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| 3. |
- Hieronymus, Jenny, 1981-
(författare)
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The global marine carbon system through time
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Carbon dioxide is an important greenhouse gas and in order to understand its effect on the climate we need to identify its sources and sinks. This thesis focuses on different aspects of the marine carbon system and the exchange of carbon between the ocean and the atmosphere.To understand the distribution of carbon between different reservoirs such as land, ocean and atmosphere, it is important to consider the origin of a carbon flux. If the carbon originates from rock, it comprises an external source. If, however, it originates from the atmosphere, such as a flux of organic carbon, it constitutes an internal exchange. We have re-calculated riverine fluxes that are commonly expressed in terms of ions, as fluxes of total carbon and alkalinity. Furthermore, we have separated the total carbon fluxes into their external and internal parts.External sources and sinks, as well as internal exchange can sometimes be more easily understood if the carbon in the ocean is separated into acidic and basic carbon (AC and BC). These two state variables have opposite effect on the partial pressure of carbon dioxide in the surface ocean. We have used these new variables to describe the effect of pyrite production during periods in the geological past when large parts of the oceans have been oxygen free, so called oceanic anoxic events. Sulfate reduction that occurs in oxygen free environments leads to an increase in alkalinity. We show that the net effect of photosynthesis, sulfate reduction and pyrite production leads to a reduction of acidic carbon and thereby a decreased surface pressure of CO2. Furthermore, we demonstrate the difference between a system with and without carbonate compensation that comprises a regulatory mechanism for the carbon system.During the anoxic events there is a shift in the composition of carbon isotopes in the system. A negative isotope shift is believed to be a result of increased supply of light carbon from volcanic activity or melting methane clathrates, while a positive shift is a result of increased burial of organic carbon. We have investigated the implications of different sources and sinks on the size of an isotope shift. This is done by comparing simple budget calculations with a more complete model. We show that carbonate compensation implies that more light carbon must be supplied to the system to obtain the same negative shift than for the simple budget calculations where sources and sinks of calcium carbonate are not considered.
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| 4. |
- Hieronymus, Jenny, 1981-, et al.
(författare)
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Unravelling the land source : an investigation of the processes contributing to the oceanic input of DIC and alkalinity
- 2013
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Ingår i: Tellus. Series B, Chemical and physical meteorology. - : Stockholm University Press. - 0280-6509 .- 1600-0889. ; 65, s. 19683-
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Tidskriftsartikel (refereegranskat)abstract
- In models of the marine carbon system, it is important to correctly represent riverine and aerial inputs of dissolved inorganic carbon (DIC) and alkalinity. We have examined the different processes contributing to this exchange. In terms of DIC, we have divided the fluxes into their internal component, constituting the carbon ultimately derived from the atmosphere, and their external component originating from rocks. We find that the only process contributing to external DIC input is carbonate and fossil carbon weathering and that erosion of organic matter ultimately constitutes a DIC sink. A number of both riverine and aerial inputs affect the alkalinity. Beside carbonate and silicate weathering, we examine processes of pyrite weathering, aerial input of sulphuric acid, and riverine and aerial inputs of various nitrogen species. Using the observation that, in the ocean, the nitrate concentration follows that of phosphate, we assume a steady state in nitrate. This leads to the surprising result that the only processes affecting the alkalinity is riverine input of nitrate, constituting an alkalinity source and input of ammonia, constituting an alkalinity sink. Furthermore, we compare the flux sizes. As expected, carbonate and silicate weathering has the largest effect on alkalinity, though we note that burial of pyrite might be of importance during periods of large-scale anoxia.
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| 7. |
- Ingvarsson, Torbjörn, 1967-, et al.
