Global Warming

Global Warming

Global Warming

Global Warming

Global Warming

Global Warming

Global Warming

Global Warming

Global Warming

Global Warming

Wednesday, 30 November 2011

NASA's Grace helps monitor U.S. drought

By Kelly Helm Smith,
National Drought Mitigation Center
Adam Voiland,
NASA's Earth Science News Team

New groundwater and soil moisture drought indicator maps produced by NASA are available on the National Drought Mitigation Center's website. They currently show unusually low groundwater storage levels in Texas. The maps use an 11-division scale, with blues showing wetter-than-normal conditions and a yellow-to-red spectrum showing drier-than-normal conditions. Image credit: NASA/National Drought Mitigation Center

The record-breaking drought in Texas that has fueled wildfires, decimated crops and forced cattle sales has also reduced groundwater levels in much of the state to the lowest levels in more than 60 years, according to new national maps produced by NASA using data from the NASA/German Aerospace Center Gravity Recovery and Climate Experiment (Grace) mission. The map are distributed by the National Drought Mitigation Center at the University of Nebraska-Lincoln.

The latest groundwater map, released on Nov. 29, shows large patches of maroon over eastern Texas, indicating severely depressed groundwater levels. The maps, publicly available on the Drought Center's website at , are generated weekly by NASA's Goddard Space Flight Center in Greenbelt, Md., using Grace gravity field data calculated at NASA's Jet Propulsion Laboratory, Pasadena, Calif., and the University of Texas Center for Space Research, Austin.

"Texas groundwater will take months or longer to recharge," said Matt Rodell, a hydrologist based at Goddard. "Even if we have a major rainfall event, most of the water runs off. It takes a longer period of sustained greater-than-average precipitation to recharge aquifers significantly."

The twin Grace satellites, which JPL developed and manages for NASA, detect small changes in Earth's gravity field caused primarily by the redistribution of water on and beneath the land surface. The paired satellites travel about 137 miles (220 kilometers) apart and record small changes in the distance separating them as they encounter variations in Earth's gravitational field.

To make the maps, scientists use a sophisticated computer model that combines measurements of water storage from Grace with a long-term meteorological dataset to generate a continuous record of soil moisture and groundwater that stretches back to 1948. Grace data go back to 2002. The meteorological data include precipitation, temperature, solar radiation and other ground- and space-based measurements.

The color-coded maps show how much water is stored now as a probability of occurrence in the 63-year record. The maroon shading over eastern Texas, for example, shows that the level of dryness over the last week occurred less than two percent of the time between 1948 and the present.

The groundwater maps aren't the only maps based on Grace data that the Drought Center publishes each week. The Drought Center also distributes soil moisture maps that show moisture changes in the root zone down to about 3 feet (1 meter) below the surface, as well as surface soil moisture maps that show changes within the top inch (2 centimeters) of the land.

"All of these maps offer policymakers new information into subsurface water fluctuations at regional to national scales that has not been available in the past," said the Drought Center's Brian Wardlow. The maps provide finer resolution or are more consistently available than other similar sources of information, and having the maps for the three different levels should help decision makers distinguish between short-term and long-term droughts.

"These maps would be impossible to generate using only ground-based observations," said Rodell. "There are groundwater wells all around the United States, and the U.S. Geological Survey does keep records from some of those wells, but it's not spatially continuous and there are some big gaps."

The maps also offer farmers, ranchers, water resource managers and even individual homeowners a new tool to monitor the health of critical groundwater resources. "People rely on groundwater for irrigation, for domestic water supply, and for industrial uses, but there's little information available on regional to national scales on groundwater storage variability and how that has responded to a drought," Rodell said. "Over a long-term dry period, there will be an effect on groundwater storage and groundwater levels. It's going to drop quite a bit, people's wells could dry out, and it takes time to recover."

