Spelling suggestions: "subject:"2physical geography."" "subject:"bphysical geography.""
1041 |
Exploratory GIS Data Analysis and Regional and Transferred Maxent Modelling of the Round Goby Neogobius Melanostomus and Chinese Mitten Crab Eriocheir Sinensis in Stockholm and Blekinge County Baltic Sea Coastal AreasReid, Devon January 2016 (has links)
This study is a multidisciplinary approach to Species Distribution Modelling (SDM) where predictive models have been developed regarding the current distribution and potential spread of two invasive species found in Baltic Sea waters. Invasive species in the Baltic have long been an ecological and economic problem and the two species studied are well known for their adaptability in colonization and detrimental effects on local ecology all over the world. First, the Round Goby (Neogobius Melanostomus) has been steadily colonizing the Swedish Baltic coastline since 2008, the impact of which on local ecosystems is not fully understood. Also, the Chinese Mitten Crab (Eriocheir Sinensis), found in Swedish waters since the 1930’s, has been known to be a robust invader of ecosystems but presence in the Baltic is still not well explained. Four high spatial resolution models have been developed, three respective Round Goby and one for Mitten Crab. Two models are specific to the Blekinge/Hanöbukten region of the Swedish Baltic Sea coast, showing predicted current distribution of Round Goby. Two are predictions of Round Goby and Mitten Crab transferred or projected to other regions, with different approaches in setting model parameters and choosing variables, showing current and potential distribution. This study features: exploratory data analysis and filtering using GIS tools, highly discriminant environmental variable selection and rejection, and several different approaches to modelling in Maxent using custom and default settings. Predictive maps have been developed showing current distribution and potential spread as well as explanatory tabular data outlining direct and indirect drivers of species presence. Maxent has proven to be a powerful predictive tool on a regional basis, and proximity to introduction locations play a major role. Maxent, used in combination with spatial data modelling, exploration and filtering techniques has yielded a valid explanatory model as well. Transferring predictions to other regions is quite sensitive, however, and can depend heavily on species, sampling strategy and similarity of habitat type. Round Goby predictions were successfully created regionally and transferred to Stockholm, but Mitten Crab predictions were not successfully transferred to Blekinge.
|
1042 |
Pluvial översvämning, kartering av riskområden : Kullö, Rindö och Resarö i Vaxholms stad / Pluvial flooding, mapping areas of risk : Kullö, Rindö and Resarö in Vaxholms stadHård, Johnnie January 2016 (has links)
Short and intense rainfall, called cloudbursts, is becoming more frequent in Sweden as an effect of climate change. With that comes an increased frequency of flooding events caused by the heavy rainfall, called pluvial flooding. This is especially problematic in urban areas where large areas of impervious surface greatly increases the volumes of surface runoff. Mapping of bluespots, locations where pluvial flooding is more likely to occur, can be an important aid towards preventing this kind of flooding. This study concerns performing such a mapping for the islands Kullö, Resarö and Rindö in the municipality Vaxholms stad, Sweden. These islands are chosen for being future high development areas. The analysis is done through hydrological modelling of a digital elevation model. From that expected runoff volumes is calculated from statistical models of precipitation data. Analysis of the result concludes that the major road, 274, is expected to be affected by flooding along two sections. Some houses and other minor roads are also affected. But the overall impact on infrastructure and social functions is low. The mapping should be able to function as a tool in the flood preventative work of Vaxholms stad and in planning of future developments.
