The Cold Curse of the Pharaohs
Most Alaskans warned about global warming have a standard reaction: Bring it on! That's for those who take the scientists' warnings seriously. Others sneer, as people are wont to do when confronted with bad news: Burn less fossil fuel? Hah! I'll give up my high-powered gas-guzzling V-8 when they pry it out of my cold, dead fingers--you know the routine.
All right, for you enthusiasts who look forward to the temperate zone relocating somewhere beyond Barrow, I have some really bad news. It involves global warming, ocean currents, and---at least peripherally---Egyptian antiquities.
It also involves going back about 120,000 years to the onset of the last ice age. The usual theory explaining the glaciers' arrival has been a lessening of summer insolation thanks to the interplay of solar cycles with terrestrial ones. Less strength in the sunlight meant less melting of leftover winter snow, particularly in the crucial zone of far northern Canada from which the greatest ice sheet came. But, though he doesn't argue about the lessened insolation, a scientist at the University of Minnesota has put forth a differing hypothesis for what really caused the ice age.
In the American Geophysical Union's publication Eos, R.G. Johnson writes, that "frequent storms moving onto Baffin Island and other areas in the presently arid Canadian subarctic more likely caused the ice age." He found supporting evidence, from types of pollen to concentrations of oxygen isotopes, in the ocean sediments laid down at the crucial time. More storms, he thinks, meant more snowfall and more cloudiness to slow that snow's melting. It was enough of a change to trigger ice sheet growth.
His findings might seem like yet another scientific "so what?" to modern Alaskans, except for the mechanism he thinks set off the storms. At the beginning of the last great glaciation, waters of the northwestern Labrador Sea and Baffin Bay heated up. The comparatively warm seawater provided energy and water vapor for the storms.
See? More heat in the right place, and we're up to our armpits in glaciers.
The next question is, why did those northern waters heat up? Johnson blames the Mediterranean Sea, or at least the water pouring out of it past Gibraltar. At about the time the ice age began, a northerly current of that outflow welled up off the coasts of Ireland and Scotland. There it bumped against and diverted the warm current stemming from the Gulf Stream, sending it---and its attendant heat---into the Labrador Sea. Thus, the world had a colder Europe and a wetter Canadian High Arctic, nicely setting the stage for the glaciers' entrance because of the Mediterranean outflow's behavior.
And the Mediterranean sent this water outward to misbehave as it did because its own conditions had changed. Probably because of the decreased insolation, the African monsoons had failed, which meant drought at the headwaters of the Nile River, which meant less fresh water reaching the Mediterranean. That changed the sea's salinity and hence the nature of its outflow into the Atlantic Ocean between Africa and Europe. It's the same sort of change, Johnson assured his readers, that might be expected because of global warming.
And, of course, the Nile's entrance into the Mediterranean has been affected by a kind of enormous man-made drought: the Aswan High Dam, the notorious cause of the drowning of ancient tombs and temples. In Johnson's understanding of things, that dam will speed the arrival of the next ice age. Between increasing global temperatures and decreasing Nile contributions, he asserts that a much colder Europe and a snowier Baffin Island will occur within the next few decades.
Johnson's views underline how everything on earth is connected to everything else, sometimes in surprising ways. But if the Baffin Island snowfields do start expanding soon, I'll think of those drowned tombs, and remember tales of the pharaohs' curses upon whoever disturbs their rest.
