ENVIRONMENTAL HISTORY AND CLIMATE DEVELOPMENT
ENVIRONMENTAL HISTORY AND CLIMATE DEVELOPMENT |
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PROJECT STAFF and PROJECT RESUMES |
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Ph.D. studentships Andreas Peter Ahlstrøm Anne Birgitte Nielsen Annett Wolf Emily Bradshaw |
Karin Gutfelt Jensen Tina Løvberg Post docs Klaus Peter Brodersen Suzanne McGowan Lucia Roncaglia |
Project Title: Development of a chironomid/lake-water temperature transfer function for lakes in southern West Greenland
Project scientist: Klaus Peter Brodersen
Climate and water temperature have an important influence on the functioning of lake ecosystems. From limnological and palaeolimnological studies of lakes, information on biological diversity and climate variability in time and space can be gleaned from physical, chemical and biological indicators preserved in the lake sediments. The lakes in southern West Greenland are particularly useful for this purpose - they are numerous, diverse and have minimal anthropogenic impact.
Larvae of the aquatic non-biting midges (Diptera: Chironomidae) are sensitive indicators of lake-water temperature. As a part of a multi-proxy palaeoecological project, models for quantitative reconstruction of climatic-induced limnological changes are being developed using subfossil remains of chironomid larvae. The method involves sampling of surface sediments of lakes covering a climate gradient along a transect from the ice sheet immediately east of Kangerlussuaq out to the coast, south of Sisimiut. Surface sediments have been taken from >50 lakes in the summers of 1996-1999. Samples have also been taken for water chemistry and have been processed for major ions and nutrients. High resolution water-temperature data have been obtained using thermistor data-loggers. Sediment samples are prepared for diatom and chironomid analysis. The resultant chironomid/temperature training set will be applied to sediment cores from southern West Greenland covering the time period since deglaciation. The reconstructions of lake water temperature are fundamental for understanding the functioning and development of modern lakes and for understanding the causes of climatic change as well as the effect on lake biota.
More info on the project, publications and abstracts on: http://brodersen.homestead.com/main.html
Project Title: High resolution sedimentary pigment records of climate change in the Arctic
Project scientist: Suzanne McGowan
Supervisors: Prof. N. John Anderson (University of Copenhagen), Rene K. Juhler (GEUS)
This project is funded by a European Union Marie Curie postdoctoral fellowship. The aims of the project are twofold:
A multi-proxy palaeolimnological approach will be taken using diatoms and pigments preserved in lake sediment records. In the Søndre Strømfjord region there are several closed basin lakes in which, because of the lack of an outflow, lake salinity is determined by the precipitation: evaporation balance. Reconstruction of palaeosalinity in such climate-sensitive sites can provide a regional terrestrial climate proxy. This project involves the use of diatoms to reconstruct palaeosalinity in closed basin lakes from the Søndre Strømfjord region by using a weighted-averaging diatom-salinity transfer function. Comparing palaeosalinity at more than one site will allow validation of the salinity reconstruction as a regional climate proxy.
Using the climate reconstruction from the diatom model, the project will then use sedimentary pigments (palaeopigments) to determine past lake algal response to climate. When deposited in lake sediments, algal pigments (chlorophylls and carotenoids) are often well preserved and some are specific to particular algal groups. The sedimentary pigments are separated by high performance liquid chromatography (HPLC) and quantified and identified using spectrophotometric methods. Thus, they can be used to reconstruct changes in past algal communities. Palaeopigment analysis will be carried out on several lakes which differ limnologically to assess how algal response to climate varies according to lake type.
Working Title: ´A study of palynodebris and dinoflagellate cysts in Holocene sediments from Greenland and Faeroe Islands fjords, and North Atlantic deep-water sites.´
Project scientist: Lucia Roncaglia
Project partners: Antoon Kuijpers and Karin Gutfelt Jensen (Survey of Denmark and Greenland, GEUS)
Affiliated institutions: Botanical Institute at the University of Copenhagen, National Museum of Denmark, Faeroe Islands Museum of Natural History, and Greenland National Museum and Archive.
