scholarly journals Geodynamic Evolution of the Western Part of the Russian Arctic and Its Diamond Potential

Oceanology ◽  
2021 ◽  
Author(s):  
N. O. Sorokhtin ◽  
N. E. Kozlov

Abstract The study of the geodynamic evolution of the Baltic Shield showed that the melts of diamondiferous kimberlites and related rocks were formed due to the pulling of “heavy” ferruginous sediments of the Early Proterozoic into subduction zones beneath the Archean cratons. Later, during the Neoproterozoic and Paleozoic stages of rifting, melts conserved in the lower crust and subcrustal lithosphere were able to penetrate into the near-surface zones of the crust and form magmatic complexes of alkaline–ultramafic and kimberlite magmatism. The authors showed that diamondiferous kimberlite and lamproite explosion pipes, as well as related carbonatite and alkaline–ultramafic intrusions, are mainly located above the subduction zones of the Svecofennian (Karelian) plates, which functioned about 2.0–1.8 Ga ago. At the same time, alkaline ultramafic intrusions and (sodium) carbonatites are located closest to the front of the subduction zone of Proterozoic plates (from 100 to 200–300 km). Then (at a distance of 200 to 400 km), there is a zone of location of calcite carbonatites and melilitites, and sometimes nondiamondiferous kimberlites. Diamondiferous kimberlite and lamproite diatremes are located farther than other similar formations approximately 300 to 600–650 km from its front. Such a regular spatial arrangement of magmatic complexes of a single series unambiguously indicates a change in depth of their origin. The farther from the surface boundary of the paleosubduction zone the magmatic bodies are located, the deeper the facies representing them.

Author(s):  
Tobias Kukulka ◽  
Todd Thoman

AbstractDispersion processes in the ocean surface boundary layer (OSBL) determine marine material distributions such as those of plankton and pollutants. Sheared velocities drive shear dispersion, which is traditionally assumed to be due to mean horizontal currents that decrease from the surface. However, OSBL turbulence supports along-wind jets; located in near-surface convergence and downwelling regions, such turbulent jets contain strong local shear. Through wind-driven idealized and large eddy simulation (LES) models of the OSBL, this study examines the role of turbulent along-wind jets in dispersing material. In the idealized model, turbulent jets are generated by prescribed cellular flow with surface convergence and associated downwelling regions. Numeric and analytic model solutions reveal that horizontal jets substantially contribute to along-wind dispersion for sufficiently strong cellular flows and exceed contributions due to vertical mean shear for buoyant surface-trapped material. However, surface convergence regions also accumulate surface-trapped material, reducing shear dispersion by jets. Turbulence resolving LES results of a coastal depth-limited ocean agree qualitatively with the idealized model and reveal long-lived coherent jet structures that are necessary for effective jet dispersion. These coastal results indicate substantial jet contributions to along-wind dispersion. However, jet dispersion is likely less effective in the open ocean because jets are shorter lived, less organized, and distorted due to spiraling Ekman currents.


2016 ◽  
Author(s):  
Karin Haglund ◽  
Björn Claremar ◽  
Anna Rutgersson

Abstract. The shipping sector contributes significantly to increasing emissions of air pollutants. In order to achieve sustainable shipping, primarily through new regulations and techniques, greater knowledge of dispersion and deposition of air pollutants is required. Regional model calculations of the dispersion and deposition of sulphur, nitrogen and particulate matter from the international maritime sector in the Baltic Sea and the North Sea have been made for the years 2009 to 2013. In some areas in the Baltic Sea region the contribution of sulphur dioxide, nitrogen oxide and nitrogen dioxide from international shipping represented up to 80 % of the total near surface concentration of the pollutants. Contributions from shipping of PM2,5 and PM10 were calculated to a maximum of 21 % and 13 % respectively. The contribution of wet deposition of sulphur from shipping was maximum 29 % of the total wet deposition, and for dry deposition the contribution from shipping was maximum 84 %. The highest percentage contribution of wet deposition of nitrogen from shipping reached 28 % and for dry deposition 47 %. The highest concentrations and deposition of the pollutants in the study were found near large ports and shipping lanes. High concentrations were also found over larger areas at sea and over land where many people are exposed. With enhanced regulations for sulphur content in maritime fuel, the cleaning of exhausts through scrubbers has become a possible economic solution. Wet scrubbers meet the air quality criteria but their consequences for the marine environment are largely unknown. The resulting potential of future acidification in the Baltic Sea, both from atmospheric deposition and from open-loop scrubber water along the shipping lanes, based on different assumptions about sulphur content in fuel and scrubber usage has been assessed. Shipping is expected to increase globally and in the Baltic Sea region, deposition of sulphur due to shipping will depend on traffic density, emission regulations and technology choices for the emission controls. To evaluate future changes scenarios are developed considering the amount of scrubber technology used. The increase in deposition for the different scenarios differs slightly for the basins in the Baltic Sea. The proportion of ocean acidifying sulphur from ships increases when taking scrubber water into account and the major reason to increasing acidifying nitrogen from ships are due to increasing ship traffic. This study also generates a database of scenarios for atmospheric deposition and scrubber exhaust from the period 2011 to 2050.


