Integrating federal research on global change and climate change

Monday March 19, 2012

Becky Fried, Policy Analyst,
Office of Science and Technology Policy, Executive Office of the President 

Multi-Year Arctic Sea Ice Area

Older, thicker ice “is the mainstay of the Arctic ice cover and historically would be the one most likely to survive the summer melt,” said Joey Comiso, a senior scientist at NASA Goddard Space Flight Center and author of the study. “Unless a sustained cooling in the Arctic happens in the near future, the Arctic Ocean will soon have very little or no sea ice-cover in the summer.” 

Typically, old ice—called multi-year sea ice when it lasts through at least two summers—is thick enough to survive multiple summertime melt seasons. Newer ice, on the other hand, is thinner and can melt seasonally, just as quickly as it was formed. The rapid disappearance of older ice means areas of the Arctic Ocean are increasingly comprised of ice-free, open water during the summer season, which has implications for global climate as well as regional communities and ecosystems. 

To measure ice cover, scientists use satellite sensors that detect microwaves emitted by the ice surface, then turn those signals into digital images. As it turns out, younger ice is saltier than older ice—a difference that results in distinctive microwave emissions that  allow satellite sensors to distinguish between old and young ice. Scientists use two primary measures to describe the amount of polar sea-ice cover: sea ice “extent”—the size of the ice-covered region, including some ice-free gaps—and sea ice “area,” which is the total area of the ice itself, not including gaps.

In 2008, the extent of multi-year Arctic sea ice hit a record minimum, reaching just 55 percent of its average extent since satellite measurements began in the late 1970s. So far, 2012 shows the second lowest multi-year ice extent ever. 

In the new study, published recently in the Journal of Climate, Comiso used microwave data from NASA’s Nimbus-7 satellite and the U.S. Department of Defense's Defense Meteorological Satellite Program to map multi-year ice area and extent in the Arctic over a 32-year period. Over three decades, the extent of multi-year sea ice decreased at a rate of 15.1 percent per decade, and the area of multi-year sea ice declined by 17.2 percent per decade. By contrast, the extent of perennial ice—or ice that has survived at least one summer (compared to multi-year ice’s two)—decreased at a rate of 12.2 percent per decade and its area declined at a rate of 13.5 percent per decade. In other words, the thickest and oldest ice is declining faster than the younger ice that surrounds it.  

Many factors may be contributing to this phenomenon, including rising surface temperatures in the Arctic generally, which result in a shorter ice-forming season and, thus, less time for sea ice to build the thickness required to survive multiple summers.

Changes in extent or area of sea ice generally can have important impacts in the Arctic and beyond. Most importantly, by lowering the region’s reflectivity and increasing the marine absorption of solar energy, loss of sea ice accelerates global warming. Moreover, sea-ice loss triggers a feedback mechanism whereby ice loss leads to more sunlight absorbed, more rapid warming, and, in turn, even more ice loss. This feedback mechanism is one reason why the Arctic has been warming approximately twice as fast as the planet as a whole.

At the same time, reduced ice cover has important implications for local communities, ecosystems, and industries that use and depend on Arctic waters. The 2004 Arctic Impacts Assessment, for example, described sea-ice loss as “likely to have devastating consequences for polar bears, ice-dependent seals, and local people for whom these animals are a primary food source.” The increased amount of open-water that results from sea-ice loss is also opening up new routes and access points for shipping and maritime industries. That presents new opportunities for regional economic activity, but also poses new regional vulnerabilities to the environmental impacts of those activities.  

As old ice continues its rapid disappearing act, these impacts will be increasingly felt during the summer months, when more and more areas of water normally protected by multiyear ice cover open up completely.

For more information on NASA’s multi-year sea ice study, please visit: http://www.nasa.gov/topics/earth/features/thick-melt.html

For more information on Arctic Change, please visit: http://www.arctic.noaa.gov/detect/index.shtml

Friday March 16, 2012 

NASA’s January 2012 Blue Marble Image of Earth’s Western Hemisphere.

NASA’s most recently launched earth-observing satellite—Suomi NPP—is proving to pack both beauty and brains. Since its launch into space in October, Suomi NPP has taken some of the most stunning images of Earth ever generated and, at the same time, has begun to collect critical data about Earth’s environment and atmosphere. The satellite, the product of a partnership between NASA, NOAA, and the Department of Defense, carries five instruments that collect a host of important information—including sea surface temperatures, ozone levels, and measures of biological productivity on land and in oceans.

Suomi NPP received significant attention in late January and again in February for its latest “Blue Marble” images—stunning, high definition composite images of Earth from space. January’s Blue Marble, which shows Earth’s western hemisphere, immediately went viral after its release. The photo-sharing site Flickr reported that the image received more than 3.1 million views as of February 1, making it one of the most viewed images in the site’s history after just one week on the web. February’s image shows Earth’s eastern hemisphere and was created from data collected during six orbits of Earth.

Suomi NPP satellite under development.

