93 research outputs found
Cosa succederebbe se le correnti dei nostri mari si fermassero
No full textTratta degli aspetti dell’oceanografia legati allo studio della circolazione oceanica ma anche di come si muovono le correnti nei nostri mari e come influenzano il clima.Manuel Bensi, oceanografo e ricercatore nel campo dell'oceanografia fisica presso OGS, Trieste. Le sue attività di ricerca si concentrano sulla circolazione oceanica, la formazione di acque dense e cambiamenti climatici nel Mar Mediterraneo e nelle regioni Polari. Ha partecipato a numerose campagne oceanografiche in Mediterraneo, Atlantico e Artico ed è autore/coautore di oltre 25 pubblicazioni scientifiche e numerosi interventi in congressi nazionali e internazionali
Effects of winter convection on the deep layer of the Southern Adriatic Sea in 2012
No full textWe analyze aspects concerning the thermohaline changes observed in the near-bottom
layer of the Southern Adriatic Pit (SAP), in the Eastern Mediterranean, after the arrival of
abundant and exceptionally dense water (rh>30 kg m23) produced in the shallow Northern
Adriatic Sea during winter 2012. For this purpose, we use temperature (T), salinity (S), and
current time series collected at the E2M3A deep-ocean observatory of the Southern
Adriatic, and Conductivity-Temperature-Depth data obtained both in the Southern and
Middle Adriatic from freely drifting profiling floats. The dense water produced in the
Northern Adriatic arrived in the central and deepest part of the SAP as a series of individual
pulses starting on 10 March 2012; while, a stronger and prolonged signal that significantly
modified the local deep water stratification arrived after 10 April 2012. As a consequence, T
and S suddenly decreased (0.15C and 0.015), thus interrupting positive T and S bottom
trends observed during the previous 5 years and producing a density increase of 0.02 kg
m23. Such variability has been rarely observed in the area. We ascribe its occurrence to the
concomitance of exceptionally harsh and long-lasting Bora wind, scarce precipitation, and
low river discharge over the Northern Adriatic during winter 2011/2012. Eventually, this
newly formed AdDW reached the Strait of Otranto during July 2012. Its characteristics
profoundly differed from those observed in the previous decade. Hence, a noticeable
variability in structure and circulation of the abyssal layers of the Ionian basin is likely to
occur in the near future
Thermohaline variability and mesoscale dynamics observed at the deep-ocean observatory E2M3A in the southern adriatic sea
No full textThermohaline properties in the Eastern Mediterranean in the last three decades: is the basin returning to the pre-EMT situation?
No full textTemperature, salinity and oxygen data collected during April and June 2011 (M84/3 and P414 cruises respectively) are analysed to derive the oceanographic characteristics of the Eastern Mediterranean (EM) basin. These observed characteristics are compared with those from previous cruises over the period 1987–2011. As a result, the interannual and decadal variability of the EM thermohaline properties are discussed in the context of the evolution of the Eastern Mediterranean Transient (EMT) and of the general circulation of the basin. We found that the state of the EM is still far from the pre-EMT conditions, though the 2011 results possibly indicate a slow return to this status. In particular, a comparison between thermohaline property evolution deriving from interannual variability of the preconditioning and air–sea interaction (heat fluxes) in the South Adriatic and the Cretan Seas reveals aspects of the alternation of the two dense water sources (Adriatic and Aegean) during the last three decades, which have strong implications for the hydrographic characteristics of the intermediate and deep layers of the Ionian and Levantine basins
Linking mixing processes and climate variability to the heat content distribution of the Eastern Mediterranean abyss
No full textThe heat contained in the ocean (OHC) dominates the Earth’s energy budget and hence represents a fundamental parameter for understanding climate changes. However, paucity of observational data hampers our knowledge on OHC variability, particularly in abyssal areas. Here, we analyze water characteristics, observed during the last three decades in the abyssal Ionian Sea (Eastern Mediterranean), where two competing convective sources of bottom water exist. We find a heat storage of ~1.6 W/m2– twice that assessed globally in the same period – exceptionally well-spread throughout the local abyssal layers. Such an OHC accumulation stems from progressive warming and salinification of the Eastern Mediterranean, producing warmer near-bottom waters. We analyze a new process that involves convectively-generated waters reaching the abyss as well as the triggering of a diapycnal mixing due to rough bathymetry, which brings to a warming and thickening of the bottom layer, also influencing water-column potential vorticity. This may affect the prevailing circulation, altering the local cyclonic/anticyclonic long-term variability and hence precondition future water-masses formation and the redistribution of heat along the entire water-column
Water Masses in the Eastern Mediterranean Sea: An Analysis of Measured Isotopic Oxygen
