Search results for "Oceano"
showing 10 items of 1626 documents
Hydrochemical mercury distribution and air-sea exchange over the submarine hydrothermal vents off-shore Panarea Island (Aeolian arc, Tyrrhenian Sea)
2017
Abstract There is a growing concern about the mercury (Hg) vented from submarine hydrothermal fluids to the marine surrounding and exchange of dissolved gaseous mercury (DGM) between the sea surface and the atmosphere. A geochemical survey of thermal waters collected from submarine vents at Panarea Island (Aeolian Islands, southern Italy) was carried out in 2015 (15–17th June and 17–18th November), in order to investigate the concentration of Hg species in hydrothermal fluids and the vertical distribution in the overlying water column close to the submarine exhalative area. Specific sampling methods were employed by Scuba divers at five submarine vents located along the main regional tecton…
Numerical evidence for thermohaline circulation reversals during the Maastrichtian
2005
[1] The sensitivity of the Maastrichtian thermohaline circulation to the opening/closing of marine communications between the Arctic and North Pacific oceans is investigated through a set of numerical experiments using the model CLIMBER-2 (Earth Model of Intermediate Complexity). We show here that the opening or closing of an Arctic-Pacific marine gateway induces transitions between different equilibrium states of the thermohaline circulation. Sensitivity tests of the inferred modes of thermohaline circulation to atmospheric CO2 level changes have also been explored. An abrupt switch in deep convection from high northern to high southern latitudes, a change consistent with isotopic evidence…
Coralline alga reveals first marine record of subarctic North Pacific climate change
2007
[1] While recent changes in subarctic North Pacific climate had dramatic effects on ecosystems and fishery yields, past climate dynamics and teleconnection patterns are poorly understood due to the absence of century-long high-resolution marine records. We present the first 117-year long annually resolved marine climate history from the western Bering Sea/Aleutian Island region using information contained in the calcitic skeleton of the long-lived crustose coralline red alga Clathromorphum nereostratum, a previously unused climate archive. The skeletal δ18O-time series indicates significant warming and/or freshening of surface waters after the middle of the 20th century. Furthermore, the ti…
Sr/Ca and Mg/Ca ratios of ontogenetically old, long-lived bivalve shells (Arctica islandica) and their function as paleotemperature proxies
2011
International audience; The Sr/Ca and Mg/Ca ratios of many biogenic skeletons provide useful paleotemperature estimates. As yet however, it has remained largely impossible to obtain such information from bivalve shells. In the present study, metal-to-calcium values in the hinge plate (aragonite, outer shell layer) of four ontogenetically old (85 to 374 year-old) specimens of the long-lived bivalve, Arctica islandica, were measured on a LA-ICP-MS. The shells were collected alive in 1868, 1986 and 2003 from three different localities around Iceland. With increasing ontogenetic age and decreasing growth rate, a distinct trend toward increasing Sr/Ca (max. 5.17 mmol/mol) and Mg/Ca values (max. …
Fluid storage and migration properties of sheared Neptunian dykes
2019
Abstract Neptunian dykes are widely reported along the Tethyan carbonate platforms and are commonly considered as subsurface baffles or barriers to fluid flow. However, the fluid storage and migration properties of sheared Neptunian dykes are poorly known. For this reason, we investigate the inner structure and fluid flow properties of two Neptunian dykes, which can be characterized by different architectures if involved or not in brittle shearing processes. The dykes strike ca. WNW-ESE and crosscutting the tight Jurassic limestones exposed at Maranfusa Mt., NW Sicily, Italy. The unsheared and sheared Neptunian dykes are almost sub-vertical and at high-angle with respect to the horizontal p…
Radiogenic isotopes: new tools help reconstruct paleocean circulation and erosion input
2001
Ocean and atmosphere circulation and continental weathering regimes have undergone great changes over thousands of years as well as tens of millions of years. During the glacial stages of the Pleistocene, ocean circulation was generally more sluggish and deep water circulation in the Atlantic had a shallower flow. At the same time, weathering on the continents was enhanced by glacial erosion, particularly in high northern latitudes, which increased the input of erosional detritus into the ocean. In addition, atmospheric pressure gradients were larger, leading to higher wind speeds and increased supply of aeolian dust to the ocean. Prior to the onset of Northern Hemisphere glaciation and pro…
Plastic ingestion by pelagic and demersal fish from the North Sea and Baltic Sea
2015
Plastic ingestion by marine biota has been reported for a variety of different taxa. In this study, we investigated 290 gastrointestinal tracts of demersal (cod, dab and flounder) and pelagic fish species (herring and mackerel) from the North and Baltic Sea for the occurrence of plastic ingestion. In 5.5% of all investigated fishes, plastic particles were detected, with 74% of all particles being in the microplastic (<5mm) size range. The polymer types of all found particles were analysed by means of Fourier transform infrared (FT-IR) spectroscopy. Almost 40% of the particles consisted of polyethylene (PE). In 3.4% of the demersal and 10.7% of the pelagic individuals, plastic ingestion was …
Marine climate and hydrography of the Coralline Crag (early Pliocene, UK): isotopic evidence from 16 benthic invertebrate taxa
2019
The taxonomic composition of the biota of the Coralline Crag Formation (early Pliocene, eastern England) provides conflicting evidence of seawater temperature during deposition, some taxa indicating cool temperate conditions by analogy with modern representatives or relatives, others warm temperate to subtropical/tropical conditions. Previous isotopic (δ18O) evidence of seasonal seafloor temperatures from serial ontogenetic sampling of bivalve mollusk shells indicated cool temperate winter (<10 °C) and/or summer (<20 °C) conditions but was limited to nine profiles from two species, one ranging into and one occurring exclusively in cool temperate settings at present. We supplement these resu…
How Offshore Groundwater Shapes the Seafloor
2018
The MARCAN project, launched last January, is working to fill a gap in our knowledge of how freshwater flowing underground shapes and alters the continental margins.
The tsunami phenomenon
2017
Abstract With human activity increasingly concentrating on coasts, tsunamis (from Japanese tsu = harbour, nami = wave) are a major natural hazard to today’s society. Stimulated by disastrous tsunami impacts in recent years, for instance in south-east Asia (2004) or in Japan (2011), tsunami science has significantly flourished, which has brought great advances in hazard assessment and mitigation plans. Based on tsunami research of the last decades, this paper provides a thorough treatise on the tsunami phenomenon from a geoscientific point of view. Starting with the wave features, tsunamis are introduced as long shallow water waves or wave trains crossing entire oceans without major energy l…