Tag Archives: sun

What to Expect from the Arctic

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Guest science writer KarenRomano Young reports from the ICESCAPEmission:

The U.S. Coast Guard Cutter Healy, our chunky red-and-white icebreaker, sits at the gates of the Arctic Ocean. In the wee hours this morning, the sun set and quickly rose again, and a rainbow stretched up into low clouds. The ICESCAPE mission had reached station 5 of a seven-stop transect of the Bering Strait, between Fairway Rock — resembling Kong Island, but with pointy ears — and Little Diomede (U.S.) — something like the “Cliffs of Insanity” in The Princess Bride. Close by is Big Diomede (Russia), topped with fog.

Movie references aside, this is a dramatic spot in which to find yourself when you wake up in the morning — or in the evening, as is the case for the half of the science crew working the night shift to process the samples.

It seems that no matter how many times a scientist has been to sea, it doesn’t get old. Greg Mitchell (below right), a specialist in ocean optics from the Scripps Institution of Oceanography, reckons he has spent about four years of his life aboard ships. His first trip to the Arctic was in 1987, his first year at Scripps. Mitchell’s research has taken him all over the world — to Antarctica and back again many times — but he hasn’t been inside the Arctic Circle since 1989. He expects change. Greg Mitchell

Observing the system…..and how it interacts with the edge of the sea ice…..and what’s going on with the ice melt…..and how it affects the ocean…..those principles won’t be any different than they were 20 years ago. “What we’re clearly seeing is that the sea ice is reducing more and more all the time,” said Mitchell. “This means less sunshine reflecting off the ice back into space, and more getting into the ocean.”

He expects the increase in sun-light on the sea to do three things:

  • “The light that’s not reflected will heat the ocean, accelerating the warming and accelerating the melting of the sea ice.”
  • “As the ocean warms it becomes more stratified. If you dive in a lake in the summertime, it’s warmer at the surface. But as you dive down, you feel the cold. That’s because the warm water is lighter than the cold water, and it stays at the surface. That’s thermal stratification. As you warm the ocean, it’ll stratify more and that will create a warm layer with a lot of light for algae to bloom (as long as they have nutrients).”
  • “More light in the ocean should cause more total photosynthesis in the Arctic, so we’ll lose habitat for polar bears but we’ll gain habitat for plankton.”

Like the rest of us, Mitchell is concerned about that. “I’m not saying it’s a good trade off. I think we should leave things alone. But the system’s changing, and as it changes we don’t know what the consequences of those changes will be. It’s hard to say what we could do. What we really need to do is to find a way for humans to have smaller footprint on earth. So we need to understand the processes better and then we need to model it.”

That’s why he’s here.

Mitchell, along with his group from Scripps, is involved in ground-truthing the optical properties of the Arctic Ocean (photos at the top and bottom of this post). That is, he’s helping to ensure that what they see at the surface squares up with the methods NASA satellites use to assess ocean color, an indicator of the level of chlorophyll and, by proxy, phytoplankton. NASA’s satellites measure the color of the ocean by flying over the earth and picking up blue, blue green, and green. If there’s not a lot of algae, the ocean is blue. If there is a lot of algae, the ocean is green.

But color is just one way of looking at phytoplankton levels. In order to truly assess the situation — for example how much carbon dioxide the phytoplankton are taking in – scientists need to assess the processes at work in the sea. “The optics don’t tell us this, so we have to take water samples, process the water, and then relate that to the optics we measure from the ship,” Mitchell said.

The global mapping you can see on the NASA site uses mathematical equations developed from the shipboard work. Satellite validation and calibration is based on the findings of scientists who go to sea and study the water to see what’s living there. Mitchell’s research group claims responsibility for about 20 percent of the global observations used by NASA for their models to convert satellite-measured optical measurements to chlorophyll estimates.

lowering gear from the Healy

The data contributes to models that allow prediction of primary production — the growth and health of organisms — under various conditions. Mitchell’s instruments include a small optical profiler — a fish-shaped instrument lowered from the Healy’s bow — and an optical package of instruments that measure water properties when it is lowered from the powerful A-frame at the stern.

“As ecologists, we don’t want to just know what color the ocean is,” he said. “We want to know how much plankton there is.” He walks to the edge of the ship and looks over the rail. “Now what we’re seeing out here is green water. There’s a lot of chlorophyll.” That means a strong pulse of phytoplankton, busy photosynthesizing the extra sunlight.

All photos shot by and courtesy of Karen Romano Young

Beautiful Radiance

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Karen Romano Young (right), a freelance writer and illustrator embedded with NASA’s ICESCAPE field campaign, sent this report from an icebreaker headed to the Arctic. You can follow the expedition on the ICESCAPE blog

Here on the U.S. Coast Guard Cutter Healy, heading north toward sampling stations in the Bering Strait, there’s plenty of light — a beautiful radiance nearly around the clock. Since arriving in Alaska on June 12, I’ve only awakened once in the middle of the night to find it dark. Last night at nearly 11 p.m., I sat drinking tea in front of my porthole, and saw a rainbow descend between strips of clouds into the grey Bering Sea. We’re in the land of the midnight sun, and as we continue north the night light will grow longer. It’s the opposite of the conditions that lead to Seasonal Affective Disorder down south where I come from (Connecticut!) For me, it’s joy.

