The Day After Tomorrow is an awful movie in almost every way. Not only is it filled with over-the-top acting and editing that values noise over story, the underlying narrative is based on climate change causing sudden horrific events around the world including bowling-ball sized hailstones and ice-tornadoes. Also, wolves.
But behind the cheesy effects and impossible events, there’s an idea that was suggested over a decade ago and since worked out in detail by climate researchers. That idea remains one of the most serious possible outcomes of climate change. And, unfortunately, it seems that the awful idea … may be coming true.
Two years ago, former NASA climate scientist James Hansen and a number of colleagues laid out a dire scenario in which gigantic pulses of fresh water from melting glaciers could upend the circulation of the oceans, leading to a world of fast-rising seas and even superstorms.
At the time, the predictions were based on computer simulations, and more than a few researchers doubted these events would play out in the real world, even if the scenario proved true. But just two years later …
The new research, based on ocean measurements off the coast of East Antarctica, shows that melting Antarctic glaciers are indeed freshening the ocean around them. And this, in turn, is blocking a process in which cold and salty ocean water sinks below the sea surface in winter, forming “the densest water on the Earth,” in the words of study lead author Alessandro Silvano, a researcher with the University of Tasmania in Hobart.
The result is that glaciers in at least two areas are melting faster than previously expected, because a layer of fresh water is staying on the surface, eroding the ice at an ever-increasing rate. This fresh water acts like a lake perched above the dense saline water, and the more ice that melts, the worse the situation becomes.
“What we found is not only a modeling study but is something that we observed in the real ocean,” said Silvano, who conducted the research in Science Advances with colleagues from several other institutions in Australia and Japan. “Our study shows for the first time actual evidence of this mechanism. Our study shows that it is already happening.”
This doesn’t mean that ice tornadoes are about to sweep through New York, or giant hail is coming soon to a city near you. It does mean that many of the effects of ocean currents—from the distribution of nutrients around the planet, to the moderating effect that warm currents have on areas like Europe, are in danger of just … stopping. That has implications for the world’s population and food supply that the word “dire” may not capture.
Rome, which is semi-tropical, is actually at roughly the same latitude as Boston. And Boston, as residents still leaning exhausted on their snow shovels after this winter can explain, is not. London and Paris are far to the north of Chicago, or even Montreal. The reason that so many European settlers in the New World died in their first winter wasn’t just that they were ignorant of the local foodstuffs, but that it was much, much colder on this side of the Atlantic and the moderating warmth of the Gulf Stream.
The Atlantic circulations were already expected to be in danger from melt waters coming off of Greenland. That the effect is already being seen near Antarctica, which was regarded as much more stable, is very much not a good thing.