24th August 2012
"Human-induced warming of the climate system is widespread."
- Intergovernmental Panel of Climate Change, IPCC), Fourth Assessment Report, 2007
"The climate is an angry beast, and we’re poking it with sticks."
- Wallace Broecker
“See that hummocky bit off there?” said Piers at the helm. “I won’t get near that. It’d sink us.”
We’re up at 76°03’ N by 009°03’ W, well over 500 miles north of the Arctic Circle in thick sea ice of “seven-tenths” coverage, as the ice pilots say. A great mass of it is drifting south at about thirty miles a day in the East Greenland Current against a light twelve-knot southerly. (Mariners designate current by the direction toward which it’s setting, wind by the direction from which it’s blowing.) The sky is cloudless, still another gorgeous day, only Earth’s curvature to limit visibility. However, the ice was slowing the CTD work. In open water, steaming at eleven knots, we’d be arriving at even the most widely spaced station in half and hour. Now at two knots, it was taking two hours, with the promise of still further delay. A ragged rectangle of shore-fast ice twelve miles long that split away from Dove Cove on east Greenland’s coast has drifted overnight right across the CTD line. We knew that thanks to a remarkable system that delivers hourly satellite photographs to a computer on the bridge. Without it, when the ship encountered such a large, impregnable barrier, the officer on watch could not know its true size or which way to turn to get around it. However, absent this sparkling weather, the system would be useless, because the satellite can’t see through cloud cover.
The ice ahead looks pretty thick to me, only slender bands of blue slicing through the jumbles of ice.
“Yes, well, you can’t always tell because of the foreshortening effect with distance,” Piers replied. A big, multi-year floe lay athwart his course to the next station. “There’s an open lead to port. I could go around the thing, but the lead could close by the time I got there. We’ll see.” He decides to go straight. As the floe slips beneath the over-hung bow, we wait for the waterline impact. The ship jolts, rises slightly, then plows through with little ado, except that her bow lurches to port, even though Piers has the helm hard to starboard. (The helm is short, knobbed lever; spoked wooden spoked wheels have gone the way of sextants.)
“They actually pay me to do this. Outrageous.” he says in his deadpan, rapid-fire delivery.
Leaning against his chair in which he never sits, the Captain stands by watchfully. It isn’t that he doesn’t trust his mates; it’s that burden of command—if something untoward happens, it’s the Captain’s fault even if it wasn’t. He tells me that Arctic Ice tends to be harder than Antarctic ice, because there’s more multi-year ice here—you can distinguish it from first-year ice by the turquoise-to-lapis color left after the salt has had time to leech out—and because of the active compression taking place in the close quarters.
It’s Wednesday morning now. They completed the CTD line overnight before the ice tightened up to the present 9/10s coverage. We’re not exactly stuck in it, but we were for a time last night, down to backing and ramming. Now we’re hardly making good a knot over the bottom, weaving in a suture pattern around our desired heading. The satellite imagery shows open water to the east, and the Captain wants to fetch it, then head north to the next and final CTD line. I’m hanging around underfoot on the bridge trying to learn something about ice piloting from Robert and the Captain between whom there is over sixty years of hard-water experience.
“One thing you want to do in these conditions,” said Robert, “is watch your wake.” I followed him to aft bridge windows. “When there’s a lot of pressure, your wake closes right up behind you.” Ours didn’t.
'But now we’ve learned that there is that darker side to our love affair.'
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One might look out over this sea of ice, watch the ship strain to overcome it and wonder, could the Arctic actually be melting? But that’s like going out in your backyard thrice a week in July with a thermometer, recording temperatures lower than last July, and concluding that the world is cooling (or vice versa). Weather and climate are of course not the same thing. Climate understanding requires long-term measurements, but we have them now. And the physics couldn’t be simpler: Carbon dioxide is a heat-trapping gas; we’ve known that since 1896 when the Swedish scientist Svante Arrhenius demonstrated the fact. Since the birth of the Industrial Revolution, we’ve dumped ever-increasing amounts of the stuff into the atmosphere, and now that they can measure carbon in the atmosphere, scientists have consistently correlated its increase directly to rising global temperature (see the Keeling Curve).
But let’s stick to the Arctic. Assaulted from above by the warming atmosphere, from the edges by the warming sea, the Greenland Ice Sheet is shedding some 200 gigatons of freshwater ice into the surrounding seas—each year. The area of land-ice coverage has shrunk by one-fifth since 1966. From the mid-1970s through the close of the century, the minimum extent of polar pack ice declined by 9%. Then in 2007 that figure suddenly doubled. Why? Scientists concluded that every natural force—warm water, clear skies, warmer air—had collaborated with abnormal unity to cause the melt back; it looked like an anomalous year, a natural variation in weather. If that seemed a relief, it didn’t last long. In 2011, a “normal” year by all the established measurements, sea ice extent declined by nearly the same alarming extent. That could be the new normal if a well-researched series of “positive feedbacks” clamp down.
The Arctic is particularly vulnerable to the warming in part because of the highly efficient transfer of heat northward from the tropics aboard the very Gulf Stream System we’ve been discussing, which, among other factors, helps produce an annual average temperature of -15° C. Compare that to the average annual Antarctic temperature of -57° C., and we see how only a few unusually warm summers can set off torrents of melt in the Arctic. And once started, a few abnormally cold winters will not right the imbalance. No, the albedo effect perpetuates the warming. Albedo is a measure of reflectivity. White ice reflects the sun’s heat (it has a high albedo), but when ice melts, the exposed dark sea absorbs heat, causing more melting, exposing more dark water, and around again in a feedback death spiral.
No scientist is willing to say categorically what will result from continued melting (sea-level rise, eroding coastlines, aggravated water-cycle disruption, extinctions, wholesale changes in the Meridional Overturning Circulation, release of methane from permafrost melting, all of the above?), but no real scientist denies that the world is warming. The fine historian of science Naomi Oreskes recently counted all the peer-reviewed scientific journals dealing directly or indirectly with climate change. She found tens of thousands. And then she compared them to the number of papers that proved that climate change was nonexistent. There were none. Zero. And though there may well be natural cycles in simultaneous play, no scientist denies that the prime cause of the warming is us. We love to burn carbon—to the tune of eight billion tons each year—and doing so has improved immeasurably the quality of our lives. But now we’ve learned that there is that darker side to our love affair.
* * *
Back on the bridge watching the strategy of nautical retreat from the ice, I’m feeling an inchoate anger. But at what? At us? For our potential to ruin this wonderful place? For our becoming a geophysical force? We didn’t mean to attain such power. But now we have, and we should know it, at least the rational among us. Maybe we’ll not find the political will to act. But we can’t say we didn’t know.
- Dallas
True information about the warming in the Arctic is profuse on the web and in shelves of books. For the above facts and figures I owe thanks to, among others, Realclimate.org, Spencer Weart’s excellent history of discovery, Global Warming and The Economist, June 16, 2012.
