Ancient Climate Seesaw
Scientists have unravelled the complex ocean and atmospheric
behaviour that caused the global climate to see-saw rapidly coming
out of the most recent ice age.
The abrupt changes to the global climate 14,700 years ago
caused Antarctica to suddenly stop warming and cool down for
around 1500 years while the Northern Hemisphere warmed
rapidly.“Forcing the climate system into a different state can trigger
climate variations that can spread globally, as seen during the
warming out of the last ice age,” said team member Claire Krause
of The Australian National University.
“This abrupt climate change unfolded very differently around
the planet due to complicated interactions between the ocean and
atmosphere. In some places in the Northern Hemisphere, the
temperature jumped 10°C in the space of a few decades.”
This understanding of how the climate can change so rapidly
will give us insights into whether similar events could be lurking
in the future.
The research, published in Nature Geoscience
(tinyurl.com/p9y6f8p), assembled 84 climate records from all over
the Southern Hemisphere, spanning Antarctic ice cores, northern
Australian cave records and fossilised rodent urine from southern
Africa. “The project brought together a lot of seemingly separate
data, and turned them into one story that is much more useful
for our understanding of climate,” Krause said.
Previous studies had focused on the more numerous Northern
Hemisphere records, and found opposing trends between the two
hemispheres due to the behaviour of ocean currents ferrying heat
northwards. However, the team found that the pattern was compli-
cated by atmospheric circulation compensating for the ocean’s
heat transport.
In the sub-tropics, atmosphere effects dominate, leading to
abrupt drying and warming. However, in the South Atlantic, the
Southern Ocean, New Zealand and Patagonia, the ocean drives
cooling that is amplified around Antarctica by expanding sea-ice.
The resulting complex pattern of climate variations during this
period in the Earth’s history had never previously been brought
together in one study and understood in such detail.12 | JAN/FEB 2016
Crazy Ants Beating Butterflies
James Cook University scientists have discovered that the invasive
yellow crazy ant is an extremely efficient killer of native butterfly
caterpillars.
Dr Lori Lach found that the formic acid-spraying pest is at least
four times more likely than the native green tree ant to find and
attack cruiser butterfly larvae.
Lach said that both ant species will attack caterpillars, but the
yellow crazy ant’s sheer numbers meant the caterpillars rarely
escaped from areas invaded by the ants. Up to 16 times more
caterpillars were attacked in sites with yellow crazy ants than in
sites with green tree ants.
The voracious yellow crazy ant has invaded about 800 ha in Far
North Queensland, with about one-third of the infested area being
rainforest. An aggressive baiting program had forced yellow crazy
ant numbers down for the time being, but Lach said scientists were
wary of what the invasion could mean if treatments don’t continue.
“The rainforest is more complex than many habitats and may be
more resilient, but we’re worried about a possible cascade of events.
Decreases in key groups, such as pollinating butterflies, will likely
have knock-on effects.”
The ants have already wiped out millions of red land crabs on
Christmas Island, which helped transform the forest landscape and
led to the death of some species.We might not be able to predict exactly what the effect will be,”
Lach said, “but we know it won’t be a good thing. The cruiser
butterfly is a species with similar habits and habitat to many other
native butterfly species.”
The ants spray formic acid in the eyes of their prey, and there are
reports of attacks on pets and people. They are known to actively
protect sugar cane pests in order to milk them for honeydew.
Lach said that current funding to the Wet Tropics Management
Authority would not be enough to eradicate the ants from the area,
which is home to 58% of Australia’s 400 butterfly species.One of the rock hyrax middens (a stalagmite of fossilised
rodent urine) in south-west Africa that was used in the
study to reconstruct past changes in precipitation.
Credit: Brian Chase“WemightnotbeabletoprediYellow crazy ants are
threatening butterfly
numbers in Far North
Queensland.