| 1. |
- Barrientos, Natalia, 1985-
(författare)
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Arctic Ocean benthic foraminifera preservation and Mg/Ca ratios : Implications for bottom water palaeothermometry
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Reconstructions of Arctic Ocean palaeotemperatures are needed to disentangle natural variability from anthropogenic changes and understand the role of ocean heat transport in forcing or providing feedbacks on Arctic climate change. Despite known complications with calcareous microfossil preservation in Arctic Ocean sediments, calcareous benthic foraminifera can be common in interglacial sequences. However, thus far they have been underutilized in palaeoceanographic studies. This thesis explores the application of the Mg/Ca palaeothermometry proxy for reconstructing bottom water temperatures (BWT) in the Arctic Ocean during the late Quaternary. This method, which is supported by previous empirical studies demonstrating a strong temperature control on trace Mg inclusion into foraminiferal shell calcite, has been applied in many ocean regions and time intervals. Until now its application in the Arctic Ocean has been sparingly explored.The results of this doctoral thesis are based on benthic foraminifera retrieved from marine sediment cores covering a wide geographical Arctic Ocean area including both the shallow and vast continental shelves and slopes to the intermediate-to-deep waters of the Lomonosov Ridge and Morris Jesup Rise. These provide the first benthic foraminifera Mg/Ca ratios from the central Arctic Ocean region. In the first study, mechanisms that could affect Mg incorporation in Arctic benthic foraminifera are investigated using oceanographic field data and six 'live' modern Arctic species (Elphidium clavatum, Nonionella labradorica, Cassidulina neoteretis, Oridorsalis tener, Cibicidoides wuellerstorfi and Quinqueloculina arctica). The result is new species-specific Mg/Ca–BWT field calibrations that provide important constraints at the cold end of the BWT spectrum (-2 to 1°C) (Paper I). Using the new Mg/Ca–BWT equation for E. clavatum, a palaeotemperature record was generated for the late Holocene (past ca. 4100 yr) from the western Chukchi Sea. The data showed BWT fluctuations from -2 to 1°C that are interpreted as showing pulses of warmer Pacific water inflow at 500–1000 yr periods, thus revealing multi-centennial variability in heat transport into the Arctic Ocean driven by low latitude forcings (Paper II). Complications with foraminiferal calcite preservation that limit Mg/Ca palaeothermometry in the Arctic were discovered and these are tackled in two additional papers. Anomalously high Mg content in benthic foraminifera from the central Arctic Ocean is linked to diagenetic contamination as a result of the unique oceanographic, sedimentary and geochemical environment (Paper III). Lastly, the dramatic post-recovery dissolution of foraminifera from a Chukchi Shelf sediment core during core storage is investigated and attributed to acidification driven by sulphide oxidation in this organic rich and calcite poor shelf setting (Paper IV).The findings of this thesis demonstrate that benthic foraminiferal Mg/Ca-palaeothermometry can be applied in the Arctic Ocean and capture small BWT change (on the order of -2 to 2°C) even at low temperatures. In practice, preservational complexities can be limiting and require special sample handling or analysis due to the high potential for diagenetic contamination in the central Arctic Ocean and rapid post coring calcite dissolution in the seasonally productive shelf seas. This Ph.D. project is a component of the multidisciplinary SWERUS-C3 (Swedish-Russian-US Arctic Ocean Climate-Cryosphere- Carbon Interactions) project that included an expedition with Swedish icebreaker Oden to the East Siberian Arctic Ocean.
