Gletsjermel

Research | Forskning - peer review

Around the Greenlandic and Antarctic coastlines, sediment plumes associated with glaciers are signi!cant sources of lithogenic material to the ocean. These plumes contain elevated concentrations of a range of trace metals, especially in particle bound phases, but it is not clear how these particles… Around the Greenlandic and Antarctic coastlines, sediment plumes associated with glaciers are signi!cant sources of lithogenic material to the ocean. These plumes contain elevated concentrations of a range of trace metals, especially in particle bound phases, but it is not clear how these particles affect dissolved (<0.2 μm) metal distributions in the ocean. Here we show, using transects in 8 glacier fjords, trends in the distribution of dissolved iron, cobalt, nickel and copper (dFe, dCo, dNi, dCu). Following rapid dFe loss close to glacier out"ows, dFe concentrations in particular showed strong similarities between different fjords. Similar dFe concentrations were also observed between seasons/years when Nuup Kangerlua (SW Greenland) was revisited in spring, mid- and late-summer. Dissolved Cu, dCo and dNi concentrations were more variable and showed different gradients with salinity depending on the fjord, season and year. The lack of consistent trends for dCu and dNi largely re"ects less pronounced differences contrasting the concentration of in"owing shelf waters with fresher glacially-modi!ed waters. Particles also made only small contributions to total dissolvable Cu (dCu constituted 83 ± 28% of total dissolvable Cu) and Ni (dNi constituted 86 ± 28% of total dissolvable Ni) within glacier plumes. For comparison, dFe was a lower fraction of total dissolvable Fe; 3.5 ± 4.8%. High concentrations of total dissolvable Fe in some inner-fjord environments, up to 77 μM in Ameralik (SW Greenland), may drive enhanced removal of scavenged type elements, such as Co. Further variability may have been driven by local bedrock mineralogy, which could explain high concentrations of dNi (25–29 nM) and dCo (6–7 nM) in one coastal region of west Greenland (Kangaatsiaq). Our results suggest that dissolved trace element distributions in glacier fjords are in"uenced by a range of factors including: freshwater concentrations, local geology, drawdown by scavenging and primary production, saline in"ow, and sediment dynamics. Considering the lack of apparent seasonality in dFe concentrations, we suggest that "uxes of some trace elements may scale proportionately to fjord overturning rather than directly to freshwater discharge "ux. Læs mere

Communication | Formidling

One potential climate mitigation solution could be to spread the fine ( One potential climate mitigation solution could be to spread the fine (< 46 μm) glacial rock flour from Greenland on agricultural fields to enhance its weathering rate with resulting CO2-uptake from the production of alkalinity. The net climate mitigation potential of this process will depend on the weathering rate, but also the embedded greenhouse gas emissions of its lifecycle. This thesis aims to estimate the net greenhouse gas balance of application with glacial rock flour on agricultural fields in Denmark. The CO2-uptake from weathering of glacial rock flour in soil was estimated from the release rates of cations in a pot experiment with perennial ryegrass (Lolium Perenne) in Denmark. There was no significant difference in cation release rates across application rates of 10, 20, 30, 40 and 50 t ha-1 of glacial rock flour, resulting in an uptake of 5.31 kg CO2 t-1 after 8.5 months across all five treatments. The effect on plant growth by the end of the experiment was non-significant but could potentially be due to temperature limitation. The greenhouse gas emissions from the lifecycle of glacial rock flour was estimated for a hypothetical “cradle-to-field” lifecycle using secondary emission data on CO2, and when possible also CH4 and N2O, for activities which are expected to be the closest proxies. It was estimated that the most “climate-optimal” lifecycle emits 26.32 kg CO2e t- 1 or 39.32 kg CO2e t-1 for glacial rock flour extracted on-land or in-water, respectively. The lifecycle greenhouse gas emissions are therefore not balanced by CO2-uptake from weathering after 8.5 months in Denmark, but it is expected that glacial rock flour eventually will lead to a net CO2-uptake of around 215 kg CO2e t-1 and 200 kg CO2e t-1 for land-based and water-based glacial rock flour, respectively, based on its geochemical composition. There is need for more long-term experiments to estimate the continued weathering rate and thereby evaluate the role of glacial rock flour in climate mitigation in this century. Læs mere

