Seasonal and interannual export production of coccolithophores in Cariaco Basin (Venezuela): tools for climatic variability
Articolo
Data di Pubblicazione:
2006
Citazione:
Seasonal and interannual export production of coccolithophores in Cariaco Basin (Venezuela): tools for climatic variability / B. De Bernardi, P. Ziveri, E. Erba, R.C. Thunell. - In: GEOPHYSICAL RESEARCH ABSTRACTS. - ISSN 1607-7962. - 8:(2006), p. 03767. ((Intervento presentato al convegno EGU General Assembly tenutosi a Vienna nel 2006.
Abstract:
Cariaco Basin shows marked seasonal and interannual variations in hydrographic
properties and primary production. Partially isolated from the open Caribbean Sea
by a series of shallow sills, Cariaco Basin is anoxic below ˜250m water depth because
of restricted water exchange and high oxygen demand created by productive
conditions associated with seasonal upwelling along the southern Caribbean margin.
Moreover, the strength of the Northeast trade winds varies seasonally, because of the
annual migration of the Intertropical Convergence Zone (ITCZ), causing a significant
seasonal change in the surface waters of the Cariaco Basin. The combination of
high biogeochemical input and the lack of bioturbation at the bottom allow the deposition
of laminated sediments that exhibit high sedimentation rates. In this study
we track changes in coccolith export production and ecology in sediment trap samples
(10,30_N; 64,40_W; from November 1996 to October 1999) and laminated core
(CAR7-1) samples from Cariaco Basin, in order to monitor and understand climate
and ocean variability in the southern Caribbean region during the last 1000 years.
During a three-year sediment trapping project in Cariaco Basin significant changes
in coccolithophore fluxes occurred in response to changes in hydrography. Seasonal
coccolith fluxes are observed with flux maxima in late-fall and winter, when the hydrographic
conditions are relatively stable. In particular, coccolithophore patterns suggest
that these trends are driven by both annual and interannual changes in the upper water
column associated with El Niño conditions. The coccolith flux recorded in core
CAR7-1 was dominated by E. huxleyi, G. oceanica and F. profunda, the same species
that dominated the sediment trap samples.We will show the significant changes occuring
down-core, reflecting hydrographic and climatic variation in ITCZ position over
the Caribbean region. Moreover, C. leptoporus in this basin may indicate an increase in
cool water due to intensification in trade winds and upwelling intensity. Total coccolith
fluxes show evidence of centennial scale variability, suggesting solar modulation
Tipologia IRIS:
01 - Articolo su periodico
Elenco autori:
B. De Bernardi, P. Ziveri, E. Erba, R.C. Thunell
Link alla scheda completa: