30 DISCOVERMAGAZINE.COM
Movin’ on Ice
Ice is always on the move. Knowing where
— and how fast — it’s going is crucial for
predicting ice sheet stability, which informs
predictions about melt rates and sea level
rise. That’s why researchers in California
have created the most precise map so
far of Antarctica’s ice velocity, which they
published in Geophysical Research Letters
in July. But that wasn’t the only Antarctic
news in 2019. In a January study in the
Proceedings of the National Academy of
Sciences, a different team found that the
melting continent has contributed more
than half an inch to global sea levels in the
past 40 years, and it’s now losing six times
more ice annually than it did in 1979.30 DISCOVERMAGAZINE.COM
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Ice sheets like LeConte Glacier in Alaska (left)
don’t just melt on their open-air surfaces; they can
also lose ice underwater. In a July Science paper,
a group of researchers used a multibeam sonar
system — the same technology anglers use to find
large schools of fish in the ocean — to directly
measure underwater melting rates for the first time.
The innovative approach shows LeConte could be
melting 100 times faster than previously estimated
by theoretical models, suggesting worldwide melt
rates may be seriously underestimated.Ice, Ice, Melty
Melt season came early this year to Greenland’s
Russell Glacier, researchers working on NASA’s
Operation IceBridge noticed in May. And new
research suggests that could become a common
occurrence across Greenland. Normally, snow
covers and protects most of a massive ice sheet
from the heat of the sun. But the snow ends at
what’s called the snowline, leaving the bare ice
exposed. A MarchScience Advances study pointed
to changes in Greenland’s snowline as a factor
accelerating ice loss in the region. Greenland’s
snowline moved about 55 feet per year from 2001
to 2012, exposing more ice to the sun’s melting rays.1000 kmIce velocity (m/yr)<1 10 1000 1000 >3000