Paleoenvironmental evolution of a late Holocen lake in the Azores archipelago
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- Bioloxía, Grao en [438]
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Paleoenvironmental evolution of a late Holocen lake in the Azores archipelagoAutor(es)
Directores
Bao Casal, RobertoHernández, Armand
Fecha
2013Centro/Dpto/Entidad
Universidade da Coruña. Facultade de CienciasDescripción
Traballo fin de grao (UDC.CIE). Bioloxía. Curso 2012/2013Resumen
[Abstract] A major source of interannual variability in the atmospheric circulation is the North
Atlantic Oscillation (NAO), which is associated with changes in the surface westerlies
across the North Atlantic onto Europe. Irregularities in the NAO are responsible for
storm track paths across the Atlantic Ocean towards Europe and, therefore, for the
amount and timing of precipitation on this continent. Despite its importance, few
historical and long-term reconstructions have been carried out and few multiproxy
reconstructions of NAO evolution have been conducted in the Azores islands located at
one end of the dipole. Since the NAO has a strong and direct influence on lacustrine
ecosystems in many ways, the study of lake sediments can provide precise information
on the long-term evolution of this climate mode. Characterization of sedimentary facies,
organic matter geochemistry and remains of diatoms have been used in this study to
determine three different climatic phases in a sediment core from Lake Empadadas
Norte (São Miguel Island, Azores). The period 1340-1460 AD is defined by a
decreasing trend in productivity and moderately shallow waters, as terrestrial inputs
dominated, suggesting a humid climate with abundant precipitations indicating a NAOphase.
Between 1460 and 1930 AD, and despite gaps in our data, the site was
characterized by a more arid climate, related to a NAO+ phase, with lower lake level
and productivity, with carbon appearing to be from mixed sources, although a series of
catastrophic events are apparent in the form of massive instantaneous alluvial
depositions. Finally, the period 1930-1950 AD, corresponds to a humid phase where
lake level and productivity is high suggesting a return to low NAO values, although not
as high as during 1340-1460 AD, and organic matter has a high percentage of terrestrial
content as a result of increased run-off. This indicates NAO variability might be the
main factor controlling water level fluctuations. We conclude that in order to
accomplish a better understanding of climate change associated to the NAO, further and
more ample studies are needed.
Palabras clave
Oscilación del Atlántico Norte
Paleobiogeografía
Lagoa Empadadas (Azores)
Paleoclimatología
Paleobotánica
Paleobiogeografía
Lagoa Empadadas (Azores)
Paleoclimatología
Paleobotánica
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