2019 ◽  
Vol 98 ◽  
pp. 12007
Author(s):  
Tianming Huang ◽  
Baoqiang Ma ◽  
Yin Long ◽  
Zhonghe Pang

In arid and semiarid area, the recharge rate is relatively limited and the unsaturated zone (UZ) is commonly thick. The moisture in the UZ may represent the water infiltrating from precipitation during the past decades to thousands of years. Therefore, the multiple geochemical tracers in soil moisture, including Cl (chloride mass balance), 3H (tritium peak displacement), NO3, 2H, 18O, can be used to estimate diffuse recharge rate and related recharge characteristics. Based on 45 UZ profiles with maximum depth of 62 m in the Ordos Basin in NW China, a typical arid and semiarid area, we has used multiple geochemical tracers to study the following recharge informations: (1) reconstruction of groundwater recharge history, (2) determination of groundwater recharge mechanism, and (3) assessment of impact of vegetation changes on groundwater recharge. The results show that the soil texture (epically the shallow soil), vegetation and precipitation mainly control the recharge rate. This study also found that shallow groundwater in arid and semiarid areas is often not in equilibrium with near-surface boundary conditions. To estimate present recharge information, the UZ must be considered. The whole recharge process from precipitation to groundwater cannot be well understood unless the UZ have been included in arid and semiarid areas.


2018 ◽  
Vol 10 (11) ◽  
pp. 1752 ◽  
Author(s):  
Toma Dabuleviciene ◽  
Igor E. Kozlov ◽  
Diana Vaiciute ◽  
Inga Dailidiene

A detailed study of wind-induced coastal upwelling (CU) in the south-eastern Baltic Sea is presented based on an analysis of multi-mission satellite data. Analysis of moderate resolution imaging spectroradiometer (MODIS) sea surface temperature (SST) maps acquired between April and September of 2000–2015 allowed for the identification of 69 CU events. The Ekman-based upwelling index (UI) was applied to evaluate the effectiveness of the satellite measurements for upwelling detection. It was found that satellite data enable the identification of 87% of UI-based upwelling events during May–August, hence, serving as an effective tool for CU detection in the Baltic Sea under relatively cloud-free summer conditions. It was also shown that upwelling-induced SST drops, and its spatial properties are larger than previously registered. During extreme upwelling events, an SST drop might reach 14 °C, covering a total area of nearly 16,000 km2. The evolution of an upwelling front during such intensive events is accompanied by the generation of transverse filaments extending up to 70 km offshore. An analysis of the satellite optical data shows a clear decline in the chlorophyll-a concentration in the coastal zone and in the shallow Curonian Lagoon, where it drops down by an order of magnitude. It was also shown that a cold upwelling front alters the stratification in the atmospheric boundary layer, leading to a sudden drop of air temperature and near-surface winds.


2014 ◽  
Vol 7 (6) ◽  
pp. 2613-2638 ◽  
Author(s):  
E. W. Blockley ◽  
M. J. Martin ◽  
A. J. McLaren ◽  
A. G. Ryan ◽  
J. Waters ◽  
...  

Abstract. The Forecast Ocean Assimilation Model (FOAM) is an operational ocean analysis and forecast system run daily at the Met Office. FOAM provides modelling capability in both deep ocean and coastal shelf sea regimes using the NEMO (Nucleus for European Modelling of the Ocean) ocean model as its dynamical core. The FOAM Deep Ocean suite produces analyses and 7-day forecasts of ocean tracers, currents and sea ice for the global ocean at 1/4° resolution. Satellite and in situ observations of temperature, salinity, sea level anomaly and sea ice concentration are assimilated by FOAM each day over a 48 h observation window. The FOAM Deep Ocean configurations have recently undergone a major upgrade which has involved the implementation of a new variational, first guess at appropriate time (FGAT) 3D-Var, assimilation scheme (NEMOVAR); coupling to a different, multi-thickness-category, sea ice model (CICE); the use of coordinated ocean-ice reference experiment (CORE) bulk formulae to specify the surface boundary condition; and an increased vertical resolution for the global model. In this paper the new FOAM Deep Ocean system is introduced and details of the recent changes are provided. Results are presented from 2-year reanalysis integrations of the Global FOAM configuration including an assessment of short-range ocean forecast accuracy. Comparisons are made with both the previous FOAM system and a non-assimilative FOAM system. Assessments reveal considerable improvements in the new system to the near-surface ocean and sea ice fields. However there is some degradation to sub-surface tracer fields and in equatorial regions which highlights specific areas upon which to focus future improvements.


