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| Titel |
Holocene paleotemperature signals based on polar firn water isotope diffusion studies from two Greenland ice cores. |
| VerfasserIn |
Vasileios Gkinis, Christian Terkelsen Holme, Bo Møllesøe Vinther |
| 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 |
250144582
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| Publikation (Nr.) |
 EGU/EGU2017-8426.pdf |
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| Zusammenfassung |
| Polar ice cores provide a wealth of paleoclimatic information that is characterised by high
temporal resolution and continuity, with water isotopic ratios of polar precipitation
(δ18O, δD) being one of the most prominent proxies for past temperatures. In particular, ice
cores from Greenland, record the series of abrupt stadial - interstadial transitions during the
last Glacial, pinpointing in time, abrupt temperature transitions adjoined by similar
accumulation trends. While the signal to noise ratio of the isotopic signal clearly
allows the observation of sizable climate changes during the Glacial, the situation
differs considerably when one looks into the Holocene. With the exception of the
8.2ky event, the signal to noise ratio of δ18O over the Holocene is extremely low,
suggesting negligible temperature changes during this period. This is contrary to
signals obtained by other proxies from marine and terrestrial records from high
latitudes.
In this study we bypass the discussion that deals with the various processes that can
negatively affect paleotemperature reconstructions based on the δ18O proxy from ice cores.
Based on two ultra-high resolution and high precision isotopic records covering the last
20,000 years from the NorthGRIP and NEEM ice cores we make use of the available spectral
information to infer polar firn paleotemperatures using a coupled densification - firn
water isotope diffusion model. The processes involved in the densification of firn
and the diffusion of water isotopes that takes place after deposition and until the
pore close-off are temperature-dependent and do not present the limitations of the
normal δ18O thermometer. We show here how this approach reveals significant
temperature changes over the Holocene. We compare the signals of the two records
and pay particular attention to the indications of a mid-Holocene climatic shift
towards colder temperatures that is apparent in both temperature reconstructions. |
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