| 1. |
- Algesten, Grete, et al.
(författare)
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Organic carbon budget for the Gulf of Bothnia
- 2006
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Ingår i: Journal of Marine Systems. - : Elsevier BV. - 0924-7963 .- 1879-1573. ; 63:3-4, s. 155-161
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Tidskriftsartikel (refereegranskat)abstract
- We calculated input of organic carbon to the unproductive, brackish water basin of the Gulf of Bothnia from rivers, point sources and the atmosphere. We also calculated the net exchange of organic carbon between the Gulf of Bothnia and the adjacent marine system, the Baltic Proper. We compared the input with sinks for organic carbon; permanent incorporation in sediments and mineralization and subsequent evasion of CO2 to the atmosphere. The major fluxes were riverine input (1500 Gg C year(-1)), exchange with the Baltic Proper (depending on which of several possible DOC concentration differences between the basins that was used in the calculation, the flux varied between an outflow of 466 and an input of 950 Gg C year(-1)), sediment burial (1100 Gg C year) and evasion to the atmosphere (3610 Gg C year(-1)). The largest single net flux was the emission of CO2 to the atmosphere, mainly caused by bacterial mineralization of organic carbon. Input and output did not match in our budget which we ascribe uncertainties in the calculation of the exchange of organic carbon between the Gulf of Bothnia and the Baltic Proper, and the fact that CO2 emission, which in our calculation represented 1 year (2002) may have been overestimated in comparison with long-term means. We conclude that net heterotrophy of the Gulf of Bothnia was due to input of organic carbon from both the catchment and from the Baltic Proper and that the future degree of net heterotrophy will be sensible to both catchment export of organic carbon and to the ongoing eutrophication of the Baltic Proper.
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| 2. |
- Andersson, Lars, et al.
(författare)
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On the dynamics of a neutrally-buoyant float in a non-linear stratified fluid
- 1984
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Ingår i: Geophysica. - 0367-4231 .- 2324-0741. ; 19:2, s. 157-167
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Tidskriftsartikel (refereegranskat)abstract
- The transient properties of a neutrally-buoyant float in a non-linearly stratified fluid is studied both theoretically and experimentally. Numerical experiments from a theoretical model based on a quadratic drag law are in agreement with data from field experiments.
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| 3. |
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| 4. |
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| 5. |
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| 6. |
- Rahm, Lars, 1948-, et al.
(författare)
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Heat balance in a shallow cove
- 1986
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Ingår i: Estuarine, Coastal and Shelf Science. - 0272-7714 .- 1096-0015. ; 23, s. 705-724
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Tidskriftsartikel (refereegranskat)
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| 7. |
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| 8. |
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| 9. |
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| 10. |
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| 11. |
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| 12. |
- Conley, D., et al.
(författare)
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The myth of the Baltic stagnation period.
- 2003
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Ingår i: Environmental Science and Technology. - 1086-931X .- 1520-6912. ; 36, s. 5315-5320
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Tidskriftsartikel (refereegranskat)
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| 13. |
- Danielsson, Åsa, 1970-, et al.
(författare)
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dentification of characteristic regions and representative stations : A study of water quality variables in the Kattegat
- 2004
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Ingår i: Environmental Monitoring & Assessment. - 0167-6369 .- 1573-2959. ; 90:1-3, s. 203-224
-
Tidskriftsartikel (refereegranskat)abstract
- Gradients in nutrient distributions and the effects of eutrophication are common features in most coastal marine areas. These structures occur in aquatic systems due to spatial differences in hydrography, nutrient loading and key biogeochemical processes. Two statistical methods, cluster analysis and probability mapping, have been used in the present study to determine characteristics and patterns in water quality variables. Combined, these two methods provide a useful toot to statistically determine spatial homogeneity and representativity of areas and stations. A case study is presented here in which water quality variables (salinity, dissolved inorganic nitrogen, dissolved inorganic phosphorus and chlorophyll) in surface waters of the Kattegat are analysed for the time period 1993-1997. It was found that morphology, the proximity to sources of nutrient loading from land, nutrient uptake and the infrequent water exchange between the Baltic Sea in the south and the Skagerrak in the north all contribute to create distinct regions of water quality. Regions with concentrations significantly different from the overall mean are identified. In addition to identification of regions with similar characteristics, representative stations (as well as not representative stations) for the respective regions were made. This type of information can be used to design new or revise old monitoring programs.