|
1043 |
Optically Stimulated Luminescence Dating and Last Glacial Climate Reconstruction from the Lingtai Loess Section, Chinese Loess Plateau / Optisk stimulerad luminescence datering och klimatrekonstruktion av den senaste istiden från Lingtai loessektion, Kinesiska loessplatånLagerbäck Adolphi, Emma January 2016 (has links)
High resolution dating of loess on the Chinese Loess Plateau (CLP) using Optically Stimulated Luminescence (OSL) has increased the understanding of past monsoon climate but also raised questions regarding dust mass accumulation rate (MAR), the presence of disturbances or gaps in the sediment record, a possible teleconnection between North Atlantic and East Asian monsoon climate, and whether these events are due to climate variability, local settings, or age model uncertainties. This study undertakes a detailed (<20cm sampling resolution) -OSL investigation of the Lingtai section to create an independent age model using linear regression, to reconstruct monsoon climate changes using magnetic susceptibility(MS) and grain size (GS) proxies, as well as to calculate MAR for the site. The data shows that between 44-15 ka climate changes from a period of strong summer monsoon to a strong winter monsoon. GS data show variable trends attributed to changes in dust storm activity and local environmental conditions. MAR data does not correlate with grain size and is different from other loess records on the CLP. Such differences are either due to local variations or age model uncertainties. No clear correlation with Heinrich events or teleconnection with North Atlantic climate is visible in the records over the Last Glacial period, and hiatuses or gaps are not obviously present at this site. It is suggested that using linear regression for continuous age model construction from the luminescence ages comes with uncertainties due to subjective bias when fitting the lines and determining shifts in the data, especially during MAR calculations. Further studies are needed to ascertain optimal methods for creating age models, and to constrain the reasons behind the variability between different sites and loess records on the CLP. / Högupplöst OSL-datering av loessjordar från CLP har ökat förståelsen av dåtida monsunklimat, men har även lyft frågan gällande MAR, närvaron av avbrott eller småskaliga event i jordsektionerna, möjligheten av en relation mellan de Nordatlantiska och Ostasiatiska monsunklimaten, och om dessa förändringar sker till följd av faktisk klimatvariation, lokala förutsättningar, eller osäkerheter i åldersmodellen. Studien genomförde en detaljerad (<20cm) OSL-undersökning av Lingtai-sektionen för att skapa en oberoende åldersmodell, återge monsunklimatförändringarna genom tillämpning av MS och GS proxies, samt beräkna MAR från platsen. Resultaten påvisar att mellan 44-15 ka förändrades klimatet från en period av stark sommar- till en stark vinter-monsun. Kornstorleks-resultaten påvisar stora variationer vilka kan kopplas till en förändring i sandstormsaktivitet samt de lokala förutsättningarna för deposition av sediment. MAR-resultaten överensstämmer inte med kornstorleksdatan och skiljer sig från den övriga empirin, detta kan bero på lokala variationer i regionen eller osäkerheter i åldermodellen. Det finns ingen klar korrelation mellan "Heinrich events" eller en "teleconnection" i sektionen, och avbrott samt störningar i sektionen är inte förekommande. Avsaknaden av korrelation antyder att användningen av regressionslinjer för att skapa kontinuerliga åldermodeller kommer innebära fortsatta osäkerheter i empirin, speciellt gällande beräking av MAR. Ytterligare studier krävs för att bestämma optimala metoder för att framställa åldersmodeller, samt att utröna orsaken till skillnaden mellan resultat från olika platser på plat
|
1044 |
Bostadsrätt, gräsmark eller skog? : Hur har exploatering för bostadsbyggande år 2000-2015 påverkat Järvakilens funktion som spridningsväg?Arleskär, Staffan January 2016 (has links)
Urbanization is a key driver of habitat loss, ecosystem degradation and has a great impact on biodiversity. Exploitation of buffer zones surrounding conservation areas and green structures in urban environment can affect biodiversity through reduced total area of habitat, increased edge effects and lost connectivity on a landscape level. The previous regional development plans for the Stockholm region, had the purpose of leaving large green structures undeveloped to secure core areas of great biological value by focusing on a dense city core. However, the latest regional development strategy puts stress on the green wedges by shifting the focal areas of the development into suburban regional city centers, in many cases close to the green wedges. The purpose of this study was to map habitat loss and changes in the total area of