@phdthesis{Grosse2005,
  author    = {Grosse, Guido},
  title     = {Characterisation and evolution of periglacial landscapes in Northern Siberia during the Late Quaternary : remote sensing and GIS studies},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-5544},
  school      = {Universit{\"a}t Potsdam},
  year      = {2005},
  abstract  = {About 24 \% of the land surface in the northern hemisphere are underlayed by permafrost in various states. Permafrost aggradation occurs under special environmental conditions with overall low annual precipitation rates and very low mean annual temperatures. Because the general permafrost occurrence is mainly driven by large-scale climatic conditions, the distribution of permafrost deposits can be considered as an important climate indicator. The region with the most extensive continuous permafrost is Siberia. In northeast Siberia, the ice- and organic-rich permafrost deposits of the Ice Complex are widely distributed. These deposits consist mostly of silty to fine-grained sandy sediments that were accumulated during the Late Pleistocene in an extensive plain on the then subaerial Laptev Sea shelf. One important precondition for the Ice Complex sedimentation was, that the Laptev Sea shelf was not glaciated during the Late Pleistocene, resulting in a mostly continuous accumulation of permafrost sediments for at least this period. This shelf landscape became inundated and eroded in large parts by the Holocene marine transgression after the Last Glacial Maximum. Remnants of this landscape are preserved only in the present day coastal areas. Because the Ice Complex deposits contain a wide variety of palaeo-environmental proxies, it is an excellent palaeo-climate archive for the Late Quaternary in the region. Furthermore, the ice-rich Ice Complex deposits are sensible to climatic change, i.e. climate warming. Because of the large-scale climatic changes at the transition from the Pleistocene to the Holocene, the Ice Complex was subject to extensive thermokarst processes since the Early Holocene. Permafrost deposits are not only an environmental indicator, but also an important climate factor. Tundra wetlands, which have developed in environments with aggrading permafrost, are considered a net sink for carbon, as organic matter is stored in peat or is syn-sedimentary frozen with permafrost aggradation. Contrary, the Holocene thermokarst development resulted in permafrost degradation and thus the release of formerly stored organic carbon. Modern tundra wetlands are also considered an important source for the climate-driving gas methane, originating mainly from microbial activity in the seasonal active layer. Most scenarios for future global climate development predict a strong warming trend especially in the Arctic. Consequently, for the understanding of how permafrost deposits will react and contribute to such scenarios, it is necessary to investigate and evaluate ice-rich permafrost deposits like the widespread Ice Complex as climate indicator and climate factor during the Late Quaternary. Such investigations are a pre-condition for the precise modelling of future developments in permafrost distribution and the influence of permafrost degradation on global climate. The focus of this work, which was conducted within the frame of the multi-disciplinary joint German-Russian research projects "Laptev Sea 2000" (1998-2002) and "Dynamics of Permafrost" (2003-2005), was twofold. First, the possibilities of using remote sensing and terrain modelling techniques for the observation of periglacial landscapes in Northeast Siberia in their present state was evaluated and applied to key sites in the Laptev Sea coastal lowlands. The key sites were situated in the eastern Laptev Sea (Bykovsky Peninsula and Khorogor Valley) and the western Laptev Sea (Cape Mamontovy Klyk region). For this task, techniques using CORONA satellite imagery, Landsat-7 satellite imagery, and digital elevation models were developed for the mapping of periglacial structures, which are especially indicative of permafrost degradation. The major goals were to quantify the extent of permafrost degradation structures and their distribution in the investigated key areas, and to establish techniques, which can be used also for the investigation of other regions with thermokarst occurrence. Geographical information systems were employed for the mapping, the spatial analysis, and the enhancement of classification results by rule-based stratification. The results from the key sites show, that thermokarst, and related processes and structures, completely re-shaped the former accumulation plain to a strongly degraded landscape, which is characterised by extensive deep depressions and erosional remnants of the Late Pleistocene surface. As a results of this rapid process, which in large parts happened within a short period during the Early Holocene, the hydrological and sedimentological regime was completely changed on a large scale. These events resulted also in a release of large amounts of organic carbon. Thermokarst is now the major component in the modern periglacial landscapes in terms of spatial extent, but also in its influence on hydrology, sedimentation and the development of vegetation assemblages. Second, the possibilities of using remote sensing and terrain modelling as a supplementary tool for palaeo-environmental reconstructions in the investigated regions were explored. For this task additionally a comprehensive cryolithological field database was developed for the Bykovsky Peninsula and the Khorogor Valley, which contains previously published data from boreholes, outcrops sections, subsurface samples, and subsurface samples, as well as additional own field data. The period covered by this database is mainly