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Water Environment & Technology (WE&T) is the premier magazine for the water quality field. WE&T provides information on what professionals demand:
cutting-edge technologies, innovative solutions, operations and maintenance, regulatory and legislative impacts, and professional development. |
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October 2007, Vol. 19, No. 10 |
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Waterline
Glaciers, Ice Caps Expected To Be Major Contributors to Sea-Level Rise
Ice loss from glaciers and ice caps is expected to cause more global sea rise during this century than the massive Greenland and Antarctic ice sheets, according to a new University of Colorado (UC) at Boulder study.
The research, primarily funded by the National Science Foundation and the National Aeronautics and Space Administration, concluded that glaciers and ice caps currently are contributing about 60% of the world’s ice to the oceans, and the rate has been markedly accelerating in the past decade, said emeritus professor Mark Meier of UC–Boulder’s Institute of Arctic and Alpine Research (INSTAAR) and lead study author. The contribution is currently about 417 km³ (100 mi³) of ice annually — a volume nearly equal to the water in Lake Erie — and is rising by about 12.5 km³ (3 mi³) per year.
In contrast, the UC–Boulder team estimated that Greenland is now contributing about 28% of the total global sea rise from ice loss, and Antarctica is contributing about 12%. Greenland is not expected to catch up to glaciers and ice caps in terms of sea-level rise contributions until the end of the century, according to the study.
A paper on the subject appears in the July 19 issue of Science Express, the online edition of Science magazine. Co-authors include UC–Boulder INSTAAR researchers Mark Dyurgerov, Ursula Rick, Shad O’Neel, Tad Pfeffer, Robert Anderson, and Suzanne Anderson, as well as Russian Academy of Sciences scientist Andrey Glazovsky.
“One reason for this study is the widely held view that the Greenland and Antarctic ice sheets will be the principal causes of sea-level rise,” said Meier, former INSTAAR director and professor in geological sciences. “But we show that it is the glaciers and ice caps, not the two large ice sheets that will be the big players in sea rise for at least the next few generations,” he said.
The accelerating contribution of glaciers and ice caps is due in part to rapid changes in the flow of tidewater glaciers that discharge icebergs directly into the ocean, according to a news release. Many tidewater glaciers are undergoing rapid thinning, stretching, and retreat, which cause them to speed up and deliver increased amounts of ice into the world’s oceans, said UC–Boulder geology professor Robert Anderson.
Water controls how rapidly glaciers slide along their beds, Anderson said. When a glacier with its “toe” in the water thins, a larger fraction of its weight is supported by water, and it slides faster and calves more ice into the ocean at the glacier terminus.
“While this is a dynamic, complex process and does not seem to be a direct result of climate warming, it is likely that climate acts as a trigger to set off this dramatic response,” said Anderson, also an INSTAAR researcher.
The human impact of this accelerated sea-level rise could be dramatic. The team estimated accelerating melt of glaciers and ice caps could add from 102 to 241 mm (4 to 9.5 in.) of additional sea-level rise globally by 2100. This does not include the expansion of warming ocean water, which could potentially double those numbers. A 0.3-m (1-ft) sea-level rise typically causes a shoreline retreat of 30 m (100 ft) or more. The World Bank (Washington, D.C.) estimates that about 100 million people now live within about 0.9 m (3 ft) of sea level.
The team summarized satellite, aircraft, and ground-based data from glaciers, ice caps, the Greenland ice sheet, the West Antarctic ice sheet, and the East Antarctic ice sheet to calculate present and future rates of ice loss for the study.
For more information, see the INSTAAR Web site at instaar.colorado.edu.
New Irrigation System ‘Listens,’ Saves Water
Is it true, as some “green thumbs” claim, that talking to our plants really helps them thrive?
If you ask U.S. Agricultural Research Service (ARS) scientist Robert Evans — who’s built a state-of-the-art irrigation system that uses the latest in wireless technology for “communicating” with his crops — the answer is probably “yes.”
An agricultural engineer, Evans isn’t so much talking as listening to plants, according to an ARS news release. Evans is using a prototype irrigation system he and colleagues developed that comprises Bluetooth technology, sensors, weather stations, and traditional irrigation equipment. According to Evans, innovations such as this system are necessary if society is to better manage its diminishing freshwater supplies — an estimated 60% of which are currently used for irrigation worldwide.
Evans works at the ARS Northern Plains Agricultural Research Laboratory in Sidney, Mont. He and ARS research associate James Kim built the novel irrigation system with two goals in mind: to increase crop survivability, and to save precious water and fertilizer.