The maps are the result of a NASA-funded project at the Drought Center and NASA Goddard to make it easier for the weekly U.S. Drought Monitor to incorporate data from the Grace satellites. The groundwater and soil moisture maps are updated each Tuesday.

Tuesday, 29 November 2011

First light for NPP satellite

An image taken by the NPP Visible Infrared Imager Radiometer Suite (VIIRS) on Nov. 21, 2011. This high-resolution image is wrapped on a globe and shows a broad swath of Eastern North America from Canada’s Hudson Bay past Florida to the northern coast of Venezuela. The NASA NPP Team at the Space Science and Engineering Center, UW-Madison created the image using 3 channels (red, green and blue) of VIIRS data. Credit: NASA/NPP Team.

By Rani Gran,
NASA Goddard Space Flight Center

GREENBELT, Md. — The Visible Infrared Imager Radiometer Suite (VIIRS) onboard NASA's newest Earth-observing satellite, NPP, acquired its first measurements on Nov. 21, 2011. This high-resolution image is of a broad swath of Eastern North America from Canada’s Hudson Bay past Florida to the northern coast of Venezuela. The VIIRS data were processed at the NOAA Satellite Operations Facility in Suitland, Md.

VIIRS is one of five instruments onboard the National Polar-orbiting Operational Environmental Satellite System Preparatory Project (NPP) satellite that launched from Vandenberg Air Force Base, Calif., on Oct. 28. Since then, NPP reached its final orbit at an altitude of 512 miles (824 kilometers), powered on all instruments and is traveling around the Earth at 16,640 miles an hour (eight kilometers per second).

"This image is a next step forward in the success of VIIRS and the NPP mission," said James Gleason, NPP project scientist at NASA's Goddard Space Flight Center, Greenbelt, Md.

VIIRS will collect radiometric imagery in visible and infrared wavelengths of the Earth's land, atmosphere, and oceans. By far the largest instrument onboard NPP, VIIRS weighs about 556 pounds (252 kilograms). Its data, collected from 22 channels across the electromagnetic spectrum, will be used to observe the Earth's surface including fires, ice, ocean color, vegetation, clouds, and land and sea surface temperatures.

"VIIRS heralds a brightening future for continuing these essential measurements of our environment and climate," said Diane Wickland, NPP program scientist at NASA headquarters in Washington. She adds that all of NPP's five instruments will be up and running by mid-December and NPP will begin 2012 by sending down complete data.

A high-resolution version of the first VIIRS image created the NASA NPP Team at the Space Science and Engineering Center, UW-Madison. Credit: NASA/NPP Team.

"NPP is right on track to ring in the New Year," said Ken Schwer, NPP project manager at NASA Goddard. "Along with VIIRS, NPP carries four more instruments that monitor the environment on Earth and the planet's climate, providing crucial information on long-term patterns to assess climate change and data used by meteorologists to improve short-term weather forecasting."

NPP serves as a bridge mission from NASA's Earth Observing System (EOS) of satellites to the next-generation Joint Polar Satellite System (JPSS), a National Oceanic and Atmospheric Administration program that will also collect weather and climate data. During NPP's five-year life, the mission will extend more than 30 key long-term datasets that include measurements of the atmosphere, land and oceans. NASA has been tracking many of these properties for decades. NPP will continue measurements of land surface vegetation, sea surface temperature, and atmospheric ozone that began more than 25 years ago.

"The task now for the science community is to evaluate VIIRS performance and determine the accuracy of its data products," said Chris Justice a professor of geography at the University of Maryland, College Park, who will be using VIIRS data in his research.

"These long-term data records are critical in monitoring how the Earth's surface is changing — either from human activity or through climate change."

The end of the IceBridge

By Alan Brown,
NASA Dryden Flight Research Center

NASA's DC-8 airborne science laboratory has completed its 2011 Operation IceBridge science flights over Antarctica, and arrived home at its base in Palmdale, Calif., Nov. 22. The IceBridge flight and science team flew a record 24 science flights during the six-week campaign, recording data from a suite of sophisticated instruments on the thickness and depth of Antarctic ice sheets and glacial movement.