the Järva green wedge, west of Stockholm, caused by development of housing areas in previously sparsley exploited buffer zones, during the period 2000 – 2015. The study uses theories of landscape ecology, remote sensing and GIS to map and quantify habitat loss between 2000 and 2015. Two different birds were used as surrogate species, one grassland habitat specialist – Corncrake (Crex crex) and one forest habitat generalist – Eurasian jay (Garrulus glandarius). The two different surrogate species were used to identify how loss of two nature types could influence biodiversity and connectivity for a group of species. Documents and development plans on regional and local scale were also used to map and predict further habitat loss and exploitation of the green wedge until 2030. The result of the study shows that grassland habitat lost nearly twice the area than forest habitat due to development of housing areas during the period 2000 to 2015. A total of 1.3 km² of grassland and 0.7 km² forest habitat were replaced by housing areas during the fifteen years covered in the study, and the Järva green wedge will have lost a total of 3.84 km² buffer zones by the year 2030. The Corncrake and other grassland specialist species is likely to get most affected when grassland suffered the greatest habitat loss in the area. Even though the Eurasian jay has a key ecological function for the Oak forest in the Järva green wedge and relies on forest habitat for successful breeding, the loss of forest habitat will probably not affect the habitat generalist species in the same way. On a regional scale, the study suggests that habitat loss and fragmentation may affect grassland specialist species more than forest generalist species. The overall connectivity in the Järva green wedge is likely to get affected by a shrinking total area caused by narrowing of the green wedge until 2030. The function of the Järva green wedge as a dispersal corridor for biodiversity in the Stockholm region will most certainly get affected by further loss of buffer zones caused by exploitation of land for housing areas.
|
1045 |
Long-term glacier mass balance of Nordenskiöldbreen, Svalbard / Långsiktig glacial massbalans för Nordenskiöldbreen, SvalbardWiklund, Sara January 2016 (has links)
The global warming that’s taking place have an impact over the Earth and the glaciers on Svalbard are undergoing rapid changes as a result. The annual air temperature has been rising on Svalbard since the early 1900’s and in a climate projection expected temperatures continue to rise. The glacial mass balance is important for monitoring glacier response to climate change. In this study the mass balance of Nordenskiöldbreen from 1957 to 2016 is modelled with a temperature-index model. The meteorological data used in the model, precipitation and air temperature, has been measured at a weather station located in Longyearbyen since 1957. The long simulation run makes trends in mass balance, precipitation and air temperature apparent. The mass balance can also be correlated to the temperature and precipitation, which provide important information on how these affect the behavior of glaciers. The results obtained can be used to predict how glaciers change in the future with climate change. In the simulation Nordenskiöldbreen’s mass balance has a negative trend, precipitation doesn’t have any trend and air temperature has a positive trend. The long-term mass balance is controlled by air temperature and the short-term interannual mass balance is caused by precipitation fluctuations. / Den globala uppvärmningen som sker just nu har en påverkan över hela jorden och glaciärer på Svalbard genomgår snabba förändringar som följd. På Svalbard har den årliga medeltemperaturen stigit sedan början av 1900-talet och i en klimatprojicering förväntas temperaturen att fortsätta stiga. Den glaciala massbalansen är viktig för att övervaka glaciärers respons till klimatförändringar. I detta arbete modelleras Nordenskiöldbreens massbalans från 1957 till 2016 med hjälp av en temperaturindex modell. Den meteorologiska data som används i modellen, nederbörd och temperatur, har mätts vid en väderstation i Longyearbyen sedan 1957. Med den långa tidsperioden i modellen blir långsiktiga trender i massbalans, nederbörd och temperatur tydliga. Massbalansen kan även korreleras mot temperatur och nederbörd, vilket ger viktig information om hur dessa påverkar glaciärers beteenden. De resultat som framkommer kan användas för att förutspå hur glaciärer förändras i framtiden med en klimatändring. I simuleringen har Nordenskiöldbreens massbalans en negativ trend, nederbörd har ingen trend och temperatur har en positiv trend. Det är temperatur som styr den långsiktiga massbalansen och den kortsiktiga mellanårs-massbalansen styrs av nederbörds fluktuationer.
