NASA has been on a mission with GRACE (Gravity Recovery and Climate Experiment) for the last 10 years, the data is in.
The GRACE mission was selected as the second mission under the NASA Earth System Science Pathfinder (ESSP) Program in May 1997. Launched in March of 2002, the GRACE mission is accurately mapping variations in Earth’s gravity field. Designed for a nominal mission lifetime of five years, GRACE is currently operating in an extended mission phase, which is expected to continue through at least 2015.
GRACE consists of two identical spacecraft that fly about 220 kilometers (137 miles) apart in a polar orbit 500 kilometers (310 miles) above Earth. GRACE maps Earth’s gravity field by making accurate measurements of the distance between the two satellites, using GPS and a microwave ranging system. It is providing scientists from all over the world with an efficient and cost-effective way to map Earth’s gravity field with unprecedented accuracy. The results from this mission are yielding crucial information about the distribution and flow of mass within Earth and its surroundings.
The gravity variations studied by GRACE include: changes due to surface and deep currents in the ocean; runoff and ground water storage on land masses; exchanges between ice sheets or glaciers and the ocean; and variations of mass within Earth. Another goal of the mission is to create a better profile of Earth’s atmosphere. GRACE results are making a huge contribution to the goals of NASA’s Science Mission Directorate, Earth Observation System (EOS) and global climate change studies.
GRACE is a joint partnership between the National Aeronautics and Space Administration (NASA) in the United States and Deutsche Forschungsanstalt für Luft und Raumfahrt (DLR) in Germany. Dr. Byron Tapley of The University of Texas Center for Space Research (UTCSR) is the Principal Investigator (PI), and Frank Flechtner of the GeoForschungsZentrum (GFZ) Potsdam is the Co-Principal Investigator (Co-PI). Project management and systems engineering activities are carried out by the Jet Propulsion Laboratory.
NASA’s Gravity Recovery and Climate Experiment (GRACE) has measured significant groundwater depletion around the world in recent years.
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Global Ice Mass Changes
This figure shows changes in global mean sea level as measured by satellite altimetry (NASA/CNES Topex/Poseidon and Jason-1; and NASA/CNES/NOAA/EUMETSAT Jason-2) between 1992 to 2012. The data have been averaged to account for long time scale variations in sea level. The average annual increase in sea level over this timeframe, depicted by the blue line, is 3.2 millimeters per year. The inset shows changes in Earth’s water mass from the beginning of 2010 to mid 2011. Blue colors indicate an increase in water mass over the continents. A new NASA study shows that most of the sea level drop in 2010-11 [red circle] was related to the mass transport of water from the ocean to the continents (primarily Australia, northern South America and Southeast Asia [blue arrows]). While the ocean “lost” water, the continents experienced a gain because of increased rainfalls brought on by the 2010/11 La Nina. By mid-2012, global mean sea level had recovered by more than the 5 millimeters it dropped in 2010/11.
Animation shows the location of mountain glaciers and ice caps around the world with data from the GRACE mission to show recent trends in ice mass loss or gain.
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Alaska’s Big Thaw
Climate change scientists say that Alaska is warming at twice the rate of the rest of the planet. Erosion, flooding and a drastically changing landscape is putting locals at the forefront of a crisis.
“It’s changing. The ice is getting thinner. Warming up early. Getting cold late. Summer is snowing, winter is raining.” The native Alaskan community of Newtok is predicted to be underwater by 2017 and locals like Reppi Swan say it’s getting harder and harder to hunt because of the rapidly disappearing ice. There are 23,000 glaciers in Alaska, and glaciologist Tad Pfeffer believes they are all shrinking. “Every day I wake up and look out my window and think, ‘wow this is scary'”, says Robin Bronen, a local of 25 years. As the imperative to relocate whole communities grows stronger, anxieties over lack of government funds or action is causing growing anger. In response locals have started filing law suits against the oil companies they hold responsible for the rising temperatures. “The government aren’t dealing with the problem. Our lawsuit is going to the source”, argues local resident Colleen Swan. Has Alaska already reached the tipping point?
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