(författare)
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Borgen och tredjemanspant
- 2013. - 4
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Bok (övrigt vetenskapligt/konstnärligt)abstract
- Borgen är vanligt förekommande som säkerhet för annans prestation. Det finns ett stort antal rättsfall i ämnet, men en modern lagstiftning saknas. Tredjemanspant, det vill säga pant som någon ställer till säkerhet för en annan persons skuld, fyller en viktig funktion för kreditväsendet och har stora likheter med borgensåtaganden.Borgen och tredjemanspant är en brett upplagd redogörelse för dessa praktiskt viktiga säkerhetsformer. I framställningen belyses många viktiga men oklara frågor förknippade med borgen och tredjemanspant. Boken riktar sig till praktiker som önskar få svar på konkreta frågeställningar, men genom den breda översikten av om- rådet belyses även teoretiskt viktiga kredit- och fordringsrättsliga frågor för den rättsvetenskapligt intresserade.Boken gavs ut i sin första upplaga 1984. Tidigare upplagor skrevs av Gösta Walin ensam. Texten har i denna upplaga setts över med avsikten att framställningen fortsatt skall vara funktionell och utgöra en naturlig fortsättning från tidigare upplagor.
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| 8. |
- Ingvarsson, Torbjörn, 1967-
(författare)
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Borgen och tredjemanspant
- 2023. - 5
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Bok (övrigt vetenskapligt/konstnärligt)abstract
- Borgen är vanligt förekommande som säkerhet för annans prestation. Det finns ett stort antal rättsfall i ämnet, men en modern lagstiftning saknas. Tredjemanspant, det vill säga pant som någon ställer till säkerhet för en annan persons skuld, fyller en viktig funktion för kreditväsendet och har stora likheter med borgensåtaganden. Borgen och tredjemanspant är en brett upplagd studie av dessa praktiskt viktiga säkerhetsformer. Boken riktar sig till praktiker som önskar att få svar på konkreta frågeställningar, men genom den breda översikten av området belyses även teoretiskt viktiga kredit- och fordringsrättsliga frågor för den rättsvetenskapligt intresserade.Boken gavs ut i sin första upplaga 1984 och Gösta Walin svarade ensam för ytterligare två upplagor. Sedan den fjärde upplagan svarar Torbjörn Ingvarsson för att hålla boken aktuell och ge den en naturlig fortsättning från tidigare upplagor.
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| 11. |
- Millqvist, Göran, et al.
(författare)
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Panträtt
- 2021. - 4
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Bok (övrigt vetenskapligt/konstnärligt)
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| 12. |
- Nilsson, Johan, et al.
(författare)
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Salinity-dominated thermohaline circulation in sill basins : can two stable equilibria exist?
- 2010
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Ingår i: Tellus. Series A, Dynamic meteorology and oceanography. - : Stockholm University Press. - 0280-6495 .- 1600-0870. ; 62:2, s. 123-133
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Tidskriftsartikel (refereegranskat)abstract
- The dynamics of a salinity-dominated thermohaline circulation in a sill basin is examined using a two-layer model. A prescribed freshwater supply acts to establish a stable stratification, working against a prescribed destabilizing temperature difference. The upper-layer outflow is in geostrophic balance and the upwelling is driven by a fixed energy supply to small-scale vertical mixing. The salinity-dominated flow may have two qualitatively different modes of operation. First, a mixing-limited regime, where the upper layer is shallower than the sill and the flow strength decreases with increasing density difference. Second, an overmixed regime, where the upper layer extends below the sill and the flow strength increases with density difference. Possibly, mixing-limited and overmixed equilibria, with widely different upper-layer depths, can exist for the same external parameters. In such cases, transitions between the two regimes are associated with abrupt changes of the salinity, depth and flow strength. The present results may be of relevance for ocean circulation in glacial climates and for interpretations of marine palaeo data, issues that are briefly discussed in the context of the Arctic Ocean.
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| 13. |
- Omstedt, Anders, 1949, et al.
