Thawing permafrost could release vast amounts of carbon and accelerate climate change by the end of this century

Dan Krotz in the Lawrence Berkeley National Labotatory News: Billions of tons of carbon trapped in high-latitude permafrost may be released into the atmosphere by the end of this century as the Earth’s climate changes, further accelerating global warming, a new computer modeling study indicates. The study also found that soil in high-latitude regions could shift from being a sink to a source of carbon dioxide by the end of the 21st century as the soil warms in response to climate change.



The research was led by Charles Koven of the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab). He conducted the research with a team of scientists from France, Canada, and the United Kingdom while he was a postdoctoral researcher at France’s Laboratoire des Sciences du Climat et de l’Environnement. The modeling was conducted at a supercomputing facility run by France’s Alternative Energies and Atomic Energy Commission.



...Their findings counter results from a comparison of models that was included in the Intergovernmental Panel on Climate Change’s 2007 fourth assessment report. The comparison found that climate change will spark a growth in high-latitude vegetation, which will pull in more carbon from the atmosphere than thawing permafrost will release.



But unlike earlier models, the new model includes detailed processes of how carbon accumulates in high-latitude soil over millennia, and how it’s released as permafrost thaws. Because it includes these processes, the model begins with much more carbon in the soil than previous models. It also better represents the carbon’s vulnerability to decomposition as the soil warms.



As a result, the new model found that the increase in carbon uptake by more vegetation will be overshadowed by a much larger amount of carbon released into the atmosphere. “Including permafrost processes turns out to be very important,” says Koven, who joined Berkeley Lab’s Earth Sciences Division as a staff scientist earlier this year. “Previous models tended to dramatically underestimate the amount of soil carbon at high latitudes because they lacked the processes of how carbon builds up in soil. Our model starts off with more carbon in the soil, so there is much more to lose with global warming.”...



A sink becomes a source, as revealed by these two simulations of net CO2 fluxes due to climate change at the end of 21st century. The control simulation on the left did not include permafrost processes. The permafrost simulation on the right included processes that depict how carbon accumulates in soil and how it decomposes. In the latter simulation, large carbon losses are seen in central Canada where substantial permafrost stocks exist that are vulnerable to warming. Units are in grams of carbon per square meter per year.

Measurements at California pier reveal extent of leakage from damaged Fukushima reactor

University of Califorinia at San Diego: Atmospheric chemists at the University of California, San Diego, report the first quantitative measurement of the amount of radiation leaked from the damaged nuclear reactor in Fukushima, Japan, following the devastating earthquake and tsunami earlier this year.



Their estimate, reported August 15 in the early, online edition of the Proceedings of the National Academy of Sciences, is based on a signal sent across the Pacific Ocean when operators of the damaged reactor had to resort to cooling overheated fuel with seawater. “In any disaster, there’s always a lot to be learned by analysis of what happened,” said senior author Mark Thiemens, Dean of the Division of Physical Sciences at UC San Diego. “We were able to say how many neutrons were leaking out of that core when it was exposed.”



On March 28, 2011, 15 days after operators began pumping seawater into the damaged reactors and pools holding spent fuel, Thiemens’ group observed an unprecedented spike in the amount of radioactive sulfur in the air in La Jolla, California. They recognized that the signal came from the crippled power plant.



Neutrons and other products of the nuclear reaction leak from fuel rods when they melt. Seawater pumped into the reactor absorbed those neutrons, which collided with chloride ions in the saltwater. Each collision knocked a proton out of the nucleus of a chloride atom, transforming the atom to a radioactive form of sulfur.



When the water hit the hot reactors, nearly all of it vaporized into steam. To prevent explosions of the accumulating hydrogen, operators vented the steam, along with the radioactive sulfur, into the atmosphere. In air, sulfur reacts with oxygen to form sulfur dioxide gas and then sulfate particles. Both blew across the Pacific Ocean on prevailing westerly winds to an instrument at the end of the pier at UC San Diego’s Scripps Institution of Oceanography where Thiemens’ group continuously monitors atmospheric sulfur.



Using a model based on NOAA’s observations of atmospheric conditions at the time, the team determined the path air took on its way to the pier over the preceding 10 days and found that it led back to Fukushima....



Air laden with radioactive sulfur can be traced to the source near the Fukushima reactor in Japan using data collected by NOAA. Image Credit: Gerardo Dominguez