Examining the genomes of octopuses that inhabit Antarctica's frigid seas is
an inventive method used by researchers to try and understand how the
continent's ice sheets receded in the distant past.
Eight-limbed sea animals mated easily across geographically dispersed
populations around 125,000 years ago, indicating an ice-free corridor during
a time when global temperatures were comparable to those of today, according
to a new research published in
Science on Thursday.
The results indicate that the West Antarctic Ice Sheet (WAIS) may be more vulnerable to collapse than previously believed, posing a
hazard to long-term sea level rise of 3.3-5 meters if global warming from
human activity cannot be contained to the 1.5 degrees Celsius limit set by
the Paris Agreement, according to the authors.
As an evolutionary biologist studying marine invertebrates, lead scientist
Sally Lau of James Cook University in Australia told AFP, "I understand and
then apply DNA and biology as a proxy of changes to Antarctica in the
past."
Turquet's octopus, she said, was a prime option for investigating WAIS as
the species is widespread over the continent and basic questions about it,
including its 12-year life span and its estimated four million-year
evolutionary history, had already been resolved by science.
They measure around 1.3 pounds (600 kilos) and are about half a foot (15
cm) long, excluding the limbs. They deposit comparatively few, but huge,
eggs on the seabed. This implies that parents have to work very hard to
ensure that their kids hatch and have a lifestyle that keeps them from going
too far away.
In several of their contemporary environments, they are also restricted by
gyres, or circular marine currents.
Lau and colleagues discovered evidence of trans-West Antarctic seaways that
formerly connected the Weddell, Amundsen, and Ross seas by sequencing the
genomes of 96 samples, most of which were unintentionally acquired as
fishing bycatch and then stored in museums for 33 years.
The history of genetic mixing suggested that WAIS collapsed twice: first
during the Last Interglacial, a warm era that lasted from 129,000 to 116,000
years ago, during the mid-Pliocene, around 3-3.5 million years ago, about
which scientists were previously certain.
"This was the last time the planet was around 1.5 degrees warmer than
pre-industrial levels," Lau stated. In comparison to the late 1700s, human
activity—primarily the combustion of fossil fuels—has boosted global
temperatures by 1.2C thus far.
"Tipping point of future WAIS collapse is close"
Before the recent Science study, a few studies also showed that WAIS
collapsed at some point in the past, but the relatively poor resolution
genetic and geological data made them far from definitive.
"This study provides empirical evidence indicating that the WAIS collapsed
when the global mean temperature was similar to that of today, suggesting
that the tipping point of future WAIS collapse is close," the authors
stated.
A 3.3-meter rise in sea level will completely change the world map,
engulfing all low-lying coastal communities.
The new research is "pioneering," according to Andrea Dutton of the
University of Wisconsin-Madison and Robert DeConto of the University of
Massachusetts, Amherst, who wrote an accompanying opinion article. They also
said that the discovery raised interesting concerns regarding whether or not
past history will be reproduced.
They did, however, draw attention to the fact that a number of important
concerns remained unsolved, such as whether rising temperatures alone were
responsible for the last ice sheet collapse or if other factors, such as
shifting ocean currents and intricate interactions between ice and solid
Earth, were also at play.
Furthermore, it's unclear if the rise in sea level will happen gradually
over millennia or more quickly.
They said, "and this latest piece of evidence from octopus DNA stacks one
more card on an already unstable house of cards," but uncertainties like
this cannot be used as an excuse for inactivity against
climate change.
Current events pertaining to Antarctic ice
The study was conducted around one month after scientists announced on
Friday that the
largest iceberg in the world
was "on the move" after being cemented to the ocean floor for 37 years. The
British Antarctic Survey reports that the iceberg, known as
A23a, is currently traveling past the northern point of the Antarctic Peninsula
and toward the Southern Ocean based on recent satellite pictures.
Dramatic footage
shot by the ship's crew, including drone footage of a pod of orcas swimming
adjacent to the gigantic iceberg, was made public earlier this month by the
survey.
The European Space Agency (ESA) has provided data indicating that the
weight of the iceberg is
around one trillion tons.
The iceberg broke off from the Antarctic coast in 1986, covering an area of
over 4,000 square kilometers (or 1,500 square miles), but it later grounded
in the Weddell Sea,
according
to the BBC.
A massive, hidden landscape of hills and valleys sculpted by ancient rivers
that have been "frozen in time" beneath the Antarctic ice for millions of years was uncovered by
geologists in October.
The study's principal author, Stewart Jamieson, a glaciologist at Durham
University in the United Kingdom, told
AFP that "no one has laid eyes on it."
According to Jamieson, the region underneath the East Antarctic Ice Sheet
is not as well-known as the surface of Mars.
The region, which covers 32,000 square kilometers (12,000 square miles),
was formerly home to woods, trees, and maybe even some wildlife.
However, Jamieson stated that it was "frozen in time" when the ice
appeared.