(författare)
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Use of Baltic Sea modelling to investigate the water cycle and the heat balance in GCM and regional climate models
- 2000
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Ingår i: Climate Research. - 0936-577X .- 1616-1572. ; 15:2, s. 95-108
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Tidskriftsartikel (refereegranskat)abstract
- Results from the first simulations with the Rossby Centre regional climate atmosphere (RCA) model were used to force 2 versions of process-oriented models of the Baltic Sea-one time-dependent, the other considering the mean state. The purpose was primarily to obtain a first scenario of the future state of the Baltic Sea. In addition, we looked at this exercise as a method to evaluate the consistency of the water cycle and the heat balance produced by atmospheric climate models. The RCA model is a high-resolution atmospheric regional model which is forced with lateral conditions from a global model. A large-scale Baltic drainage basin hydrological model, forced by the RCA model, was used to simulate river runoff. Using RCA model data from the control run we found that that the temperature and ice conditions in the Baltic Sea were reasonably realistic while the salinity field was poorly reproduced. We conclude that the modelling of the water cycle needs considerable improvement. We also conclude that the time for the Baltic Sea to respond to the water cycle is much longer than the integration period so far used with the RCA model. Forcing the ocean models with RCA model data from a future scenario with an enhanced greenhouse effect gives an increased sea-surface temperature and a much reduced extent of ice in the Baltic Sea due to climate warming. Also the salinity is reduced, which implies possible serious effects on the future marine life in the Baltic Sea. The results demonstrate that accurate atmospheric modelling of not only the heat balance but also the water cycle is crucial for Baltic Sea climate simulations.
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| 15. |
- Rahm, Lars, 1948-, et al.
(författare)
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On thermal convection in stratified fluids
- 1979
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Ingår i: Geophysical and Astrophysical Fluid Dynamics. - : Informa UK Limited. - 0309-1929 .- 1029-0419. ; 13, s. 51-65
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Tidskriftsartikel (refereegranskat)abstract
- The study of the mechanisms controlling the stratification in closed fluid regions is an important branch of geophysical fluid dynamics. Part of this subject can be handled with a simple linear model, consisting of a buoyancy layer at the non-horizontal boundaries of a container and an advective-diffusive interior coupled by volume continuity. The model is valid under the following conditions: firstly, the buoyancy-frequency characterizing the solution must be sufficiently large to give rise to a flow pattern of boundary layer type and, secondly, the non-horizontal walls must not have too large thermal conductivity.The main purpose of the present paper is to summarise previous work done by the authors in this field and to present some consequences of their theory not previously discussed.Three important cases are discussed; certain stationary solutions, the decay of a given stratification and the build up of a stratification in a homogeneous fluid. The experimental results concerning the afore-mentioned cases are presented.
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| 16. |
- Rahm, Lars, 1948-, et al.
(författare)
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On thermally forced stratified rotating fluids
- 1980
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Ingår i: Journal of Fluid Mechanics. - 0022-1120 .- 1469-7645. ; 97:4, s. 807-828
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Tidskriftsartikel (refereegranskat)abstract
- Axisymmetric steady motion of an inhomogeneous rotating fluid is considered. A system of equations, with appropriate boundary conditions, controlling the smooth interior fields is derived under the assumption of small dissipation and small side-boundary conductance. It is argued that this system, being derived without linearization of the equations, might form the basis of valuable numerical analysis. Assuming sufficiently weak forcing, i.e. high insulation of the non-horizontal boundaries, a linear system is derived. An explicit solution is presented and discussed for a particularly simple and important case.
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| 17. |
- Walin, Gösta, 1938, et al.
