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| Titel |
The variability of the isotopic signal during the last Glacial as seen from the ultra-high resolution NEEM and NorthGRIP ice cores. |
| VerfasserIn |
Vasileios Gkinis, Bo Møllesøe Vinther, Christian Terkelsen Holme, Emilie Capron, Trevor James Popp, Sune Olander Rasmussen |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250145627
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| Publikation (Nr.) |
 EGU/EGU2017-9588.pdf |
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| Zusammenfassung |
| The continuity and high resolution available in polar ice core records constitutes them an
excellent tool for the study of the stadial-interstadial transitions, notably through the study of
the water isotopic composition of polar precipitation (δ18O, δD ). The quest for the highest
resolution possible has resulted in experimental sampling and analysis techniques that have
yielded data sets with a potential to change the current picture on the climatic signals of the
last Glacial. Specifically, the ultra-high resolution δ18O signals from the NorthGRIP and
NEEM ice cores, present a variability at multi-annual and decadal time scales, whose
interpretation gives rise to further puzzling though interesting questions and an obvious
paradox.
By means of simple firn isotope diffusion and densification calculations, we firstly
demonstrate that the variability of observed signals is unlikely to be due to post depositional
effects that are known to occur on the surface of the Greenland ice cap and alter the
δ18O composition of the precipitated snow. Assuming specific values for the δ18O
sensitivity to temperature (commonly referred to as the δ18O slope), we estimate
that the temperature signal during the stadials has a variability that extents from
interstadial to extremely cold levels with peak-to-peak fluctuations of almost 35
K occurring in a few years. Similarly, during interstadial phases the temperature
varies rapidly from stadial to Holocene levels while the signal variability shows a
maximum during the LGM, with magnitudes of up to 15‰ that translate to ≈ 50 K
when a δ18O slope of 0.3‰K−1 is used. We assess the validity of these results and
comment on the stability of the δ18O slope. Driven by a simple logical queue, we
conclude that the observed δ18O variability reflects a climatic signal although not
necessarily attributed 100% to temperature changes. From this we can assume that there
occur climatic mechanisms during the previously thought stable stadial phases that
allow for swift changes, with magnitudes comparable if not greater to that of the
stadial-interstadial transitions. We are thus tempted to propose that rapid climate
change is the normal mode of climate during the last Glacial and that some of the
mechanisms associated with the stadial-interstadial transitions are possibly in play
also during other, phenomenally more stable times of the Glacial climate record. |
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