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| 14. |
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| 15. |
- Danielsson, Åsa, 1970-, et al.
(författare)
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Large-scale mercury variations in Lake Vänern (Sweden) 1974-1998.
- 2001
-
Ingår i: Environmental Monitoring & Assessment. - 0167-6369 .- 1573-2959. ; 75, s. 223-234
-
Tidskriftsartikel (refereegranskat)abstract
- Lake Vanern, the largest lake in Sweden, has been seriously contaminated with mercury during the 20th century. In the 1970's and 80's the direct load, mainly from a chlor-alkali industry in the area, of mercury was drastically reduced as a response to new legislation, from three to five tons down to between five and ten kg yr(-1). Large amounts of the disposed pollutant have accumulated in the sediments. The question posed in this work is now, is the effect of the drastic load reduction after more than two decades visible in the sediments? The question is relevant as large areas still are blacklisted for fishing, but also as a follow-up of a major remedy action. The lake also serves as a freshwater reservoir for even Sweden's second largest city. This work synthesises and compares data of mercury in the sediments from three major field programs, in 1974, 1984 and 1998. The interest is focused on both spatial heterogeneity and temporal trends. In 1974, the surface concentrations are significantly higher than in subsequent surveys. Significant differences are also found between 1984 and 1998. Significant spatial differences within the lake are found for respective year. The most contaminated area is located in the north, close to the major point source (a former chlor-alkali industry). This is also the area with the largest improvement, as a direct response to the reduction in load. Further from the outlet, the recovery is more affected by burial and transport processes out into the deeper basins.
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| 16. |
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| 17. |
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| 18. |
- Davies, Peter A., et al.
(författare)
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The interaction between topography and a nonlinearly stratified rotating fluid
- 1982
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Ingår i: Physics of fluids. - : AIP Publishing. - 1070-6631 .- 1089-7666 .- 0031-9171. ; 25:11, s. 1931-1934
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Tidskriftsartikel (refereegranskat)abstract
- Laboratory experiments have been conducted in which a spherical solid obstacle has been towed steadily through a thermally stratified rotating fluid in order to determine the effects of the density‐profile shape upon the attenuation with height of the disturbance produced by the obstacle. The existence of a cutoff level in the fluid beyond which the disturbance is not detected is illustrated, and the dependence of this level upon local variations in density profile is studied. Measurements of velocity above and behind the obstacle are reported.
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| 19. |
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| 20. |
- Humborg, Christoph, et al.
(författare)
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Dissolved silicate dynamics in boreal and subarctic rivers - vegetation control over temperature?
- 2005. - 1
-
Ingår i: The Silicon Cycle: Human Perturbations and Impacts on aquatic systems. - Washington, DC : Island Press. ; , s. 53-69
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Silicon is among the most abundant elements on earth. It plays a key but largely unappreciated role in many biogeochemical processes, including those that regulate climate and undergird marine food webs. The Silicon Cycle is the first book in more than 20 years to present a comprehensive overview of the silicon cycle and issues associated with it. The book summarizes the major outcomes of the project Land-Ocean Interactions: Silica Cycle, initiated by the Scientific Community on Problems of the Environment (SCOPE) of the International Council of Scientific Unions (ICSU). It tracks the pathway of silicon from land to sea and discusses its biotic and abiotic modifications in transit as well as its cycling in the coastal seas. Natural geological processes in combination with atmospheric and hydrological processes are discussed, as well as human perturbations of the natural controls of the silicon cycle.
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| 21. |
- Humborg, C., et al.
(författare)
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Silicon retention in river basins : Far-reaching effects on biogeochemistry and aquatic food webs in coastal marine environments
- 2000
-
Ingår i: Ambio. - 0044-7447 .- 1654-7209. ; 29:1, s. 45-50
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Tidskriftsartikel (refereegranskat)abstract
- Regulation of rivers by damming as well as eutrophication in river basins has substantially reduced dissolved silicon (DSi) loads to the Black Sea and the Baltic Sea. Whereas removal of N and P in lakes and reservoirs can be compensated for by anthropogenic inputs in the drainage basins, no such compensation occurs for DSi. The resulting changes in the nutrient composition (DSi:N:P ratio) of river discharges seem to be responsible for dramatic shifts in phytoplankton species composition in the Black Sea. In the Baltic Sea, DSi concentrations and the DSi:N ratio have been decreasing since the end of the 1960s, and there are indications that the proportion of diatoms in the spring bloom has decreased while flagellates have increased. The effects on coastal biogeochemical cycles and food web structure observed in the Black Sea and the Baltic Sea may be far reaching, because it appears that the reductions in DSi delivery by rivers are probably occurring worldwide with the ever increasing construction of dams for flow regulation.
