Tiny fossils hold answers to big questions on climate change
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| Dr Jenny Pike, School of Earth and Ocean Sciences. (Credit: Image courtesy of Cardiff University) |
The
western Antarctic Peninsula is one of the fastest warming regions on the
planet, and the fastest warming part of the Southern Hemisphere. Scientists
have debated the causes of this warming, particularly in light of recent
instrumental records of both atmospheric and oceanic warming from the region.
As the atmosphere and ocean warm, so the ice sheet (holding an equivalent of 5
metres of global sea level rise, locked up in ice) becomes vulnerable to
collapse.
Now research led by Cardiff University published in Nature Geosciencehas used a unique 12,000 year
long record from microscopic marine algae fossils to trace glacial ice entering
the ocean along the western Antarctic Peninsula.
The
study has found that the atmosphere had a more significant impact on warming
along the western Antarctic Peninsula than oceanic circulation in the late
Holocene (from 3500-250 years ago).
This
was not the case prior to 3500 years ago, and is not the case in the modern
environment. The study has also shown that this late Holocene atmospheric
warming was cyclic (400-500 year long cycles) and linked to the increasing
strength of the El Niño -- Southern Oscillation phenomenon (a climate pattern
centred in the low latitude Pacific Ocean) demonstrating an equatorial influence
on high latitude climate.
Dr
Jennifer Pike, School of Earth and Ocean Sciences said: "Our research is
helping to understand the past dynamic behaviour of the Antarctic Peninsula Ice
Sheet. The implications of our findings are that the modern observations of
ocean-driven warming along the western Antarctic Peninsula need to be
considered as part of a natural centennial timescale cycle of climate
variability, and that in order to understand climate change along the Antarctic
Peninsula, we need to understand the broader climate connections with the rest
of the planet."
Ice
derived from land has a very distinctive ratio of oxygen isotopes. This
research is the highest resolution application in coastal Antarctic marine
sediments of a technique to measure the oxygen isotope ratios of microscopic
marine algae fossils (diatom silica). When a large amount of glacial ice is
discharged into the coastal ocean, this alters the oxygen isotope ratio of the
sea water that the marine algae are living in. This creates a clear imprint in
the fossils that reveals the environmental conditions of the time. The
scientists used the oxygen isotope ratio of the fossils to reconstruct the
amount of glacial ice entering the coastal ocean in the past 12,000 years, and
to determine whether the variations in the amount of ice being discharged were
the result of changes in the ocean or atmospheric environment.
Professor
Melanie Leng, from the British Geological Survey and Chair of Isotope
Geosciences in the Department of Geology, University of Leicester, said:
"Technologically the analysis of the oxygen isotope composition of diatom
silica is extremely difficult, the British Geological Survey is one of a very
few research organisations in the world that can undertake this type of analysis.
For this research project the methodology has been developed over the last five
years with the specific aim of investigating the different amounts of melting
in the polar regions. It's fair to say we are world leading pioneers in this
technique."
The research
is co-authored with Cardiff University by the universities of Nottingham,
Leicester and the British Geological Survey and was funded by the Natural
Environment Research Council (NERC).
Source: Cardiff University
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Posted by Unknown
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