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| Titel |
10Be in late deglacial climate simulated by ECHAM5-HAM – Part 1: Climatological influences on 10Be deposition |
| VerfasserIn |
U. Heikkilä, S. J. Phipps, A. M. Smith |
| 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 ; 9, no. 6 ; Nr. 9, no. 6 (2013-11-25), S.2641-2649 |
| Datensatznummer |
250085265
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| Publikation (Nr.) |
 copernicus.org/cp-9-2641-2013.pdf |
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| Zusammenfassung |
| Reconstruction of solar irradiance has only been possible for the Holocene so
far. During the last deglaciation, two solar proxies (10Be and 14C)
deviate strongly, both of them being influenced by climatic changes in a
different way. This work addresses the climate influence on 10Be
deposition by means of ECHAM5-HAM atmospheric aerosol–climate model
simulations, forced by sea surface temperatures and sea ice extent created by
the CSIRO Mk3L coupled climate system model. Three time slice simulations
were performed during the last deglaciation: 10 000 BP ("10k"),
11 000 BP ("11k") and 12 000 BP ("12k"), each 30 yr long. The same,
theoretical, 10Be production rate was used in each simulation to isolate
the impact of climate on 10Be deposition. The changes are found to
follow roughly the reduction in the greenhouse gas concentrations within the
simulations. The 10k and 11k simulations produce a surface cooling which is
symmetrically amplified in the 12k simulation. The precipitation rate is only
slightly reduced at high latitudes, but there is a northward shift in the
polar jet in the Northern Hemisphere, and the stratospheric westerly winds
are significantly weakened. These changes occur where the sea ice change is
largest in the deglaciation simulations. This leads to a longer residence
time of 10Be in the stratosphere by 30 (10k and 11k) to 80 (12k) days,
increasing the atmospheric concentrations (25–30% in 10k and 11k and
100% in 12k). Furthermore the shift of westerlies in the troposphere leads
to an increase of tropospheric 10Be concentrations, especially at high
latitudes. The contribution of dry deposition generally increases, but
decreases where sea ice changes are largest. In total, the 10Be
deposition rate changes by no more than 20% at mid- to high latitudes, but
by up to 50% in the tropics. We conclude that on "long" time scales (a
year to a few years), climatic influences on 10Be deposition remain
small (less than 50%) even though atmospheric concentrations can vary
significantly. Averaged over a longer period, all 10Be produced has to
be deposited by mass conservation. This dominates over any climatic
influences on 10Be deposition. Snow concentrations, however, do not
follow mass conservation and can potentially be impacted more by climate due
to precipitation changes. Quantifying the impact of deglacial climate
modulation on 10Be in terms of preserving the solar signal locally is
analysed in an accompanying paper (Heikkilä et al., 10Be in late
deglacial climate simulated by ECHAM5-HAM – Part 2: Isolating the solar
signal from 10Be deposition). |
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