Monday, July 11, 2011
How deep is the ocean's capacity to buffer against climate change? As one of the planet's largest single carbon absorbers, the ocean takes up roughly one-third of all human carbon emissions, reducing atmospheric carbon dioxide and its associated global changes.
But whether the ocean can continue mopping up human-produced carbon at the same rate is still up in the air. Previous studies on the topic have yielded conflicting results, says University of Wisconsin-Madison assistant professor Galen McKinley.
In a new analysis published online July 10 in Nature Geoscience, McKinley and her colleagues identify a likely source of many of those inconsistencies and provide some of the first observational evidence that climate change is negatively impacting the ocean carbon sink.
"The ocean is taking up less carbon because of the warming caused by the carbon in the atmosphere," says McKinley, an assistant professor of atmospheric and oceanic sciences and a member of the Center for Climatic Research in the Nelson Institute for Environmental Studies.
The analysis differs from previous studies in its scope across both time and space. One of the biggest challenges in asking how climate is affecting the ocean is simply a lack of data, McKinley says, with available information clustered along shipping lanes and other areas where scientists can take advantage of existing boat traffic. With a dearth of other sampling sites, many studies have simply extrapolated trends from limited areas to broader swaths of the ocean.
McKinley and colleagues at UW-Madison, the Lamont-Doherty Earth Observatory at Columbia University, and the Universite Pierre et Marie Curie in Paris expanded their analysis by combining existing data from a range of years (1981-2009), methodologies, and locations spanning most of the North Atlantic into a single time series for each of three large regions called gyres, defined by distinct physical and biological characteristics.They found a high degree of natural variability that often masked longer-term patterns of change and could explain why previous conclusions have disagreed. They discovered that apparent trends in ocean carbon uptake are highly dependent on exactly when and where you look – on the 10- to 15-year time scale, even overlapping time intervals sometimes suggested opposite effects.
"Because the ocean is so variable, we need at least 25 years' worth of data to really see the effect of carbon accumulation in the atmosphere," she says. "This is a big issue in many branches of climate science – what is natural variability, and what is climate change?"
Working with nearly three decades of data, the researchers were able to cut through the variability and identify underlying trends in the surface CO2 throughout the North Atlantic.
During the past three decades, increases in atmospheric carbon dioxide have largely been matched by corresponding increases in dissolved carbon dioxide in the seawater. The gases equilibrate across the air-water interface, influenced by how much carbon is in the atmosphere and the ocean and how much carbon dioxide the water is able to hold as determined by its water chemistry.
But the researchers found that rising temperatures are slowing the carbon absorption across a large portion of the subtropical North Atlantic. Warmer water cannot hold as much carbon dioxide, so the ocean's carbon capacity is decreasing as it warms.
In watching for effects of increasing atmospheric carbon on the ocean's uptake, many people have looked for indications that the carbon content of the ocean is rising faster than that of the atmosphere, McKinley says. However, their new results show that the ocean sink could be weakening even without that visible sign.
"More likely what we're going to see is that the ocean will keep its equilibration but it doesn't have to take up as much carbon to do it because it's getting warmer at the same time," she says. "We are already seeing this in the North Atlantic subtropical gyre, and this is some of the first evidence for climate damping the ocean's ability to take up carbon from the atmosphere."She stresses the need to improve available datasets and expand this type of analysis to other oceans, which are relatively less-studied than the North Atlantic, to continue to refine carbon uptake trends in different ocean regions. This information will be critical for decision-making, since any decrease in ocean uptake may require greater human efforts to control carbon dioxide levels in the atmosphere.
| The President answers a tweeted question on space policy |
President Barack Obama lauded NASA's final space shuttle launch Friday (July 8), saying that the blastoff marks the end of one chapter of human spaceflight, but also the start of a new one.
"Today's launch may mark the final flight of the Space Shuttle, but it propels us into the next era of our never-ending adventure to push the very frontiers of exploration and discovery in space," Obama said in a statement.
Atlantis launched into space at 11:29 a.m. EDT (1529 GMT) from the Kennedy Space Center in Florida, marking the final flight of the space shuttle program, which NASA is shutting down after 30 years of spaceflight. The shuttle is carrying four astronauts on a 12-day delivery mission to the International Space Station.
"Behind Atlantis and her crew of brave astronauts stand thousands of dedicated workers who have poured their hearts and souls into America's Space Shuttle program over the past three decades," said Obama, who did not attend the launch but did tour Atlantis with his family before launch. "To them and all of NASA's incredible workforce, I want to express my sincere gratitude. You helped our country lead the space age and you continue to inspire us each day." [Photos: President Obama and NASA]
American icon's last voyage
NASA is retiring its space shuttle fleet to make way for a new exploration program aimed at deep space missions. Thousands of NASA and shuttle contractor workers are expected to lose their jobs once the program is no more.
Previously, the agency planned to replace the shuttle program with a new one aimed at returning astronauts to the moon. But Obama canceled that plan and gave NASA a new directive for deep space exploration, including a crewed asteroid mission by 2025.
"And I have tasked the men and women of NASA with an ambitious new mission: to break new boundaries in space exploration, ultimately sending Americans to Mars. I know they are up to the challenge – and I plan to be around to see it," Obama said.
Obama's comments came just days after he said NASA needs to develop new technologies in order allow faster and longer spaceflights.
"Frankly I have been pushing NASA to revamp its vision," Obama said on July 6 in answer to question from a Twitter user during a Town Hall event. "The shuttle did some extraordinary work in low orbit: experiments, the International Space Station, moving cargo. It was an extraordinary accomplishment and we're very proud of the work that it did. But now what we need is that next technological breakthrough." [Video: See Obama's Full Comments]
Future of U.S. spaceflight
NASA currently plans to use a new space capsule, called the Multi-Purpose Crew Vehicle, for future deep space missions. The vehicle is based on work for the agency's Orion spacecraft developed for the previous moon plan.
The heavy-lift rocket for the new program is called the Space Launch System, but the details of the booster are not yet final. This week, NASA officials said they plan to settle on a design for the new rocket by the end of summer.
NASA's space exploration plan will lead to new advances in science and technology, as well spur education, innovation and economic growth, the president said.
A major hurdle to Obama's deep space exploration vision is NASA's budget, which is mired in a maze of congressional battles over cutbacks.
On Thursday, the House Appropriations commerce, justice and science committee, which oversees NASA funding, released a $16.8 billion 2012 budget proposal for the agency that is nearly $2 billion less than what Obama proposed in his 2012 budget request.
The House proposal includes $1.95 billion for the Space Launch System, which is $150 million more than the heavy-lift rocket received for 2011 but nearly $700 million less the amount recommended in the NASA Authorization Act of 2010, which Obama signed into law in October.
In the meantime, Obama said Americans should take pride in the accomplishments of the shuttle program and he wished the shuttle's veteran astronaut crew well.
"Congratulations to Atlantis, her astronauts, and the people of America's space program on a picture-perfect launch, and good luck on the rest of your mission to the International Space Station, and for a safe return home," Obama said in the Friday statement. "I know the American people share my pride at what we have accomplished as a nation, and my excitement about the next chapter of our preeminence in space."