The long article below discusses in detail the data showing a weakening of the Gulf Stream function over the last century (maybe two centuries). The Gulf Stream moves hot water from the Equator north to northwestern Europe, such that average temperatures there in the winter are as much as 40 degrees warmer than at the same latitude in Canada. The weakening seems to happen when volumes of fresh water, less dense than salt water, fail to sink even after cooling, halting the flow caused when warm Gulf Stream waters cool and sink off Europe and then wander south deep in the ocean. There is a worldwide current flow as well, taking about 1,000 years for a full cycle. A warming Arctic has melted volumes of sea ice and Greenland glacier ice and this less dense fresh water, not sinking as it should, seems to be slowing the Gulf Stream.
What happens if the Gulf Stream collapses, and the transfer of heat slows or stops? Waters get hotter around the Equator, and colder near the North Pole. Europe and North America and Asia will become colder; in the case of Europe, much colder. Entire weather patters will change in ways impossible to predict. The much colder conditions might even start off another ice age, because perhaps winter snows won’t melt year to year and over decades and centuries a huge ice sheet forms.
While it looks like the Gulf Stream may have been slowing even before the last half century of warming, especially near the North Pole, recent warming, allegedly caused by man’s industrial growth and CO2 emissions, may have ironically accelerated the melting of fresh water ice in the north such that the Gulf Stream slowdown, or even collapse, has been hastened, thereby hastening a return to cold conditions and even the next ice age.
If we go back to the last warm time before this one, the Eemian 120,000 years ago, which lasted about 10,000-15,000 years, we learn the earth was one or two degrees Centigrade warmer than today, arctic ice nearly all gone, and sea levels 10-20 feet higher. Maybe, back then, the melting of the Arctic and Greenland ice slowed the current and brought on the cold, and the ice. Maybe, in fact, the entire system of ice ages over the last two million years, at roughly 100,000 year intervals, happened the same way – the marine current systems shift and adjust such that warmer Equatorial waters are sent north to warm the north of Europe and start the melting of the ice, until the great ice sheets are gone, ushering in a relatively warmer and stable time when temperatures are more stable and warmer, until the warmth itself sends enough fresh water into the northern ocean to slow the current and bring back the cold. And then, once the cold is established, again and again during the ice age there are fits and starts to recreate that warmer flow, resulting in the documented frequent warmings and coolings, still all colder than during an interglacial, until, finally, one takes “hold” and a 10-20,000 year interglacial emerges.
The Younger Dryas, a period lasting 1,000 years shortly after the end of the last ice age, might have been caused when a great glacial flood burst into the Atlantic and slowed or stopped the Gulf Stream, bringing back cold conditions for ten centuries. Maybe this flood was the great flood that drained a huge lake south of Hudson’s Bay. That flood hit the sea at around 40 degrees north, well south of the latitiude of the Greenland glaciers. Maybe the cold time was shorter because at that latitude the warmth of the ocean and the Gulf Stream handled the less dense fresh water better than a thousand miles to the north.
It is interesting that while the current alarm about climate change is the cooking of the earth, it may well be that it is precisely this “cooking” that triggers the next cold time, or ice age, by sending all that Greenland fresh water into the fast cooling Gulf Stream south of Iceland.
We, or our grandchildren, or theirs, are going to find out.
Posted in Real or Folk Tale? and tagged climate change, global warming, Gulf Stream, ice age, weather, Younger Dryas by Charles Sheldon with no comments yet.