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| 2. |
- Bernhardson, Martin
(författare)
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Aeolian dunes of central Sweden
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In the Swedish inland there are aeolian deposits present, ranging from scattered single dunes to dune fields of more than 10 km2. These dune fields often pass unnoticed since they presently are covered by vegetation. However, they contain a rich palaeoenvironmental archive. Only a few research papers have been published regarding these aeolian deposits during the last 90 years. The primary scope of this thesis has been to determine why these dunes formed, when they formed, and what they can tell us about the environment during their formation. The results from these investigations are presented in four research papers.The shape and orientation of a dune is determined by the local environment during its formation, such as the abundance of sediment available for entrainment by the wind, groundwater table fluctuations, changes to precipitation and temperature, presence/absence of vegetation, mode of the wind et cetera. By determining the type of dunes it is possible to determine the local environment during their formation. If one also can determine when these dunes formed and stabilised one can determine the palaeoenvironment, and in extension the palaeoclimate, during a specific time period.In this thesis, new findings are presented regarding the geomorphology, geochronology and palaeoenvironment of a number of dunes and dune fields in south and central Sweden, based on state-of-the-art methods, such as LiDAR (light detection and ranging) based remote sensing and optically stimulated luminescence dating. The previous hypotheses concerning the formation of these dunes have also been evaluated.The findings show that the dunes of central Sweden are primarily of a transverse type, i.e. their dune ridges are transverse to the dune forming winds and they were formed in a setting devoid of vegetation and with an abundance of sediment. The primary dune forming winds for these transverse dunes appear to have been north-westerly and westerly winds. The investigated dunes further to the south show signs of having been reworked after their initial formation and are often of a parabolic type, i.e. curved/crescentic in shape with their arms facing upwind. These dunes have been described as strongly linked to the presence of vegetation, and can often be considered secondary dune forms. These more southern dunes appear to also mainly have been formed by north-westerly and westerly winds, although they display a bigger scatter in wind directions than the more northern dunes.The luminescence ages suggest that most of the dunes formed during the early Holocene, and later events of sand drift have been uncommon with only minor impact on the dune morphology. There seems to have been a primary dune stabilisation phase ~10-9 ka, irrespective of the latitude of the dune fields. This means that some dune fields formed close after local deglaciation, while others formed millennia later. This suggests that dune formation and dune stabilisation of central Sweden have been controlled by regional environmental conditions. Extremely low lake levels in southern and south-central Sweden 10.5-9.5 ka BP in conjunction with an unstable climate during early Holocene probably delayed dune stabilisation by vegetation. After the vegetation had stabilised the dunes, they became much more resilient to further fluctuations in the climate.
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| 3. |
- Linkhorst, Annika
(författare)
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Greenhouse gas emission from tropical reservoirs : Spatial and temporal dynamics
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The emission of methane (CH4) and carbon dioxide (CO2) from reservoirs has been estimated to make up for about 1.3% of the global anthropogenic greenhouse gas emission. The impoundment of a river leads to the accumulation of sediment that is brought in from inflowing rivers, and the sediment organic matter is degraded to CH4 and CO2. CH4 is of particular concern as its global warming potential is 34 times stronger than that of CO2. In the tropics, high temperatures and high availability of fresh organic matter from high net primary production fuel CH4 and CO2 production. As the construction of hydropower plants is currently undergoing a boom, especially in the tropics, reservoir emission is probably bound to increase.The emission of CH4 and CO2 from reservoir surfaces is, however, highly variable, which makes current estimates uncertain. This thesis is built on the hypothesis that the spatial and temporal variability of greenhouse gas emission in tropical reservoirs, particularly of CH4 ebullition (the emission via gas bubbles), is so large that the sampling strategy affects whole-system estimates of greenhouse gas emission.This thesis shows that greenhouse gas emission from the four studied tropical reservoirs in Brazil varied greatly at different timescales – over 24 hours, between days and between seasons. Seasonal variability was identified as the most important temporal scale to be covered for CH4 ebullition inventories. In addition, the spatial variability of gas emission was large for all pathways. The variability of CH4 ebullition across space, for example, was estimated to be almost as large as its variability between seasons, and patterns of spatial variability in diffusive CH4 and CO2 emission differed between seasons. For both ebullition and diffusion, river inflow areas were prone to elevated greenhouse gas emission.This thesis shows that for retrieving solid emission estimates, there is no alternative to time-consuming measurements in the field. Measurements should be repeated at least once during each hydrological season (i.e. falling and rising water level). The seasonal surveys should cover space at a high resolution, including areas with and without river inflows, and different water column depths. CH4 ebullition made up for 60–99% of the total CO2-equivalent emission from the whole water surface of the studied reservoirs, with the highest contribution in the most productive reservoir. The most variable greenhouse gas emission pathway is therefore the most important one to be measured at appropriate resolution, particularly in productive reservoirs.
