Take in the companion radio feature and slide show at The California Report weekly magazine. Gretchen’s slide show also appears below.

Photo: Gretchen Weber

During the two weeks I spent in the Arctic at Toolik Field Station this summer, there was a lot of talk about positive feedbacks and how what happens in the Arctic can affect the entire planet. Thawing permafrost, which I explore in my radio piece for The California Report, is cause for some of the greatest concern.

Another is the loss of sea ice. Mean summer temperatures in the Arctic have risen about three degrees Fahrenheit since 1960, and summer sea ice is shrinking more than 11% per decade.  This year ranks third for the minimum Arctic summer sea ice extent since satellite record-keeping began in 1979.   2007 and 2008 hold the records, and 2009 is in fourth place.

Shrinking sea ice matters not just because it’s an indication of warming, but also because it can accelerate it.  Sea ice keeps polar regions cool by reflecting sunlight and heat, which helps moderate the global climate system. When sea ice isn’t there, the sun hits the surface of the Arctic Ocean instead.   The ocean is relatively dark in color, so instead of reflecting 80% of the sunlight, it absorbs 90%.  This heats up the ocean and the Arctic–which, of course, melts more ice.

Another potential feedback scientists are looking at is “shrubification” (try tossing that one into a conversation), but whether it’s a positive or negative feedback remains up for discussion. As the Arctic warms, the boreal forest is moving north and the tundra itself is changing.  The vegetation is shifting to more woody and leafy plants, like birch, and this change could have varying effects on the climate system. On one hand, more leaves mean more photosynthesis, which could mean that the Arctic vegetation could increase its CO2 uptake, acting as a carbon sink by absorbing CO2 from the atmosphere. On the other hand, increased leafy vegetation would make the landscape darker, which would make it absorb more heat, and that warming could potentially offset any effects of increased CO2 uptake.  Also, the woodier, leafier plants can create protected areas where snow can gather, insulating the ground and keeping it warm.  This too, could have warming effects that offset any additional photosynthesis.

“The takeaway is that it’s complicated, and there’s a potential for large positive feedbacks if things continue in the direction they’re going,” said Donie Bret-Harte, a biologist at the University of Fairbanks and the Associate Field Director at Toolik. “And those large positive feedbacks are things that we won’t be able to control.”

Gretchen Weber in the Valley of the Thermokarsts, ready for the mosquitoes. (Photo: Susan Moran)

Bret-Harte said that some scientists are concerned that the Earth may pass a tipping point, and then it won’t matter how much humans recycle their waste or invest in renewable power or reduce their emissions from burning fossil fuels.  The positive feedback loop will take on a life of its own.

“It’s important to remember that these natural feedbacks that come from melting ice and snow and permafrost are not things we can legislate a solution to,” she said.

“If, they start going, and things get warming, and everything starts to thaw, you can’t say, ‘Well, let’s have a treaty and we’ll stop the thawing,’ because that won’t happen.”

One of the positive feedbacks that scientists are most concerned about in the Arctic, is thawing permafrost, which I explore more in-depth in my radio feature.  With that is a slide show from my reporting trip to “The Valley of the Thermokarsts,” a region on the North Slope of Alaska’s Brooks Range, where researcher Andrew Balser digs into the permafrost for clues about why these areas where chunks of permafrost thaw, form where they do.

Jeff Dozier approaches an instrument tower on Mammoth Mountain. Photo: Molly Samuel

When Jeff Dozier, a hydrologist at UC Santa Barbara, goes to work, he gets to enjoy quite a view. His snow lab is perched halfway up Mammoth Mountain in the central Sierra. We took a gondola to get up there; the other passengers were skiers and snowboarders itching to get out on the freshly fallen snow.

But the instrument platform from which we enjoyed views of the White Mountains is really only half the story. Dozier’s computer lab has much less of a view. In fact, it has no view. It’s buried under the snow, accessible only through what he calls a “Santa Claus entrance” (in the picture above, you can see the entrance–it’s the white tubular “chimney” extending down into the snow from the center of the platform).

The snow lab, operated by both UCSB and the U.S. Army Cold Regions Research and Engineering Laboratory (CRREL), uploads information about the snowpack to a website every fifteen minutes. You can see nearly real-time readings on, among other things, snow depth, temperature, humidity, and radiation.

Dozier in the computer lab. Photo: Molly Samuel

Radiation is an important one. Instruments called radiometers are mounted on the tower. Some point up, measuring the radiation coming from the sun; others point down, measuring how much is reflected back to the sky by the snow.

“Albedo” is the measurement of how reflective the snow is. Something completely white that reflects all of the sun’s energy has an albedo of one; something black, that absorbs all the energy, is zero. Bright, freshly fallen snow has a high albedo, typically above 0.8.

Even if the term is new to you, albedo is probably a familiar concept. As I reported for KQED’s The California Report this morning, Hans Moosmuller of the University of Nevada’s Desert Research Institute explains it in terms of outfits: on a sunny day, if you wear a black sweater you’ll be warmer than if wear a white one. You may notice it with roofs, too. I grew up in Atlanta, in a house with a black roof. Before my parents got an air conditioner, the upstairs bedrooms were unbearable in the summer. If we’d had a white

These radiometers measure radiation coming from the sun. Photo: Molly Samuel

roof, it would have been a little more bearable (though I can’t say it would have helped with Atlanta’s other charming summer attributes, humidity and mosquitoes).

The color sweater you wear has no bearing on the earth’s climate. Roof color could have an effect on a large enough scale. What really matters are the huge swaths of dark and light that cover the globe: ocean and snow.

When warming causes sea ice near the poles to melt faster, areas that had a high albedo (ice is very reflective) become  areas with a very low albedo (the blue ocean absorbs more radiation than forests or plain dirt). Moosmuller says it creates a feedback loop. The more dark spots there are, the more radiation is absorbed. So melting speeds up, and warming increases, exposing even more dark areas, and so on.

Pollution plays an important role that’s coming under increasing scrutiny. Deposits of soot or dust make the snow darker, so it melts faster, exposes more dark ground, and there’s that feedback loop again. In the Himalayas soot, also known as black carbon, from stoves, tailpipes, factories, and fires is having a measurable impact.

In the Rockies, there’s a similar problem caused by dust kicked up from ranches. Tom Painter of the University of Utah says the snow in the Colorado River Basin melts a full month earlier than normal. The difference the dust makes is so drastic, Painter says, that “We’re in an entirely new regime for snow melt…it would be like if we started measuring climate impacts fifty years from now.”

No one has yet done a long-term study on the effects of dust and soot on the Sierra Nevada snow pack. Moosmuller says he’s beginning to look into it now. In the summer, black carbon drifts into the mountains from California’s cities, ports, highways and farms in the Central Valley. Tony Van Curen, in a research project at UC Davis, has found that soot blows over from Asia, too.

There is good news in all of this: Black carbon, unlike most greenhouse gases, lingers in the atmosphere only for a couple of weeks. So reducing emissions could have a relatively quick impact.

Listen to the radio piece.