Project description: The project is closely affiliated to the `Greenland Holocene Paleo-Hydrographic Project`, and funded by the Carlsberg Foundation.
The aim of the research is to elucidate paleo-hydrographic changes in the Holocene of the North Atlantic by systematically documenting for the first time the distribution of particulate organic debris (in particular dinoflagellate cysts) in well-dated sediment cores from south-west and west Greenland fjords, the south-east Greenland shelf, Reykjanes Ridge and the Faeroe Islands. The results from the different sites will be compared, thereby providing a comparison between environments on the Greenland shelf, the "open" North Atlantic, and the north-west European continental margin. It is also the aim to study temporal changes in these parameters at a limited number of localities, based on stratigraphic changes in palynofacies and dinoflagellate cyst assemblage.
The aim will be achieved by a quantitative and qualitative study of palynodebris and dinoflagellate cysts (1) in core samples from coastal to offshore setting in waters off Greenland and the Faeroe Islands, and on the Mid-Atlantic (Reykjanes) Ridge south of Iceland, in order to provide information on changes in temperature, salinity, trophic level and energy level with distance from shoreline in the same Holocene time slice; and (2) in closely spaced samples from a number of key cores, in order to provide information on temporal changes in temperature, salinity, trophic level and energy level over a well dated time interval in the Holocene.
Working title: Estimation of ice sheet ablation from remote sensing analysis and energy balance modelling
Project affiliated student: Andreas Peter Ahlstrøm
Supervisors: Carl Egede Bøggild, PhD (Geological Survey of Denmark and Greenland), Birger Ulf Hansen, PhD (Institute of Geography, University of Copenhagen)
Project partners: Geological Survey of Denmark and Greenland (GEUS), Danish Center for Remote Sensing (DCRS) at the Technical University of Denmark (DTU), National Survey and Cadastre (KMS), Aarhus University (AAU) and the Greenland Survey (ASIAQ) in Nuuk.
PhD description: The Ph.D. project is part of the IMERSUAQ project to determine the Inland Ice meltwater contribution to the Tasersiaq basin in West Greenland, funded by the Danish Natural Science Research Council. The goal of the Ph.D. project is to relate energy balance modelling, field observations and remotely sensed data for the dual purpose of mass balance modelling in the context of climate change and run-off estimation for hydro-power feasibility studies.
An ambitious field programme involving several institutions will provide the necessary data, including a detailed digital elevation model (DEM) and surface velocity field acquired from airborne laser altimetry and spaceborne InSAR, a series of ice sheet mass balance and climatological measurements from automatic weather stations and field work, an investigation of meltwater chemistry to determine origin, melt event timing and conduit structure and finally a continous record of basin water discharge. Albedo distribution is to be retrieved from NOAA-AVHRR (temporal) and Landsat 7 ETM+/Terra ASTER (spatial). Additional information about melt extent is attainable from passive microwave sensing and analysis of the extensive amount of SAR data collected could provide new applications to mass balance modelling, such as penetration characteristics, surface properties and velocity field calculations.
The climate data and the DEM are to be utilised in a distributed energy balance model to determine the ablation rate of the ice sheet in that particular region. The idea is to integrate the ablation information with the hydrological measurements, the meltwater chemistry investigations and the surface velocity field to obtain an overview of the processes governing the mass balance of the Greenland Ice Sheet and to assess the feasibility of determining ice sheet mass balance solely by remote sensing methods. The accomplishment of this goal would lend confidence to the reliability of investigations on the influence of climate change on the great ice sheets, which in turn governs sea level changes, and would shed light on the direction of the observed holocene climate variability. Simultaneously, it is the ambition to ease the estimation of the meltwater contribution from the Greenland Ice Sheet to hydrological basins under investigation for hydro-power potential. The desired outcome is a sort of white book which would be useful for the Greenland authorities, represented by the Greenland Survey (ASIAQ).
Working title: Pollen-based quantitative estimation of land-cover
Project affiliated student: Anne Birgitte Nielsen
Supervisors: Bent Odgaard(Geological Survey of Denmark and Greenland), Thomas Balstrøm(Institute of Geography, University of Copenhagen) and John Anderson (Institute of Geography, University of Copenhagen).
