Study Ecosystem Changes

Less Algae, Not Clearer Water, Keeps Tahoe Blue

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Lake Tahoe is renowned for its intense blue hue. (Image credit: Wikimedia Commons)

Lake Tahoe’s iconic blueness is more strongly related to the lake’s algal concentration than to its clarity, according to research in “Tahoe: State of the Lake Report 2015,” released today by the Tahoe Environmental Research Center (TERC) of the University of California, Davis. The lower the algal concentration, the bluer the lake.

Data from a research buoy in the lake, owned and operated by NASA’s Jet Propulsion Laboratory, Pasadena, California, enabled Shohei Watanabe, a postdoctoral researcher at TERC, to create a Blueness Index that quantified Lake Tahoe’s color for the first time.

The assumption that lake clarity is tied to blueness has driven advocacy and management efforts in the Lake Tahoe Basin for decades. But Watanabe’s research showed that at times of the year when the lake’s clarity increases, its blueness decreases, and vice versa.

Watanabe combined the blueness measurements with data on clarity. Clarity is measured by observing the depth at which a dinner-plate-sized white disk remains visible when lowered into the water. He was surprised to find that blueness and clarity did not correspond. In fact, they varied in opposite directions.

This is due to seasonal interplay among sediment, algae and nutrients in the lake. Clarity is controlled by sediment. Blueness is controlled by algal concentration, which in turn is controlled by the level of nutrients available to the algae.

The JPL buoy used in the study is one of four buoys established by NASA with support from TERC to calibrate and validate measurements taken by satellites flying overhead. “This particular buoy has instruments beneath the water looking up and an instrument on the buoy looking down,” said JPL’s Simon Hook, who collaborated with Watanabe during his research. “The combination of instruments in and above the water was used in this study to look at how light is being scattered and attenuated.

That tells you something about both the color and the clarity of the lake.”

The finding is good news, according to Geoffrey Schladow, director of TERC and a civil engineering professor at UC Davis. “It shows that we better understand how Lake Tahoe works, and it reinforces the importance of controlling nutrient inputs to the lake, whether from the forest, the surrounding lawns or even from the air. It’s particularly encouraging that blueness has been increasing over the last three years.”

Past State of the Lake Reports
The University of California, Davis, has conducted continuous monitoring of Lake Tahoe since 1968, amassing a unique record of change for one of the world’s most beautiful and vulnerable lakes.

In the UC Davis Tahoe: State of the Lake Report, we summarize how natural variability, long term change and human activity have affected the lake’s clarity, physics, chemistry and biology over that period.

UC Davis provides acess to past reports, starting at 2007 to the current report. You can access them on the UC Davis Past website at: Past State of Lake Tahoe’s Reports.

More Information From the Reseacher and NASA
For more information on Watanabe’s research and other highlights of the State of the Lake report, visit: http://news.ucdavis.edu/search/news_detail.lasso?id=11265

NASA uses the vantage point of space to increase our understanding of our home planet, improve lives and safeguard our future. NASA develops new ways to observe and study Earth’s interconnected natural systems with long-term data records. The agency freely shares this unique knowledge and works with institutions around the world to gain new insights into how our planet is changing.

For more information about NASA’s Earth science activities, visit: http://www.nasa.gov/earth

NASA Study Finds Indian, Pacific Oceans Temporarily Hide Global Warming

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An Argo float, foreground. The new study included direct measurements of ocean temperatures from the global array of 3,500 Argo floats and other ocean sensors. Image credit: Argo program. (Image Credit: Germany/Ifremer)

A new NASA study of ocean temperature measurements shows that in recent years, extra heat from greenhouse gases has been trapped in the waters of the Pacific and Indian oceans. Researchers say this shifting pattern of ocean heat accounts for the slowdown in the global surface temperature trend observed during the past decade.

Researchers Veronica Nieves, Josh Willis and Bill Patzert of NASA’s Jet Propulsion Laboratory, Pasadena, California, found a specific layer of the Indian and Pacific oceans between 300 and 1,000 feet (100 and 300 meters) below the surface has been accumulating more heat than previously recognized. They also found the movement of warm water has affected surface temperatures. The results were published Thursday in the journal Science.

During the 20th century, as greenhouse gas concentrations increased and trapped more heat energy on Earth, global surface temperatures also increased. However, in the 21st century, this pattern seemed to change temporarily.

