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| Titel |
Iberian margin sequence of events within the ocean-atmosphere-sea-ice system |
| VerfasserIn |
B. Martrat, J. O. Grimalt, M. Canals |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250029277
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| Zusammenfassung |
| A specific core not only becomes referential when its radiometric chronostratigraphy is
sufficiently robust; it proves even more useful for palaeoclimate assessment, when
multiproxy studies are performed on its strata. A multiproxy approach definitely enriches
the description of events and is crucial before making any comparison with other
palaeoarchives close to the areas studied, or before establishing any long distance
connection.
This study presents an intra- and inter-event stratigraphy. The sequence of events is
defined by means of the Uk-²37- sea surface temperature (SST) reconstruction in Iberian
margin cores, while relying on as many variables as possible, e.g. uncalibrated AMS-14C
dates, δ18Ocalcite measurements of planktonic and benthic microscopic fauna; abundances of
species of foraminifera, continental or coccolithophora flora, fossil organic compounds, total
organic carbon, magnetic susceptibility, detrital lithics, etcetera. From this analysis, the
events observed became known as Iberian margin interstadials (IMI) and stadials (IMS)
[Martrat et al., 2007, SCIENCE, 317: 502], given that the Iberian margin sites were
doubtlessly concordant. At the same time, some interesting internal differences arise between
sites and events, providing clues about palaeoclimate mechanisms as yet to be explored. For
example, a breakdown of the events reveals that ice volume accumulated in terrestrial
environments might still be low at the time temperatures dropped and tree populations,
having exceeded their tolerance limit, crashed; this situation could also be the reverse,
i.e. during intervals of ice growth, forest conditions might persist in appropriate
refugia and even expand at the time surface temperatures –oceanic and atmospheric–
were recovering. These events are understood only if the role of internal stochastic
mechanisms, thresholds (e.g. freshwater forcing, length of the dry season-¦) and the
partially chaotic component of the climate system are taken into consideration. The
oscillations defined are not expected to be exactly the same as events described by
other proxies in distant or relatively closer regions, either in intensity or rates of
change. |
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