Communication | Formidling

It is widely accepted that the anthropogenic emission of greenhouse gasses leads to global climate change. If global temperatures continue to rise, the frequency of extreme weather phenomena such as droughts and tropical storms will increase to a point of significant socio-economic impact. To mitiga… It is widely accepted that the anthropogenic emission of greenhouse gasses leads to global climate change. If global temperatures continue to rise, the frequency of extreme weather phenomena such as droughts and tropical storms will increase to a point of significant socio-economic impact. To mitigate such changes, several CO2 removal strategies have been proposed, including enhanced weathering. Weathering reduces atmospheric CO2 via the reaction of carbonic acid and the minerals constituting the continental crust. Glacial rock flour from Greenland may be utilized for enhanced weathering as it has a large surface area from the natural grinding process, increasing its reactivity. However, the lack of current knowledge on the material means its use as a climate mitigation technique is contentious. The aim of this project is to probe the mineralogy and chemical composition of the material and use this information to conduct a geochemical simulation of its dissolution. 28 samples were analyzed with X-ray diffraction (XRD) and Pair distribution function (PDF) analysis of synchrotron X- ray scattering data. The particle size distribution was determined with laser diffraction and the surface area of the material determined with the Brunauer-Emett-Teller (BET) method. The results show that the mineral assemblage consists of quartz, plagioclase, microcline, albite, biotite, chlorite, muscovite, and epidote in proportions which corresponds to a granodioritic composition. The bulk material was separated gravitationally into four size fractions. XRD of these fractions show that the coarser is dominated by quartz, whereas the finest fraction consists mainly of phyllosilicates and amphibole. The geochemical software PHREEQC was utilized to model the dissolution of the material. Comparison between modelled and experimental concentrations from dissolution shows that the model is able to reproduce observed Si concentrations. However, inconsistency between modelled and observed concentrations of Ca, Mg, Na and K indicate that fast, non-stoichiometric, dissolution is dominating the first 71 hours of reaction. The simulations indicate that precipitation of clay minerals alter the rate of ion increase in solution in the later stage; which is why the accumulation rate plateaus. Ca ions which could potentially precipitate as carbonate minerals, and sequester CO2, are kept from oversaturation due to the formation of Ca-rich secondary clays. The results indicate that GRF can increase the alkalinity of the local water and consume CO2 at a relatively high rate in the short-term. However, in the long-term, the rate of cation release, and therefore CO2 consumption, decreases. Læs mere

Research | Forskning - peer review

Ice flow dynamics of the Greenland ice sheet control the production of sediment. Future acceleration in glacial flow and ice sheet melt will amplify Greenland’s supply of sediment to the coastal zone. Globally, sand and gravel reserves are rapidly depleting while the demand is increasing, largely du… Ice flow dynamics of the Greenland ice sheet control the production of sediment. Future acceleration in glacial flow and ice sheet melt will amplify Greenland’s supply of sediment to the coastal zone. Globally, sand and gravel reserves are rapidly depleting while the demand is increasing, largely due to urban expansion, infrastructural improvements and the enhancement of coastal protection in response to climate change. Here, we show that an abundance of sand and gravel provides an opportunity for Greenland to become a global exporter of aggregates and relieve the increasing global demand. The changing Arctic conditions help pave a sustainable way for the country towards economic independence. This way, Greenland could benefit from the chal- lenges brought by climate change. Such exploitation of sand requires careful assessment of the environmental impact and must be implemented in collaboration with the Greenlandic society. Læs mere

Communication | Formidling

In a global world where climate change and a growing population increase the requirements for food, the need for fertile soil becomes a problem, especially in the tropics. New research shows that Greenlandic Glacier Rock Flour (GRF) can be used to remineralise nutrient depleted soils and thus, to so… In a global world where climate change and a growing population increase the requirements for food, the need for fertile soil becomes a problem, especially in the tropics. New research shows that Greenlandic Glacier Rock Flour (GRF) can be used to remineralise nutrient depleted soils and thus, to some extent, alleviate some of these problems. This project investigates whether GRF ́s fertility potential depends on the size of the glacier thermal regime and locations. Glacier Rock Flour was collected from different sites in Greenland, Svalbard, Alaska and Argentina for comparison. Incubation experiments were carried out by mixing 10% GRF with soil/sand in the ratio 1:1. The level of available potassium and phosphorus was measured after two and four weeks and compared to a control sample only containing the soil/sand. The analysis shows that there is a difference in the available K depending on location, while the P analysis is more inconsistent. Based on the results, the main factor for nutrient release is the particle size of the GRF, and this is mainly influenced by the thermal regime of the glacier and the bedrock. The results also show that the physical properties and soil environment affect the release of potassium and phosphorus the most. Overall, GRF from Greenland seems to be more suitable for remineralisation compared to GRF from other locations, especially when looking at the available potassium. Læs mere

Communication | Formidling

Microorganisms have been acknowledged for centuries as key influencers on their surrounding environment. Scientific research has recently been able to validate and explore this using high throughput sequencing techniques that offer the potential to efficiently investigate the biodiversity in environ… Microorganisms have been acknowledged for centuries as key influencers on their surrounding environment. Scientific research has recently been able to validate and explore this using high throughput sequencing techniques that offer the potential to efficiently investigate the biodiversity in environmental samples. Advanced DNA sequencing techniques combined with modern microbial cultivation can provide a profound conception of a microbial community’s genotypic and phenotypic characteristics from a single environmental sample. I have combined both techniques in this MSc thesis, with a focus on analysing and inferring the microbial properties of Greenlandic glacial rock flour (GRF). GRF is currently being explored as a novel soil mineraliser, due to its promising mineralogical properties and the fact it represents an abundant and sustainable resource. I therefore characterised the microbial community of both pure GRF samples, and also following blending with agricultural soils to examine any resulting consequences to the agricultural soil microbial communities. The MSc thesis begins with an introduction containing a description of GRF, the microbiology related to the subject and the techniques used in this thesis. Subsequently this is followed with a first manuscript “Taxonomic profiling of the microbial community of Greenlandic glacial rock flour - a novel soil mineraliser” describing the microbial community of GRF, and then a second manuscript “Exploring the microbial consequences of applying the Greenlandic glacial rock flour soil mineraliser to depleted agricultural soils” analysing the microbial consequences (negative and/or positive) over time associated to GRF. Lastly, overall perspectives and conclusions are presented. Læs mere