“Greenhouse gases continued to trap extra heat, but for about 10 years starting in the early 2000s, global average surface temperature stopped climbing and even cooled a bit,” said Willis.


In the study, researchers analyzed direct ocean temperature measurements, including observations from a global network of about 3,500 ocean temperature probes known as the Argo array. These measurements show temperatures below the surface have been increasing.

Maps of temperature trends at four layers in the global ocean show the patterns of heat below the surface, 2003-2012. The warmest water appears at depths of about 330-660 feet (100-200 meters, third panel from the top) in the western Pacific and Indian oceans, left of center. Image credit: NASA Earth Observatory

The Pacific Ocean is the primary source of the subsurface warm water found in the study, though some of that water now has been pushed to the Indian Ocean. Since 2003, unusually strong trade winds and other climatic features have been piling up warm water in the upper 1,000 feet of the western Pacific, pinning it against Asia and Australia.

“The western Pacific got so warm that some of the warm water is leaking into the Indian Ocean through the Indonesian archipelago,” said Nieves, the lead author of the study.

The movement of the warm Pacific water westward pulled heat away from the surface waters of the central and eastern Pacific, which resulted in unusually cool surface temperatures during the last decade. Because the air temperature over the ocean is closely related to the ocean temperature, this provides a plausible explanation for the global cooling trend in surface temperature.

Cooler surface temperatures also are related to a long-lived climatic pattern called the Pacific Decadal Oscillation, which moves in a 20- to 30-year cycle. It has been in a cool phase during the entire time surface temperatures showed cooling, bringing cooler-than-normal water to the eastern Pacific and warmer water to the western side. There currently are signs the pattern may be changing to the opposite phase, with observations showing warmer-than-usual water in the eastern Pacific.

“Given the fact the Pacific Decadal Oscillation seems to be shifting to a warm phase, ocean heating in the Pacific will definitely drive a major surge in global surface warming,” Nieves said.

Previous attempts to explain the global surface temperature cooling trend have relied more heavily on climate model results or a combination of modeling and observations, which may be better at simulating long-term impacts over many decades and centuries. This study relied on observations, which are better for showing shorter-term changes over 10 to 20 years. In shorter time spans, natural variations such as the recent slowdown in global surface temperature trends can have larger regional impacts on climate than human-caused warming.

Pauses of a decade or more in Earth’s average surface temperature warming have happened before in modern times, with one occurring between the mid-1940s and late 1970s.

“In the long term, there is robust evidence of unabated global warming,” Nieves said.

NASA uses the vantage point of space to increase our understanding of our home planet, improve lives and safeguard our future. NASA develops new ways to observe and study Earth’s interconnected natural systems with long-term data records. The agency freely shares this unique knowledge and works with institutions around the world to gain new insights into how our planet is changing.

For more information about NASA’s Earth science activities, visit: http://www.nasa.gov/earth

NASA Soil Moisture Mission Begins Science Operations

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High-resolution global soil moisture map from SMAP’s combined radar and radiometer instruments Southern U.S. SMAP soil moisture retrievals from April 27, 2015 High-resolution global soil moisture map from SMAP’s combined radar and radiometer instruments, acquired between May 4 and May 11, 2015 during SMAP’s commissioning phase. The map has a resolution of 5.6 miles (9 kilometers). The data gap is due to turning the instruments on and off during testing. Image Credit: NASA/JPL-Caltech/GSFC

NASA’s new Soil Moisture Active Passive (SMAP) mission to map global soil moisture and detect whether soils are frozen or thawed has begun science operations.
Launched Jan. 31 on a minimum three-year mission, SMAP will help scientists understand links among Earth’s water, energy and carbon cycles; reduce uncertainties in predicting climate; and enhance our ability to monitor and predict natural hazards like floods and droughts. SMAP data have additional practical applications, including improved weather forecasting and crop yield predictions.

A first global view of SMAP’s flagship product, a combined active-passive soil moisture map with a spatial resolution of 5.6 miles (9 kilometers), is available at:  http://www.jpl.nasa.gov/spaceimages/details.php?id=PIA19337.

During SMAP’s first three months in orbit, referred to as SMAP’s “commissioning” phase, the observatory was first exposed to the space environment, its solar array and reflector boom assembly containing SMAP’s 20-foot (6-meter) reflector antenna were deployed, and the antenna and instruments were spun up to their full speed, enabling global measurements every two to three days.