The aircraft departed its deployment base at Punta Arenas, Chile, Tuesday morning Nov. 22 and after a refueling stop in Santiago, Chile, set course for Los Angeles International Airport for customs clearance. The flying lab continued on to the Dryden Aircraft Operations Facility in Palmdale, arriving about 8:30 p.m. that evening after almost 15 hours in the air.

A highlight of the IceBridge mission was the discovery during a low-level overflight Oct. 14 of a large crack that had recently begun across the Pine Island Glacier ice shelf, a precursor to the separation of an estimated 310-square-mile iceberg into the ocean in the near future. The growth of the estimated 18-mile-long rift was documented on several subsequent flights.

This is a pilot's eye view of the display from the Airborne Topographic Mapper developed by NASA's Wallops Flight Facility that allowed the DC-8 pilots to fly the exact route flown previously in earlier IceBridge missions, assuring that data collected can be compared to the previous years. Credit: NASA/Dick Ewers

The final science flights on Nov. 17 and 19 focused on the middle of the Antarctic Peninsula and the George VI Sound on the peninsula's western side.
Mission manager Chris Miller's report on the former noted that clear weather over the eastern side of the peninsula provided "a rare opportunity to collect data over glaciers that are more regularly shrouded in cloud." The mostly clear weather allowed the science team to collect data at low altitudes of only 1,500 feet above ground for almost seven hours out of the more than 11 hours the team was aloft.

After a down day on Nov. 18 for crew rest and aircraft maintenance, the converted four-engine jetliner-turned-flying-laboratory was airborne again on its final science mission of the 2011 Antarctic IceBridge campaign Nov. 19. The IceBridge team found perfect weather conditions over their survey target, the George VI Sound on the western side of the Antarctic Peninsula.

Data collection began with a long transect down the center of the sound, Miller reported, and then continued with 11 flight data lines stitching across the sound, shore to shore. Minor glitches with the Digital Mapping System and the aircraft's GPS system complicated one of the flight tracks for the Airborne Topographic Mapper instrument during the flight, but Miller said all objectives were met and the ATM data should be recoverable in post flight processing.

"Views of mountain peaks and ranges were abundant," during the 11-hour flight, he added.

The frozen, inhospitable surface features of Alexander Island in Antarctica were viewed at close range during one of the final low-level flights by NASA's DC-8 flying laboratory during the 2011 Operation IceBridge mission. Credit: NASA/Chris Miller

Due to fuel supply issues at Punta Arenas, a 25th and final science flight on Nov. 20 was cancelled, and the team prepared for its Nov. 22 departure back to the United States.

Including the transit flights between Punta Arenas and California, the modified 45-year-old flying laboratory logged about 308 flight hours during the Operation IceBridge, including 127 hours of actual data collection from its suite of seven specialized instruments. The instruments and science teams represented several NASA centers, the University of Kansas, the University of California at Santa Cruz and the Lamont-Doherty Earth Observatory at Columbia University.

Operation IceBridge was begun in 2009 to bridge the gap in data collection after NASA's ICESat-1 satellite stopped functioning and when the ICESat-2 satellite becomes operational in 2016. By comparing the year-to-year readings of ice thickness and movement both on land and on the sea, scientists can learn more about the trends that could affect sea-level rise and climate around the globe. In addition to NASA's DC-8, a smaller Gulfstream V aircraft operated by the National Science Foundation and the National Center for Atmospheric Research also participated in this fall's IceBridge mission.

DC-8 research pilot Troy Asher, who flew the final science flight, offered his reflections on this fall's Antarctic campaign.
"As you will undoubtedly hear from other reports from the science and mission director community, this has been a fantastic deployment from many different aspects," he said.

