Months later, an analysis conducted by scientists atNASA’s Goddard Space Flight Center including Si-Chee Tsay andSheng-Hsiang Wang showed that over the next ten days following thearrival of the dust, satellite instruments on Aqua and SeaWiFS detecteda marked jumped in phytoplankton abundance (shown by the green circle in the chart above). That’s notable because the nutrient-limited ocean water in the area isn’t known to support much life.
The key ingredient that triggered the bloom, the scientists believe, was iron and phosphorus within the dust particles. Many types of phytoplankton require trace amounts of key nutrients to thrive and blooms can’t easily occur when levels are low, as they are in the northern South China Sea. Satellites have observed dust plumes triggering phytoplankton blooms in the past, but this is the first time the phenomenon has been observed in the South China Sea, an area where heavy dust deposition is relatively infrequent.
To understand how the Antarctic ice sheet is going to behave in the future, scientists first need to know how much snow and ice is in there. And a major step in determining that figure is calculating how much snow accumulates each year on the frozen continent.
Researchers from the Satellite Era Accumulation Traverse (SEAT) are extracting ice cores in central West Antarctica to update snow accumulation records, since the majority of previously collected cores only extend to the mid-1990s. The scientists analyzed three of the five cores collected during their 2010-2011 field campaign, and their preliminary results show that snow accumulation has decreased significantly (up to 40 percent) across central West Antarctica during the last decade.
“This is the opposite of what you’d expect at a time when there’s a significant warming of West Antarctica,” says Landon Burgener, of the SEAT team, who presented the group’s preliminary results at the American Geophysical Union’s Fall Meeting.
Higher temperatures mean higher water evaporation, which in theory should lead to more snowfall. The measured decrease in snow accumulation goes against the predictions of global climate models, so why is it happening? It might have to do with less frequent, weaker storms in the area, says Summer Rupper, one of the principal investigators of the SEAT project. Less storms means that the extra moisture in the atmosphere ends up falling back to Earth somewhere else, probably over the ocean. Next, the team will examine the (scarce) existing weather data for West Antarctica to see if it’s true that the area is becoming less stormy. Rupper also wants to use ground-based radar data to study how representative the cores are of the places where they were extracted.
Meanwhile, other members of the SEAT team are currently in Antarctica to collect eight more cores that they will analyze to see if they also show a decline in snow accumulation.
Text by Maria-José Viñas. Photo and map courtesy of the SEAT team: The photo (top) shows members of the team drilling an ice core during the 2010-2011 season; the map (above) shows the drilling sites in central West Antarctica. Follow the work of the SEAT researchers in Antarctica on their blog, “Notes from the field.”
A new, updated map reveals how the Antarctic continent looks under the ice, detailing each mountain range and valley. Beyond its undeniable beauty, this high-resolution map of Antarctica’s bed topography, dubbed BEDMAP2, will help scientists model how ice sheets and glaciers respond to changes in the environment.
A large international consortium of Antarctic field programs, including NASA IceBridge, contributed information to this updated map of bed elevation and ice thickness for Antarctica and the Southern Ocean. The first version of BEDMAP was completed in 2000. The new version, which was presented on Dec. 5 at the American Geophysical Union’s 2011 Fall Meeting, incorporates seismic and radar data from about 265,000 km of airborne surveys over the ice.
“We are lacking fundamental data on ice thickness and bedrock elevation over large parts of Antarctica, because these areas are hard to reach,” said IceBridge project scientist Michael Studinger. “We’ll continue to fill in critical information gaps on places such as the Recovery Glacier in Coats Land, East Antarctica. This area has long been on the wish list of ice sheet modelers, but it is very far away from all research bases.”
This year, IceBridge’s DC-8 aircraft was able to fly four times over Recovery Glacier from Punta Arenas, Chile. “We have collected a landmark data set that will fill a critical hole in new BEDMAP compilations,” Studinger said.
Text by Maria-José Viñas. Image courtesy of the BEDMAP Consortium. The new version of BEDMAP will soon be freely available. Read more about the BEDMAP2 on the project’s website.
You’ve most likely seen color-coded, real-time AIRNOW maps of air quality on the web or on television that show whether the air is safe, unhealthy, or hazardous. What you may not realize is that the network of ground-based instruments the EPA uses to make those maps has large gaps in some parts of the country, particularly in sparsely populated areas of the Great Plains and Intermountain West. (Red in the map above indicates areas without ground monitoring stations; black dots show the locations of stations).
To address this problem, an effort sparked by recent advances in satellite measurements of air pollution seeks to integrate NASA and NOAA satellite measurements into the AIRNOW system. The accuracy of satellite measurements of air quality can vary depending on the weather, the topography, the brightness of the underlying surface and other factors, so the researchers leading the effort are developing a method that selectively incorporates only the reliable satellite data. The researchers are still refining the technique and the system isn’t yet operational, but preliminary case studies suggest the technique will be up and running by 2013.