The commissioning phase also was used to ensure that SMAP science data reliably flow from its instruments to science data processing facilities at NASA’s Jet Propulsion Laboratory in Pasadena, California, and the agency’s Goddard Space Flight Center in Greenbelt, Maryland.

“Fourteen years after the concept for a NASA mission to map global soil moisture was first proposed, SMAP now has formally transitioned to routine science operations,” said Kent Kellogg, SMAP project manager at JPL. “SMAP’s science team can now begin the important task of calibrating the observatory’s science data products to ensure SMAP is meeting its requirements for measurement accuracy.”

Together, SMAP’s two instruments, which share a common antenna, produce the highest-resolution, most accurate soil moisture maps ever obtained from space. The spacecraft’s radar transmits microwave pulses to the ground and measures the strength of the signals that bounce back from Earth, whereas its radiometer measures microwaves that are naturally emitted from Earth’s surface.

“SMAP data will eventually reveal how soil moisture conditions are changing over time in response to climate and

Southern U.S. SMAP soil moisture retrievals from April 27, 2015, when severe storms were affecting Texas. Top: radiometer data alone. Bottom: combined radar and radiometer data with a resolution of 5.6 miles (9 kilometers). The combined product reveals more detailed surface soil moisture features.

how this impacts regional water availability,” said Dara Entekhabi, SMAP science team leader at the Massachusetts Institute of Technology in Cambridge. “SMAP data will be combined with data from other missions like NASA’s Global Precipitation Measurement, Aquarius and Gravity Recovery and Climate Experiment to reveal deeper insights into how the water cycle is evolving at global and regional scales.”

The new global image shows dry conditions in the southwestern United States and in Australia’s interior. Moist soil conditions are evident in the U.S. Midwest and in eastern regions of the United States, Europe and Asia. The far northern regions depicted in these SMAP maps do not indicate soil moisture measurements because the ground there was frozen.

Zooming in on the data allows a closer look at the benefits of combining SMAP’s radar and radiometer data. A segment of a SMAP orbit covering the central and southern United States on April 27 is available at: http://www.jpl.nasa.gov/spaceimages/details.php?id=PIA19338.

The upper part of the image shows the radiometer-based estimate of soil moisture at a spatial resolution of 22.5 miles (36 kilometers). The lower part of the image shows the active-passive, or merged high-resolution (5.6 miles, or 9 kilometers), radar- and radiometer-derived soil moisture product.

In the days prior to this data collection, intense rainstorms pounded northern Texas. The areas affected by the storm in northern Texas and the Gulf Coast are visible in much greater detail. Such detail can be used to improve local weather forecasts, assist in monitoring drought in smaller watersheds, and forecast floods.

Over the next year, SMAP data will be calibrated and validated by comparing it against ground measurements of soil moisture and freeze/thaw state around the world at sites representing a broad spectrum of soil types, topography, vegetation and ground cover. SMAP data also will be compared with soil moisture data from existing aircraft-mounted instruments and other satellites.

Preliminary calibrated data will be available in August at designated public-access data archives, including the National Snow and Ice Data Center in Boulder, Colorado, and Alaska Satellite Facility in Fairbanks. Preliminary soil moisture and freeze/thaw products will be available in November, with validated measurements scheduled to be available for use by the general science community in the summer of 2016.

NASA uses the vantage point of space to increase our understanding of our home planet, improve lives and safeguard our future. NASA develops new ways to observe and study Earth’s interconnected natural systems with long-term data records. The agency freely shares this unique knowledge and works with institutions around the world to gain new insights into how our planet is changing.

For more information on SMAP, visit: http://www.nasa.gov/smap.

For more information about NASA’s Earth science activities, visit: http://www.nasa.gov/earth.

It’s the Final Act for Larsen B Ice Shelf, NASA Finds

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Antarctica’s Larsen B Ice Shelf is likely to shatter into hundreds of icebergs like this one before the end of the decade, according to a new NASA study. Image credit: NSIDC/Ted Scambos

A new NASA study finds the last remaining section of Antarctica’s Larsen B Ice Shelf, which partially collapsed in 2002, is quickly weakening and is likely to disintegrate completely before the end of the decade.

