|
Woods
Hole Oceanographic Institution (WHOI) scientists have found that
carbon is stored in the soils and sediments of the Ganges-Brahmaputra
basin for a surprisingly long time, making it likely that global
warming could destabilize the pool of carbon there and in similar
places on Earth, potentially increasing the rate of CO2 release into
the atmosphere. The study, published in the current online edition of
Nature Geoscience, examined the radiocarbon content of river
sediments collected from the Ganges-Brahmaputra system draining the
Himalayas. The basin, the scientists say, "represents one of the
largest sources of terrestrial biospheric carbon to the ocean."
Using
radiocarbon dating, WHOI researchers Valier Galy and Timothy Eglinton
found that organic carbon resides in the basin for anywhere from 500
to 17,000 years. Downstream, in the Gangetic floodplain, the longest
residence times range from 1,500 to 3,500 years.
Valier
Galy
WHOI
Researcher
 "The
relatively long carbon residence time in the Ganges system was a
surprise, primarily because of the region's dynamically high rates of
physical erosion and sediment transport. We thought it was likely
that the organic matter there was young, but what gets exported there
sits in the soil for quite some time -- 3,000 years on average.
That's pretty old. The good news is that the Ganges-Brahmaputra basin
"is not contributing rapidly to CO2 in the atmosphere. The bad
news is that makes the region more susceptible to global warming.
That has "big implications for the global carbon cycle, because
the longer it is stored in the soil, the longer it is kept away from
the atmosphere as CO2. The buildup of CO2 in the atmosphere is
thought to be largely responsible for global warming. Future
environmental changes may dictate that carbon will not stay as long
in the soil. If this happens, the net source of CO2 in the atmosphere
will increase. Even though there have been few similar studies in
other low latitude regions, the results of the WHOI study could
portend global warming effects elsewhere in the world. Our study
shows that ancient soil carbon exists in a globally significant
tropical system. We therefore hypothesize that similar stocks of
ancient carbon may exist elsewhere at low latitude. Global warming
would likely destabilize this ancient carbon, generating an extra
flux of CO2 to the atmosphere, hence further warming. This may not be
too important over the short-term -- decades, for example, but over a
longer time scale -- tens of thousands of years -- it can be
important."
|
Various
climate projections predict a 4-degree C warming in the region by
2050, according to the last Intergovernmental Panel on Climate Change
(IPCC) report.
The
work was funded by the National Science Foundation.
Source: Woods
Hole Oceanographic Institution
Journal
Reference:
Valier
Galy, Timothy Eglinton. Protracted storage of biospheric carbon in
the Ganges–Brahmaputra basin. Nature Geoscience, 2011; DOI:
10.1038/ngeo1293
|
|