But while the satellite is churning out eye-pleasing images, it’s also busy collecting data that will help us better understand how Earth is changing. Among the five instruments aboard the satellite is the latest version of the Clouds and the Earth’s Radiant Energy System (CERES)—which measures Earth’s energy budget, or balance of incoming and outgoing energy. Having accurate, timely measurements of minute changes in Earth’s energy budget is crucial to increasing our understanding of long-term climate change, including the potential impacts of heat-trapping gasses on ocean and atmospheric temperatures and  sea-level.

At the same time, the Visible Infrared Imaging Radiometer Suite (VIIRS) instrument is monitoring cloud systems, which strongly influence Earth’s energy budget by either reflecting incoming sunlight or blocking energy that would otherwise radiate into space. Scientists want to understand the effects of such cloud characteristics as thickness, altitude, and distribution on energy budgets and climate change. 

As Suomi NPP continues its anticipated 5-year mission, meteorological and earth scientists around the world will gain new information to better understand how Earth is changing. We’ll also be sure to see more beautiful pictures of our planet.

Wednesday March 14, 2012 

Screen shots of USGCRP's new Resource Library website.

Screen shot of USGCRP's previous resource website: "GCRIO".

Tuesday March 13, 2012

Jerry Miller, Assistant Director, Ocean Sciences, and
Tom Armstrong, Executive Director, U.S. Global Change Research Program,
Office of Science and Technology Policy, Executive Office of the President

A new study concludes that the current rate of ocean acidification is higher than at any time in at least the last 300 million years and attributes this ecosystem-threatening change to the huge quantities of carbon dioxide being released into the atmosphere from fossil-fuel burning and deforestation. The study’s investigators, at Columbia University and other institutions, scrutinized Earth’s geologic record for times in ancient history when natural events such as intensive volcanic activity may have similarly led to CO₂ releases or ocean acidification. Although none of those ancient chemical changes appear to have been as extreme as those occurring today, there is nonetheless evidence that they contributed to serious ecological disruptions. That suggests that current trends similarly pose serious threats to marine ecosystems, the researchers conclude in the journal Science.

Oceans are major storage depots for carbon dioxide (CO₂), with levels naturally remaining in rough equilibrium with carbon dioxide levels in the air above. Thus, as human activities like fossil-fuel burning have driven up carbon content in the atmosphere, the world’s oceans have taken up more and more of that carbon. In fact, more than a quarter of the CO₂ released into the atmosphere each year is absorbed by oceans, causing changes in natural seawater chemistry. Among the most significant of these chemical changes has been a gradual increase in the concentrations of carbonic acid and other chemicals—a  process called acidification. This shift, which is already being observed around the world, lowers the concentration and availability of ocean carbonates—a class of chemicals that many marine organisms need to build their skeletons and shells.

Whether and to what extent a more acidic ocean environment is impacting or will impact marine ecosystems is a question that scientists have sought to answer for decades. Nailing down specific impacts is difficult because the complexity of ocean ecosystems far exceeds that which can be fully replicated and analyzed in a laboratory. Just consider the elaborate system of ocean currents, weather patterns, atmospheric conditions, food webs, ocean chemistry, and other factors that play a dynamic role in shaping the marine environment.

In the new study, scientists sought to address that problem by analyzing evidence of ancient changes in marine organisms that correspond to periods in history when the rate of change in atmospheric CO₂ concentration and ocean acidity were particularly high. The study is careful to point out that while no historic event perfectly compares to the current state of our climate and oceans, valuable lessons may still lurk in the geologic record. 

The study found a correlation between periods of rapid acidification and periods when the shell-like plates that cover certain types of algae and plankton shrunk in size.The study also found that at the boundary between Paleocene and Eocene periods (about 55 million years ago), a large release of carbon caused temperatures and ocean acidity to rise, leading to mass extinctions of deep-sea foraminifers—one of the most common marine plankton species—as well as the collapse of coral reefs in shallow waters.   

Because a variety of co-occurring environmental changes may have contributed to these marine ecosystem changes, scientists can’t directly or fully attribute them to ocean acidification. However, they still provide clues about possible causes and consequences of changes to the marine environment—information that is critical not only to scientists, but to communities and local economies that depend on ocean resources for food and income.

For example, studies and monitoring in the Arctic Ocean, the Puget Sound, shellfish hatcheries in the Pacific Northwest and elsewhere have concluded that acidification is already having impacts on marine life, such as compromising the ability of oysters and other organisms to build the protective shells they need to survive. Other reports, such as the U.S. Global Change Research Program’s most recent National Climate Assessment have found that ocean acidification poses a significant threat to coral reefs and the rich ecosystems, local fishing industries, and tourism economies they support.

These threats are among the reasons why the Obama Administration’s National Ocean Council lists among its nine priority objectives strengthening the“resiliency of coastal communities and marine and Great Lakes environments and their abilities to adapt to climate change impacts and ocean acidification.”

For more on ocean acidification, please visit: http://www.noaa.gov/video/administrator/acidification/index.html

Visit the OSTP Blog here: http://www.whitehouse.gov/blog