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| 4. |
- Acosta Navarro, Juan Camilo, 1983-
(författare)
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Anthropogenic influence on climate through changes in aerosol emissions from air pollution and land use change
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Particulate matter suspended in air (i.e. aerosol particles) exerts a substantial influence on the climate of our planet and is responsible for causing severe public health problems in many regions across the globe. Human activities have altered the natural and anthropogenic emissions of aerosol particles through direct emissions or indirectly by modifying natural sources. The climate effects of the latter have been largely overlooked. Humans have dramatically altered the land surface of the planet causing changes in natural aerosol emissions from vegetated areas. Regulation on anthropogenic and natural aerosol emissions have the potential to affect the climate on regional to global scales. Furthermore, the regional climate effects of aerosol particles could potentially be very different than the ones caused by other climate forcers (e.g. well mixed greenhouse gases). The main objective of this work was to investigate the climatic effects of land use and air pollution via aerosol changes.Using numerical model simulations it was found that land use changes in the past millennium have likely caused a positive radiative forcing via aerosol climate interactions. The forcing is an order of magnitude smaller and has an opposite sign than the radiative forcing caused by direct aerosol emissions changes from other human activities. The results also indicate that future reductions of fossil fuel aerosols via air quality regulations may lead to an additional warming of the planet by mid-21st century and could also cause an important Arctic amplification of the warming. In addition, the mean position of the intertropical convergence zone and the Asian monsoon appear to be sensitive to aerosol emission reductions from air quality regulations. For these reasons, climate mitigation policies should take into consideration aerosol air pollution, which has not received sufficient attention in the past.
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| 5. |
- Kelly, Julia
(författare)
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Carbon exchange in boreal ecosystems: upscaling and the impacts of natural disturbances
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Boreal forests and peatlands are globally significant carbon stores but they are threatened by rising air temperatures and changes in precipitation regimes and the frequency of natural disturbances. Predicting how the boreal biome will respond to climate change depends on being able to accurately model and upscale the greenhouse gas fluxes between these ecosystems and the atmosphere. This thesis focuses on developing simple, empirical, remote sensing models of ecosystem respiration (ER) and assessing how ER varies over space and in response to natural disturbances such as drought and wildfire. Paper I and II tested the opportunities and limitations offered by newly available, miniaturized thermal cameras, which can capture images of surface temperature at sub-decimeter resolution. Since temperature is one of the most important factors driving ER, these cameras provide an opportunity to map ER in unprecedented detail. In Paper III, satellite land surface temperature (LST) data was used to model ER across several Nordic peatland sites to examine whether remote sensing models can capture variations in ER between sites. In addition, Paper II and III highlighted the impacts of the extreme 2018 drought that affected large parts of Europe on peatland CO2 fluxes. The drought also led to a severe wildfire season in Sweden and Paper IV investigated how the effects of fire on forest soils depended on burn severity, salvage-logging and stand age.Producing reliable surface temperature measurements from miniaturized thermal cameras requires careful data collection and processing and one of the main outcomes of this thesis is a set of best practices for thermal camera users. Despite including larger uncertainties than traditional soil or air temperature measurements, thermal data from these cameras is suitable for modeling ER in peatland ecosystems. The ER maps that can be produced using UAV thermal cameras offer a unique resource for evaluating how ER varies within a flux tower footprint and could reveal potential biases in flux tower measurements. Indeed, this thesis demonstrated that there is substantial spatial variation in ER, both within and between peatlands. Vegetation composition played a significant role in driving this spatial variation as well as the response of peatlands to drought. Nevertheless, using only LST and the Enhanced Vegetation Index (EVI2) as model inputs captured a large proportion of the variability of daily ER across multiple peatlands. With further developments, such a modeling approach could represent a simple and effective way of estimating peatland ER across Scandinavia. In terms of wildfire impacts on boreal forest soils, stand age had a significant impact on soil respiration, nutrient availability and microclimate, whereas salvage-logging did not, in the first year after fire. Furthermore, the effects of drought and wildfire on ER depended on their severity, but during both extreme water stress in peatlands and after severe burning in forests, ER decreased. It is important that this negative feedback is accounted for in ER models to avoid overestimating carbon loss from northern ecosystems in response to disturbances and climate change.
