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| Titel |
Evidence for a three-phase sequence during Heinrich Stadial 4 using a multiproxy approach based on Greenland ice core records |
| VerfasserIn |
M. Guillevic, L. Bazin, A. Landais, C. Stowasser, V. Masson-Delmotte, T. Blunier, F. Eynaud, S. Falourd, E. Michel, B. Minster, T. Popp, F. Prié, B. M. Vinther |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1814-9324
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| Digitales Dokument |
URL |
| Erschienen |
In: Climate of the Past ; 10, no. 6 ; Nr. 10, no. 6 (2014-12-02), S.2115-2133 |
| Datensatznummer |
250117082
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| Publikation (Nr.) |
 copernicus.org/cp-10-2115-2014.pdf |
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| Zusammenfassung |
Glacial climate was characterised by two types of abrupt events. Greenland
ice cores record Dansgaard–Oeschger events, marked by abrupt warming
in-between cold, stadial phases. Six of these stadials appear related to
major Heinrich events (HEs), identified from ice-rafted debris (IRD) and large
excursions in carbon- and oxygen-stable isotopic ratios in North Atlantic deep
sea sediments, documenting major ice sheet collapse events. This finding has
led to the paradigm that glacial cold events are induced by the response of
the Atlantic Meridional Overturning Circulation to such massive freshwater
inputs, supported by sensitivity studies conducted with climate models of
various complexities. These models also simulate synchronous Greenland
temperature and lower-latitude hydrological changes.
To investigate the sequence of events between climate changes at low
latitudes and in Greenland, we provide here the first 17O-excess
record from a Greenland ice core during Dansgaard–Oeschger events 7 to 13,
encompassing H4 and H5. Combined with other ice core proxy records, our new
17O-excess data set demonstrates that stadials are generally
characterised by low 17O-excess levels compared to interstadials.
This can be interpreted as synchronous change of high-latitude temperature
and lower-latitude hydrological cycle (relative humidity at the oceanic
source of evaporation or change in the water mass trajectory/recharge) and/or
an influence of local temperature on 17O-excess through kinetic
effect at snow formation. As an exception from this general pattern, stadial
9 consists of three phases, characterised first by Greenland cooling during
550 ± 60 years (as shown by markers of Greenland temperature
δ18O and δ15N), followed by a specific lower-latitude fingerprint as identified from several proxy records (abrupt
decrease in 17O-excess, increase in CO2 and methane mixing
ratio, heavier δD-CH4 and
δ18Oatm), lasting 740 ± 60 years, itself
ending approximately 390 ± 50 years prior to abrupt Greenland warming.
We hypothesise that this lower-latitude signal may be the fingerprint of
Heinrich event 4 in Greenland ice cores. The proposed decoupling between
stable cold Greenland temperature and low-latitude climate variability
identified for stadial 9 provides new targets for benchmarking climate model
simulations and testing mechanisms associated with millennial variability. |
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