Chinese researchers identify new ‘geochemical switch’ regulating Earth’s Climate
GUANGZHOU, 1 October (BelTA — China Daily) — The shifts in marine
sulfate concentrations can flip the way that methane is consumed on the
seafloor, acting as a geochemical switch that modulates Earth’s climate,
according to a research article published in the journal Nature
Geoscience.
The researchers of the study, from the Guangzhou
Institute of Geochemistry (GIG) of the Chinese Academy of Sciences
(CAS), warned that a similar switch may emerge again as the modern
Arctic Ocean warms and freshens at an accelerating pace.
They
noted that the Earth endured an extreme period of global warming and
ocean acidification, known as the Paleocene-Eocene Thermal Maximum, 56
million years ago. Such an event mirrors many features of today’s
climate crisis.
Methane is the second-most important greenhouse
gas following carbon dioxide, and vast quantities of it are locked up
under the seafloor. Until recently, scientists have been concerned that
the methane released from the seafloor would surge directly into the
atmosphere, thereby contributing to global warming.
However,
recent studies have shown that most methane released from the seafloor
dissolves rapidly into seawater and is then «digested» by various
microbes, with only a small amount ever reaching the atmosphere.
During
these processes, microbes utilize sulfate as their «fuel» to convert
methane energy with high efficiency, while simultaneously generating
alkaline by-products that help counteract ocean acidification, said
Zhang Yige, a professor at the GIG.
However, 56 million years ago, the sulfate concentration in Arctic waters was less than one-third of its current level.
With
sulfate in critically short supply, methane diffused into the water
column. Therefore, the aerobic bacteria ignited a rapid «flash-burn» of
methane, releasing a surge of carbon dioxide into the water.
The
researchers disclosed that the carbon dioxide levels in the Arctic Ocean
56 million years ago were significantly higher than the global average.
This shows that the Arctic Ocean had transformed from a «sponge» that
absorbed carbon dioxide to a «chimney» that emitted it.
Their study highlights potential major perturbations to Arctic carbon cycling under future climate change.
