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| Titel |
10Be in late deglacial climate simulated by ECHAM5-HAM – Part 2: Isolating the solar signal from 10Be deposition |
| VerfasserIn |
U. Heikkilä, X. Shi, 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 ; 10, no. 2 ; Nr. 10, no. 2 (2014-04-01), S.687-696 |
| Datensatznummer |
250116946
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| Publikation (Nr.) |
 copernicus.org/cp-10-687-2014.pdf |
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| Zusammenfassung |
| This study investigates the effect of deglacial climate on the deposition of
the solar proxy 10Be globally, and at two specific locations, the GRIP
site at Summit, Central Greenland, and the Law Dome site in coastal
Antarctica. The deglacial climate is represented by three 30 year time slice
simulations of 10 000 BP (years before present = 1950 CE), 11 000 and
12 000 BP, compared with a preindustrial control simulation. The model used
is the ECHAM5-HAM atmospheric aerosol–climate model, driven with sea-surface
temperatures and sea ice cover simulated using the CSIRO Mk3L coupled climate
system model. The focus is on isolating the 10Be production signal,
driven by solar variability, from the weather- or climate-driven noise in the
10Be deposition flux during different stages of climate. The production
signal varies at lower frequencies, dominated by the 11 year solar cycle
within the 30 year timescale of these experiments. The climatic noise is of
higher frequencies than 11 years during the 30 year period studied. We
first apply empirical orthogonal function (EOF) analysis to global 10Be
deposition on the annual scale and find that the first principal component,
consisting of the spatial pattern of mean 10Be deposition and the
temporally varying solar signal, explains 64% of the variability. The
following principal components are closely related to those of precipitation.
Then, we apply ensemble empirical decomposition (EEMD) analysis to the time
series of 10Be deposition at GRIP and at Law Dome, which is an effective
method for adaptively decomposing the time series into different frequency
components. The low-frequency components and the long-term trend represent
production and have reduced noise compared to the entire frequency spectrum
of the deposition. The high-frequency components represent climate-driven
noise related to the seasonal cycle of e.g. precipitation and are closely
connected to high frequencies of precipitation. These results firstly show
that the 10Be atmospheric production signal is preserved in the
deposition flux to surface even during climates very different from today's
both in global data and at two specific locations. Secondly, noise can be
effectively reduced from 10Be deposition data by simply applying the EOF
analysis in the case of a reasonably large number of available data sets, or
by decomposing the individual data sets to filter out high-frequency fluctuations. |
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