Mobilisation of Buried 'Black carbon' - Deposits flow from soil to oceans

By sampling rivers all around the world, the researchers estimated that the annual amount of black carbon flowing via rivers to the ocean is 27 million tons per year.

A smaller proportion of black carbon created during combustion will remain in soil than have been estimated before.

Contrary to previous understanding, burying black carbon in the ground to restrain climate change will not create a permanent carbon reserve.

Instead, a part of black carbon will dissolve from soil to rivers. The flux of dissolved black carbon from the rivers to the ocean was estimated in a research article published in Science.

The burning of organic matter creates 40 million tons of black carbon every year. Black carbon is formed through the incomplete combustion of organic matter, e.g. in forest fires, slash-and-burn and controlled burning of fields.

The general assumption has been that black carbon would remain in soil even for millions of years.

However, recently published research indicates that a remarkable proportion of black carbon in soil will dissolve to the water system.

In the light of new research results, much discussed "bio-carbon" may not be that beneficial in terms of mitigating climate change.

Carbon is given the prefix "bio" when it is used both for energy production and soil enrichment. In any case, the stability of carbon in soil has been a central factor of bio-carbon applications.

By sampling rivers all around the world, the researchers estimated that the annual amount of black carbon flowing via rivers to the ocean is 27 million tons per year.

"Each sample included a significant amount of black carbon," says a research participant Anssi Vahatalo  Senior Lecturer from the University of Jyvaskyla, Helsinki.

"On average, the amount of black carbon was ten per cent of the amount of dissolved organic carbon. The results prove that the proportion of water soluble black carbon may be as much as 40 per cent of black carbon created annually.

Anssi Vahatalo

Water samples from the largest rivers in the world
The basis of the research was the 'Big river'-project started by Senior Lecturer Anssi Vahatalo while he was working as an Academy Research Fellow at the University of Helsinki before moving to the University of Jyvaskyla. For this project, water samples were collected from the ten largest rivers in the world.

"These rivers carry one third of fresh water running to oceans, and their catchment area covers 28% of the whole land area in the world. Water samples were taken, e.g. from Amazon, the largest river in the world," says Vahatalo.

In addition to the samples used in the river project, the research published in Science was supplemented with samples from many other rivers all over the world. The total number of researched samples was 174.

Mars Marte Vallis: New 3-D reconstructions show buried flood channels

3D visualization of the buried Marte Vallis channels beneath the martian surface. 

Marte Vallis consists of multiple perched channels formed around streamlined islands. 

These channels feed a deeper and wider main channel. 

NB: the surface has been elevated, and scaled by a factor of 1/100 for clarity. 

The colour scale represents the elevation of the buried channels relative to a martian datum (NB: the values are negative because the elevation of the surface of Mars in this region is also negative - below the average global elevation).

Image: Smithsonian/NASA/JPL-Caltech/Sapienza University of Rome/MOLA Team/USGS

New maps of the subsurface of Mars show for the first time buried channels below the surface of the red planet. Mars is considered to have been cold and dry over the past 2.5 billion years, but these channels suggest evidence of flooding.

Understanding the source and scale of the young channels present in Elysium Planitia-an expanse of plains along the equator, and the youngest volcanic region on the planet-is essential to comprehend recent Martian hydrologic activity and determine if such floods could have induced climate change.

The findings are reported by a team from NASA's Goddard Space Flight Center, the Jet Propulsion Laboratory, the Planetary Science Directorate in the Southwest Research Institute and the Smithsonian Institution, led by Smithsonian scientist Gareth A.

Morgan, in a paper, "3D Reconstruction of the Source and Scale of Buried Young Flood Channels on Mars" scheduled for publication in the journal Science.

As a consequence of extensive volcanism throughout the past several hundred million years, young lava covers most of the surface of Elysium Planitia, burying evidence of its recent geologic history, including the source and most of the length of the 1,000 kilometer-long Marte Vallis channel system.

Marte Vallis has a similar morphology to more ancient channel systems on Mars that likely formed by the catastrophic release of ground water; however, little is known about Marte Vallis due to its burial by lava.

The team used data from the Shallow Radar on board the NASA Mars Reconnaissance Orbiter spacecraft to probe the subsurface of Elysium Planitia. They were able to map the buried channels and establish that the floods originated from a now buried portion of the Cerberus Fossae fracture system.

"Our findings show that the scale of erosion was previously underestimated and that channel depth was at least twice that of previous approximations," said Morgan, geologist at the National Air and Space Museum's Center for Earth and Planetary Studies and lead author on the paper.

"The source of the floodwaters suggests they originated from a deep groundwater reservoir and may have been released by local tectonic or volcanic activity. This work demonstrates the importance of orbital sounding radar in understanding how water has shaped the surface of Mars."

Mars Reconaissance Orbiter: Radar Map Of Buried Martian Ice

A radar on NASA's Mars Reconnaissance Orbiter has detected widespread deposits of glacial ice in the mid-latitudes of Mars.

Extensive radar mapping of the middle-latitude region of northern Mars shows that thick masses of buried ice are quite common beneath protective coverings of rubble.

The ability of NASA's Mars Reconnaissance Orbiter to continue charting the locations of these hidden glaciers and ice-filled valleys - first confirmed by radar two years ago - adds clues about how these deposits may have been left as remnants when regional ice sheets retreated.

The subsurface ice deposits extend for hundreds of kilometers, or miles, in the rugged region called Deuteronilus Mensae, about halfway from the equator to the Martian north pole.

Jeffrey Plaut of NASA's Jet Propulsion Laboratory, Pasadena, Calif., and colleagues prepared a map of the region's confirmed ice for presentation at this week's 41st Lunar and Planetary Science Conference near Houston.

The Shallow Radar instrument on the orbiter has obtained more than 250 observations of the study area, which is about the size of California.

"We have mapped the whole area with a high density of coverage," Plaut said. "These are not isolated features. In this area, the radar is detecting thick subsurface ice in many locations." The common locations are around the bases of mesas and scarps, and confined within valleys or craters.