High Arctic Paraglacial Coastal Evolution in Northern Billefjorden, Svalbard

Mateusz Strzelecki High Arctic Paraglacial Coastal Evolution in Northern Billefjorden, Svalbard In contrast to mid and low latitude coasts, relatively little is known regarding the potential impacts of climate and sea-level change on cold region coastal margins. This is an important area of research given the pace of recent climate change and future predictions. Svalbard provided a superb location to quantify how High Arctic coasts are responding to climate warming and the associated paraglacial landscape transformation. The geographical focus for the thesis is Petuniabukta and Adolfbukta, the northernmost bays of Billefjorden, central Spitsbergen. The study area has a sheltered location, a semi-arid, sub-polar climate, limited wave fetch and tidal range, and rapid retreat rate of all surrounding glaciers. Using a combination of geomorphological, sedimentological, remote sensing and dating methods, the thesis investigates the processes that control coastal evolution over annual, century and millennial timescales. Interannual changes observed between 2008 and 2010 show that High Arctic gravel-barriers are resilient to the impact of local storms and the operation of sea-ice processes. The results of a Schmidt Hammer test demonstrate a significant reduction in rock resistance with decreasing distance from the modern shoreline. Shoreline changes since the end of the Little Ice Age (late 19th/early 20th century) reflect a dramatic increase in sediment supply associated with retreating local ice masses, a shortened winter sea-ice season and melting of permafrost. A new approach of dating of juvenile marine molluscs found in uplifted raised beaches enables the development of a new model of relative sea-level change in the study area. The thesis demonstrates that existing models of paraglacial coastal evolution, developed on mainly temperate latitude coasts, are not applicable to the High Arctic. Whilst the fundamental importance of the sediment supply and relative sea-level is noted, in the High Arctic these processes are modified by climate-driven factors that influence sediment delivery from terrestrial sources, the extent of sea-ice, permafrost as well as river discharge and slope stability. A new model of paraglacial coastal evolution is proposed that captures these processes and recognises the importance of bedrock topography as a key control on landforms preservation

Cold shores in warming times – current state and future challenges in High Arctic coastal geomorphological studies

Many of the existing intellectual paradigms regarding the functioning of the polar coastal zone are now out-dated, based on descriptive geomorphology and a limited process-based understanding. Currently, among many components of Arctic landscape adjusting to global warming, the coastal zone is probably the most critical one both in terms of rapidity of environmental change as well as importance for human communities living in circumpolar regions. This issue was often raised during the 4th International Polar Year 2007-2008 and encouraged the scientific community to focus on the state of cold region coasts in more detail. In this paper I summarize the most recent developments in Arctic coastal geomorphology with a particular focus on the Svalbard Archipelago and draw attention to the research challenges awaiting further investigation. This paper highlights the need for a greater understanding of the controls on High Arctic coastal geoecosystems, especially given the potential for accelerated warming and sea-level rise in the coming decades and centuries. Many of presented views benefited from discussions with Professor Andrzej Kostrzewski – to whom this volume is dedicated

The origin of sandstone boulder aprons along the escarpments of the Stołowe Mountains: are they all rockfall-derived? A new insight into an old problem using the CONEFALL 1.0 software

A characteristic feature of sandstone-capped escarpments in the Stołowe Mountains is the occurrence of extensive boulder mantles which extend from the rock face to the footslope over distances of 300–500 m. The hypothesis implying rockfall as the process of boulder release from the rock face and subsequent transport is tested by means of Conefall 1.0 software, designed to simulate run-out zones of rockfalls. The actual extent of boulder mantles is much larger than the simulated extent, which casts doubt on the applicability of rockfall scenario. Alternative hypotheses are briefly discussed and it is concluded that a similar morphological effect can be achieved by in situ caprock disintegration and sub-caprock slope lowering and retreat

Multidecadal (1960–2011) shoreline changes in Isbjørnhamna (Hornsund, Svalbard)