|
1046 |
Short-Term Surface Velocity Changes During Summer in the Lower Part of the Ablation Area Using Differential GPS Survey, Storglaciären, Sweden / Korttidsvariationer i isflöde under sommaren i det nedre ablationsområdet på Storglaciären undersökta med differentiell GPSGrenot, David January 2016 (has links)
short time scale. Four differential GPS stations were installed in the lower ablation area of Storglaciären in Sweden for one week in August 2012. The position data over the period were then compared with the environment information including temperature, precipitation, known hydrology and topography.The instantaneous velocity results show 9 acceleration events in correlation to temperature and precipitation. The increase of the meltwater inputs drive increases of the motion supposedly through water pressures and basal sliding.Strain determination using the stations geometry showed that the lower part of the survey area had an extensive behavior when the upper part was showing compressive properties. A deformation event occurring the 14th of august shows an elongation deformation along the centerline from the front of the glacier resulting in a lateral compression on the upper part due to shear stress closer to the margin.It was proposed that the force driving the elongation is due to the increase of water pressure on the front of the glacier where the internal hydrological system pass from a complex multi-branched system to a channelized output. / Syftet med detta projekt var att studera sambandet mellan en glaciärs hydrologi och isrörelse under korta tidsperioder (minuter till timmar). I augusti 2012 installerades fyra differentiella GPS-stationer under en veckas tid i nedre ablationsområdet på Storglaciären i Sverige. Positionsdata under perioden jämfördes sedan med miljöinformation inklusive temperatur, nederbörd, avrinning från glaciären och topografi.De uppskattade hastighetsresultaten visar på 9 olika accelerationshändelser som relaterar till tempe-ratur och nederbörd. En ökad införsel av smältvatten driver upp vattentrycket vid glaciärens botten som minskar friktionsmotståndet och glaciären får ökad basal glidning.Isdeformationsberäkningar mellan DGPS-stationerna visar att den nedre delen av undersök-ningsområdet hade extensionell deformation i isrörelseriktningen medan den övre delen visade kompression vinkelrätt mot denna riktning. Deformationshändelsen den 14 augusti visar det motsatta med extensionell deformation längs mittlinjen från fronten av glaciären vilket resulterar i en lateral kompression i den övre delen av det undersökta området kanske orsakade av skjuvspänning vid marginalen.Det föreslås att utsträckningen av glaciären under dessa händelser är på grund av en ökning av vattentrycket i det område där det interna subglaciala hydrologiska systemet ändras från en komplex multigrenade system högre upp i ablationsområdet till ett kanaliserat system vid fronten.
|
1047 |
En obruten fjällmiljö och konflikten med vindkraften : En studie om rumsliga landskapspreferenser och vindkraftens påverkan på de svenska fjällenHaeffner, Oscar January 2014 (has links)
De svenska fjällen skyddas i dagsläget av miljömålet Storslagen fjällmiljö, ett mål som ämnar bevara fjällens ursprunglighet och därmed skydda dem mot ingrepp. Den svenska regeringen har även inrättat 13 områden klassade som obruten fjällmiljö, områden vars natur- och kulturvärden ska värnas om och som, i så stor utsträckning som möjligt, ska hållas orörda. Båda dessa skyddsformer hotas nu av de planer som finns på att bygga ut vindkraften i landet. I denna studie undersöks den visuella påverkan som finns från dagens vindkraftverk samt den ökade visuella påverkan som genom fattade beslut är på väg. Metoden för studien är en rumslig GIS-analys som undersöker hur stora områden som vindkraften påverkar visuellt. Detta kopplas sedan till studier kring platskänsla, platsidentitet och vindkraftens konflikt med landskapet. Studien har visat att vindkraftverken i de svenska fjällen har en signifikant visuell påverkan på de obrutna fjällen och att miljömålet Storslagen fjällmiljö i dagsläget inte ser ut att uppnås. Dock måste nämnas att hur den framtida förändringen av landskapsbilden i de svenska fjällen kommer att uppfattas till stor grad beror på varje individs koppling till landskapet som förändras. / In the Swedish mountains the government has established 13 areas, covering around 10 % of the country, as areas of undisturbed mountain regions. These areas are to be protected against activities threatening environmental and cultural values. There is also an environmental goal aiming to maintain the originality of the Swedish mountains called Storslagen fjällmiljö, in translation: A magnificent mountain landscape. These two factors are being threatened by the future plans of increasing the number of wind turbines in these areas. In this study the visual effects of the existing and not yet existing wind turbines are being examined by performing a GIS-analysis. This is analyzed based on place sensitivity and people’s relation to their surrounding landscape. The study has shown that wind turbines have a significant visual impact on the undisturbed mountain regions and that the environmental goal aiming to keep the originality of the mountains does not reach its target. However, it must be pointed out that this future change in the scenic landscape of the Swedish mountains also can be seen as something good, this depending strongly on your relationship with the landscape.
