A new NASA
climate simulation suggests that extremely large volcanic eruptions
called flood basalt eruptions can significantly warm Earth's climate
and devastate
the ozone layer that shields life from the sun's ultraviolet radiation.
Unlike brief, explosive volcanic eruptions that occur over hours or days,
flood basalts are regions with a series of eruptions, perhaps
centuries each, and occurring over periods of hundreds
to thousands of years, sometimes even longer.
Some happen at about the same time as mass extinction events, and many
are associated with extremely warm periods in Earth's history.
Researchers used the Goddard Earth Observing System Chemistry Climate Model
to simulate one such flood basalt eruption.
The four year long phase of the Columbia River basalt
that occurred between 15 to 17 million years ago in the Pacific Northwest,
the model
calculated the effects of the eruption on the troposphere,
the lowest layer of the atmosphere with most of the water vapor and weather
and the stratosphere that is mostly dry and calm.
Scientists expected to see intense cooling in simulations.
However, they found that a brief cooling period of about two years
was overwhelmed by an intense warming effect.
In the simulation, the Amazon and East Central Australia
reached monthly mean temperatures of 49 degrees
Celsius in the Arabian Peninsula.
July mean temperatures were equal to or exceeded
55 degrees Celsius
in the central United States.
There were extreme monthly mean temperatures equal to
or exceeding 40 degrees Celsius
the simulations predicted a reduction in the ozone
by about two thirds over global average values,
which is roughly equivalent to the whole planet
having an ozone thinning comparable to a severe Antarctic ozone hole.
Eruptions emit
sulfur dioxide gas into the atmosphere
which converts to solid sulfate aerosols.
These aerosols reflect visible sunlight,
which causes the initial cooling effect
but also absorb infrared radiation,
which warms the upper atmosphere.
In the simulation, most portions of the atmosphere
were almost completely opaque to the sun.
Warming this region of the atmosphere allows water vapor
that's usually near the surface to get mixed into the dry stratosphere.
Water vapor is a greenhouse gas that emits infrared radiation to warm the planet.
In the simulation, there was a 10000% increase
in stratospheric water vapor
These flood basalt eruptions also appear to have been common on other
terrestrial worlds in our solar system, such as Mars and Venus.
Although Mars and Venus may have had oceans of water
in the distant past, both are currently very dry.
Scientists are investigating how these worlds lost
most of their water to become inhospitable for life.
And if the predictions of this simulation are correct, extensive flood
basalt eruptions could have contributed to their arid fates.