The figure above shows the technique researchers are developing tofuse ground observation and satellite observations of the small particles (PM2.5) that causes health problems. Groundobservations have high uncertainties (shown in the darkest blue) indifferent areas than the satellite observations. The right combinationof the two – see the fused maps at the bottom of the figure – will be more accurate than either the ground network or satellite measurements alone.
Text by Adam Voiland. AdamPasch of Sonoma Technology presented a poster about this topic at theAmerican Geophysical Union fall meeting in San Francisco on Dec. 5, 2011. Video producedby Sonoma Technology. Imagery courtesy of Adam Pasch.
Himalayan glaciers feed rivers and lakes across South Asia that more than a billion people depend upon for fresh water. It’s for this reason – and the fact that many have experienced rapid changes in recent decades – that scientists keep an especially watchful eye on ice in the region.
Much of the data collected to date suggests the prognosis isn’t good. As Goddard Space Flight Center atmospheric scientist William Lau detailed during a presentation at the American Geophysical Union’s fall meeting, air temperatures in the region have been rising at more than 5 times the rate of global warming. And at high elevations in the eastern Himalayas glaciers have been observed retreating by about 1 percent per decade for the last twenty to thirty years. (In contrast, glaciers in the western Himalayas have been relatively stable).
Though greenhouse gases are responsible for part of the warming, Lau’s research finds that two major processes, both associated with airborne particles called aerosols, also play a critical role. The first, a meteorological hypothesis known as the elevated head pump, involves a shift in the monsoon cycle driven by pollution and dust in the region that Lau’s modeling shows brings warmer and wetter conditions to the Himalayan Plateau. The second involves the deposition of dark particles on snow surfaces so that they decrease the albedo and increase temperatures.
The 2011 La Niña, one of the strongest in recent decades, absorbed so much moisture from the oceans and dropped it as precipitation over northern parts of Australia and South America that global mean sea levels fell by about half a centimeter. That was the key point that Eric Lindstrom, an oceanographer based at NASA headquarters, made today while giving a presentation at NASA’s outreach booth at the American Geophysical Union’s fall meeting. He gave the talk with the help of a sophisticated visualization system — called the Hyperwall — that’s capable of displaying large sets of data. The system consists of nine 42-50“ flat-screen monitors arranged in a 3 X 3 array. As Lindstrom pointed out, the fast transition from the 2009-10 El Niño to the 2010-11 La Niña triggered changes in precipitation patterns across the tropics, transferring enough water over land to cause global mean sea level to fall during the spring and summer of 2011. Data from NASA’s GRACE and TRMM satellites have confirmed that the “extra” water and rain has ended up over land as freshwater (see below). The drop in sea level happened despite the background rate of global mean sea level rise, which has been fairly steady at 3.2 millimeters per year since the early 1990s.
What’s happening to Himalayan glaciers, rivers, lakes, and streams has become one of the most important – and widely debated – topics in science.
There’s certainly no shortage of questions. Which of the 15,000 glaciers in the region are retreating and which growing? How many glacial lakes are on the verge of bursting their banks and flooding downstream communities? Will the region’s great rivers, such as the Indus and the Ganges, be able to withstand the region’s changing climate and rapid population growth and continue to sustain the hundreds of millions of people who depend on them? How can devastating floods, such as the one that struck Pakistan last year, be avoided?
Firm answers to such questions have been hard to come by in recent decades because of the limited monitoring resources available in many key countries in the region. Now, however, a new effort, dubbed HIMLA and led by Molly Brown of NASA’s Goddard Space Flight Center, aims to change this by harnessing state-of-the-art, satellite-based monitoring and modeling techniques.
As part of the effort, scientists will feed data from satellite instruments such as MODIS and ASTER into a hydrological model that will produce daily snow/water equivalence maps that will feed into other hydrological models to determine how much freshwater flows into the region’s rivers from snow and glaciers. The ultimate goal: an early warning system that, like the Famine Early Warning System Network does for drought, will help predict floods before they happen.
Tropical cyclones and hurricanes generate the most headlines, but it’s mid-latitude storms churning through heavily populated parts of North America, Europe, and Asia that make the weather most of us actually experience.
Climate models predict that these mid-latitude storms should shift poleward and that the intensity and frequency of the storms could change as global temperatures rise, but actual evidence of such a shift has been difficult to pin down. However, a recently published analysis of 25 years of cloud data captured by satellites offers a compelling piece of evidence that suggests storm tracks are indeed shifting.
The research, led by (former) Scripps Institute of Oceanography scientist Frida Bender, shows that storms tracks have shifted poleward, narrowed, and grown less cloudy since 1983, particularly in the Southern Hemisphere. The analysis, based on data from the International Satellite Cloud Climatology Project, finds that storm tracks have shifted by about 0.4 degrees over the last 25 years.
