Scripps Institution of Oceanography / University of California, San Diegohttp://www.eurekalert.org/pub_releases/ ... 112403.php
In a research first, an international team of scientists used Carbon-14 (14C) to shed light on why many abrupt climate warming events through the past 100,000 years have been accompanied by increases in atmospheric methane concentration. Their findings suggest that huge meltdowns of frozen methane-which some scientists had proposed as the cause of the methane increases, as well as significant contributors to the warming itself-most likely did not occur during the warming events.
Methane is one of the most important greenhouse gases. Measurements of 14C concentrations in the gas can tell scientists how a sample of methane originated but the difficulty of applying the procedure to ancient air samples had long dissuaded researchers from attempting it. Over the course of five years, Vas Petrenko of Scripps Institution of Oceanography at UC San Diego and his colleagues collected glacial ice from the edge of the Greenland ice sheet that formed around the times of two abrupt climate change events that took place 11,600 years ago and 14,500 years ago. They extracted the ancient air trapped inside bubbles in the ice to analyze the methane they contained.
Every ton of glacial ice the team melted down yielded only about 20 micrograms of ancient methane, a sample size typically too small for 14C analysis. The tiny sample sizes they had to work with required that the team push the boundaries of 14C measurement procedures.
The greenhouse gas, methane, has stopped growing in the global background atmosphere and could begin to decrease, CSIRO researchers announced today. http://news.psu.edu/story/205463/2006/0 ... ic-methane
"Methane is the second most important gas after carbon dioxide. It is responsible for a fifth of the enhanced greenhouse effect over the past 200 years," says Dr Paul Fraser, a chief research scientist at CSIRO Atmospheric Research.
"Over the past four years there has been no growth in atmospheric methane concentrations compared to a 15% rise over the preceding 20 years and a 150% rise since pre-industrial times. This is a very exciting result," says Dr Fraser.
The results are from Cape Grim, Tasmania, Australia's important greenhouse gas monitoring facility operated by the Bureau of Meteorology and CSIRO.
University Park, Pa. -- Icy chunks of frozen methane and water are not responsible for the periodic increases in atmospheric methane recorded in Greenland ice cores, according to a Penn State geoscientist.http://ucsdnews.ucsd.edu/archive/newsre ... tlands.asp
The ice core samples from the Greenland Ice Sheet Project II cover the last 40,000 years and present a picture of the Earth's climate over that time span.
An expansion of wetlands and not a large-scale melting of frozen methane deposits is the likely cause of a spike in atmospheric methane gas that took place some 11,600 years ago, according to an international research team led by Scripps Institution of Oceanography at UC San Diego.
Photo of Jeff Severinghaus
Scripps Institution of Oceanography geoscientist Jeff Severinghaus extracts blocks of ice from an ice sheet in Greenland. Severinghaus participated in an international analysis of methane trapped in the ice sheet to understand the origins of a sudden burst of atmospheric methane 11,600 years ago. Photo: Vas Petrenko, University of Colorado, Boulder
The finding is expected to come as a relief to scientists and climate watchers concerned that huge accelerations of global warming might have been touched off by methane melts in the past and could happen again now as the planet warms. By measuring the amount of carbon-14 isotopes in methane from air bubbles trapped in glacial ice, the researchers determined that the surge that took place nearly 12,000 years ago was more chemically consistent with an expansion of wetlands. Wetland regions, which produce large amounts of methane from bacterial breakdown of organic matter, are known to have spread during warming trends throughout history.
“This is good news for global warming because it suggests that methane clathrates do not respond to warming by releasing large amounts of methane into the atmosphere,” said Vasilii Petrenko, a postdoctoral fellow at University of Colorado, Boulder, who led the analysis while a graduate student at Scripps.
This is good news for global warming because it suggests that methane clathrates do not respond to warming by releasing large amounts of methane into the atmosphere,”http://www.ia.ucsb.edu/pa/display.aspx?pkey=1704
(Santa Barbara, Calif.) –– Methane, a potent greenhouse gas, is emitted in great quantities as bubbles from seeps on the ocean floor near Santa Barbara. About half of these bubbles dissolve into the ocean, but the fate of this dissolved methane remains uncertain. Researchers at the University of California, Santa Barbara have discovered that only one percent of this dissolved methane escapes into the air –– good news for the Earth's atmosphere.
Coal Oil Point (COP), one of the world's largest and best studied seep regions, is located along the northern margin of the Santa Barbara Channel. Thousands of seep fields exist in the ocean bottom around the world, according to David Valentine, associate professor of Earth Science at UC Santa Barbara. Valentine along with other members of UCSB's seeps group studied the plume of methane bubbles that flows from the seeps at COP.
Their results will soon be published as the cover story in Volume 34 of Geophysical Research Letters. This research effort is the first time that the gas that dissolves and moves away from COP, the plume, has been studied.
The amount of methane release from COP seeps is around two million cubic feet per day, according to Valentine. About 100 barrels of oil oozes out of this area as well. Methane warms the Earth 23 times more than carbon dioxide when averaged over a century. Thus the fate of the methane bubbles from the seeps is an important environmental question.
"We found that the ocean has an amazing capacity to take up methane that is released into it –– even when it is released into shallow water," said Valentine. "Huge amounts of gas are coming up here, creating a giant gas plume. Until now, no one had measured the gas that dissolves and moves away, the plume."
Clathrates as the new sword of Damocles? Really the level of alarmist clap trap here takes clap trap to a new level.