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| Titel |
Heinrich Stadial 4: sequence of events from North to South seen in high resolution Greenland and Antarctic ice cores and suggestion of synchronization to North Atlantic marine records |
| VerfasserIn |
Myriam Guillevic, Lucie Bazin, Christopher Stowasser, Amaëlle Landais, Valérie Masson-Delmotte, Frédéric Prié, Thomas Blunier, Frederique Eynaud, Elisabeth Michel, Bo M. Vinther |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250077138
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| Zusammenfassung |
| The last glacial period was affected by the occurrence of rapid climatic events at the
millennial time scale known as Dansgaard-Oeschger (DO) events. In Greenland,
these events are composed of a rapid temperature increase of 5-16-ă in less than a
century, a warm phase lasting several centuries (InterStadial, GI) followed by a more
gradual temperature decrease, and finally a cold phase (Stadial, GS). An Antarctic
counterpart to each GI of the Last Glacial Period has been identified in Antarctic ice
cores. In the North Atlantic Ocean, marine cores also record changes in surface
temperature as well as the occurrence during cold phases of ice rafted debris horizons,
corresponding to massive icebergs discharges, known as Heinrich (H) events. It has never
been possible to identify the presence of H events from temperature proxies in
Greenland ice cores. It thus remains difficult to compare the durations of H events and
GS.
Here, we focus on the time period covering DO 9 to 7 (41 to 34 ka b2k according to
the GICC05/AICC2012 time scales), with H event 4 occurring during GS 9. We
present a compilation of high resolution measurements (about 60 years) of this period
based on Greenland and Antarctic ice cores data (ice and gas) synchronized on the
new time scale AICC2012. Proxies for local Greenland temperature (δ15N-N2,
δ18O-H2O) record GS9 as a uniform period lasting ~1850 years, followed by a sharp
transition to GI8. This pattern is also seen in continuous methane concentration data
(NEEM ice core, Greenland) showing a large increase by ~100 ppbv at the GS9 - GI8
transition.
However, using additional proxies and a detailed inspection of the methane profile, GS9
can be divided into 3 phases. The first 600 years of GS9 (phase 1) are characterized by low
CO2 and methane concentration, intermediate δD of CH4 (tracer of methane sources), high
NEEM 17O-excess (proxy for vapor source relative humidity) and a progressive increase in
EDML δ18O. The transition between phase 1 and phase 2 is marked by an abrupt
increase of CO2 and CH4 concentration and δD-CH4 as well as a decrease of NEEM
17O-excess. All proxies stay constant during the 850 years of phase 2. At the transition
between phase 2 and phase 3, 400 years before the onset of GI8, we observe an
abrupt increase in NEEM 17O-excess and an abrupt decrease in δD-CH4 while
methane concentration remains constant. In Antarctica, EDML δ18O progressively
decreases.
We speculate that these different phases may be linked to different atmospheric and/or
oceanic conditions during GS9 probably related to the occurrence of H event 4. To explore
this hypothesis, we propose a synchronization of North Atlantic marine records to ice cores
records. |
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