No full textWe investigate aspects of the water mass structure of the Adriatic and Ionian basins (Eastern Mediterranean Sea) and their interdecadal variability through statistical analyses focused on δ18Ο measurements carried out in 1985, 1990, and 2011. In particular, the more recent δ18Ο measurements extend throughout the entire water column and constitute, to the best of our knowledge, the largest synoptic dataset encompassing different sub-basins of the Mediterranean Sea. We study the statistical linkages between temperature, salinity, dissolved oxygen and δ18Ο. We find that δ18Ο is largely independent from the other parameters, and it can be used to trace major water masses that are typically found in the basins, including the Adriatic Dense Water, the Levantine Intermediate Water, and the Cretan Intermediate and Dense Waters. Finally, we explore the possibility of using δ18Ο concentration as a proxy for dominant modes of large-scale oceanic variability in the Mediterranean Sea
L’arcivescovo Turpino nella Chanson de Roland e nel Rolandslied
No full textFor modern readers of the Chanson de Roland (late 11th c.) and of its German version, the Rolandslied (late 12th c.), the Archbishop Turpin is an intriguing but bewildering character: he is a member of the Church who despises the idea of a life meant to fight evil only by means of prayers, and at the same time he takes active part in the war against the infidels. This paper briefly retraces the process that led to the convergence of oratores and bellatores, and analyzes the different forms of representation of Turpin in the two poems, in order to throw light on the attitude of each author to the thorny issue of militarized clergy in the 11th and 12th centuries
Polar region on a changing planet: learning from the past, exploring the future
No full textSessione S 15. Polar region on a changing planet: learning from the past, exploring the future
The polar areas are complex, interlinked systems whose environmental changes driven by climate variations have a fundamental impact on the rest of the planet. Ice melting associated to increasing atmospheric and ocean surface temperatures, is responsible for progressive sea level rise threatening coastal urbanization and infrastructures, and alteration of the atmosphere-ocean coupling system responsible for precipitation patterns around the world.
The information about past climate changes are especially guarded in the glacial and geological records of the polar areas, very sensitive also to small temperature changes which can lead to large environmental feedback.
This session welcomes contributions reporting the state-of-the-art in polar sciences, including geology, oceanography, glacial geology and geomorphology, glaciology and related modelling exploring the future climatic trend of polar region
Structure and variability of the abyssal water masses in the Ionian Sea in the period 2003-2010
No full textThis study presents aspects of the spatial and temporal variability of abyssal water masses in the Ionian Sea, as derived from recent temperature, salinity, dissolved oxygen and velocity observations and from comparisons between these and former observations. Previous studies showed how in the Southern Adriatic Sea the Adriatic Deep Water (AdDW) became fresher (ΔS ≈ −0.08) and colder (ΔT ≈ −0.1°C) after experiencing warming and salinification between 2003 and 2007. Our data, collected from October 2009 to July 2010 from two bottom moorings, one within the Strait of Otranto and the other in the northern Ionian, confirm this tendency: a bottom vein of southward-flowing AdDW, whose temperature and salinity continuously decreased during the observation time, was detected there. Typically, the vein travel time between the two stations ranged between 45 and 50 days. This gave us a temporal estimate for AdDW anomaly propagation towards the Ionian abyss from their Adriatic generation region. The density excess of the observed vein was always enough to enable its existence as a bottom-arrested current. This evidence confirms that, at that time (2009 and 2010), the Adriatic Sea was greatly contributing to the formation of Eastern Mediterranean Deep Water (EMDW), the bottom water of the Eastern Mediterranean. Hence, based on these results and on the evidence that, from 2003 to 2009, abyssal Ionian waters became saltier and warmer under the time-lagged influence of AdDW, possible future changes in the EMDW characteristics, as a response to Adriatic variability, are discussed
The Syabru-Bensi hydrothermal system in central Nepal: 1. Characterization of carbon dioxide and radon fluxes
No full textThe Syabru-Bensi hydrothermal system (SBHS), located at the Main Central Thrust zone in central Nepal, is characterized by hot (30–62°C) water springs and cold (<35°C) carbon dioxide (CO2) degassing areas. From 2007 to 2011, five gas zones (GZ1–GZ5) were studied, with more than 1600 CO2 and 850 radon flux measurements, with complementary self-potential data, thermal infrared imaging, and effective radium concentration of soils. Measurement uncertainties were evaluated in the field. CO2 and radon fluxes vary over 5 to 6 orders of magnitude, reaching exceptional maximum values of 236 ± 50 kg m−2 d−1 and 38.5 ± 8.0 Bq m−2 s−1, with estimated integrated discharges over all gas zones of 5.9 ± 1.6 t d−1 and 140 ± 30 MBq d−1, respectively. Soil-gas radon concentration is 40 × 103 Bq m−3 in GZ1–GZ2 and 70 × 103 Bq m−3 in GZ3–GZ4. Strong relationships between CO2 and radon fluxes in all gas zones (correlation coefficient R = 0.86 ± 0.02) indicate related gas transport mechanisms and demonstrate that radon can be considered as a relevant proxy for CO2. CO2 carbon isotopic ratios (δ13C from −1.7 ± 0.1 to −0.5 ± 0.1‰), with the absence of mantle signature (helium isotopic ratios R/RA < 0.05), suggest metamorphic decarbonation at depth. Thus, the SBHS emerges as a unique geosystem with significant deep origin CO2 discharge located in a seismically active region, where we can test methodological issues and our understanding of transport properties and fluid circulations in the subsurface
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