| 1. |
- Tabiri, S, et al.
(författare)
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- 2021
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swepub:Mat__t
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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. |
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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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| 7. |
- 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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