Latest Holocene Climate Variability Revealed by a High-Resolution Multiple Proxy Record off Lisbon (Portugal).
Abstract
The North Atlantic Oscillation (NAO) is known to have a major influence on the wintertime climate of the Atlantic basin and surrounding countries, determining precipitation and wind conditions at mid-latitudes. A comparison of Hurrell's NAO index to the mean winter (January-March) discharge of the Iberian Tagus River reveals a good negative correlation to negative NAO, while the years of largest upwelling anomalies, as referred in the literature, appear to be in good agreement with positive NAO. On this basis, a better understanding of the long-term variability of the NAO and Atlantic climate variability can be gained from high-resolution climate records from the Lisbon area. Climate variability of the last 2,000 years is assessed through a mutiple proxy study of sedimentary sequences recovered from the Tagus prodelta deposition center, off Lisbon (Western Iberia). Physical properties, XRF and magnetic properties from core logging, grain size, δ18O, TOC, CaCO , total alkenones, n-alkanes, alkenone SST, diatoms, benthic and planktonic foraminiferal assemblage compositions and fluxes are the proxies employed. The age model for site D13902 is based on AMS C-14 dates from mollusk and planktonic foraminifera shells, the reservoir correction for which was obtained by dating 3 pre-bomb, mollusk shells from the study area. Preliminary results indicate a Little Ice Age LIA alkenone derived SSTs around 15°C followed by a sharp and rapid increase towards 20°C. In spite the strong variability observed for most records, this low temperature interval is marked by a general increase in organic carbon, diatom abundance and total alkenone concentration pointing to higher upwelling related productivity. Major peaks in magnetic susceptibility and grain size are interpreted as the record of flood-like events that are likely to reflect times of primarily negative NAO.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2002
- Bibcode:
- 2002AGUFMPP72A0419A
- Keywords:
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- 4267 Paleoceanography