PhD description: The PhD is registered at the University of Copenhagen, co-supervised by the a Institute of Geography and is affiliated to the Danish Research Councils project Agrar 2000.
The aim of the Ph.D. project is to collect a calibration data set, consisting of pollen assemblages from lake sediments dating from around AD 1800, and land cover on historical maps from the same period, and to use these data to find a model for the correlation between pollen sedimentation in lakes, and the composition of the surrounding landscape of landcover categories such as arable fields, forest, meadow and heath, in Denmark. This will allow a more detailed interpretation of late Holocene pollen diagrams in terms of quantitative landscape composition, and thus hopefully lead to a better understanding of the history of the cultural landscape. 30 lakes have been selected to cover different parts of Denmark. They have been selected to be as uniform as possible, with areas ranging from 3,6 to 36 ha. and no significant inlets. Lakes with depths over 4m. have been preferred. Furthermore, pollen samples from larger lakes (over 1000 ha.) will be used to estimate regional pollen loading in different parts of the country, because this contributes to the pollen sedimentation in the smaller lakes, as well as the local vegetation. The level of lake sediment corresponding to ca. AD 1800 will be found using 210Pb dating, extrapolated back in time. From the AD 1800 level pollen will be counted, to a terrestrial pollen sum of at least 1000.
Different land cover categories will be digitised from the so-called Reduced Parish maps, made in scale 1:20:000 based on cadastral maps in scale 1:4000 from the period 1806-1820. Using GIS, the land cover data will be combined with existing data on geographical conditions such as surface geology, soil composition, hydrology and topography. Relationships between these geographical data and the pollen data will be analysed, using various numerical methods.
Modern theories on pollen dispersal and deposition will be used. This means, among other things, that in order to reflect pollen dispersal, the land cover data must be weighted, depending on the distance from the lakes, so that the area nearest is given the highest weight. It also means that regional pollen loading must be estimated, because it makes up a large proportion of the pollen deposition in the lakes, a proportion that is independent of the vegetation near the lake. This is why the large lakes are included in the project.
PhD working title: 'Natural dynamics of Draved Forest, Jutland'
Project affiliated student: Annett Wolf
Supervisors: Richard Bradshaw(Geological Survey of Denmark and Greenland), Peter Friis Møller (Geologiscal Survey of Denmark and Greenland), and Jens Emborg Department of Economics and Natural Resources (The Royal Veterinary and Agricultural University)
PhD description: Spatial patterns of existing trees. Different spatial models are applied to test whether trees are randomly distributed or show a clustered or even distribution. These methods are used for testing patterns for all trees and for individual species. Furthermore the relationships between different species will be tested. Patterns among living, dead and newly established trees will be tested for randomness as well. The existing data of coordinates of trees larger than 100 mm dbh (diameter at breast height) are used. The suggested methods are Ripley’s K-function and the nearest neighbour method. Two different methods are used, for looking at constancy between the results. Computer models are developed, using Delphi 5.0. A course concerning spatial statistics was undertaken at the Swedish University of Agricultural Sciences (SLU), in Alnarp.
Regeneration pattern, recruitment pattern. The relation between overstory and understory trees will be tested for spatial randomness. A 30 × 40 m plot was laid in a region where dead trees were found. No obvious gaps existed in this area. The existing trees were recorded using 2 × 2 m grid cells. All trees were recorded in each cell and diameter 300 mm above the ground was measured. Using spatial statistics it will be tested, whether regeneration is related to the living and/or dead trees. The existing data for regeneration based on a 5 × 5 m grid covering the whole forest will also be used for this analysis. Areas will be picked out on the map, where a dead tree is situated (gap) and areas without any obviously dead tree (non-gap). Regeneration data will be compared for those two classes for the surveys immediately preceding and following tree death.
Growth pattern. The existing data of Draved forest include measurements of dbh from about 10 time intervals. The resulting growth rate will be tested in different ways. Spatial statistics will test, whether there is a pattern in the growth rate per se, e.g. areas with higher growth rates. Multivariate statistics will be used to show how individual growth rates are dependent on the neighbouring trees. Species identity, diameter, crown class and growth rate will be used as variables.