|
1048 |
Characterization of plant-water interaction in Kilombero River Catchment in Tanzania using Normalized Difference Vegetation Index (NDVI)Minas, Michael Getachew January 2014 (has links)
Remote-sensing based indices such as Normalized Difference Vegetation Index have yielded valuable information about plant health. As the availability of water is one of the factors that controls plant's response to their environment, it is possible to indirectly studythe hydrology of an area via vegetation indices. Hence the thesis work used this tool to characterize the potential shifts in vegetation cover within and between years in Kilombero river catchment in Tanzania and make connection to the hydrology in the area. Separate time series analyses conducted on data pertaining to NDVI values and the areal coverage variability of arbitrarily defined NDVI-classes. The former data was extracted from a naturally vegetated wetland in the middle of the catchment while the latter from the topographically defined areas of the catchment. Results from the analyses showed that bothdatasets are sensitive to the seasonal rainfall while at inter-annual scale the areal coverage variability displayed significant correlations with past precipitation. Meanwhile the relatively higher sensitivity of the lowland area‟s NDVI to precipitation conforms to the initial assumption which emphasizes the importance of the wetland sub-catchment codenamed 1KB17 in describing Kilombero‟s hydrology. But the datasets show weak trends and it was not possible to make accurate future predictions on the hydrological conditions in the area. Meteorological distortions like clouds and environmental processes such as climate patterns or disturbances might have caused the problem in trend detection. Further studies needed to shed more light on the connection between land cover and hydrologic response in Kilombero.
|
1049 |
Tillämpning av oskarp logik i GIS-baserad skredanalys : Cuenca del Arga i Navarra, SpanienPalmkron, Katarina January 2014 (has links)
Målet med denna studie är att framställa en modell för sannolikheten för skred i Cuenca del Arga i Navarra, Spanien, med hjälp av GIS och oskarp logik. Utifrån denna modell framställs en karta som visar områden där det finns sannolikhet för skred. Övergripande har metoden skett i fyra steg. Först har en skredindexkarta framställts, sedan har medlemsfunktioner skapats utifrån dessa med hjälp av skredriskparametrar. De ingående parametrarna har varit sluttningsvinkel, topografisk fuktighetsindex, avstånd till vattendrag, jordmån och markanvändning. Sedan har medlemsfunktionerna applicerats på parametrarna, som sedan slutligen kombinerats genom WLC (weighted linear combination). Detta resulterade i en sannolikhetskarta för skred med fem klasser. / The aim of this study is to construct a model in GIS (geographical information system) for landslide susceptibility mapping for Cuenca del Arga in Navarre, Spain, to identify potential areas for landslides. The model is based on fuzzy logic approach and the parameters are overlaid with WLC (weighted linear combination).