2007 ◽  
Vol 64 (5) ◽  
pp. 956-962 ◽  
Author(s):  
Rüdiger Voss ◽  
Jörn O. Schmidt ◽  
Dietrich Schnack

Abstract Voss, R., Schmidt, J. O., and Schnack, D. 2007. Vertical distribution of Baltic sprat larvae: changes in patterns of diel migration? – ICES Journal of Marine Science, 64: 956–962. Ontogenetic and diurnal vertical migration patterns of Baltic sprat larvae were investigated for the periods 1989–1990 and 1998–2002. Comparison of the results led to the hypothesis that the diel vertical migration behaviour of sprat larvae >10 mm has changed. In 1989 and 1990, sprat larvae migrated to the surface at night, whereas they stayed 30–50 m deep by day. From 1998 to 2002, sprat larvae showed no signs of diel vertical migration, remaining in warmer, near-surface water by day and night. This behavioural change coincided with a more general change in the Baltic ecosystem, i.e. an increase in near-surface temperature and a general increase in abundance of the major prey organism (Acartia spp.) of Baltic sprat larvae, with more pronounced aggregation in surface waters.


1980 ◽  
Vol 68 (3-4) ◽  
pp. T31-T35 ◽  
Author(s):  
Rutger Wahlström

2020 ◽  
Vol 134 ◽  
pp. 39-59
Author(s):  
Louis Sicking

Zuiderzee towns in the Baltic. ‘Vitten’ and ‘Vögte’ – Space and urban representatives in late-medieval ScaniaThe Scania peninsula in the southwest of present-day Sweden was one of the most important trading centres of medieval Northern Europe due to the seasonal presence of immense swarms of herring which attracted large numbers of fishermen and traders. Streching back from the beach of Scania were the so-called vitten, which the traders, grouped by region or city, held as their own, legally autonomous trade settlements, from the Danish King. Initially, these were seasonal trading colonies that were occupied only for the duration of the fair, which began in August and ended in November. In the late Middle Ages the vitten developed into miniature towns, modest off-shoots from the traders‘ mother city. The presence on a small peninsula (c 50 km2) of so many fishermen and merchants who did business together and came from different cities could easily have led to tensions and conflict. What was the relationship between the spatial arrangement of the vitten at Scania and the urban representatives of the vitten, the so-called vögte or governors? This question is addressed by focusing on the vitten of the Zuiderzee towns. Their vitten, among which were numbered those of eastern Zuiderzee cities like Kampen and Zutphen as well as those of western cities like Amsterdam, Brielle and Zierikzee, were part of the Hanse. However, the vitten of these cities have been virtually neglected in historiography. The territorial or local-topographical development of these vitten was characterized by regional concentration: the Zuiderzee vitten were located close or adjacent to one another. The new vitten of Zierikzee and Amsterdam bordered on that of Kampen. Traders from cities and towns without their own vitte were housed in a vitte of a neighboring city: those of Deventer and Zwolle, for instance, in the vitte of  Kampen, those of Enkhuizen and Wieringen in the Amsterdam vitte and those from Schouwen island in the vitte of Zierikzee. The vitten of the eastern Zuiderzee towns were founded at the beginning of the fourteenth century, that is on average half a century earlier than those of the western Zuiderzee towns. The count of Holland and Zealand initially appointed the Zierikzee vogt or governor for all his subjects. Later on, the cities in his counties then had their own governors, first appointed by the count, later by the city (with or without the count‘s approval). The development of the representation of Holland and Zeeland towns in Scania differs from what was characteristic of the eastern Zuiderzee towns. Neither the Count /Duke of Guelders nor the bishop of Utrecht (as overlord of the Oversticht) attempted to interfere with the individual towns‘ governors or the vitten. The trend towards territorialisation in Scania was unmistakable. Although foreign traders, by reason of their origins, were subject to the jurisdiction of their mother city (the personality principle), a fact reflected in the responsibility of the vogt for the citizens in question, they were also increasingly spatially limited in Scania. This was a consequence of the limited space available, of the pursuit of control over one’s own community, and of the goal of allowing different urban groups to live together peaceably, prevent conflicts and guarantee the conduct of international trade. In this way the vitten, in particular those of the Zuiderzee towns that were further away from their mother cities, can be understood as urban colonies overseas.


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