A section of a gravel-dominated coast in Isbjørnhamna (Hornsund, Svalbard) was analysed to calculate the rate of shoreline changes and explain processes controlling coastal zone development over last 50 years. Between 1960 and 2011, coastal landscape of Isbjørnhamna experienced a significant shift from dominated by influence of tide-water glacier and protected by prolonged sea-ice conditions towards storm-affected and rapidly changing coast. Information derived from analyses of aerial images and geomorphological mapping shows that the Isbjørnhamna coastal zone is dominated by coastal erosion resulting in a shore area reduction of more than 31,600 m2. With ~3,500 m2 of local aggradation, the general balance of changes in the study area of the shore is negative, and amounts to a loss of more than 28,000 m2. Mean shoreline change is −13.1 m (−0.26 m a−1). Erosional processes threaten the Polish Polar Station infrastructure and may damage of one of the storage buildings in nearby future

Decoding Complex Erosion Responses for the Mitigation of Coastal Rockfall Hazards Using Repeat Terrestrial LiDAR

A key factor limiting our understanding of rock slope behavior and associated geohazards is the interaction between internal and external system controls on the nature, rates, and timing of rockfall activity. We use high-resolution, monthly terrestrial light detection and ranging (LiDAR) surveys over a 2 year monitoring period to quantify rockfall patterns across a 0.6 km-long (15.3 × 103 m2) section of a limestone rock cliff on the northeast coast of England, where uncertainty in rates of change threaten the effective planning and operational management of a key coastal cliff top road. Internal system controls, such as cliff material characteristics and foreshore geometry, dictate rockfall characteristics and background patterns of activity and demonstrate that layer-specific analyses of rockfall inventories and sequencing patterns are essential to better understand the timing and nature of rockfall risks. The influence of external environmental controls, notably storm activity, is also evaluated, and increased storminess corresponds to detectable rises in both total and mean rockfall volume and the volumetric contribution of large (>10 m3) rockfalls at the cliff top during these periods. Transient convergence of the cumulative magnitude–frequency power law scaling exponent (ɑ) during high magnitude events signals a uniform erosion response across the wider cliff system that applies to all lithologies. The tracking of rockfall distribution metrics from repeat terrestrial LiDAR in this way demonstrably improves the ability to identify, monitor, and forecast short-term variations in rockfall hazards, and, as such, provides a powerful new approach for mitigating the threats and impacts of coastal erosion

Arctic rock coast responses under a changing climate

It has been widely reported that Arctic sea ice has decreased in both extent and thickness, coupled with steadily rising mean annual temperatures. These trends have been particularly severe along the rock coast of southern Svalbard. Concerns have been raised over the potential for higher energy storms and longer ice-free open water seasons to increase the exposure of Arctic coasts, and consequently the concentration of infrastructure critical to Arctic community survival, to enhanced rates of erosion. Here we present and apply innovative remote sensing, monitoring and process analyses to assess the impact of recent coastal climatic changes. High resolution analyses demonstrate that the small scale (<0.001 m3) changes that are rarely considered quantitatively exhibit geomorphic responses distinct from those of larger, more readily detected cliff failures. We monitor temperature depth profiles in both the shore platform and the cliff face to show rock sensitivity over time to both global and local influences. The results demonstrate the efficacy of thermal processes on Arctic rock cliffs relative to platforms, and may hold implications for understanding strandflat development rates. New three-dimensional thermography (thermal mapping) and process zone characterisation has been used to spatially assess the sensitivity of Arctic rock coast responses to contemporary processes on deglaciating coasts. Through the spatial and temporal analyses of key geomorphic behaviour zones and comparison over a range of sites, the complex and changing interplay between subaerial weathering and cryogenic and intertidal processes has been highlighted. These data challenge long standing assumptions over the future of Arctic rock coasts and identify new, focused lines of enquiry on the decline in cryogenic processes and understanding the sensitivity of Arctic rock coasts to climatic changes

Drift-dependent changes in iceberg size-frequency distributions

Although the size-frequency distributions of icebergs can provide insight into how they disintegrate, our understanding of this process is incomplete. Fundamentally, there is a discrepancy between iceberg power-law size-frequency distributions observed at glacial calving fronts and lognormal size-frequency distributions observed globally within open waters that remains unexplained. Here we use passive seismic monitoring to examine mechanisms of iceberg disintegration as a function of drift. Our results indicate that the shift in the size-frequency distribution of iceberg sizes observed is a product of fracture-driven iceberg disintegration and dimensional reductions through melting. We suggest that changes in the characteristic size-frequency scaling of icebergs can be explained by the emergence of a dominant set of driving processes of iceberg degradation towards the open ocean. Consequently, the size-frequency distribution required to model iceberg distributions accurately must vary according to distance from the calving front