the Late Pleistocene and the Holocene, but also the basal deposits of the sedimentary sequence, interpreted as Pliocene to Early Pleistocene, are contained. Remote sensing was applied for the observation of periglacial strucures, which then were successfully related to distinct landscape development stages or time intervals in the investigation area. Terrain modelling was used for providing a general context of the landscape development. Finally, a scheme was developed describing mainly the Late Quaternary landscape evolution in this area. A major finding was the possibility of connecting periglacial surface structures to distinct landscape development stages, and thus use them as additional palaeo-environmental indicator together with other proxies for area-related palaeo-environmental reconstructions. In the landscape evolution scheme, i.e. of the genesis of the Late Pleistocene Ice Complex and the Holocene thermokarst development, some new aspects are presented in terms of sediment source and general sedimentation conditions. This findings apply also for other sites in the Laptev Sea region.},
  subject      = {Dauerfrostboden},
  language  = {en}
}
@phdthesis{Lantuit2008,
  author    = {Lantuit, Hugues},
  title     = {The modification of arctic permafrost coastlines},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-19732},
  school      = {Universit{\"a}t Potsdam},
  year      = {2008},
  abstract  = {The arctic region is undergoing the most rapid environmental change experienced on Earth, and the rate of change is expected to increase over the coming decades. Arctic coasts are particularly vulnerable because they lie at the interface between terrestrial systems dominated by permafrost and marine systems dominated by sea ice. An increased rise in sea level and degradation of sea-ice as predicted by the Intergovernmental Panel on Climate Change in its most recent report and as observed recently in the Arctic will likely result in greater rates of coastal retreat. An increase in coastal erosion would result in dramatic increases in the volume of sediment, organic carbon and contaminants to the Arctic Ocean. These in turn have the potential to create dramatic changes in the geochemistry and biodiversity of the nearshore zone and affect the Arctic Ocean carbon cycle. To calculate estimates of organic carbon input from coastal erosion to the Arctic Ocean, current methods rely on the length of the coastline in the form of non self-similar line datasets. This thesis however emphasizes that using shorelines drawn at different scales can induce changes in the amount of sediment released by 30\% in some cases. It proposes a substitute method of computations of erosion based on areas instead of lengths (i.e. buffers instead of shoreline lengths) which can be easily implemented at the circum-Arctic scale. Using this method, variations in quantities of eroded sediment are, on average, 70\% less affected by scale changes and are therefore a more reliable method of calculation. Current estimates of coastal erosion rates in the Arctic are scarce and long-term datasets are a handful, which complicates assessment and prognosis of coastal processes, in particular the occurrence of coastal hazards. This thesis aims at filling the gap by providing the first long-term dataset (1951-2006) of coastal erosion on the Bykovsky Peninsula, North-East Siberia. This study shows that the coastline, which is made of ice-rich permafrost, retreated at a mean annual rate of 0.59 m/yr between 1951and 2006. Rates were highly variable: 97.0 \% of the rates observed were less than 2 m/yr and 81.6\% were less than 1m/yr. However, no significant trend in erosion could be recorded despite the study of five temporal subperiods within 1951-2006. The juxtaposition of wind records could not help to explain erosion records either and this thesis emphasizes the local controls on erosion, in particular the cryostratigraphy, the proximity of the Peninsula to the Lena River Delta freshwater plume and the local topographical constraints on swell development. On ice-rich coastal stretches of the Artic, the interaction of coastal dynamics and permafrost leads to the occurrence of spectacular "C-shaped" depressions termed retrogressive thaw slumps which can reach lengths of up to 650 m. On Herschel Island and at King Point (Yukon Coastal Plain, northern Canada), topographical, sedimentological and biogeochemical surveys were conducted to investigate the present and past activity of these landforms. In particular, undisturbed tundra areas were compared with zones of former slump activity, now stabilized and re-vegetated. This thesis shows that stabilized areas are drier and less prone to plant growth than undisturbed areas and feature fundamentally different geotechnical properties. Radiocarbon dating and topographical surveys indicated until up to 300 BP a likely period of dramatic slump activity on Herschel Island, similar to the one currently observed, which led to the creation of these surfaces. This thesis hypothesizes the occurrence of a ~250 years cycle of slump activity on the Herschel Island shoreline based on the surveyed topography and cryostratigraphy and anticipates higher frequency of slump activity in the future. The variety of processes described in this thesis highlights the changing nature of the intensity and frequency of physical processes acting upon the arctic coast. It also challenges current perceptions of the threats to existing industry and community infrastructure in the Arctic. The increasing presence of humans on Artic coasts coupled with the expected development of shipping will drive an increase in economical and industrial activity on these coasts which remains to be addressed scientifically.},
  language  = {en}
}