Up here where there used to be more ice, the radiance is, well, radiating. This is the key: the Arctic ice reflects sunlight back into space. If there’s no ice, the sunlight goes into the water, warming it, and creating an environment in which phytoplankton — tiny plantlike algae at the water’s surface — can thrive. There’s less ice because our atmosphere is trapping greenhouse gases — carbon dioxide and methane — and the result is a warming Arctic.

Many of the 40-plus scientists participating in ICESCAPE, a NASA-led research cruise, are involved in studying the effects of sunlight. ICESCAPE stands for Impacts of Climate Change on the Eco-System of the Arctic Pacific Environment, and its purpose is to bring ice scientists and ocean scientists together to gather a greater understanding of the conditions in the Bering, Chukchi, and Beaufort Seas.

Who better to begin a discussion of the sun’s warming effects than a University of Washington scientist named Bonnie Light? Light has been working in the Arctic Ocean since 1998 when, as a grad student, she boarded the Canadian icebreaker Des Grosseilliers, which had purposely pulled up to the edge of the 1997 autumn ice and got fro-zen in through the 1998 thaw. That was the SHEBA (Surface Heat Budget of the Arctic) project, designed to increase understanding of the Arctic system.

Getting frozen in to the ice was a nod to the so-called “father of Arctic science,” Fridtjof Nansen, who purposely did the same a century earlier to prove his theory that the ice cap drifted. One of the purposes of SHEBA was to provide a baseline for under-standing Arctic conditions that might be affected by global warming. Several other scientists aboard ICESCAPE also participated in SHEBA, including Bonnie’s group leader and co-chief scientist Don Perovich.

The flight to the SHEBA site from Barrow, Alaska — the northernmost city in the United States — was the first time Light saw sea ice. “I’d calculated the total square kilometers that the Arctic ice cap occupies many, many times,” she said, “but to be in a little air-plane and fly over it and just see it…this endless stretch of pack ice was really striking.” During the ICESCAPE cruise she is eager to explore the western coast of Alaska for the first time.

“People have told me that the sea ice in the Chukchi Sea has already begun to open up and is very loose this year,” Light says. She expects to be one of the “ice party,” the group of scientists that descends from the deck of the Healy (shown left), via a basket dangling from a crane, to work on the ice. “I don’t know if we’ll get out on it or not. We’ll have to just wait and see what it looks like when we get there. It’s something I’m not sure a satellite can tell you.”

Light is interested in the physics of solar irradiance – what happens to the sun’s light in ice on a small-scale, but also at the larger scale of the melt ponds that form atop sea ice. One of the experiments she’ll conduct involves a comparison of how sun radiates through bare ice and ice that has a melt pond on top. “We already know that melt ponds make really good skylights,” she says. But could they accelerate melting of already-melting ice, hastening the tipping point between ice cover and open sea? Bonnie Light’s ICESCAPE experience could tell.

Image Information: Courtesy of the U.S. Coast Guard (bottom left) and Karen Romano Young (top right).

Fun with Aureoles and Aerosols

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      Credit: Earth Science Picture of the Day/Rob Rathkowski

Earth Science Picture of the Day (EPOD)
recently ran a series of photos that illustrates nicely the impact that small airborne particles called aerosols can have on light.

As EPOD notes, the size of an aureole — the halo-like circle that appears around the sun when viewed through a haze or mist — depends on the amount of aerosol in the air. More aerosols mean more light is scattered, which produces larger aureole). Since most aerosols are concentrated near Earth’s surface, the aureole at sea level appears much larger than it would high on a mountain peak. You can try this experiment yourself to get a sense of the aerosol load in the air you’re breathing.

Aerosols are a major preoccupation for climate scientists as the particles—including dust, ash, sea salt, soot, and industrial pollutants—can scatter light and affect Earth’s energy balance. Infusions of ash and sulfate from volcanic eruptions, for example, are capable of cooling global temperatures by 0.3 degrees Celsius. Likewise, sulfate aerosols from factories and power plants can mask global warming somewhat and are often bandied around as possible components of geoengineering schemes.

Want to learn more about how aerosols scatter light? EPOD has another post on the topic that compares aureoles at sunsets in the Netherlands before (below left) and after (below right) the arrival of a massive volcanic ash cloud from the eruption of Eyjafjallajökull. Also, for optics aficionados, a site called Atmospheric Optics will walk you through a number of interesting examples of aerosols and atmospheric water and ice scattering light.

        Credit: Earth Science Picture of the Day/Kosmas Gazeas
— Adam Voiland, NASA’s Earth Science News Team