom of a single "Great Lake". This Great Lake had formed from meltwater and rain during the retreat of the last ice age and it was huge. But for millennia the massive body of fresh water was caught behind a mighty ice dam filling the valley leading to the Atlantic Ocean. Unlike an earthen dam, ice floats in water and melts as temperatures pick up. Slowly liquid water crept under the ice plug and weakened it's moorings while liquid from the glacier itself settled to the bottom as the ice age relented. It may have taken five years or five-thousand for the water to tirelessly tunnel further and further under the mountain of ice until an underground stream was flowing through the glacier. Finally, as the buried river grew in intensity and the foundation gave way, the frozen plug floated on the water, and it was carried away crumbling.
The Great Ice Dam in artist's rendition
That mountain of fresh water, topped off with tumbling ice bergs, that moved across the US-Canadian border down the St. Lawrence River Valley to the Northeast would have been an apocalyptic flood like no modern human has ever recorded. Once it gathered steam any remaining ice plugs in the way wouldn't be able to stand up to that kind of force. If anyone was there to see it, it would have been the last thing they ever saw. And when the deluge dumped into the Atlantic Ocean, the lighter, cold, fresh water spread over the salty ocean top as easily as an Exxon oil slick oozing from a tanker breach. Like a giant smothering lid, this layer of ice-cold water shot across the Atlantic Ocean and forced the warmer salt water down into the depths of the Atlantic long before it could deliver its warmth to the European and Norwegian coastlines: That would shut down the conveyor for a while!
The Younger Dryas cold snap, AKA The Big Freeze of ~12,000 years ago
The effects of this event on climate in Europe were nothing short of catastrophic. Forests froze where they stood. Animal and plant species dropped in their tracks by the thousands. In the space of less than fifty-years the climate of modern day Italy and Spain went from semitropical conditions to the harsh environment of North Dakota. The British Isles plunged into the same deep freeze we see today in Alaska. Norway and Austria would have been utterly uninhabitable as both regions were consumed by permafrost. The entire Baltic Sea may have iced over. Greenland and Iceland would be submerged under the polar cap.
If something like this happened today, the fertile valleys and grain fields of Europe, Asia, and North America would be decimated. Critical ports would be shut down. Drought would turn woodland into frigid dustbowls. Tundra, a refrigerated desert, could overtake the old growth forests in just a few short years. Like flipping an executioner's switch, multitudes would starve to death in the space of a single season or flee for their lives to more friendly climes. Billions of desperate refugees from Eurasia, Canada, and the northern US, would pour south in a wave of mass, starving, panic unrivaled in recorded history.
At the same time the northern climes are plunged into a sudden ice age, the tropics, now deprived of a a primary vector of heat dissipation, would heat up. The resulting hurricanes could make Katrina look like a gentle summer shower. The remaining sea lanes would be a demolition derby of shipping, runaway ice bergs, massive tropical storms, and hypercanes. And the storms might form so often the equatorial inter-tropical zone would be sandwiched by bands of whirling vortices more or less permanently encircling the planet. From space our world's midsection might start to resemble a terrestrial, blue-white version of the planet Jupiter.
So a goddam good question is, could it happen again in our own time and what might set it off? There is a great deal of debate about that. But the chilling answer is possibly yes; The Greenhouse Effect.
Park your car at the grocery store in the midday sunlight. By the time you come back it has warmed up inside, maybe it's even blistering hot. The reason is because your car windows are transparent to light, but not to heat. The light streams through the glass into the interior and reflects back as heat which cannot stream out. The temperature rises quickly. Leave a pet or a baby inside even for a few minutes on a mild summer day and this Greenhouse Effect can kill them in the time it takes to pick up a prescription at Walmart.
Carbon dioxide, methane, even water vapor, all have the same property. They're more transparent to light than to heat. When those kinds of substances build up in the atmosphere, it's like rolling up the planetary windows on a hot summer day. Only we can't roll them back down, open a door, or turn on the AC. And this time it's the surface of our entire planet that's stuck helplessly, like an infant, in the stifling, lethal, heat.
To produce the same effect as the Big Freeze, all that's needed is an influx of a lot of freshwater into the northern Atlantic Ocean. Doesn't matter where it comes from, ice dam breaking or a million fire hoses, that's all it takes. A rapid rise of just a degree or two might set off this deadly chain of events. The southerly edges of the North Polar ice caps, normally permanent, could retreat ... Fresh water would seep invisibly into the ocean by the lake-load stifling the formation of cold salty water to fire the return leg of the AC. Ice bergs would cleave off and sail south in record numbers melting billions of gallons of fresh water into the critical region of warmer flow thus capping the other end.
We might see the effect from satellite photos over a few decades, but the actual volume needed is relatively small on a global scale. Just a little nibbling around the edges of the polar iceline cuts off the AC at both ends. A few scores of miles here and there, a tiny pullback, translates into billions of tons of fresh water. Barely noticeable, easily discounted by folks who would rather ignore it, deny it; call it a myth. And we can't roll the car windows down or at least not very quickly; once these gases are out there, they're out there for a good long while. We're sealed inside the greenhouse.
Computer models and geological evidence both concur: That life giving Atlantic Conveyor can break down. And aside from increasing the frequency of storms like hurricanes and typhoons, inundating coastal cities, or producing famine by way of drought, the big picture is that, paradoxically, global warming could go on to freeze civilization in its tracks.
Storm ravaged earth or snowball planet? Either one is a possible future and perhaps far quicker than we think
We just don't know enough about any of this. A global greenhouse effect may be the only thing preventing the onset of another ice age right now. Or it could tip us into a Permian Extinction and proceed to push us over the Venusian precipe. Or it might trigger a return of the killer Wally Broekcer was following: The Big Freeze.
The K-T Impactor, the Siberian Traps, the Yellowstone Super Caldera, Coronal Ejectors, Gamma Ray Bursters, and now a killer with a human name; Katrina. These and many more are all reasons why any political ideology that conflicts with scientific reality must be restrained from interfering with public policy. They cannot be negotiated with. They are unimpressed with philosophy or religion. They're immortal, immune to capture, and without mind or morals. And now add the Icebox Killer; only one among a deadly menagerie of natural serial killers lurking in the shadows of history and the farthest reach of our cosmos. Each and everyone waiting to strike from inanimate ambush. We can't destroy these stalkers, not for now anyway. But, using science, engineering, and a modicum of leadership, we might be able to send a few of them up the river for life with no parole.
Update: For those of you who like seeing science take a front-seat and right-wing delusional ideology getting its ass kicked, my friend Chris Mooney will be on Air America AND the Daily Show on Monday, September 12, discussing his new book The Republican War on Science.