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| 6. |
- Monteux, Sylvain, 1989-
(författare)
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A song of ice and mud : Interactions of microbes with roots, fauna and carbon in warming permafrost-affected soils
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Permafrost-affected soils store a large quantity of soil organic matter (SOM) – ca. half of worldwide soil carbon – and currently undergo rapid and severe warming due to climate change. Increased SOM decomposition by microorganisms and soil fauna due to climate change, poses the risk of a positive climate feedback through the release of greenhouse gases. Direct effects of climate change on SOM decomposition, through such mechanisms as deepening of the seasonally-thawing active layer and increasing soil temperatures, have gathered considerable scientific attention in the last two decades. Yet, indirect effects mediated by changes in plant, microbial, and fauna communities, remain poorly understood. Microbial communities, which may be affected by climate change-induced changes in vegetation composition or rooting patterns, and may in turn affect SOM decomposition, are the primary focus of the work described in this thesis.We used (I) a field-scale permafrost thaw experiment in a palsa peatland, (II) a laboratory incubation of Yedoma permafrost with inoculation by exotic microorganisms, (III) a microcosm experiment with five plant species grown either in Sphagnum peat or in newly-thawed permafrost peat, and (IV) a field-scale cold season warming experiment in cryoturbated tundra to address the indirect effects of climate change on microbial drivers of SOM decomposition. Community composition data for bacteria and fungi were obtained by amplicon sequencing and phospholipid fatty acid extraction, and for collembola by Tullgren extraction, alongside measurements of soil chemistry, CO2 emissions and root density.We showed that in situ thawing of a palsa peatland caused colonization of permafrost soil by overlying soil microbes. Further, we observed that functional limitations of permafrost microbial communities can hamper microbial metabolism in vitro. Relieving these functional limitations in vitro increased cumulative CO2 emissions by 32% over 161 days and introduced nitrification. In addition, we found that different plant species did not harbour different rhizosphere bacterial communities in Sphagnum peat topsoil, but did when grown in newly-thawed permafrost peat. Plant species may thus differ in how they affect functional limitations in thawing permafrost soil. Therefore, climate change-induced changes in vegetation composition might alter functioning in the newly-thawed, subsoil permafrost layer of northern peatlands, but less likely so in the topsoil. Finally, we observed that vegetation encroachment in barren cryoturbated soil, due to reduced cryogenic activity with higher temperatures, change both bacterial and collembola community composition, which may in turn affect soil functioning.This thesis shows that microbial community dynamics and plant-decomposer interactions play an important role in the functioning of warming permafrost-affected soils. More specifically, it demonstrates that the effects of climate change on plants can trickle down on microbial communities, in turn affecting SOM decomposition in thawing permafrost.
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| 7. |
- Sjöström, Jenny, 1978-
(författare)
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Mid-Holocene mineral dust deposition in raised bogs in southern Sweden : Processes and links
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Atmospheric mineral dust is a key component of the climate system, which affects insolation, brings nutrients to marine and terrestrial ecosystems, and acts as a cloud condensation nuclei. To reconstruct past patterns in terrestrial dust deposition natural archives may be utilized, such as loess, dunes, lakes, and peat bogs. Bogs became an established dust archive in the early 2000s, and the number of studies has since increased. However, most studies use single records to represent dust deposition, meaning that we have limited understanding of regional paleodust dynamics or about the representativeness of single bog records. This thesis aims to address these uncertainties by comparing paleodust deposition between bogs located on a 65 km transect. The thesis includes a methodological development for organic matter removal from peat samples for XRD mineral analysis (Paper I) and two peat paleodust reconstruction studies (Paper II, III). The first paleodust reconstruction from Draftinge Mosse (mosse translates to bog in English), Småland, showed that four dust events (DE) were recorded during the ombrotrophic stage (Paper II). These results were compared to a previously conducted study on Store Mosse, 20 km northeast of Draftinge Mosse, which showed similar patterns in DE and peat accumulation rate (PAR), indicating that the events were at least regional in character. However, the magnitude of the DE differed, which was related to differences in the sizes of the two bogs. The second paleodust reconstruction, from (Davidsmosse) located c. 25 km from the west coast, recorded many more DE (14) compared to the more inland sites (Paper III). Two longer periods saw numerous DE, dominated by coarse particles: between 2800 and 2130 cal BP, and from 1000 towards 490 cal BP. These two periods occurred during regionally cold periods. Human activities also intensified during the latter period, possibly amplifying the DE. Most of these episodic events were not recorded at the inland sites, and the Davidsmosse record seemed to be more in line with previously constructed coastal paleostorm records. That the bog located closer to the coast recorded many more events compared to the inland sites suggests that the location of a bog will influence the aeolian events recorded. However, the DE observed at the inland sites were also recorded at Davidsmosse, indicating that the inland events might represent winds that were sustained over longer distance, or alternatively, that regionally dry conditions prevailed during these periods. The paleostorm records from south-western Sweden, including the new results from Davidsmosse presented here, suggest that storm intensities have varied during the last 3000 years, with increased storminess frequency coupled to colder episodes related to extended sea ice and a southward shift of storm tracks. When comparing DE and PAR at both sites studied here, a recurring pattern of increased accumulation rates were observed during a majority of DE, supporting the suggestion of previous studies that dust deposition may affect peat growth, and thus also peat carbon sequestration.Combining elemental data with XRD mineral analysis enabled anchoring of elemental inferences with mineral observations, allowed identification of authigenic minerals, and aided in source tracing. Despite the fact that local factors affect mineral deposition and PAR, this work has outlined some of the possible mechanisms behind these observations (e.g. distance to the coast, or bog size difference) which may be important for future peat paleodust studies to consider. For example, future studies should include grain size analysis (down-core, as well as across a bog surface); pollen analysis to further elaborate on human activities and vegetation cover; and further investigate differences in mass accumulation rates between bogs.