Mortality agencies. Windblown trees from the storm in autumn 1999 will be recorded. The height and diameter will be measured of the fallen trees and of living trees nearby. Growth rate and crown classification can be calculated from the existing data set. It will be tested, whether there are differences in these parameters between species and between the fallen and the standing trees.
PhD working title: 'Response of lake nutrient regimes and lake biota to long-term changes in catchment land-use'
Project affiliated student: Emily Bradshaw
Supervisors: Professor N. John Anderson (Institute of Geography, University of Copenhagen) and Professor Morten Søndergaard (Freshwater Biological Laboratory, University of Copenhagen)
PhD description: The PhD is registered at the University of Copenhagen, co-supervised by the Freshwater Biological Laboratory and is affiliated to the SMP-II project 'Changing Landscapes', co-ordinated by the University of Southern Denmark.
Danish lakes today are characteristically shallow, turbid and nutrient rich. Their present status as hypertrophic systems dominated by phytoplankton has resulted in their being a major focus of research, especially with regard to understanding processes that are important for their management and restoration. While their present state clearly is not their natural one, as indicated by some documentary evidence from the turn of the century and the limited palaeolimnological studies that have been undertaken, it is unclear over what time period the lakes have been disturbed.
The primary approach of the research is diatom-based palaeolimnology. Pollen and macrofossil analyses (Peter Rasmussen, GEUS) of sediment cores from Danish lakes combined with historical evidence can provide information on the developing cultural landscape in Denmark over the last 6000 years. The timescales and biological response of lakes to disturbance and land-use change can also be evaluated using remains (of e.g. diatoms) in the same sediment samples. The application of new diatom-nutrient training sets will then permit the quantification of long-term in-lake phosphorus concentrations.
Recent papers:
Bradshaw, E.G., V.J. Jones, H.J.B. Birks & H.H. Birks, 2000. Diatom responses to late-glacial and early-Holocene environmental changes at Kråkenes, western Norway, Journal of Paleolimnology, 23, 21-34.
Rasmussen, P., & E. Bradshaw, 1999. Sø og Land. Relationer mellem arealanvendelse og søudvikling i et langtidsperspektiv in Årsberetning for 1998, Danmarks og Grønlands Geologiske Undersøgelse (GEUS), Copenhagen (in Danish)
Bradshaw, E. G. & N. J. Anderson: Validation of a diatom-phosphorus calibration set for Sweden, Freshwater Biology, in press.
PhD working title: 'Holocene paleo-hydrographic changes in Greenland coastal waters and fjords, and possible implications for human settlement.'
Project affiliated student:
Karin Gutfelt Jensen
Supervisors: Antoon Kuipers Ph.D., (Geological Survey of Denmark and Greenland), Professor Øjvind Moestrup (Botanical Institute, University of Copenhagen) and Nalan Koç Ph.D. (Norwegian Polar Institute).
Project partners: Geological Survey of Denmark and Greenland (GEUS), Botanical Institute at the University of Copenhagen, National Museum of Denmark, Durham University, Amsterdam Free University, GEOMAR Institute in Kiel, and the Netherlands Institute of Applied Geoscience TNO (NITG).
PhD description: The Ph.D.-project is affiliated to the project "Holocene paleo-hydrographic changes in Greenland coastal waters and fjords, and possible implications for human settlement", and funded by the Special North Atlantic Research Programme of the Danish Research Agency.
The aims of the project are two-fold:
While global annual average temperature has been steadily rising since the early 1980's, a cooling trend in West Greenland temperature records has been observed during the last decade. This adds to the records of slight cooling in the Labrador Sea and southern Greenland since the 1960's.
Since the mid 1980's, changes have been observed in the North Atlantic deep water formation; a cessation of convective deep water renewal has been reported in the Greenland Sea, and convection has started to prevail in the Labrador Sea. These areas off Greenland are, apart from Antarctic waters, the only sites with direct exchange between the atmosphere and the deep ocean.