What’s more, the analysis suggests that changes in the location and intensity of storms could amplify global warming. The researchers detected what amounts to a 2 percent decline in storm tracks over the 25 year record. The decline in cloudiness is of particular importance because it suggests that intensity of storms is likely decreasing. And since clouds reflect large amounts of sunlight, reduced cloudiness means that ocean surfaces beneath storm systems are likely growing warmer.
Bender and colleagues’ study reminds us of the importance of changes in the large-scale clouds associated with frontal storms in storm-track regions. Not only do the polewards shifts in storm-track location profoundly affect precipitation patterns in mid-latitude regions, but associated changes in cloudiness also exert a significant positive feedback on global warming.
Imagine that all the aerosols (the miniscule particles of pollution, dust, sea salt, and many other things) floating around in the air over the United States suddenly disappeared. What would their absence mean for the climate? Loretta Mickley, a climatologist and aerosol expert from Harvard University, has tackled just that question by running a series of simulations with a high-resolution computer model developed at NASA’s Goddard Institute for Space Studies.
Her conclusion: the elimination of the particles would increase ground temperatures across the eastern United States, cause more springtime rain to fall, and drive an uptick in heat waves. All of this would be driven by something scientists call the “direct effect” of aerosols – the particles’ ability to warm or cool the atmosphere by either absorbing or scattering incoming energy from the sun. (In this case, the model didn’t account for the “indirect effects” of aerosols – how the particles affect clouds, a detail that can have an impact on how they affect the climate as well).
Atmospheric Environmentpublished a study that details the experiments in July of 2011. Here’s how Mickley summarized the findings:
We find that removing U.S. aerosol significantly enhances the warming from greenhouse gases in a spatial pattern that strongly correlates with that of the aerosol. Warming is nearly negligible outside the United States, but annual mean surface temperatures increase by 0.4-0.6 K in the eastern United States. Temperatures during summer heat waves in the Northeast rise by as much as 1-2 K due to aerosol removal, driven in part by positive feedbacks involving soil moisture and low cloud cover. Reducing U.S. aerosol sources to achieve air quality objectives could thus have significant unintended regional warming consequences.
There’s good reason to consider how falling levels of aerosols will affect the climate. In the United States, several kinds of aerosol particles have actually seen their numbers fall steadily as regulations have gone into place to clean up the air for the sake of public health. Emissions of sulfur dioxide, for example, a gas produced by coal power plants that generates reflective sulfate particles has fallen by 83 percent since 1980.
As flood waters continue to inundate Thailand and drought parches Texas, the Intergovernmental Panel on Climate Change and Goddard Institute for Space Studies Director James Hansen have both released new statements about the connection between extreme weather and climate change. Although linking extreme weather to climate change has generated controversy in the past, both of the new reports point plainly to a connection.The IPCC, an international organizational that represents the scientific consensus of hundreds of leading climatologists, put it this way in the executive summary of its new report.
It is very likely that there has been an overall decrease in the number of cold days and nights, and an overall increase in the number of warm days and nights, on the global scale, i.e., for most land areas with sufficient data. It is likely that these changes have also occurred at the continental scale in North America, Europe, and Australia.There have been statistically significant trends in the number of heavy precipitation events in some regions. It is likely that more of these regions have experienced increases than decreases, although there are strong regional and subregional variations in these trends.
There is medium confidence that some regions of the world have experienced more intense and longer droughts, in particular in southern Europe and West Africa, but in some regions droughts have become less frequent, less intense, or shorter, e.g., in central North America and northwestern Australia.There is evidence that some extremes have changed as a result of anthropogenic influences, including increases in atmospheric concentrations of greenhouse gases. It is likely that anthropogenic influences have led to warming of extreme daily minimum and maximum temperatures on the global scale. There is medium confidence that anthropogenic influences have contributed to intensification of extreme precipitation on the global scale.
There is limited to medium evidence available to assess climate-driven observed changes in the magnitude and frequency of floods at regional scales because the available instrumental records of floods at gauge stations are limited in space and time, and because of confounding effects of changes in land use and engineering. Furthermore, there is low agreement in this evidence, and thus overall low confidence at the global scale regarding even the sign of these changes.
Meanwhile, Hansen has released the draft of a new paper (pdf) that also tackles the topic of extreme weather and climate. He’s somewhat less equivocal in his summary of the state of the science:
The “climate dice” describing the chance of an unusually warm or cool season, relative to the climatology of 1951-1980, have progressively become more “loaded” during the past 30 years, coincident with increased global warming. The most dramatic and important change of the climate dice is the appearance of a new category of extreme climate outliers. These extremes were practically absent in the period of climatology, covering much less than 1% of Earth’s surface. Now summertime extremely hot outliers, more than three standard deviations (σ) warmer than climatology, typically cover about 10% of the land area. Thus there is no need to equivocate about the summer heat waves in Texas in 2011 and Moscow in 2010, which exceeded 3σ – it is nearly certain that they would not have occurred in the absence of global warming. If global warming is not slowed from its current pace, by mid-century 3σ events will be the new norm and 5σ events will be common.