Talk by Takuro Kobashi, NIPR – Niels Bohr Institute - University of Copenhagen

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Niels Bohr Institute > Calendar > 2011 > Talk by Takuro Kobashi...

Talk by Takuro Kobashi, NIPR

Greenland surface temperature over the past 4000 years estimated from trapped air in an ice core.

Several methods have been developed to reconstruct Greenland's temperatures,
such as the oxygen isotopes of ice in ice cores (δ18Oice) and borehole
thermometry, but these methods have several drawbacks. The measured ice core
parameter δ18Oice is known to be affected not only by local temperature
changes but also by changes in moisture source regions, moisture transport
pathways and precipitation seasonality. Borehole thermometry is accurate but
rapidly loses temporal resolution with increasing age into the past, owing
to heat diffusion in ice sheets.

A new method has been developed to reconstruct surface temperature variability
for relatively stable climates such as the Holocene through simultaneous,
high-precision analyses of δ15N and δ40Ar in trapped air in ice cores with tight
chronological control. An advantage of this method is that the reconstructed
surface decadal temperatures are physically constrained and are not subject to
bias from seasonal temperature swings, as gas diffusion averages out any surface
temperature variability that is shorter than a few decades.

So far, we successfully reconstructed the past 4000 years of Greenland summit
temperature changes. I will also talk about the possible mechanisms of the
Greenland temperature change over the past 1000 years.