NASA's Dryden Flight Research Center director David McBride emailed his congratulations to the science team and the flight and ground crews on the completion of the 2011 mission over Antarctica.

"This was a great campaign and it makes all proud," McBride added.

Thursday, 10 November 2011

To the ends of the Earth

A close-up image of the crack spreading across the ice shelf of Pine Island Glacier shows the details of the boulder-like blocks of ice that fell into the rift when it split. For most of the 18-mile stretch of the crack that NASA’s DC-8 flew over on Oct. 26, 2011, it stretched about 240 feet wide, as roughly seen here. The deepest points ranged from about 165 to 190 feet, roughly equal to the top of the ice shelf down to sea level. Scientists expect the crack to propagate and the ice shelf to calve an iceberg of more than 300 square miles in the coming months. This image was captured by the Digital Mapping System (DMS) aboard the DC-8. Credit: NASA/DMS.

UPDATE: In further research, it has come to our attention that Pine Island Glacier last calved a large iceberg in 2007.

PUNTA ARENAS, CHILE — NASA's airborne expedition over Antarctica this October and November has measured the change in glaciers vital to sea level rise projections and mapped others rarely traversed by humans.

Operation IceBridge, nearing completion of its third year, is the largest airborne campaign ever flown over the world's polar regions. Bridging a gap between two ice elevation mapping satellites, and breaking new scientific ground on its own, IceBridge has charted the continued rapid acceleration and mass loss of Pine Island Glacier this fall.

IceBridge has now generated three years of laser altimetry data over certain locations to continue the record from NASA's Ice Climate and Elevation Satellite (ICESat), which stopped operating in 2009. IceBridge measurements show Pine Island following its rapid deterioration that began around 2006. Combined IceBridge and ICESat data show the glacier is losing more than six times as much mass per year — mass loss was measured at 7 gigatons a year in 2005 and about 46 gigatons a year in 2010 — making it one of the most significant climate change response trends that scientists see worldwide. For comparison, the Chesapeake Bay holds about 70 gigatons of water.

Satellites still operating, such as NASA's Gravity Recovery and Climate Experiment (GRACE), can provide a large-scale picture of this trend. But it takes a more focused mission such as Operation IceBridge to gather higher-resolution data near the surface to piece together the dynamic interactions of ice, bedrock and ocean currents behind specific changes, and to improve the models that scientists use to predict how much an unstable ice sheet like West Antarctica will contribute to sea level rise.

Two planes make up this year's Antarctica 2011 campaign — NASA's DC-8 flying laboratory, based at Dryden Flight Research Center, Palmdale, Cal., and a Gulfstream-V owned by the National Science Foundation and operated by the National Center for Atmospheric Research. The campaign also spotted and flew over a large rift developing across the Pine Island ice shelf on Oct. 14. A natural process, the crack could calve a new iceberg of about 350 square miles of surface area in the coming weeks or months. Pine Island Glacier hasn't calved a major iceberg since 2001.

The National Science Foundations/National Center for Atmospheric Research (NSF/NCAR) Gulfstream-V flew high-attitude missions during IceBridge Antarctica 2011. Credit: NCAR.

On a follow-up flight on Oct. 26 to gather data around Pine Island's grounding line, the DC-8 was able to fly along the crack for about 18 miles at an altitude of 3,000 feet, making what are believed to be the first detailed airborne measurements of an active calving rift.

In flights to Slessor and Recovery glaciers, which have only been traversed by humans once and twice respectively, IceBridge made a historic and scientifically important suite of measurements. Perhaps most significantly for these rarely studied regions of East Antarctica, an ice-penetrating radar instrument onboard the DC-8 was able to measure the topography of the bedrock underneath the ice sheet. Without a better understanding of the shape and contour of the bedrock, it is impossible to know how much ice sits on top of the continent in all. Topography also greatly influences the speed and direction of a glacier's ice flow.

