Enormous grounded icebergs and an unprecedented
amount of sea ice in Antarctica's Ross
Sea have nearly isolated one of the continent's
most populous Adelie penguin colonies,
making it difficult for the birds to return
from their feeding grounds in the open
sea, according to researchers funded by
the National Science Foundation (NSF).
The numbers of Adelie penguins at Cape
Crozier, about 130,000 breeding pairs
in most years, "are at the low side" of
the normal range, said David Ainley of
H.T. Harvey & Associates of San Jose,
California. A smaller colony of Adelies
at Cape Royds will "fail totally" this
year, he added.
Meanwhile, a small colony of about 1,200
Emperor penguins at Cape Crozier failed
to raise chicks, according to Gerald Kooyman
of the Scripps Institution of Oceanography.
He said the birds probably abandoned efforts
to breed when the icebergs, pushing southward,
destroyed and closed off their usual breeding
area. Those that did breed, and attempted
to hatch the egg or raise the chick in
the area, failed during incubation or
soon after hatching.
The icebergs are designated B-15A and C-16.
Iceberg B-15A is 37 kilometers (20 nautical
miles) wide and 87 kilometers (47 nautical
miles) long. Berg C-16 is roughly 18.5
kilometers (10 nautical miles) wide by
55 kilometers (30 nautical miles) long.
The icebergs broke away from the Ross
Ice Shelf in March 2000 and gradually
migrated west to a point northeast of
McMurdo Sound, creating a barrier that
altered wind and current patterns.
Early this season, the sea ice extended
roughly 128 kilometers (80 miles) north
of McMurdo Station, the main U.S. research
station in Antarctica, located on Ross
Island. At this time of year, the ice
edge typically extends between 24 and
32 kilometers (15 and 20 miles) north
of the station. Recent storms have reduced
the extent of the ice greatly; it now
extends 61 kilometers (33 nautical miles)
from McMurdo.
The extensive sea ice has increased the
distance between the breeding colonies
and food sources in the open sea. The
birds must now walk rather than swim to
their colonies. Their average walking
speed is roughly 1 to 2 kilometers (.6
to 1.2 miles) per hour. They can swim
at an average of 7 to 8 kilometers (4.3
to 4.9 miles) per hour.
The Adelie colony at Cape Crozier is the
sixth largest in the world. The Emperor
Penguin colony is one of the smallest
for that species, at about 1200 pairs,
but was the first discovered. Members
of explorer Robert Falcon Scott's expedition
first visited the colony at the beginning
of the 20th century.
A classic story of Antarctic science and
adventure, "The Worst Journey in the World,"
by Apsley Cherry-Garrard includes a description
of an attempt by three men of Scott's
party to collect the first Emperor penguin
eggs from Cape Crozier. Early in the 20th
century, the eggs were scientific curiosities
because Emperor penguins were incorrectly
thought to be a "missing link" between
dinosaurs and birds. The researchers survived
horrendous blizzards, confined for several
days to a shelter they had erected in
haste, in order to bring back the eggs.
The Adelie colony at Cape Royds is the
longest-studied in Antarctica. Next to
it is a hut erected by Ernest Shackleton
during his first Antarctic expedition
early in the 20th century.
The colony has been monitored annually
since 1959 by scientists from Landcare
Research NZ and, most recently, by Ainley's
group.
The colony had been increasing in recent
years because sea ice had been dissipating.
It is the southernmost Adelie penguin
colony in the world, and its existence
is now in jeopardy.
Researchers supported by the U.S. Antarctic
Program have banded Adelie penguins at
Cape Crozier and elsewhere on Ross Island
with individual numbers, allowing them
to be identified at a later date. The
penguins' response to the icebergs likely
will provide major new insights into the
biology, resolve and resilience of this
species.
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A view from space of Ross Island and the
iceberg fragments. NSF's McMurdo Station,
the main U.S. research station in Antarctica,
is on the peninsula on the right hand
side of the island.
A larger
version is here.
Credit: NASA: Multi-angle
Imaging SpectroRadiometer (MISR) instrument.
David Ainley, an NSF-funded penguin researcher,
answers a question during the weekly science
lecture at McMurdo Station.
Credit: Peter West/NSF
An Emperor penguin.
Credit: Peter West/NSF
Several Emperor penguins huddle against
the elements in Antarctica
Credit: Peter West/NSF
A small group of Adelie penguins at the
edge of the sea ice in January 2000.
Credit: Peter West/NSF
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