A team led by Ala Khazendar of NASA’s Jet Propulsion Laboratory in Pasadena, California, found the remnant of the Larsen B Ice Shelf is flowing faster, becoming increasingly fragmented and developing large cracks. Two of its tributary glaciers also are flowing faster and thinning rapidly.

“These are warning signs that the remnant is disintegrating,” Khazendar said. “Although it’s fascinating scientifically to have a front-row seat to watch the ice shelf becoming unstable and breaking up, it’s bad news for our planet. This ice shelf has existed for at least 10,000 years, and soon it will be gone.”

Ice shelves are the gatekeepers for glaciers flowing from Antarctica toward the ocean. Without them, glacial ice enters the ocean faster and accelerates the pace of global sea level rise. This study, the first to look comprehensively at the health of the Larsen B remnant and the glaciers that flow into it, has been published online in the journal Earth and Planetary Science Letters.

Khazendar’s team used data on ice surface elevations and bedrock depths from instrumented aircraft participating in NASA’s Operation IceBridge, a multiyear airborne survey campaign that provides unprecedented documentation annually of Antarctica’s glaciers, ice shelves and ice sheets. Data on flow speeds came from spaceborne synthetic aperture radars operating since 1997.

http://www.jpl.nasa.gov/video/download.php?id=1376&download=hdmov

Khazendar noted his estimate of the remnant’s remaining life span was based on the likely scenario that a huge, widening rift that has formed near the ice shelf’s grounding line will eventually crack all the way across. The free-floating remnant will shatter into hundreds of icebergs that will drift away, and the glaciers will rev up for their unhindered move to the sea.

Located on the coast of the Antarctic Peninsula, the Larsen B remnant is about 625 square miles (1,600 square kilometers) in area and about 1,640 feet (500 meters) thick at its thickest point. Its three major tributary glaciers are fed by their own tributaries farther inland. 

“What is really surprising about Larsen B is how quickly the changes are taking place,” Khazendar said. “Change has been relentless.”

The remnant’s main tributary glaciers are named Leppard, Flask and Starbuck — the latter two after characters in the novel Moby Dick. The glaciers’ thicknesses and flow speeds changed only slightly in the first couple of years following the 2002 collapse, leading researchers to assume they remained stable. The new study revealed, however, that Leppard and Flask glaciers have thinned by 65-72 feet (20-22 meters) and accelerated considerably in the intervening years. The fastest-moving part of Flask Glacier had accelerated 36 percent by 2012 to a flow speed of 2,300 feet (700 meters) a year — comparable to a car accelerating from 55 to 75 mph.

Flask’s acceleration, while the remnant has been weakening, may be just a preview of what will happen when the remnant breaks up completely. After the 2002 Larsen B collapse, the glaciers behind the collapsed part of the shelf accelerated as much as eightfold — comparable to a car accelerating from 55 to 440 mph.

The third and smallest glacier, Starbuck, has changed little. Starbuck’s channel is narrow compared with those of the other glaciers, and the small glacier is strongly anchored to the bedrock, which, according to authors of the study, explains its comparative stability.

“This study of the Antarctic Peninsula glaciers provides insights about how ice shelves farther south, which hold much more land ice, will react to a warming climate,” said JPL glaciologist Eric Rignot, a coauthor of the paper.

The research team included scientists from JPL; the University of California, Irvine; and the University Centre in Svalbard, Norway. The paper is online at: http://go.nasa.gov/1bbpfsC.

NASA uses the vantage point of space to increase our understanding of our home planet, improve lives and safeguard our future. NASA develops new ways to observe and study Earth’s interconnected natural systems with long-term data records. The agency freely shares this unique knowledge and works with institutions around the world to gain new insights into how our planet is changing.

For more information about NASA’s Earth science activities, visit: http://www.nasa.gov/earth.

NASA Administrator Statement on House Authorization Bill That “Guts the Earth Science Programs”

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April 30, 2015
RELEASE 15-080
NASA Administrator Statement on House Authorization Bill 

The following is a statement from NASA Administrator Charles Bolden on the House of Representatives’ NASA authorization bill:

“The NASA authorization bill making its way through the House of Representatives guts our Earth science program and threatens to set back generations worth of progress in better understanding our changing climate, and our ability to prepare for and respond to earthquakes, droughts, and storm events.   

“NASA leads the world in the exploration of and study of planets, and none is more important than the one on which we live.

“In addition, the bill underfunds the critical space technologies that the nation will need to lead in space, including on our journey to Mars.”