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| 22. |
- Ittekot, Venu, et al.
(författare)
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Carbon Silicon Interactions.
- 2003. - 1
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Ingår i: Interactions of the Major Biogeochemical Cycles: Global Change and Human Impacts. - New York : Island Press. - 1559630655 - 9781559630658 ; , s. 311-336
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- The circulation and interactions of major elements such as carbon, nitrogen, phosphorus, sulphur, oxygen, and hydrogen are critical for the maintenance of the earth's ecosystems. Human activities including agriculture, industry, and urbanization alter element interactions and contribute to major environmental problems ranging from climate change and depletion of the ozone layer to acidification of soils to the destruction of coral reefs.Interactions of the Major Biogeochemical Cyclesis a new scientific assessment of element interactions in the biosphere. It provides an up-to-date review of biogeochemistry and its effects on earth's systems, with leading experts in biogeochemical cycling in atmospheric, land, freshwater, and marine environments offering chapters that summarize and synthesize information in each discipline.The book opens with chapters on cross-cutting issues that have significance in understanding global change effects and their potential management. These chapters address:* trends in element interactions in response to global changethe effects of natural disturbancesnew approaches and methods for advancing our understanding of element interactionsthe potential for managing element interactions to address major environmental issues
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| 23. |
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| 24. |
- Jönsson, Anette, et al.
(författare)
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Wave dynamics of the Baltic
- 2002
-
Ingår i: Ocean Engineering. - 0029-8018 .- 1873-5258. ; 30, s. 107-126
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Tidskriftsartikel (refereegranskat)
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| 25. |
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| 26. |
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| 27. |
- Pacini, N, et al.
(författare)
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Nutrient Processes and Consequences.
- 2008
-
Ingår i: Ecohydrology; Processes, Models and Case Studies. - Oxford : Oxford University Press. - 9781845930028 ; , s. -391
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- This book contains 15 chapters dealing with the integration of ecology with hydrology at the river basin scale. The patterns and processes in the catchment including nutrients, lotic vegetation and aquatic faunal processes are covered. In addition, the benefits and risks of ecological modelling to water management and nutrient budget modelling for lakes and watershed restoration are discussed. The roles of ecohydrology in managing the savannah ecosystem, agricultural landscape, and watershed development are explored.
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| 28. |
- Pers, Charlotta, et al.
(författare)
-
Changes in apparent oxygen removal in the Baltic proper deep water
- 2000
-
Ingår i: Journal of Marine Systems. - 0924-7963 .- 1879-1573. ; 25:3-4, s. 421-429
-
Tidskriftsartikel (refereegranskat)abstract
- By developing a steady state diagnostic model for a stratified deep-water mass, one is able to quantify both the mass flows and apparent oxygen removal in the Baltic proper deep water. The model is based on continuity of the assumed conservative observable volume, salinity and temperature. Second degree polynomials are fitted to observed vertical profiles of temperature as well as oxygen concentration to give a functional correspondence with the used spatial variable salinity. These relations are used in the model that calculate the water flows, oxygen flows and oxygen removal during four periods between 1959 and 1997. The model forms a boundary value problem, which is solved with a finite difference scheme. The model seems to give reasonable estimates of the flows. The oxygen removal is mainly balanced by inflow of oxygen with incoming water. The oxygen consumption is 4-8 ╡1 O2 1-1 day -1, which corresponds to a degradation of organic matter in the range 30-60 g C m-2 year-1. (C) 2000 Elsevier Science B.V.
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| 29. |
- Pers, Charlotta, et al.
(författare)
-
Statistical modelling of the phosphate variations in the Baltic proper
- 1997
-
Ingår i: Boreal environment research. - 1239-6095 .- 1797-2469. ; 2:3, s. 303-315
-
Tidskriftsartikel (refereegranskat)abstract
- A statistical model of the variation of phosphate concentration in the upper layers of the Baltic proper was formed, with the aim of studying the magnitude of this variation and to be able to adjust corrupted time series. The large variation observed is only partially explained by seasonal variations and geographical structures. Despite inclusion of longterm trends and annual variations, the residuals showed a substantial correlation within and between the time series.
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| 30. |
- Pettersson, Catharina, et al.