NASA's DC-8 handled the low-attitude missions and carried the bulk of the IceBridge science instruments. Credit: NASA/Tony Landis.

"At a time when glaciers and ice sheets are showing rapid changes, we need consistent data that shows how and why that change is happening," IceBridge project scientist Michael Studinger said. "With three years of IceBridge data in hand, we have successfully continued the ice sheet elevation record in key areas and broken new ground in understanding the nature of the bedrock under ice sheets and the shape of the seafloor under ice shelves."

A gravimeter aboard the DC-8 senses changes in gravity fields to map the sea floor. This bathymetry controls ocean currents, which can inject warming waters under ice shelves and accelerate their thinning, as is happening at Pine Island and other glaciers.

The G-V was outfitted with one instrument for this campaign — a laser-ranging topographic mapper called the Land, Vegetation and Ice Sensor (LVIS). The instrument is suited for measuring large swaths of the surface at high altitudes. The G-V flew at around 45,000 feet for most of its 2011 missions.

Meanwhile, the DC-8 carries multiple instruments which are better suited for low-altitude flying. Once the plane reaches its science target, it flies at about 1,500 feet, allowing the radars, gravimeter, digital cameras and the Airborne Topographic Mapper (ATM), which captures higher resolution details of the ice surface than is possible from satellites. The DC-8's range and speed can also reach more remote, unstudied locations and cover more ground than smaller aircraft or ground traverses.

"This has been an excellent campaign for the science side of the mission, and it's our job to put the plane in positions to make that possible," said Mission Manager Walter Klein, based at Dryden.

One example of the flight side of the mission enabling science occurred during the second Pine Island Glacier flight, when the pilots flew the DC-8 by sight over the calving rift in the glacier's ice shelf at an altitude of 3,000 feet.

During the IceBridge Antarctica 2011 campaign, the DC-8 has flown 13 missions covering 51,600 miles, while the G-V has flown 11 science missions covering about 50,000 miles. As planned, the G-V left Punta Arenas to return to the United States on Weds., Nov. 2. The DC-8 is scheduled to remain in Punt Arenas up to mid-November, when it will return to its home base of Dryden Flight Research Center in Palmdale, Cal.

The next flight leg of IceBridge once the mission team wraps up in Punta Arenas will be based in Greenland in the Northern Hemisphere spring of 2012. IceBridge is scheduled to fly one Arctic and one Antarctic leg each year until ICESat-2 launches in 2016.

More . . .

Friday, 4 November 2011

Watching the birth of an iceberg

A photo from the window of NASA's DC-8 shows the rift across the Pine Island Glacier ice shelf running off toward the horizon.Credit: Michael Studinger/NASA

PUNTA ARENAS, CHILE – After discovering an emerging crack that cuts across the floating ice shelf of Pine Island Glacier in Antarctica, NASA's Operation IceBridge has flown a follow-up mission and made the first-ever detailed airborne measurements of a major iceberg calving in progress.

NASA's Operation Ice Bridge, the largest airborne survey of Earth's polar ice ever flown, is in the midst of its third field campaign from Punta Arenas, Chile. The six-year mission will yield an unprecedented three-dimensional view of Arctic and Antarctic ice sheets, ice shelves and sea ice.

Pine Island Glacier last calved a significant iceberg in 2001, and some scientists have speculated recently that it was primed to calve again. But until an Oct. 14 IceBridge flight of NASA's DC-8, no one had seen any evidence of the ice shelf beginning to break apart. Since then, a more detailed look back at satellite imagery seems to show the first signs of the crack in early October.

While Pine Island has scientists' attention because it is both big and unstable – scientists call it the largest source of uncertainty in global sea level rise projections – the calving underway now is part of a natural process for a glacier that terminates in open water. Gravity pulls the ice in the glacier westward along Antarctica's Hudson Mountains toward the Amundsen Sea. A floating tongue of ice reaches out 30 miles into the Amundsen beyond the grounding line, the below-sea-level point where the ice shelf locks onto the continental bedrock. As ice pushes toward the sea from the interior, inevitably the ice shelf will crack and send a large iceberg free.

