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| Titel |
Atmospheric patterns driving Holocene productivity in the Alboran Sea (Western Mediterranean): a multiproxy approach. |
| VerfasserIn |
Blanca Ausin, José-Abel Flores, Francisco Javier Sierro, Isabel Cacho, Iván Hernández-Almeida, Belen Martrat, Joan Grimalt |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250088580
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| Publikation (Nr.) |
 EGU/EGU2014-2754.pdf |
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| Zusammenfassung |
| Abstract
This study is aimed to reconstruct productivity during the Holocene in the Western
Mediterranean as well as to investigate what processes account for its short-term
variability. Fossil coccolithophore assemblages have been studied along with Mg/Ca and
Uk’37-estimated Sea Surface Temperature (SST) and other paleoenvironmental proxies. The
study site is located in a semi-permanent area of upwelling in the Alboran Sea. This
productive cell is of special interest since is closely related to local hydrological dynamics
driven by the entering Atlantic Jet (AJ). The onset of this productive cell is suggested at 7.7
ka cal. B.P. and linked to the establishment of the anticyclonic gyres. From 7.7 ka cal.
BP to present, the N ratio and accumulation rate of Florisphaera profunda show
successive upwelling and stratification events. This alternation is simultaneous to
changes in the Western Mediterranean Deep Water (WMDW) formation rate in the
Gulf of Lions [Frigola et al., 2007], along with changes in Mg/Ca-estimated SST,
relative abundance of reworked nannoliths, pollen grains record [Fletcher et al.,
2012] and n-hexacosan-1-ol index. Two scenarios are proposed to explain short-term
climatic and oceanographic variability: [1] Wetter climate and weaker north-westerlies
blowing over the Gulf of Lions trigger a slackening of the WMDW formation.
Consequently, a minor AJ inflows the Alboran Sea leading to less vertical mixing and a
deepening of the nutricline and hence, long-term stratification events. [2] Arid climate
and stronger north-westerlies enable WMDW reinforcement. In turn, increased AJ
triggers vertical mixing and nutricline shoaling, and therefore, productive periods.
Finally, changes in atmospheric patterns (e.g. the winter North Atlantic Oscillation;
[Olsen et al., 2012]) prove to be useful in explaining the WMDW formation in
the Gulf of Lions and associated short-term productivity variations in the Alboran
Sea.
References
Fletcher, W. J., M. Debret, and M. F. Sanchez Goñi (2012), Mid-Holocene emergence of a
low-frequency millennial oscillation in western Mediterranean climate: Implications for
past dynamics of the North Atlantic atmospheric westerlies, The Holocene, 23,
153-166.
Frigola, J., A. Moreno, I. Cacho, M. Canals, F. J. Sierro, J. A. Flores, J. O. Grimalt, D.
A. Hodell, and J. H. Curtis (2007), Holocene climate variability in the western
Mediterranean region from a deepwater sediment record, Paleoceanography, 22,
PA2209.
Olsen, J., N. J. Anderson, and M. F. Knudsen (2012), Variability of the North Atlantic
Oscillation over the past 5,200 years, Nature Geosci, 5, 808-812. |
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