(författare)
-
Changes in molecular weight of humic substances in the Gulf of Bothnia
- 1996
-
Ingår i: Environment International. - : Elsevier BV. - 0160-4120 .- 1873-6750. ; 22:5, s. 551-558
-
Tidskriftsartikel (refereegranskat)abstract
- Humic substances were isolated in the brackish Gulf of Bothnia utilizing two techniques: ion exchange on DEAE-cellulose and hydrophobic interaction on XAD-8 resin. The salinity of the water resulted in different yields for the two adsorbents. With XAD-8 resin, 30–80% of the organic carbon was isolated, whereas 5–20% was isolated on the DEAE-cellulose. The concentration of total organic carbon was rather constant but the concentration of humic substances decreased with increasing salinity. Gel filtration was used to measure the homogeneity of the humic fraction. Humic substances isolated in December were more homogeneous than those isolated in June, which indicates a degradation during the summer period which might be caused by photolysis or increased microbial degradation during the warm season.
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| 31. |
- Pettersson, Catharina, et al.
(författare)
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Photodegradation of aquatic humic substances : an important factor for the Baltic carbon cycle?
- 1997
-
Ingår i: Boreal environment research. - 1239-6095 .- 1797-2469. ; 2:2, s. 209-215
-
Tidskriftsartikel (refereegranskat)abstract
- Although humic substances (HS) are often considered as chemically stable and non-biodegradable in a marine environment, it is well known that exposure to light will lead to a decomposition of these substances. Laboratory experiments of photodegradation by UV-irradiation of aquatic humic substances and natural water resulted in a rapid and quantitative degradation. Seasonal variations in the humic fraction of the total organic carbon (TOC) was indicated in field studies in humic-rich water in Sweden. The HS/TOC-ratio was considerably higher during the dark part of the year than during the light season. Both the laboratory results and the field studies indicate the potential importance of photodegradation of HS and formation of CO2 for the global carbon cycle, though other mechanisms like microbial degradation are possible. Furthermore, the formation of biodegradable low-molecular weight organic acids from terrestrial humic substances may be essential for partly heterotrophic systems like the Bothnian Bay.
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| 32. |
- Rahm, Lars, 1948-
(författare)
-
A note on some hydrographic properties of the Eastern Gotland Basin
- 1988
-
Ingår i: Beiträge fur Meereskunde. - 0067-5148. ; 58, s. 47-58
-
Tidskriftsartikel (refereegranskat)abstract
- Mean values of salinity, temperature and oxygen concentrations are determined for the hydrographic station Gotland Deep (BY15) by field data obtained from the Fishery Board of Sweden for the period 1957-1982. These estimates are compared with the corresponding values of the entire basin, the Eastern Gotland Basin, which are attained by a volume-weighted procedure based on eight hydrographic stations in this area.
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| 33. |
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| 34. |
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| 35. |
|
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| 36. |
- Rahm, Lars, 1948-, et al.
(författare)
-
Dissolved silicate dynamics in boreal and subarctic rivers - vegetation control over temperature?
- 2006. - 1
-
Ingår i: The Silicon Cycle. - New York : Island Press. ; , s. 53-69
-
Bokkapitel (refereegranskat)abstract
- Silicon is among the most abundant elements on earth. It plays a key but largely unappreciated role in many biogeochemical processes, including those that regulate climate and undergird marine food webs. The Silicon Cycle is the first book in more than 20 years to present a comprehensive overview of the silicon cycle and issues associated with it. The book summarizes the major outcomes of the project Land-Ocean Interactions: Silica Cycle, initiated by the Scientific Community on Problems of the Environment (SCOPE) of the International Council of Scientific Unions (ICSU). It tracks the pathway of silicon from land to sea and discusses its biotic and abiotic modifications in transit as well as its cycling in the coastal seas. Natural geological processes in combination with atmospheric and hydrological processes are discussed, as well as human perturbations of the natural controls of the silicon cycle.
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| 37. |
- Rahm, Lars, 1948-, et al.