(författare)
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Baroclinic boundary currents with downstream decreasing buoyancy: A study of an idealized Nordic Seas system
- 2004
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Ingår i: Journal of Marine Research. - 0022-2402. ; 62:4, s. 517-543
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Tidskriftsartikel (refereegranskat)abstract
- The dynamics of a baroclinic boundary current losing buoyancy along its path is analyzed both theoretically and using a numerical ocean-circulation model. A fundamental ingredient in our analysis is that the side boundaries of the ocean basin are sloping gently down to the deep ocean. Theoretically we find that the coastal boundary current develops two branches: one seaward baroclinic jetstream and one barotropic current, which is confined to the continental slope. The baroclinic jetstream decreases its transport as the buoyancy is lost from the surface layer. This decrease in transport is compensated by an increase in the barotropic flow on the slope. When the buoyancy is lost altogether, the entire volume transport occurs in the barotropic slope current. In our numerical experiments we focus on the penetration of warm water over a sill into a cold semi-enclosed basin. The flow enters as a baroclinic current with a thickness approximately equal to the sill depth and proceeds around the basin on essentially the same depth while being transformed to a barotropic slope current which leaves the basin over the sill. It should be noted that the circulation does not involve any renewal of the deep water in the cold basin, except in the initial spin up of the system. We suggest that our results can illuminate some basic aspects of the dynamics in the Nordic Seas, which are invaded by North Atlantic surface water over the Greenland-Scotland Ridge. One striking example; is the observations reported by Orvik et al. (2001), which show that the flow of Atlantic water along the Norwegian coast has two branches: A baroclinic jetstream and a shelf-bound barotropic current. The existence of this double-flow structure is to be expected from our theoretical considerations and numerical simulations.
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| 21. |
- Walin, Gösta, et al.
(författare)
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Panträtt
- 2012. - 3
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Bok (övrigt vetenskapligt/konstnärligt)
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| 23. |
- Walin, Gösta, 1938, et al.
(författare)
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Source-related variables for the description of the oceanic carbon system
- 2014
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Ingår i: Geochemistry Geophysics Geosystems. - : American Geophysical Union (AGU). - 1525-2027. ; 15:9, s. 3675-3687
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Tidskriftsartikel (refereegranskat)abstract
- The oceanic carbon system is commonly described in terms of the two state variables total carbon, DIC, and alkalinity, Alk. Here we suggest the use of alternative source adapted state variables, Acidic Carbon, AC and Basic Carbon, BC, defined by and related to (DIC, Alk) with a simple linear transformation. (AC, BC) can be interpreted as representing respectively the supply to the system of carbon dioxide and dissolved carbonate, keeping in mind that supply of hydrogen ions acts to transform from basic carbon to acidic carbon. Accordingly these variables tell us how much carbon dioxide or dissolved carbonate we actually have in the water, despite the fact that the major part of the carbon resides in bicarbonate ions. We claim that using these source-related variables as a compliment to the traditional variables, offers a number of advantages in the formulation of continuity equations, as well as in the interpretation of observations and modeling results. The traditional definition of alkalinity is related to a measuring procedure rather than to the supply of material to the system. Here we demonstrate that alkalinity, though defined in the traditional way, may be interpreted in terms of sources and sinks acting on the system. In the case of ocean water this amounts to twice the supply of dissolved carbonate minus the net supply of free hydrogen ions. We argue that this interpretation is a useful complement to the traditional definition. Every process that affects the state of the carbon system may be quantified in terms of supply of carbon dioxide, F-a, carbonate ions, F-b, or hydrogen ions, E.
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- Walin, Gösta, et al.
(författare)
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Theory and experiments on the control of the stratification in almost-enclosed regions
- 1979
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Ingår i: Journal of Fluid Mechanics. - 0022-1120 .- 1469-7645. ; 90:2, s. 315-325
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Tidskriftsartikel (refereegranskat)abstract
- A comparison is made between the theoretically predicted and the observed stratification in a container which is traversed by a prescribed flux of fluid. Two different geometries were used illustrating respectively a useful procedure for the control of a stratified laboratory system and a mechanism which is believed to be geophysically significant, e.g. for the control of the stratification in certain estuaries. The behaviour of the fluid system was in all cases characterized by an almost stagnant interior with a boundary layer at the non-horizontal wall of buoyancy-layer type. Agreement between theory and experiment was satisfactory within experimental errors, say 10% of the overall temperature difference.
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