Browsing by Subject "hydrology"
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(2019)Permafrost peatlands have the capacity to store significant amounts of carbon, and thus they act as important controllers of the climate. Approximately 14% of the world’s soil organic carbon pool is stored in permafrost peatlands, which are sensitive to climatic fluctuations due to their location in the high latitudes of the subarctic zone. Permafrost peatlands also act as a habitat for a large number of moisture-sensitive organisms, such as bryophytes and testate amoebae, which can be used to study how the hydrology of peatlands has changed and will continue to change throughout time, giving us an opportunity to predict the future of peatlands under a changing climate. In this Master’s Thesis I examined the testate amoebae composition and used these species as indicators to study hydrological fluctuations from three subarctic permafrost peatland cores extracted from Taavavuoma and Abisko in northern Sweden. The species compositions were combined with radiocarbon (14C) and lead (210Pb) dates to reconstruct the past water table levels for the late Holocene, spanning four climatic periods. The reconstructions were then compared to past studies on testate amoebae to understand how permafrost peatlands and their species assemblages respond to changes in the hydrology of the active layer of the peat. Out of the study sites only the Taavavuoma cores spanned the Dark Age Cold Period (DACP) and Medieval Climate Anomaly (MCA). Species compositions in both cores indicated fluctuating water tables during the DACP, but during the MCA the results began to contradict with one site showing a wetter, and the other a drier MCA. Two out of three study sites indicated a wetter Little Ice Age and a drier Post-Industrial Warming, supporting past studies indicating similar results, whereas one study site gave opposite results. The results indicated large variability in testate amoebae assemblages throughout time, indicating that the hydrology of peatlands can change very abruptly and vary considerably even on a local scale. Modelling is however complicated by the poorly known ecology of testate amoebae, which is why a multi-proxy approach is essential to reliably predict the future fate of permafrost peatlands.
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(2019)Permafrost peatlands have the capacity to store significant amounts of carbon, and thus they act as important controllers of the climate. Approximately 14% of the world’s soil organic carbon pool is stored in permafrost peatlands, which are sensitive to climatic fluctuations due to their location in the high latitudes of the subarctic zone. Permafrost peatlands also act as a habitat for a large number of moisture-sensitive organisms, such as bryophytes and testate amoebae, which can be used to study how the hydrology of peatlands has changed and will continue to change throughout time, giving us an opportunity to predict the future of peatlands under a changing climate. In this Master’s Thesis I examined the testate amoebae composition and used these species as indicators to study hydrological fluctuations from three subarctic permafrost peatland cores extracted from Taavavuoma and Abisko in northern Sweden. The species compositions were combined with radiocarbon (14C) and lead (210Pb) dates to reconstruct the past water table levels for the late Holocene, spanning four climatic periods. The reconstructions were then compared to past studies on testate amoebae to understand how permafrost peatlands and their species assemblages respond to changes in the hydrology of the active layer of the peat. Out of the study sites only the Taavavuoma cores spanned the Dark Age Cold Period (DACP) and Medieval Climate Anomaly (MCA). Species compositions in both cores indicated fluctuating water tables during the DACP, but during the MCA the results began to contradict with one site showing a wetter, and the other a drier MCA. Two out of three study sites indicated a wetter Little Ice Age and a drier Post-Industrial Warming, supporting past studies indicating similar results, whereas one study site gave opposite results. The results indicated large variability in testate amoebae assemblages throughout time, indicating that the hydrology of peatlands can change very abruptly and vary considerably even on a local scale. Modelling is however complicated by the poorly known ecology of testate amoebae, which is why a multi-proxy approach is essential to reliably predict the future fate of permafrost peatlands.
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(2009)Industrial plantations of eucalyptus are sharply increasing in Asia. Although supplying raw material for the pulp and paper industry, easing deforestation on native forests and increasing carbon sequestration to help counter global warming, there are several concerns about the environmental effects of industrial eucalyptus plantations. These concerns include invasiveness of eucalyptus and loss of biodiversity, loss of land for food production, loss of soil fertility due to short rotation times and biomass removal, and excessive water-use and reduced catchment water yields. With protagonists on both sides, there is a need to research and examine the environmental effects of industrial eucalyptus plantations in southern China. We modelled and mapped the spatial distribution of water balance components across a small (752 ha) catchment in Guangxi province in relation to land-use, including industrial and local community plantations of eucalyptus and agriculture. Studies about the spatial distribution of water-use by eucalyptus across the landscape are few. WATBAL, a water balance model with a monthly time step, was parameterized and used to derive water balance components for 180 selected locations in the catchment. From the model output, continuous (predictive) surfaces for monthly (long-term average) potential (PET) and actual evapotranspiration (AET), evapotranspiration deficit (PET- AET), surface runoff and drainage below rooting zone were generated using GIS (ArcGIS 9.2). Averaged across the catchment, annual (October- September) actual evapotranspiration accounted for 77 %, surface runoff for 15 % and drainage below rooting zone for 8 % of rainfall. Differences between land-use types were relatively small, but areas of highest actual evapotranspiration and lowest surface runoff were associated with the oldest (6-7 years old) forested areas, including pure and mixed eucalyptus industrial plantations and local community, coppiced plantations on the slopes. The areas with the lowest actual evapotranspiration were associated with agricultural crops in the bottom of the catchment. The clear dominance of actual evapotranspiration in the water balance of all land-use types reflects the dominating role of the evaporative potential of the climate, with land-use cover, soil and topography factors playing secondary roles. While water-use was the highest for the forested areas, eucalyptus per se did not use more water than mixed plantations or those of the local community. Tree cover in general reduced surface runoff and therefore would reduce the risk of erosion. Using our modelling and mapping approach, we were able to assess the water-use and other components of the water balance of eucalyptus plantations and other land use types for this catchment. The study showed the importance of having suitable and adequate ground truth data in order to derive reliable and useful interpolation surfaces using ArcGIS.
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The future of Narsap Sermia: Documenting the retreat of a tidewater glacier in Southwest Greenland (2023)The behaviour of Greenland's tidewater glaciers is crucial for the understanding of the Greenland Ice Sheet. The retreat of those marine-terminating glaciers has far-reaching implications, impacting not only the regional hydrography but also the diverse fjord ecosystems. Here, this study investigated the rapid retreat of Narsap Sermia (NS), a tidewater glacier located in Southwest Greenland. Between 1987 and 2022, the volume of ice discharged from NS increased by 45%, a rate more than double the Greenlandic mean. This destabilization led to retreat events occurring in three distinct episodes: 2004-2005, 2010-2012, and 2019-2021. The study identified that changes in subglacial hydrology were pivotal in triggering and sustaining these retreats. Drainage of ice-dammed lakes or increased meltwater resulting from heatwaves over the ice sheet suddenly increased subglacial freshwater discharge, subsequently instigating these retreat events. Once initiated, exposure to elevated ocean temperatures or retreat into a glacial trough further sustained ice loss at the terminus, eventually resulting in a collapse of the glacial front. As of the summer of 2023, Narsap Sermia is still retreating, and the study anticipates that further retreat of approximately 3 kilometers is inevitable. Subsequently, should air and ocean temperatures continue to rise, Narsap Sermia is poised to retreat further for 30 km, dramatically transitioning into a land-terminating glacier. This drastic transformation could occur in as little as 30 years, with profound consequences for local eco-hydrology and nearby communities.
Now showing items 1-4 of 4