|
1050 |
External Conditions Effects on the Self-Organised Criticality of the Calving Glacier Front of Tunabreen, Svalbard / Externa faktorers effekt på den själv-organiserade kritikaliteten av Tunabreens kalvningsfront, SvalbardWestrin, Pontus January 2015 (has links)
Mass balance processes in glaciers are important for determining the growth or retreat of ice. Calving, the mechanical breakage of ice bergs from a glacier front, is a poorly understood phenomenon. This process has great importance to the mass balance of many glaciers, for example on Antarctica and in the Arctic. A recent paper by Åström et al. (2014) compare calving fronts to Self-Organized Critical (SOC) systems, especially the Abelian sand pile model, meaning that the calving front will stay at a critical state at all times. Fluctuations in external conditions will cause the glacier front to either retreat or advance. The calving frequency and size distribution of Tunabreen, a tidewater glacier in Svalbard, was studied during August and September, 2014, with the use of a time-lapse camera set up in front of the calving front. An 11-day period is studied in detail and compared to certain external factors, i.e. tide, air temperature, humidity, atmospheric pressure, wind speed and wind direction. The results are also compared to the relationships found by Åström et al. (2014). The results vary: tide relationships are found as the amplitude reaches above 1 meter, but seize to correlate as the tide falls off. Temperature trends are found for certain periods, but are of low credibility. Humidity, atmospheric pressure, wind speed and wind direction show low to no correlation with the calving size distribution. Fragment size distribution and calving rates show good correlation with the results from Åström et al. (2014). This helps to confirm the theory of SOC applied to calving fronts. Time-lapse photography is deemed as a good way to observe calving fronts, but have certain problems which are mostly related to the weather. Longer time periods would be needed to find better long term relationships between external conditions and calving frequencies, but data is hard to acquire and time consuming to process. The theory of SOC applied to calving fronts is promising and opens up new discussions for the research community. / Massbalansprocesser för glaciärer är viktiga för att bestämma om isen drar sig tillbaka eller avancerar. Den mekaniska brytningen av isberg från glaciärer kallas kalvning. Kalvning är väldigt viktig för ett flertal glaciärers massbalans, exempelvis för landisen på Antarktis och glaciärer i Arktis. Ny forskning visar att kalvande glaciärfronter alltid försöker befinna sig i ett kritiskt läge, liknande ett så kallat Self-Organized Critical (SOC) system. Detta kan liknas vid hur en sandhög försöker befinna sig vid sin kritiska sluttningsvinkel när ett konstant flöde av sandkorn adderas. Adderandet av sandkorn kan jämföras med hur externa förhållanden, så som temperatur och tidvatten, ändras. När dessa värden ändras med tid så kommer fronten kalva, mycket likt hur sandhögen rasar när sandkorn tillförs. Externa förhållanden kommer alltså styra om glaciären kalvar eller inte, och när.En time-lapse-kamera installerades framför Tunabreen, en tidvatten glaciär på Svalbard, under Augusti-September, 2014. Bilderna över Tunabreens kalvningsfront, som varade över en 11-dagars period, användes för att ta ut varje enskild kalvingshändelse. Denna data jämfördes sedan med tidvatten, temperatur, luftfuktighet, atmosfäriskt tryck, vindhastighet och vindriktning. Resultaten jämfördes även med de förhållanden som visades i den nya studien som beskrevs tidigare.Resultaten är blandade. När tidvattnets amplitud var större än 1 meter så följer kalvningen tidvattnets mönster, men detta avtar när amplituden är mindre. Temperaturen visar viss korrelation, men endast för kortare perioder. Då temperaturens förhållande till kalvningen inte följer under de högsta och lägsta värden som fanns så bedöms temperaturen ha låg trovärdighet som kontrollerande faktor. Luftfuktighet, atmosfäriskt tryck, vindhastighet och vindriktning visar låg, till ingen, korrelation med kalvning. Storleksfördelningen av fragment och kalvningshastigheten har god korrelation med forskningen kring SOC, resultaten hjälper till att bekräfta denna teori. Time-lapse-fotografi bedöms som en bra metod för att observera kalvningsfronter, men har ett flertal problem som relaterar till det lokala vädret.Längre tidsperioder behövs för att bedöma om förhållanden stämmer på lång sikt. Data är svår att förvärva och tidskrävande att behandla. SOC stämmer bra in på kalvningsfronter vilket öppnar upp nya diskussioner inom forskningsvärlden.
|
Page generated in 0.0646 seconds