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| 8. |
- Valinia, Salar
(författare)
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Credible targets for environmental management : evaluating reconstructions of reference values for ecological status in surface waters
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In the year 2000, countries of the European Union agreed to harmonise water management by implementing the European Water Framework Directive (WFD). The WFD uses good ecological status as the overall goal, which is defined as minor deviation from an undisturbed state. Reference conditions provide the means of estimating water status and ecological integrity, which are the focal point of decision-making processes. When determining reference conditions, the WFD prescribes the use of all available knowledge so as to reduce the predictive uncertainties. While the goal of achieving conditions similar to an undisturbed state can be desirable, the use of reference conditions as a target creates inherent complexity on multiple levels. This thesis focuses on evaluating the implications of different interpretations and implementations of WFD reference conditions for status assessment of Swedish surface waters. Specifically, the objectives were to: (I) define the implications of different reference condition criteria and understand the diversity of ways in which the term is used, (II) compare independent estimates of reference conditions estimated using historical fish archives and biogeochemical modelling for acidification assessment, (III) evaluate recovery from acidification of acid sensitive Swedish lakes and analyse potential confounding factors influencing future management, (IV) develop empirical models to estimate historical and present temporal trends in lake total organic carbon concentrations. Together and individually these studies have developed methods and models in which predictive uncertainties associated with reference conditions have been reduced. This thesis show how multiple methods can be used to reduce the uncertainties in surface water reference condition estimates as well as presenting approaches to the use of all available information as prescribed by the WFD. Furthermore, this thesis highlight the multiple competing, but equally valid, approaches to estimate reference conditions based on knowledge from different sources. In this thesis, it is argued that representations of the undisturbed state are a moving target and greater acceptance for multiple reference conditions based on all available knowledge is needed.
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| 9. |
- Verheijen, Hendricus, 1989-
(författare)
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Factors regulating the origin and magnitude of carbon dioxide emissions from high-latitude lakes
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Lake ecosystems receive, transmit and process terrestrial carbon and thereby link terrestrial, aquatic and global carbon cycles. Most lakes evade CO2 to the atmosphere, but the annual magnitude of CO2 evasion, as well as sources and mechanisms underpinning CO2 evasion from lakes are still largely unresolved. CO2 evasion from lakes can be sourced from direct external input from the catchment, but CO2 can also be produced in-lake from organic carbon breakdown. Both sources have been shown to be of importance to individual systems, but a landscape perspective is still missing. Globally, most lakes are in northern high latitudes, but due to infrequent seasonal sampling the magnitude of CO2 evasion on an annual scale is largely unknown, as are constraining variables of in-lake metabolism (i.e. production and consumption of CO2). As a consequence of these knowledge gaps, there is little possibility to predict future lake carbon cycling, for instance due to changing dissolved organic carbon (DOC) input or lake temperature resulting from global warming.In this thesis I aim to resolve these knowledge gaps surrounding the magnitude, cycling and sources of CO2 evasion from high-latitude (mainly arctic) lakes. By combining the estimates of annual CO2 evasion and metabolism, I investigated the magnitude of CO2 evasion, as well as the contribution of the internal carbon processing to CO2 evasion. Inclusion of ice-melt evasion allows to assess the importance, and drivers, of ice-melt CO2 evasion on the annual scale. Furthermore, by pooling lakes from multiple different lake surveys I was able to analyse the lake and landscape variables associated with high-latitude lake metabolism. Finally, through use of an experimental pond facility I manipulated dissolved organic carbon input and temperature to explore the effects of future climate conditions on lake carbon cycling and CO2 evasion.I found that both external input and internal CO2 production can contribute to CO2 evasion from lakes, but it is often dominated (>75%) by a single