world saw headlines about one of the largest icebergs ever calved a
few weeks ago. But a smaller one on the other end of the globe might
have bigger consequences.
chunk of ice, which broke free in the Arctic last week, is more
worrisome to climate scientists who are watching one of Earth's
largest glaciers shed pieces in a way that stands to raise sea
with the Delaware-sized iceberg that split off of West Antarctica
earlier this month, this one is almost paltry — the size of three
Manhattans or so. It came off the ice shelf that buttresses the
Petermann Glacier at the height of seasonal warming in the Arctic
contrast, the recent Antarctic iceberg, while massive, did not have a
clear connection to climate. Even if it foreshadows the split-up of
the ice sheet to which it was attached, it would not raise sea levels
noticeably. The Arctic calving has a much clearer link to climate
of the Petermann Glacier has sped up in recent years, dumping
land-based ice into the ocean at a faster rate and drawing more ice
down from the center of Greenland, said Laurence Dyke, a researcher
at the Geological Survey of Denmark and Greenland. Meanwhile, the ice
shelf that braces it and slows the rate of flow is disintegrating as
climate change transforms the region.
could call it the canary in the coal mine. If that big glacier there
is changing quickly, and it is, it's a worrying sign for what's
happening in the rest of Greenland,” he said.
iceberg itself is not particularly notable, according to Dyke. But it
could lead to an expansion of major cracks upstream in the ice shelf,
causing it to break up more quickly. Most troubling to researchers is
a crack at the center of the shelf. It's an unusual place for cracks
to form, and it could connect to separate cracks forming at the
loss of the iceberg also brings the shelf to a state not observed in
the 150 years of tracking the glacier — and potentially much
longer, Dyke said. The ice shelf bracing the glacier lost major
pieces in 2010 and 2012. Both those icebergs were the size of several
glaciers in Greenland are a primary contributor to global sea-level
rise, and they're expected to increasingly lose their mass in the
future. Petermann accounts for almost 10 percent of the Greenland ice
sheet; it alone could raise sea levels by a foot.
Petermann retreats, it will draw down ice from the center of
Greenland, all of which will have a direct effect on sea-level
increase. Researchers have cautioned that sea levels could rise by 3
feet at the end of the century, but a more rapid disintegration of
Arctic glaciers would make that number larger. A study published
earlier this year in Nature showed
that the rate of melting in Greenland has increased fivefold in the
last 25 years.
temperatures in the region have risen, and that has spurred a greater
rate of melting. There are other links to climate change. As the seas
warm, they erode ice shelves from underneath.
you've got this double whammy effect of the ocean warming from
beneath and atmosphere warming from the surface, it's really chewing
at this glacier,” Dyke said. “Ultimately, it's why it's having
this big retreat.”
has lost two ice shelves in the last few decades, and it only has two
left, said Andreas Muenchow, a researcher at the University of
He said the drama of a new iceberg is the culmination of
years of melting.
who gets daily updates from equipment underneath the ice shelf, said
ocean temperatures are steadily rising. As sea ice melts, warm water
is flowing in from the Arctic ocean. That increases circulation as
wind moves the open water around more freely.
a small, steady, measurable drip, and it's this drip, drip, drip that
is eroding these glaciers,” Muenchow said. “It's not always what
you see and what's a dramatic event, like an iceberg breaking up.
It's this year-round drip, drip, drip by the ocean underneath that
really determines what's happening by weakening the ice shelf from