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| Titel |
Leads and lags between the Antarctic temperature and carbon dioxide during the last deglaciation |
| VerfasserIn |
Léa Gest, Frédéric Parrenin, Dominique Raynaud, Tyler J. Fudge |
| 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 |
250138270
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| Publikation (Nr.) |
 EGU/EGU2017-1242.pdf |
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| Zusammenfassung |
| To understand causal relationships in past climate variations, it is essential to have accurate
chronologies of paleoclimate records. Ice cores in Antarctica provide important paleoclimate
variables, such as local temperature and global atmospheric CO2. Unfortunately, temperature
is recorded in the ice while CO2 is recorded in the enclosed air bubbles. The ages of the
former and of the latter are different since air is trapped at 50-120 m below the surface. For
the last deglacial warming, 18,000 to 11,000 years ago, Parrenin et al. (Science,
2013) inferred that CO2 and Antarctic temperature started to increase in phase
while CO2 lagged temperature at the beginning of the Holocene period. However,
this study suffers from various uncertainties that we tried to address in the current
study.
First, Antarctic temperature was inferred from a stack of 5 Antarctic ice cores that were
not always accurately synchronized. Here we use a stack of 4 Antarctic ice cores which are
all accurately synchronized thanks to volcanic peak matching. Second, Parrenin et al.
(Science, 2013) used a relatively low-resolution CO2 record from the EPICA Dome C ice
core. Here, we use the more recent and higher resolution CO2 record from the West Antarctic
Ice Sheet Divide ice core. Third, the air trapping depth was deduced on the low accumulation
EPICA Dome C ice core using the gravitational enrichment of the δ15N isotopes and
assuming a zero convective depth, a hypothesis that was not proved. Here, we use the higher
accumulation WAIS Divide ice core, where the ice-air age shift is one order of magnitude
smaller, and therefore better constrained. Finally, we use an improved mathematical
method to infer break points in the Antarctic temperature and atmospheric CO2
records.
We find that, at the onset of the last deglaciation and the onset of the Bølling-Allerød
period, the phasing between CO2 and Antarctic temperature is negligible within a range of
130 years. Then CO2 slightly leads by 200 ± 90 years at the onset of the Younger-Dryas
period. Finally, Antarctic temperature significantly leads by 460 ± 95 years at the onset of the
Holocene period. Our results further supports the hypothesis of no convective zone at EPICA
Dome C during the last deglaciation, as assumed by Parrenin et al. (Climate of the past, 2012,
On the gas-ice depth difference (Delta depth) along the EPICA Dome C ice core) |
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