Identifying the diverse sources of methane
in shallow Arctic lakes
R
esearch on the changing ecology of thousands of
shallow lakes on the North Slope of Alaska suggests
that in scenarios of increasing global temperatures,
methane-generating microbes (found in thawing lake
sediments) may ramp up production of the potent
greenhouse gas—which has a global warming potential
25 times greater than carbon dioxide.
Five years of collaborative research, led by DRI’s
Alison Murray, Ph.D., and Paula Matheus Carnevali,
a doctoral student at DRI, found that the methane
detected in lake sediments in this region can arise from
both ancient thermogenic sources deep in the earth,
or from shallow contemporary biological sources. The
study marked an important step in recognizing that
there are different methane sources in close proximity
that may respond differently in the changing Alaskan
Arctic ecosystems.
RESEARCH
STORIES FROM ACROSS
THE INSTITUTE
Volcanic eruptions that changed human
history
IT
4
is well known that large volcanic eruptions contribute
to climate variability. However, quantifying these
contributions has proven challenging due to
inconsistencies in both historic atmospheric data
observed in ice cores and corresponding temperature
variations seen in climate proxies such as tree rings.
A study published in the journal Nature in July 2015,
led (or first authored) by Michael Sigl, Ph.D., an assistant
research professor at DRI and doctoral fellow with the
Paul Scherrer Institute in Switzerland, resolved these
inconsistencies with a new reconstruction of the timing
and associated radiative forcing of nearly 300 individual
volcanic eruptions extending as far back as the early
Roman period.
The study showed that 15 of the 16 coldest summers
recorded between 500 B.C. and 1,000 A.D. followed large
volcanic eruptions—with four of the coldest occurring
shortly after the largest volcanic events found on record.
The reconciliation of ice-core records and other
records of past environmental change is helping climate
scientists and modelers around the world define the role
that large climatic perturbations may have had in the
rise and fall of civilizations throughout human history.