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| 2. |
- Bravo, L, et al.
(författare)
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- 2021
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swepub:Mat__t
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| 3. |
- Tabiri, S, et al.
(författare)
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- 2021
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swepub:Mat__t
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| 4. |
- Bensi, M., et al.
(författare)
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Deep flow variability offshore south-west Svalbard (fram strait)
- 2019
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Ingår i: Water. - : MDPI AG. - 2073-4441. ; 11:4
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Tidskriftsartikel (refereegranskat)abstract
- - Water mass generation and mixing in the eastern Fram Strait are strongly influenced by the interaction between Atlantic and Arctic waters and by the local atmospheric forcing, which produce dense water that substantially contributes to maintaining the global thermohaline circulation. The West Spitsbergen margin is an ideal area to study such processes. Hence, in order to investigate the deep flow variability on short-term, seasonal, and multiannual timescales, two moorings were deployed at ~1040 m depth on the southwest Spitsbergen continental slope. We present and discuss time series data collected between June 2014 and June 2016. They reveal thermohaline and current fluctuations that were largest from October to April, when the deep layer, typically occupied by Norwegian Sea Deep Water, was perturbed by sporadic intrusions of warmer, saltier, and less dense water. Surprisingly, the observed anomalies occurred quasi-simultaneously at both sites, despite their distance (~170 km). We argue that these anomalies may arise mainly by the effect of topographically trapped waves excited and modulated by atmospheric forcing. Propagation of internal waves causes a change in the vertical distribution of the Atlantic water, which can reach deep layers. During such events, strong currents typically precede thermohaline variations without significant changes in turbidity. However, turbidity increases during April-June in concomitance with enhanced downslope currents. Since prolonged injections of warm water within the deep layer could lead to a progressive reduction of the density of the abyssal water moving toward the Arctic Ocean, understanding the interplay between shelf, slope, and deep waters along the west Spitsbergen margin could be crucial for making projections on future changes in the global thermohaline circulation. © 2019 by the authors.
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| 5. |
- Tesi, Tomaso, et al.
(författare)
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Flood-driven transport of sediment, particulate organic matter, and nutrients from the Po River watershed to the Mediterranean Sea
- 2013
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Ingår i: Journal of Hydrology. - : Elsevier BV. - 0022-1694 .- 1879-2707. ; 498, s. 144-152
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Tidskriftsartikel (refereegranskat)abstract
- The Po River (Northern Italy) discharge represents a considerable input of the land-derived material entering the Mediterranean Sea. Most of its particulate and dissolved constituents are supplied to the sea in response to short-lived climate events. Although these floods exert first-order control on the transport of organic and inorganic elements, both composition and magnitude of the river material are poorly constrained during high discharge periods. In order to fill this knowledge gap, in this study we carried out an event response sampling in the Po River in November 2011. Beginning in early November, intense rainfall occurred in the Po watershed that resulted in a flood of similar to 6000 m(3) s(-1) year return period). Water samples were collected from the river before and during the flood. Dissolved nitrate, nitrite, ammonia, and silicate were measured and the particulate material was analyzed for total suspended sediment, elemental composition, delta C-13, delta N-15, grain-size, and Cs-137 activity. Our results showed a temporal decoupling between solid and water discharge implying that predicted sediment loads simply derived from sediment rating curves could potentially give rise to large errors, especially when calculations are used to understand the sediment export in response short-lived events. The suspended organic material during high flow was dominated by soil organic matter while high delta N-15 indicated the influence of an additional N-15-enriched source (e.g., manure, sewage, and algal biomass) during low discharge. Because the concentrations of nitrite and ammonia were positively correlated with the content of particulate material in suspension, we inferred that nitrite and ammonia concentrations were driven by either bacteria activity (ammonification-nitrification) or ionic exchange whose rates were proportional to concentration of the suspended material. In addition, due to the dilution with nitrate-poor rainfall, the concentration of nitrate decreased with increasing water discharge. High concentrations of nitrate were instead attributable to the influx of nitrate-rich water from groundwater that is chronically contaminated and constitutes most of the baseflow during low flow. Our results indicate that the event-dominated transport in the Po drainage basin is particularly important for the organic matter supply as flood events account for at least one-third of the particulate annual export (organic carbon and nitrogen). Finally, this study has demonstrated the utility of event-response sampling for understanding the importance of event-dominated transport in rivers.
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| 6. |
- Tesi, Tommaso, et al.
(författare)
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Source, diagenesis, and fluxes of particulate organic carbon along the western Adriatic Sea (Mediterranean Sea)
- 2013
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Ingår i: Marine Geology. - : Elsevier BV. - 0025-3227 .- 1872-6151. ; 337, s. 156-170
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Tidskriftsartikel (refereegranskat)abstract
- In this study, we investigated the modern organic carbon (OC) cycling along the clinoform-shaped deposit that developed after the attainment of the modern sea-level in the Adriatic Sea (similar to 5.5 kyr cal BP). Newly acquired data were combined with published results to characterize the (i) origin, (ii) diagenesis, and (iii) fluxes of OC along the Adriatic clinoform. delta C-13, Delta C-14, and lignin phenols were used to constrain the composition of CC accumulating in surface sediments. Sediment cores collected at different water depths were used to describe the early diagenesis during burial in different regions. In addition, on the basis of an extensive number of accumulation rates and CC data, we assessed the flux of CC to the seabed and its burial. Our results showed that terrigenous CC is the dominant CC source in the Po prodelta mainly in the form of pre-aged soil-derived CC and vascular plant fragments. Along the clinoform, both Delta 14C and the concentration of lignin-derived phenols decreased with increasing distance from the Po prodelta indicating the influence of an additional pool of aged CC that gradually becomes more important because of its selective preservation during the sediment transport. As a result, degradation rates (k) decreased along the clinoform as a function of the sediment oxidative history. The calculated half-life of reactive OC (t(1/2)) was similar to 14.6 yrs in the Po prodelta whereas topset/forest deposits south of this region exhibited higher values, similar to 100 yrs, indicating the presence of refractory material. In the distal bottomset region, the tip was particularly high ranging from similar to 255 to similar to 912 yrs. Because of the significant southward component of the sediment transport, the CC deposition in the southern surface sediments exceeded the local CC input via rivers (ratio deposition/input 12). Conversely, the northern Adriatic was characterized by a marked imbalance (ratio deposition/input 0.3-0.5). According to our calculations, the CC flux to the seabed along the clinoform was similar to 309 Gg of C per year whereas the OC burial was similar to 180 Gg of C per year, corresponding to an overall burial efficiency of similar to 59%.
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