So how does their technology work? Scattered across a field are sensors that, like little thermometers, constantly take the temperature of the plants and soil around them. Bluetooth enables the sensors to transmit data wirelessly back to the base station, which then instructs individual sprinkler heads exactly how much water to dole out, the news release states.
The new system washes away one of the biggest challenges facing irrigators: the endless variation in soil types that can exist across a field.
For example, clay and sandy soils have nearly opposite behaviors: One practically repels water, while the other sucks it in readily. But in a particular field, these soils may be close neighbors, leading to an inevitable underwatering or overwatering scenario.
However, according to ARS, Evans’ and Kim’s system treats a field not as a one-size-fits-all soil zone, but as a collection of smaller, individual plots, each with its own set of organic idiosyncrasies.
For more information, see the July issue of Agricultural Research at www.ars.usda.gov/is/AR/archive.
Study Identifies Critical Link Influencing Ocean’s Ability To Store Carbon Dioxide
A major study by the Woods Hole Oceanographic Institution (WHOI; Woods Hole, Mass.) has shed new light on the dim layer of the ocean called the “twilight zone” — where mysterious processes affect the ocean’s ability to absorb and store carbon dioxide accumulating in the atmosphere.
The results of two international research expeditions to the Pacific Ocean, published April 27 in the journal Science, show that carbon dioxide — taken up by photosynthesizing marine plants in the sunlit ocean surface layer — does not necessarily sink to the depths, where it is stored and prevented from re-entering the atmosphere as a greenhouse gas. According to a WHOI news release, carbon dioxide transported to the depths on sinking marine particles is often consumed by animals and bacteria and recycled in the twilight zone — 100 to 1000 m below the surface — and never reaches the deep ocean.
The researchers found that only 20% of the total carbon in the ocean surface made it through the twilight zone off Hawaii, while 50% did so in the northwest Pacific near Japan, the release states.
The twilight zone acts as a gate, allowing more sinking particles through in some regions and fewer in others, complicating scientists’ ability to predict the ocean’s role in offsetting the impacts of greenhouse gases, WHOI says. It also adds a new wrinkle to proposals to mitigate climate change by fertilizing the oceans with iron — to promote blooms of photosynthetic marine plants and transfer more carbon dioxide from the air to the deep ocean.
“The twilight zone is a critical link between the surface and the deep ocean,” said Ken Buesseler, a biogeochemist at WHOI and lead author of the new study in Science, co-authored by 17 other scientists. “We’re interested in what happens in the twilight zone, what sinks into it, and what actually sinks out of it. Unless the carbon that gets into the ocean goes all the way down into the deep ocean and is stored there, the oceans will have little impact on the atmosphere and hence, climate.”
Buesseler was a leader of the project, funded primarily by the National Science Foundation (Arlington, Va.), called VERTIGO (VERtical Transport in the Global Ocean). More than 40 biologists, chemists, physical oceanographers, and engineers from 14 institutions and seven countries participated in the two VERTIGO cruises in 2004 and 2005 to investigate how marine plants die and sink, or are eaten by animals and converted into sinking fecal pellets.
These sinking particles, often called “marine snow,” supply food to organisms deeper down, including bacteria that decompose the particles, according to the press release. In the process, carbon is converted back into dissolved organic and inorganic forms that are recirculated and reused in the twilight zone and that can make their way to the surface and back into the atmosphere.
While many studies have investigated the surface of the ocean, little research has been conducted on the carbon cycle below, according to WHOI. The VERTIGO team examined a variety of processes to open a new window into the difficult-to-explore twilight zone. They used a wide array of new tools, including an experimental device that enabled them to collect marine snow falling into the twilight zone.
The problem is that particles sink slowly but are swept sideways by ocean currents traveling many thousands of meters per day, the press release states. To collect sinking particles, scientists use cones or tubes that hang beneath buoys or float up from the sea floor. That, Buesseler said, “is like putting out a rain gauge in a hurricane.”
Buesseler and WHOI engineer Jim Valdes developed Neutrally Buoyant Sediment Traps — free-floating devices that sink to a programmed depth within the twilight zone and neither sink nor rise. They are swept along with the currents for several days, collecting particles, and are programmed to resurface, transmit their position via satellite, and wait for recovery, more than 16 to 32 km (10 to 20 mi) away from where they were dropped into the ocean.
“Only with continued observations and new techniques can we hope to understand this often overlooked layer in the ocean that is as important to the global carbon cycle as the sunlit surface layer where atmospheric carbon dioxide first enters the ocean,” Buesseler said.
Contact Buesseler at kbuesseler@whoi.edu.
©2007 Water Environment Federation. All rights reserved. |
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