NASA AQUA MODIS Image: Totten Glazier melt rate linked to Sea Ice conditions

This image shows the Totten Glacier ice shelf in East Antarctica (the wrinkled white area at top left) on Sept. 25, 2013. 

Two large open-water polynyas appear on the sea ice below and to the right of the shelf, as well as several smaller ones. 

The open-water areas are bright black. 

The stippled diagonal line from lower left to upper right is the outer edge of the sea ice, with cloud cover to the right of that line. 

The image is from the Moderate Resolution Imaging Spectroradiometer (MODIS) instrument on NASA's Aqua satellite. 

Credit: NASA.

A new NASA-led study has discovered an intriguing link between sea ice conditions and the melting rate of Totten Glacier, the glacier in East Antarctica that discharges the most ice into the ocean.

The discovery, involving cold, extra salty water - brine - that forms within openings in sea ice, adds to our understanding of how ice sheets interact with the ocean, and may improve our ability to forecast and prepare for future sea level rise.

"I was curious why Totten was changing so fast when the glacier just next to it wasn't changing much," said Ala Khazender of NASA's Jet Propulsion Laboratory, Pasadena, Calif., lead author of the new study, published online Dec. 5 in the journal Nature Communications.

Combining satellite observations with ocean numerical modeling, Khazender and his colleagues developed a hypothesis that reductions in the volume of brine would increase Totten's thinning and melting.

Additional research supported that hypothesis.

Ice loss seen in Antarctica is generally attributed to the well-documented rise in temperature of the surrounding ocean, but scientists are still puzzling out the mechanisms behind the regional variations that they are observing.

The new study highlights the key role of processes occurring on small geographic scales in determining how global climate change can affect the stability of ice sheets.

Satellite observations from NASA's ICESat-1, which measures how much ice surfaces are rising or falling over time, revealed that Totten Glacier was thinning rapidly.

It currently discharges enough ice into the surrounding ocean to fill Lake Erie in just over a week.

The nearby Moscow University Glacier and its floating ice shelf were showing little change. Why the difference?

"We were convinced that the answer must be in the ocean," Khazender said.

The ocean around Antarctica is warmer than both the continent's icy surface and the polar air. Ice shelves (the floating front edges of glaciers that extend tens to hundreds of miles offshore) melt more because of contact with ocean water below them than they do because of sunlight.

Melting at the undersides of ice shelves is part of Antarctica's natural water cycle, but when glaciers start melting unusually quickly, it's a sign that something is off balance.

Khazender and his team of colleagues from JPL; UCLA; the University of California, Irvine; and Utrecht University in the Netherlands combined ICESat remote sensing observations from 2003 to 2008 with ocean numerical computer models to seek insights into the interaction between the ice shelves and their ocean basin.

More information: For more information on ICESat, visit: icesat.gsfc.nasa.gov/ .For more information on the ECCO2 ocean modeling and data synthesis project, visit: ecco2.jpl.nasa.gov/

NASA Mars Rover Curiosity: Discovers Conditions Once Suited for Ancient Life

An analysis of a rock sample collected by NASA's Curiosity rover shows ancient Mars could have supported living microbes.

Scientists identified sulfur, nitrogen, hydrogen, oxygen, phosphorus and carbon -- some of the key chemical ingredients for life -- in the powder Curiosity drilled out of a sedimentary rock near an ancient stream bed in Gale Crater on the Red Planet last month.

"A fundamental question for this mission is whether Mars could have supported a habitable environment," said Michael Meyer, lead scientist for NASA's Mars Exploration Program at the agency's headquarters in Washington. "From what we know now, the answer is yes."

Clues to this habitable environment come from data returned by the rover's Sample Analysis at Mars (SAM) and Chemistry and Mineralogy (CheMin) instruments.

The data indicate the Yellowknife Bay area the rover is exploring was the end of an ancient river system or an intermittently wet lake bed that could have provided chemical energy and other favorable conditions for microbes.

The rock is made up of a fine-grained mudstone containing clay minerals, sulfate minerals and other chemicals. This ancient wet environment, unlike some others on Mars, was not harshly oxidizing, acidic or extremely salty.

The patch of bedrock where Curiosity drilled for its first sample lies in an ancient network of stream channels descending from the rim of Gale Crater. The bedrock also is fine-grained mudstone and shows evidence of multiple periods of wet conditions, including nodules and veins.

Curiosity's drill collected the sample at a site just a few hundred yards away from where the rover earlier found an ancient streambed in September 2012.

"Clay minerals make up at least 20 percent of the composition of this sample," said David Blake, principal investigator for the CheMin instrument at NASA's Ames Research Center in Moffett Field, Calif.

These clay minerals are a product of the reaction of relatively fresh water with igneous minerals, such as olivine, also present in the sediment. The reaction could have taken place within the sedimentary deposit, during transport of the sediment, or in the source region of the sediment. The presence of calcium sulfate along with the clay suggests the soil is neutral or mildly alkaline.

Scientists were surprised to find a mixture of oxidized, less-oxidized, and even non-oxidized chemicals, providing an energy gradient of the sort many microbes on Earth exploit to live. This partial oxidation was first hinted at when the drill cuttings were revealed to be gray rather than red.

"The range of chemical ingredients we have identified in the sample is impressive, and it suggests pairings such as sulfates and sulfides that indicate a possible chemical energy source for micro-organisms," said Paul Mahaffy, principal investigator of the SAM suite of instruments at NASA's Goddard Space Flight Center in Greenbelt, Md.

An additional drilled sample will be used to help confirm these results for several of the trace gases analyzed by the SAM instrument.

"We have characterized a very ancient, but strangely new 'gray Mars' where conditions once were favorable for life," said John Grotzinger, Mars Science Laboratory project scientist at the California Institute of Technology in Pasadena, Calif.

"Curiosity is on a mission of discovery and exploration, and as a team we feel there are many more exciting discoveries ahead of us in the months and years to come."

Scientists plan to work with Curiosity in the "Yellowknife Bay" area for many more weeks before beginning a long drive to Gale Crater's central mound, Mount Sharp.

Investigating the stack of layers exposed on Mount Sharp, where clay minerals and sulfate minerals have been identified from orbit, may add information about the duration and diversity of habitable conditions.