Ice cores show simultaneous changes of carbon dioxide and Antarctic temperature during
the last deglacial warming
and Global warming preceded by increasing carbon dioxide concentrations during the last
deglaciation
Ice cores show simultaneous changes of carbon dioxide and Antarctic temperature during
the last deglacial warming
3/8/13
Source: Alfred Wegener Institute for Polar and Marine Research (AWI)
http://www.research-in-germany.de/124988/2013-03-08-ice-cores-show-simultaneous-changes-of-carbon-dioxide-and-antarctic-temperature-during-the-lastdeglacial-warming,sourcePageId=8240.html
Synchronous Change of Atmospheric CO2 and Antarctic Temperature During the Last Deglacial Warming.
F. Parrenin, et al Science March 2013
Bremerhaven, 28 February 2013. Atmospheric carbon dioxide and the Antarctic temperature increased synchronously
during the last deglacial warming 20,000 to 10,000 years ago. A European team of researchers comes to this conclusion
after having re-analysed the age of the enclosed air bubbles in the Antarctic ice core EPICA Dome C. The study, in which
the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, was involved, appeared now in the
scientific journal Science.
Changes in the chemical composition of the atmosphere in the past can be reconstructed from air bubbles enclosed in
Antarctic ice. In this way it has been possible to determine the natural variability of the greenhouse gas carbon dioxide
over the past 800,000 years from ice cores. Over the same time window and on the same ice core changes in Antarctic
temperature were also reconstructed. How quickly air bubbles were deposited in ice cores at which depth has now been
recalculated under the lead of the French Laboratoire de Glaciologie et Geophysique de l’Environnement. With the
assistance of the nitrogen isotope 15 N they were able to show that the enclosed air in the EPICA Dome C ice core during
the transition from the last glacial to the current interglacial period is older than hitherto assumed. This ice core was
obtained in the EPICA project (European Project for Ice Coring in Antarctica).
“We have discovered that previous age calculations of the enclosed gases are too inaccurate based on what we know
today,” says Dr. Peter Köhler, physicist at the Alfred Wegener Institute (AWI), Helmholtz Centre for Polar and Marine
Research and co-author of the Science study. Temperature and greenhouse gas measurements of the ice cores are made
at different depths. Every depth is then assigned an age. The necessary age models for temperature and greenhouse
gases differ here. Temperature changes are reconstructed indirectly via the isotopy of the water molecules of the ice.
Concentrations of greenhouse gases are measured directly from the antique air bubbles which must have been
completely separated from the atmosphere when they were formed. This happens at the lower end of the firn during
the so-called bubble close-off at a lock-in depth of around 100 meters where snow compacts to form ice.
During a re-analysis of the lock-in depth in the EPICA Dome C ice core the researchers have now recalculated the
thickness of the firn layer by using the nitrogen isotope 15 N . What they found was that the carbon dioxide content of
the atmosphere increased “synchronously” with the Antarctic temperature during the transition from the last glacial to
the interglacial period 20,000 to 10,000 years ago. “Synchronously” is defined by the scientists in this study as time
differences of less than 200 years during the four known abrupt changes between both climate variables in the period
examined.
“We describe the synchronous rise in the Antarctic temperature and the global atmospheric carbon dioxide content
during the last transition from a glacial cold stage to an interglacial warm period. This synchronicity suggests that there
are probably strong feedback mechanisms which link the two climate variables. It is important to note here that our
study only shows details about the synchronicity of these two variables. If we wish to completely understand how the
end of the last glacial period occurred, we also need to incorporate data on temperature changes from other parts of
the Earth. Furthermore, we must be able to set our results and those of other time series into the correct temporal
context. For this final interpretation also the application of state-of-the-art climate models will be necessary”, explains
AWI physicist Köhler.
Global warming preceded by increasing carbon dioxide concentrations during the last
deglaciation
Jeremy D. Shakun, et al
Nature 484,49–54(05 April 2012)
Abstract
The covariation of carbon dioxide (CO2) concentration and temperature in Antarctic ice-core records suggests a close
link between CO2 and climate during the Pleistocene ice ages. The role and relative importance of CO2 in producing
these climate changes remains unclear, however, in part because the ice-core deuterium record reflects local rather
than global temperature. Here we construct a record of global surface temperature from 80 proxy records and show
that temperature is correlated with and generally lags CO2 during the last (that is, the most recent) deglaciation.
Differences between the respective temperature changes of the Northern Hemisphere and Southern Hemisphere
parallel variations in the strength of the Atlantic meridional overturning circulation recorded in marine sediments. These
observations, together with transient global climate model simulations, support the conclusion that an antiphased
hemispheric temperature response to ocean circulation changes superimposed on globally in-phase warming driven by
increasing CO2 concentrations is an explanation for much of the temperature change at the end of the most recent ice
age.