(författare)
-
Ecological Economic Interactions : Considerations for Coastal Zone Management
- 2004
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Coastal zones are the meeting point for land and ocean. Besides these land-ocean interactions, the coastal zone can also be distinguished by the many and strong interactions between the biotic and abiotic systems and the regional economy. Around the world coastal systems are coping with ncreased human pressures in the form of an increased demand for space and other resources as a result of for example population growth, migration and an expansion of tourism. In addition, coastal areas have to deal with natural pressures resulting from large scale interactions of the atmospheric, water, soil and biological systems including climatic change.Derivations from the natural material and energy flows in the coastal zone are often a result of changes in land-use and other man-induced impacts within the watershed, the coastal zone or in the ocean. A considerable part of the changes do not originate in the coastal zone itself but are caused by land based activities upstream in the catchment area (see for example the case studies below of the Baltic Sea and the Black Sea). In general, there is a lack of understanding of the interdependence of natural and human systems and processes, especially for river basins and coasts. Furthermore, there is only limited knowledge of how activities in the catchment area influence the coastal zone. Consequently, in order to aid policy formulation and decision-making, the interactions between natural and human systems in respectively the catchment area and the coastal zone as well as the connection between them, need to be identified, studied, and at least partly understood.In attempting a linked analysis of natural and human processes, special attention should be paid to the different temporal and spatial scales on which they operate. One of the most important issues that needs further studying is the temporal and spatial disparity between processes and activities in the catchment area and effects in the coastal zone. This includes the time lags and spatial disparity between activities and their effects as well as the time ags between effects of activities and the time decision makers need to take action to identify, study and eventually reduce these impacts. Each of these issues will now be elaborated upon.
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| 38. |
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| 39. |
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| 40. |
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| 41. |
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| 42. |
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| 43. |
- Rahm, Lars, 1948-, et al.
(författare)
-
Observed changes in pelagic and hydrographic conditions of the Baltic Sea.
- 2001
-
Ingår i: A Systems Analysis of the Changing Baltic Sea.. - Heidelberg : Springer. - 3540677690 - 9783540677697 ; , s. 329-351
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- During recent decades, large-scale effects of pollution on marine estuaries and even entire enclosed coastal seas have become apparent. One of the first regions where this was observed is the Baltic Sea, whereby the appearance of anoxic deep basins, extensive algal blooms and elimination of top predators like eagles and seals indicated effects of both increased nutrient inputs and toxic substances.This book describes the physical, biochemical and ecological processes that govern inputs, distribution and ecological effects of nutrients and toxic substances in the Baltic Sea. Extensive reviews are supplemented by budgets and dynamic simulation models.This book is highly interdisciplinary and uses a systems approach for analyzing and describing a marine ecosystem. It gives an overview of the Baltic Sea, but is useful for any marine scientist studying large marine ecosystems.
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| 44. |
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| 45. |
- Rahm, Lars, 1948-
(författare)
-
On the diffusive salt flux of the Baltic proper
- 1985
-
Ingår i: Tellus. Series A, Dynamic meteorology and oceanography. - : Stockholm University Press. - 0280-6495 .- 1600-0870. ; 37A:1, s. 87-96
-
Tidskriftsartikel (refereegranskat)abstract
- Turbulent cross-isohaline salt fluxes in the Baltic proper are studied with the aid of a one-dimensional “advection-diffusion” model. The theoretical framework of this model has been outlined by Walin. It is based on time-averaged T-S data from both the inflow and interior regions of the Baltic. The results obtained are in good agreement with some estimates of the mixing properties in the region. Based on this investigation, a discussion of the properties of the model and its applicability to a real estuarine system is performed.
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| 46. |
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| 47. |
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| 48. |
- Rahm, Lars, 1948-
(författare)
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On the thermal adjustment of an almost-enclosed fluid region with through-flow
- 1986
-
Ingår i: International Journal of Heat and Mass Transfer. - : Elsevier BV. - 0017-9310 .- 1879-2189. ; 29:10, s. 1479-1485
-
Tidskriftsartikel (refereegranskat)abstract
- The dynamics of a heat-up process in a horizontally enclosed fluid region, with an imposed through-flow and subject to weak thermal forcing, is investigated. Based on a boundary layer approach, a simple one-dimensional model for the interior fluid region is derived. The predicted response of the temperature field agrees well with numerical solutions of the corresponding undegenerate one-dimensional problem. The analytical results are in reasonably close agreement with numerical results presented in a companion paper by Hyun and Hyun (Int. J. Heat Mass Transfer 29, 1487–1493 (1986)).
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| 49. |
- Rahm, Lars, 1948-, et al.
(författare)
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On thermal convection in stratified fluids
- 1979
-
Ingår i: Geophysical and Astrophysical Fluid Dynamics. - : Informa UK Limited. - 0309-1929 .- 1029-0419. ; 13, s. 51-65
-
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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| 50. |
- 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
-
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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