A mysterious hole nearly the size of South Carolina has opened in Antarctica's ice



polynya
The
hole in the sea ice as seen by NASA satellite imagery on
September 25.


NASA


  • A massive hole called a polynya recently appeared
    in Antarctica’s frozen sea ice.
  • The hole is unusual because it’s huge and far from the
    coast where such open water patches more frequently
    appear.
  • Another larger version of this polynya was
    observed in the mid 1970s.

A massive hole opened in the middle of the frozen Weddell Sea of
Antarctica last month.

Persistent areas of open water in places where you’d expect sea
ice, such as in the Arctic and Antarctic, are known as polynyas,

according to the National Snow and Ice Data Center
.

This Weddell polynya, however, is somewhat remarkable.

No one knows why it formed, and the hole is located quite
far from the sea ice coastline, where such
openings more frequently appear. And
despite being exposed
to freezing wintry winds over the past
month, the polynya has persisted —
so whatever force caused it to form is strong enough to keep
it from refreezing.

But it’s not the first time this particular hole has appeared.
Scientists observed a similar polynya in the
same area of Antarctica in 1974, according
to NASA Earth Observatory
. It reappeared during the austral
winters of 1975 and 1976, then disappeared and it
didn’t re-emerge for decades. It re-appeared again in August
2016, though significantly smaller than it had been in the 1970s.

Now it’s back and bigger than last year. The
largest estimates
 of the hole’s current size put it
around 80,000 square kilometers or just over 30,000 square
miles — almost as big as South Carolina. That’s still far
smaller than the 1970s version, which
reached 300,000 square kilometers
, about the size of Arizona.

It’s easy to assume that a massive hole in sea ice is
related to climate change, but that may not be the case. Some
scientists speculate that the formation of the Weddell polynya is
part of a cyclical process, though the details are unclear.

“Why was the Weddell polynya present in the 1970s, and then
absent until its recent reappearance?” Willy Weeks, a retired sea
ice geophysicist from University of Alaska in Fairbanks told
NASA Earth Observatory when the hole first re-emerged in 2016.
“Did the Weddell polynya occur before 1970, and we are looking at
a periodic process that shows itself about every 40 years? If
there were earlier occurrences, there is no record of them.”


Polynya
Sea
ice and clouds blanket the Weddell Sea around Antarctica in this
satellite image from September 25, 2017. A robotic float surfaced
inside the hole at the location marked in yellow, which could
help reveal exact what’s going on there.


SOCCOM


 

Polynyas allow heat to escape the ocean, cooling the
top layer of water. As that water becomes colder and denser, it
sinks, allowing more warm water to rise and keep the hole open.
That sinking water contributes to the cold water mass known as
Antarctic Bottom Water, according
to NASA
, which feeds into deep ocean currents and contributes
to ocean circulation around the globe.

It’s possible that the phenomenon is a key part of the process
that supplies Antarctic Bottom Water, according
to Earther’s
in-depth look at the polynya
.

Part of the reason this polynya remains so mysterious is
that it’s hard to explore sites like this. Winter air
temperatures there are thought to be about negative 20
degrees Celsius and there are few flights or expeditions in
Antarctica during the winter months.

But scientists might now have a better shot at figuring out
what’s happening, thanks to a key new source of data
from a National Science Foundation-sponsored group
studying climate in the Southern Ocean. A robotic float that was
meant to be sending data from the Weddell Sea surprisingly
surfaced inside the polynya last month, according to a news
release from the Southern Ocean Carbon and Climate Observations
and Modeling project at Princeton.

That robot began sending data that’s now being
processed, after which the group may be able to report new
findings.

The information could help reveal answers about what
triggers the formation of these mysterious holes.



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