Three weeks ago I suggested the West Antarctic ice sheet will probably melt soon, as it did during the previous interglacial period 125,000 years ago, raising ocean levels by at least 25 feet. Today, I turn to the Arctic.
I've followed climate disruption since 1975 when I began including it in my physics course for nonscientists, and by now I've read more books about it than I care to count. Nevertheless, I found American journalist and adventurer Dahr Jamail's recent book "The End of Ice" a page-turner and well worth my time.
Jamail notes early on that atmospheric carbon (i.e., carbon dioxide) concentrations have varied from 180 to 280 ppm (parts-per-million) as Earth cycled through successive glacial and interglacial periods during the ice ages of the past 2 million years. Thus a 100 ppm shift in carbon levels is linked with roughly 100 feet of sea level rise. Today's carbon level is 410 ppm, 130 ppm higher than normal for interglacial periods. Thus as global ice "equilibrates" to that higher carbon concentration, we can expect 130 feet of sea level rise -- unless we find a feasible way to remove carbon from the atmosphere.
The book's dramatic final chapter is set in the Arctic. Jamail's base for his Arctic travels is Utqiagvik, formerly "Barrow," the most northern town on Alaska's north coast. During the flight to Utqiagvik, there was no ice in sight in the huge Beaufort Sea north of Alaska, even from 30,000 feet up on that clear day.
There's more afoot in the Arctic than the rapidly vanishing ice of Greenland and the Arctic ocean. Permafrost is thawing everywhere. Arctic permafrost soils store vast amounts of carbon totaling twice the carbon content of Earth's atmosphere. The poles are warming twice as fast as the rest of the planet -- 3.5 degrees Fahrenheit during the past 30 years. As permafrost melts, it releases its carbon, enhancing global warming, which melts more permafrost, etc. It's called "positive feedback." Fifty-five million years ago, similar permafrost feedback could have caused the "thermal maximum" that suddenly warmed the planet by 10 degrees.
The changes today in Alaska are dramatic, with 10-degree temperature increases at the permafrost's upper surface 5 feet underground, and 5 degrees even at 60 feet underground. Locals note that the permafrost layer, which once began a foot below the surface, now begins 5 feet underground. This is changing the terrain as melting permafrost causes the ground to sink, methane explosions and eruptions create giant craters, the ocean invades the land, and millions of dollars are spent shoring up infrastructure in a losing battle against melting land and rising seas.
Another greenhouse gas, atmospheric methane, has more than doubled during the past two centuries. Methane is one of the most potent global warmers, trapping 28 times as much heat per mass unit as carbon.
The Arctic ocean is mostly isolated from other oceans except in the north Atlantic, where warm mid-latitude waters that transport heat into the Arctic are strengthening due to climate disruption. The warming ocean causes permafrost beds in the Barents Sea to melt, releasing its methane and creating another vicious feedback circle. The Chukchi, Beaufort and Bering seas could follow suit. Scientists monitor the East Siberian Sea, where massive methane emissions are expected within two decades. Methane "plumes" bubbling up from the ocean floor have recently increased by factors as large as a thousand. Due to feedbacks, releases in one region can trigger releases in other hotspots.
Gradual methane increases are occurring across much of the Arctic, accelerating warming. As the Arctic warms, the temperature difference between equator and pole will decline. Since this thermal gradient, along with Earth's rotation, drives the natural west-to-east transport of air, the declining gradient will cause massive climate shifts everywhere.
The East Siberian Sea covers the largest undersea shelf in the world, comprising 8 percent of the world's total continental shelf. This shelf holds a significant fraction of the world's methane hydrates (methane compressed into ice). As they warm, they abruptly emit their methane, which could result in globally significant emissions in a matter of minutes.
This is no joke, folks. We're in trouble.
Jamail, a nature lover, mourns. He concludes we are probably headed for catastrophic changes including a die-back to one or two billion caused by, among other things, food shortages due to high temperatures in equatorial and temperate zones.
But such speculations are always highly suspect. Certainly, fast vigorous action can improve our chances. In three weeks, I'll discuss solutions.
Commentary on 02/26/2019