Palaeoceanographic studies and coupled atmosphere-ocean models indicate that climate changes in the North Atlantic region are closely related to changes in surface circulation and in the production of North Atlantic deep water.
In this project cores will be taken from south-west and west Greenland in order to compare regional hydrographic patterns. The Ph.D.-project will take a multi-proxy palaeoceanographic approach using diatoms, stable isotopes as well as other relevant geo-chemical and sedimentological records from high-resolution sediment cores. Diatoms are sensitive to environmental changes, e.g. salinity, temperature and nutrients, and therefore valuable indicators when determining the hydrographic conditions. As salinity and sea surface temperatures can provide hydrographic proxies, the project attempts to reconstruct past changes in sea surface temperature and salinity by the application of diatom-based transfer functions.
Through comparison with Greenland lake- and ice core data, the work will contribute to a better understanding of atmosphere-ocean interaction and long-term climate patterns of the seas around Greenland. Comparison with relevant Holocene climate records from north-west Europe may help explaining the interrelationship between the cooling trend observed on Greenland and documented global (Northwest European) warming.
The record of Paleo-Eskimo cultures on Greenland's west coast shows various major immigration and cultural stages of which the initial phase of the oldest (Saqqaq) culture has been dated at near 4,3 ka. In addition, the southwards expansion of the Thule culture coincided with the beginning of the Little Ice Age, 1200-1300 AD. Archaeological evidence from Western Canada and eastern North America shows much earlier human occupation of high-latitude areas, i.e. at the Pleistocene-Holocene boundary. It thus seems that the Holocene southward migration of Inuit in Greenland occurred when Holocene climate deteriorated, i.e. in Middle Holocene times and at the beginning of the Little Ice Age. This may be coincidence, or might be related to changes of the (marine) physical environment directly affecting resource utilisation. The further objective of this project is to establish a highly detailed (AMS C-14) chronology focusing on Mid-Holocene and Little Ice Age-related hydrographic changes that could have implications for the Eskimo and Norse settlement stages. In order to study possible links between these changes and the physical (marine) environment and human settlement history, extensive dating of archaeological material is envisaged as well.
PhD working title: 'Registration of natural changes and anthropogene influence on the natural environment in lacustrine deposits in the Late Postglacial'
Project affiliated student:
Tina Løvberg
Supervisors: Bent Odgaard(Geological Survey of Denmark and Greenland), and Svend Funder Geological Museum (University of Copenhagen)
PhD description: The PhD is registered at the University of Copenhagen, and is affiliated to the Danish Research Councils project Agrar 2000.
PhD description: The aim of the investigation is to trace important changes in the vegetational development during the last c. 6.000 years and link these changes to human activity e.g. disturbances by fire and erosion in the catchment area. The palaeoecological reconstructions of the investigated area are based on pollen, charred particle and mineral magnetic analyses of sediment cores. The project has been designed as a paired site study in which a hypotesis on the relationships between environmental variables e.g. mineral magnetic properties and charred particles, and the respons of the vegetation as registered in pollen diagrams from one lake is set up and tested on similar relationships between data sets from another lake.
Two lakes, Lake Birkerød og St. Gribsø (see photograph), 13 km apart and both situated in the northeastern part of Denmark, have been chosen. The lakes have similar size, an overall similarity in catchment sediments, no inlets and only minor outlets. Earlier pollen records indicate that St. Gribsø is situated in an area which have been densely forested since the beginning of Holocene. Historical records indicate that Lake Birkerød is situated in an area which have been heavily influenced by humans since the Early Medieval period. By comparing the pollen records and the results of the mineral magnetic and charred particle analysis from the two sites using a series of numerical analyses an attempt will be made to infer the human influence on the vegetational development.
References
Løvberg, T.: Sen Weichsel til Holocæn sedimentologi og
pollenanalyse: lakustrine aflejringer i Store Åmose, Vestsjælland. Geologisk
Tidsskrift, hæfte 2, pp. 116–125, København, 1998–08–20
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Last modified: - © Geological Survey of Denmark and Greenland (GEUS)