source and forest cover increased the amount to which the internal source contributed to annual CO2 evasion. I also found that the concentration of DOC in the lakes was inversely correlated to the proportion of CO2 lost at ice-melt. As a result, the ice-melt season is of significant importance to the annual CO2 evasion from low DOC high-latitude lakes, and omission can underestimate the magnitude of annual CO2-evasion by ~50%. Metabolism in these types of clear-water, low nutrient systems is dominated by benthic (on the sediment) production. Consequently, in-lake metabolism in these high-latitude clear-water lakes is largely constrained by lake depth and basin shape, and the potential for ice-scouring to disturb the benthic system in littoral areas. Convex lakes with predominantly shallow sediments were thus less productive compared to concave lakes where benthic production is less affected by ice-scouring. Finally, increasing DOC inputs (e.g. as a result of changes in climatic conditions) positively related to the amount of CO2 produced within and evaded from the lakes. However, warming was found to decrease in-lake CO2 production and evasion, potentially via increased nutrient limitation of carbon mineralization (i.e. more energy expanded for nutrient uptake in order to break down organic carbon in warmer water), and changes in community structure (e.g. different macrophytes). This thesis thus clearly outlines the annual magnitude (both open water and the specific importance of ice-melt), source contribution (quantified for many lakes rather than single systems) as well as the lake and landscape factors of note to source contribution (i.e. forest cover and DOC input increased internal cycling, especially in shallow and concave systems). Taken together, the results advance understanding the mechanisms behind cycling and evasion of CO2 in earth’s most common lake type.
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| 10. |
- Költringer, Chiara Amalia
(författare)
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Past environment and sediment dynamics in the Black Sea-Caspian Sea region from Southern Russian loess sequences
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Loess deposits are excellent past climate and environment archives and contain records of aeolian mineral dust accumulation. Loess deposits stretch across Eurasia and sequences along the Lower Volga in the Northern Caspian lowland in the South East European Plain represent a key link between European and Asian loess. They were deposited during phases of Caspian Sea sea-level low stands in the Late Quaternary and are confined by deposits of marine sediments from transgressive phases. These sea-level fluctuations of the Caspian Sea and their driving factors are not well resolved, and one obstacle is the lack of palaeoclimate information during phases of sea-level low stands. In contrast to the marine sediments, the continental deposits are understudied and the origin and formation of the material is debated. As a consequence, loess along the Lower Volga is often left out from palaeoclimate reconstructions in the region. This thesis aims to resolve the origin, formation and post-depositional modification of this loess and determines its aeolian origin. Provenance analyses show that Lower Volga loess particles were formed due to glacial grinding and were transported over long distances via rivers prior to near-source aeolian deposition, where the loess experienced phases of pedogenic and cryogenic reworking. While no temporal changes in material supply can be identified for Lower Volga loess, a remarkable spatial variability is seen in dust sources over the wider East European Plain and in the South Caspian Sea region. This variability is linked to material input from multiple local sources, while the larger material supply to the region has broadly similar provenance and derives mainly from areas of continental and mountain glaciation, transported via rivers prior to aeolian deflation. This thesis explores the potential of Lower Volga loess for palaeoclimate reconstructions in Eurasia, and shows a generally cold and arid climate in the Northern Caspian lowland during the Late Quaternary Caspian Sea regression, with strong dusty winds, punctuated by slightly more humid and/or warmer periods. The thesis shows that enviromagnetic methods are suitable for palaeoclimate reconstructions from such cold climate loess, as long as several methods are applied in combination and interpreted appropriately. It also provides information about the magnetic fabric of Lower Volga loess. The findings of this thesis in broader implication show that the Caspian Sea level is only secondarily influenced by local-regional climate variation and that Quaternary Northern Hemisphere glaciation is the primary controller via river discharge to the Caspian Sea.
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