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| It’s early summer 1994, 12:34 p.m. local time, and the
Canadian Twin Otter research aircraft is flying 20 meters (about 65
feet) above the boreal forest canopy near Prince Albert, Saskatchewan.
Scientists are busy measuring the exchanges of gas and heat between the
forest and the lower atmosphere when the plane flies into an unseen
vortex of intense, heat-induced winds—a "dust devil," as these phenomena
are called in desert regions of the southwestern United States.
Instruments aboard the aircraft clock the wind shift across the wall of
the vortex at nearly 20 meters per second (45 miles per hour) and the
updraft at the center of the vortex at 11 meters per second (25 miles
per hour). Without warning, the strong winds catapult the Twin Otter
upward and sideways in a few seconds. Fortunately, the pilot is able to
stabilize the aircraft and return the plane and crewmembers safely to
the ground, albeit a little shaken up. That summer the Twin Otter flew
into eight such vortices in four months (MacPherson and Betts, 1997).
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by David Herring
Boreal Ecosystem Series · Introduction to BOREAS · The Mystery of the Missing Carbon · Should We Talk About the Weather? · Evolving in the Presence of Fire Coming Soon:
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 As an integral part
of NASA’s Boreal Ecosystem-Atmosphere Study (BOREAS)
measurement strategy, a team of researchers, including Alan K. Betts from
Vermont, used instruments aboard the Twin Otter and on forest towers to
measure interactions between the forest and the lower atmosphere. During
each season from 1994—97, data were collected on the
exchanges of heat, momentum, carbon dioxide, ozone and water vapor to
gain insights into the ongoing "dialogue" that occurs between the boreal
ecosystem and the atmosphere. Their goal is to understand how changes
in air temperature, moisture and carbon dioxide levels may impact the
boreal ecosystem and what role the boreal forest plays in global-scale
climate changes.
One of Betts’ primary research objectives was to quantify the amount of heat emitted and light reflected by the boreal forest. The vortices of hot air that occasionally sent his colleagues on the Twin Otter "thrill rides" reinforced what other measurements were showing—the boreal forest stores and releases significantly more heat to the atmosphere in the spring and early summer than scientists previously thought.
The data used in this study are available in one or more of NASA's Earth Science Data Centers. |
The boreal forest canopy as seen from the top of a tower about 30 meters above the ground. To measure the fluxes of heat and gases exchanged between the forest ecosystem and the lower atmosphere, the BOREAS team mounted sensitive instruments on these towers at multiple sites in the Canadian boreal forest. Measurements from these flux towers were complimented by measurements made aboard the Twin Otter research aircraft flying at roughly this altitude. (Photograph courtesy BOREAS project) | ||
 by David Herring and Robert Kannenberg |
Boreal Ecosystem Series · Introduction to BOREAS · The Mystery of the Missing Carbon · Should We Talk About the Weather? · Evolving in the Presence of Fire Coming Soon:
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| Scientists estimate that between 1 and 2 billion metric tons of carbon per year are "missing" from the global carbon budget. Or, more precisely, they cannot account for the location of between 15 and 30 percent of the carbon released into the atmosphere each year from fossil fuel burning (Sellers et al. 1997). Worldwide, humans annually release about 7 billion tons of carbon. Of that amount, 3 billion tons remain in the atmosphere, 2 billion tons are absorbed into the ocean, and…the rest? Scientists assume land vegetation absorbs the rest, but they don’t know exactly where or how much. |
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The main motivation for studying Earth’s global carbon cycle is to enable scientists to predict future levels of carbon dioxide in the atmosphere. According to Steven C. Wofsy, an environmental scientist at Harvard University, the ability to predict carbon dioxide levels is important if Earth scientists are to answer fundamental questions like how much will global temperatures rise over time, and how will this affect other aspects of Earth’s climate? "Are those 2 billion tons of carbon missing permanently, or
temporarily?" Wofsy asks. "You’re at a loss to predict if you
don’t know why the carbon is disappearing and if it will stay
gone."
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Ecologist Joe Berry checking instruments at the top of a tower in Saskatchewan, Canada. He is surrounded by 120-year-old black spruce, one of the predominant trees in the boreal forest. (Photograph courtesy BOREAS project) | ||
The data used in this study are available in one or more of NASA's Earth Science Data Centers. |
The circumpolar range of the boreal forest. From Hare and Ritchie (1972) (Map courtesy BOREAS project) |
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Everyone Complains About the Weather
In a concerted effort to solve the mystery of the missing carbon, NASA led an
interdisciplinary Boreal Ecosystem-Atmosphere Study (BOREAS) from 1994-97 that
spanned two Canadian provinces. Wofsy, along with members of 85 other science
teams from five nations, participated in the investigation. Their prime suspect
was the boreal forest. Named after Boreas, Greek god of the north wind,
boreal refers to the mostly evergreen forest that encircles the Earth at
high northern latitudes–between 43°N-65°N–occupying between
16 to 20 million square kilometers of the Earth’s land surface. Could this
cold, mostly coniferous ecosystem be the culprit?