NASA, USGS Begin Work on Landsat 9 to Continue Land Imaging Legacy

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NASA and the U.S. Geological Survey (USGS) have started work on Landsat 9, planned to launch in 2023, which will extend the Earth-observing program’s record of land images to half a century.

The Landsat program has provided accurate measurements of Earth’s land cover since 1972. With data from Landsat satellites, ecologists have tracked deforestation in South America, water managers have monitored irrigation of farmland in the American West, and researchers have watched the growth of cities worldwide. With the help of the program’s open archive, firefighters have assessed the severity of wildfires and scientists have mapped the retreat of mountain glaciers.

The President’s fiscal year 2016 budget calls for initiation of a Landsat 9 spacecraft as an upgraded rebuild of Landsat 8, as well as development of a low-cost thermal infrared (TIR) free-flying satellite for launch in 2019 to reduce the risk of a data gap in this important measurement. The TIR free flyer will ensure data continuity by flying in formation with Landsat 8. The budget also calls for the exploration of technology and systems innovations to provide more cost effective and advanced capabilities in future land-imaging missions beyond Landsat 9, such as finding ways to miniaturize instruments to be launched on smaller, less expensive satellites.

“Moving out on Landsat 9 is a high priority for NASA and USGS as part of a sustainable land imaging program that will serve the nation into the future as the current Landsat program has done for decades,” said John Grunsfeld, associate administrator for science at NASA Headquarters, Washington. “Continuing the critical observations made by the Landsat satellites is important now and their value will only grow in the future, given the long term environmental changes we are seeing on planet Earth.”

Because an important part of the land imaging program is to provide consistent long-term observations, this mission will largely replicate its predecessor Landsat 8. The mission will carry two instruments, one that captures views of the planet in visible, near infrared and shortwave-infrared light, and another that measures the thermal infrared radiation, or heat, of Earth’s surfaces. These instruments have sensors with moderate resolution and the ability to detect more variation in intensity than the first seven satellites in the Landsat program.

The Landsat 9 mission is a partnership between NASA and the USGS. NASA will build, launch, perform the initial check-out and commissioning of the satellite; USGS will operate Landsat 9 and process, archive, and freely distribute the mission’s data.

“Landsat is a remarkably successful partnership,” said Sarah Ryker, USGS deputy associate director for climate and land use change, Reston, Virginia. “Last year the White House found that GPS, weather satellites, and Landsat are the three most critical types of Earth-orbiting assets for civil applications, because they’re used by many economic sectors and fields of research. Having Landsat 9 in progress, and a long-term commitment to sustainable land imaging, is great for natural resource science and for data-driven industries such as precision agriculture and insurance.”

NASA’s Goddard Space Flight Center in Greenbelt, Maryland, will lead development of the Landsat 9 flight segment. Goddard will also build the Thermal Infrared Sensor (TIRS), which will be similar to the TIRS that the center built for Landsat 8. The new improved TIRS will have a five-year design lifetime, compared to the three-year design lifetime of the sensor on Landsat 8.

“This is good news for Goddard, and it’s great news for the Landsat community to get the next mission going,” said Del Jenstrom, the Landsat 9 project manager at NASA Goddard. “It will provide data consistent with, or better than, Landsat 8.”

With decades of observations, scientists can tease out subtle changes in ecosystems, the effects of climate change on permafrost, changes in farming technologies, and many other activities that alter the landscape.

“With a launch in 2023, Landsat 9 would propel the program past 50 years of collecting global land cover data,” said Jeffrey Masek, Landsat 9 Project Scientist at Goddard. “That’s the hallmark of Landsat: the longer the satellites view the Earth, the more phenomena you can observe and understand. We see changing areas of irrigated agriculture worldwide, systemic conversion of forest to pasture – activities where either human pressures or natural environmental pressures are causing the shifts in land use over decades.”

“We have recognized for the first time that we’re not just going to do one more, then stop, but that Landsat is actually a long-term monitoring activity, like the weather satellites, that should go on in perpetuity,” Masek said.

NASA uses the vantage point of space to increase our understanding of our home planet, improve lives, and safeguard our future. NASA develops new ways to observe and study Earth’s interconnected natural systems with long-term data records. The agency freely shares this unique knowledge and works with institutions around the world to gain new insights into how our planet is changing.

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