Abstract
Geochemical and oceanographic data, acquired throughout 6 months by the GEOSTAR-2 benthic observatory in southern Tyrrhenian Sea, evidenced ocean-lithosphere interactions in the 1900-m deep Benthic Boundary Layer (BBL), distinguishing two water masses with different origin and, possibly, benthic residence time. Gas concentration, helium isotopic ratios, radioactivity, temperature, salinity and vertical component of the current converged towards the indication of a BBL characterised by a colder and fresher western water (WW), which is episodically displaced by the cascading of the warmer and saltier Eastern Overflow Water (EOW). The benthic WW has higher concentration of geochemical tracers diffusing from the seafloor sediments. The data set shows the potential of long-term, continuous and multiparametric monitoring in providing unique information which cannot be acquired by traditional, short-term or single-sensor investigations.
Highlights
The Benthic Boundary Layer (BBL) is the dynamic interface between the lithosphere and the ocean where many physical, geochemical and biological processes play an important role in environmental globalGiuseppe Etiope, Paolo Favali, Jean-Luc Fuda, Francesco Italiano, Matthias Laubenstein, Claude Millot and Wolfango PlastinoOil platforms are sited on the BBL, and cables and pipelines are lain across it
This paper presents geochemical and oceanographic data obtained from the automatic water sampler, the CTD and the Acoustic Doppler Current Profiler (ADCP) to show how multidisciplinary and integrated monitoring at deep BBLs may provide various original and unique information, which cannot be acquired by traditional, short-term or single-sensor recordings
The various geochemical and oceanographic data are basically coherent converging towards the indication of a BBL mainly characterised by a colder and fresher western water which is episodically displaced by the cascading of a warmer and saltier eastern water
Summary
The Benthic Boundary Layer (BBL) is the dynamic interface between the lithosphere (seafloor) and the ocean (seawater) where many physical, geochemical and biological processes play an important role in environmental globalGiuseppe Etiope, Paolo Favali, Jean-Luc Fuda, Francesco Italiano, Matthias Laubenstein, Claude Millot and Wolfango PlastinoOil platforms are sited on the BBL, and cables and pipelines are lain across it. GEOSTAR-2 (GEophysical and Oceanographic STation for Abyssal Research) is the first European deep-sea observatory for geophysical and environmental monitoring at the seabed becoming operative in 2000. It was deployed in September 2000 from the Italian R/V Urania, in the Southern Tyrrhenian Sea, between the islands of Sicily and Ustica, at about 1900 m b.s.l. More than 4100 h of data were recorded continuously This mission represented the longest experiment using a complex module, with an intelligent unit, deployed at great depth
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