"We are actually now witnessing how it happens and it’s very exciting for us," said IceBridge project scientist Michael Studinger, Goddard Space Flight Center, Greenbelt, Md. "It’s part of a natural process but it’s pretty exciting to be here and actually observe it while it happens. To my knowledge, no one has flown a lidar instrument over an actively developing rift such as this."

A primary goal of Operation IceBridge is to put the same instruments over the exact same flight lines and satellite tracks, year after year, to gather meaningful and accurate data of how ice sheets and glaciers are changing over time. But discovering a developing rift in one of the most significant science targets in the world of glaciology offered a brief change in agenda for the Oct. 26 flight, if only for a 30-minute diversion from the day's prescribed flight lines.

The IceBridge team observed the rift running across the ice shelf for about 18 miles. The lidar instrument on the DC-8, the Airborne Topographic Mapper, measured the rift's shoulders about 820 feet apart (250 meters) at its widest, although the rift stretched about 260 feet wide along most of the crack. The deepest points from the ice shelf surface ranged 165 to 195 feet (50 to 60 meters). When the iceberg breaks free it will cover about 340 square miles (880 square kilometers) of surface area. Radar measurements suggested the ice shelf in the region of the rift is about 1,640 feet (500 meters) feet thick, with only about 160 feet of that floating above water and the rest submerged. It is likely that once the iceberg floats away, the leading edge of the ice shelf will have receded farther than at any time since its location was first recorded in the 1940s.

In October, 2011, NASA's Operation IceBridge discovered a major rift in the Pine Island Glacier in western Antarctica. This crack, which extends at least 18 miles and is 50 meters deep, could produce an iceberg more than 800 square kilometers in size. IceBridge scientists returned soon after to make the first-ever detailed airborne measurements of a major iceberg calving in progress. Credit: NASA/Goddard/Jefferson Beck

Veteran DC-8 pilot Bill Brockett first flew the day's designed mission, crisscrossing the flow of the glacier near the grounding line to gather data on its elevation, topography and thickness. When it came time to investigate the crack, Brockett flew across it before turning to fly along the rift by sight. The ATM makes its precision topography maps with a laser than scans 360 degrees 20 times per second, while firing 3,000 laser pulses per second. When flying at an altitude of 3,000 feet, as during this flight, it measures a swath of the surface about 1,500 feet wide. As the crack measured at more than 800 feet wide in places, it was important for Brockett to hold tight over the crevasse.

"The pilots did a really nice job of keeping the aircraft and our ATM scan swath pretty much centered over the rift as you flew from one end to the other," said Jim Yungel, who leads the ATM team out of NASA's Wallops Island Flight Facility in Virginia. "It was a real challenge to be told…we’re going to attempt to fly along it and let’s see if your lidar systems can map that crack and can map the bottom of the crack.

"And it was a lot of fun on a personal level to see if something that you built over the years can actually do a job like that. So, yeah, I enjoyed it. I really enjoyed seeing the results being produced."

While the ATM provided the most detailed measurements of the topography of the rift, other instruments onboard the DC-8 also captured unique aspects. The Digital Mapping System, a nadir-view camera, gathered high-definition close-ups of the craggy split. On the flight perpendicular to the crack, the McCORDS radar also measured its depth and the thickness of the ice shelf in that region.

Catching the rift in action required a bit of luck, but is also testimony to the science benefit of consistent, repeated trips and the flexibility of a manned mission in the field.

"A lot of times when you’re in science, you don’t get a chance to catch the big stories as they happen because you’re not there at the right place at the right time," said John Sonntag, Instrument Team Lead for Operation IceBridge, based at Goddard Space Flight Center. "But this time we were."


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