Regional Climate Modelling over Europe at Glacial Times

The climate on Earth has continuously fluctuated throughout the world's history under the influence of internal and external forcing factors. A key challenge for climate science is the understanding of the different drivers and mechanisms that define the climate of the past and its fluctuations. Glacial climate states are of great interest in climate research as their conditions are highly different compared to today's climate. Climate modelling functions as a complementary tool to further investigate the role of forcing factors such as surface conditions in glacial climates. Global climate models are used to describe the Earth's system; however, they show wide disagreement when simulating the climate of the past over the continents. This disagreement may be related to a variety of factors, including the coarse model resolution and an incomplete representation of Earth system processes. The application of regional climate models improves the representation of these processes due to their higher spatial resolution. Still, the accuracy of the simulated regional climate strongly depends on the representation of the surface conditions in the models. Even though the surface conditions become more realistic, deviations can still be evident in the simulations, especially in precipitation. These biases may impact the results obtained through hydrological and glacier modelling that follows next in the modelling chain. Accordingly, the central goal of this thesis is to investigate the role of the glacial surface conditions in the European glacial climate using the regional climate model WRF. Two studies are carried out to achieve this central goal. An additional study presents a method to adjust deviations in simulated precipitation at glacial times, e.g., the simulated precipitation of the previous two studies. The first study assesses the importance of resolution and land{atmosphere feedbacks on the climate of Europe. To that end, a more accurate glacial land cover is generated using an asynchronous coupled land{atmosphere modelling experiment that combines a global climate model, a regional climate model, and a dynamic vegetation model. The regional climate and land cover models are run at high (18 km) resolution. The asynchronous coupling shows that the land{atmosphere coupling achieves quasi-equilibrium after four iterations. Simulated climate and land cover agree reasonably well with independent reconstructions based on paleoenvironmental proxies. This study determines the importance of land cover on the climate of Europe at the Last Glacial Maximum (LGM) using a sensitivity simulation with an LGM climate but present-day land cover. Results show that the LGM land cover leads to colder and drier summer conditions around the Alps and warmer and drier climate in southeastern Europe. This finding does not only demonstrate that LGM land cover plays an important role in regulating the regional climate, but it also indicates the need of using realistic glacial land cover estimates to accurately simulate the regional glacial climate. The second study investigates the sensitivity of the glacial Alpine hydro-climate to northern hemispheric and local ice-sheet changes. Therefore, sensitivity simulations are carried out with a 2 km horizontal resolution over the Alps for the LGM and the Marine Isotope Stage 4 (MIS4). During winter, the findings show wetter conditions in the southern part of the Alps under LGM conditions compared to present day. This wetting can be traced back to dynamical processes, i.e., changes in the wind speed and direction. In summer, drier conditions are found in most of the Alpine region during LGM. These drier conditions can be attributed to thermodynamic processes, i.e., lower temperatures. The MIS4 climate shows enhanced winter precipitation compared to the LGM, which is explained by its warmer climate compared to the LGM, i.e., by thermodynamics. An increase of the northern hemispheric ice-sheet thickness leads to a significant intensification of glacial Alpine hydro-climate conditions, which is mainly explained by dynamical processes. Changing only the Fennoscandian ice sheet is less influential on the Alpine precipitation, whereas modifications in the local Alpine ice-sheet topography significantly alter the Alpine precipitation. These findings demonstrate that the northern hemispheric and local ice-sheet topography are of great importance at regulating the Alpine hydro-climate. The third study presents a new correction method for precipitation over complex terrain that explicitly considers orographic characteristics. This method offers a good alternative to the standard empirical quantile mapping (EQM) method during colder climate states, in which the orography strongly deviates from the present-day state, e.g., at the LGM. The new method and its performance are presented for Switzerland using regional climate model simulations at 2 km resolution for present day and LGM conditions. In present-day conditions, the comparison between simulations and observations shows a strong seasonality and, especially during colder months, a height dependence of the bias in precipitation. The new method is able to fully correct the seasonal precipitation bias induced by the global climate model. A rigorous temporal and spatial cross-validation with independent data exhibits robust results. The application of the new bias-correction method to the LGM demonstrates that it is a more appropriate correction compared to the standard EQM under highly different climate conditions as the latter imprints present-day orographic features into the LGM climate. The last chapter of this thesis is dedicated to highlight some key results of the studies of this thesis and to outline possible follow-up studies and potential benefits for other studies and the scientific community

Geological structure, recharge processes and underground drainage of a glacierised karst aquifer system, Tsanfleuron-Sanetsch, Swiss Alps

The relationships between stratigraphic and tectonic setting, recharge processes and underground drainage of the glacierised karst aquifer system ‘Tsanfleuron-Sanetsch' in the Swiss Alps have been studied by means of various methods, particularly tracer tests (19 injections). The area belongs to the Helvetic nappes and consists of Jurassic to Palaeogene sedimentary rocks. Strata are folded and form a regional anticlinorium. Cretaceous Urgonian limestone constitutes the main karst aquifer, overlain by a retreating glacier in its upper part. Polished limestone surfaces are exposed between the glacier front and the end moraine of 1855/1860 (Little Ice Age); typical alpine karrenfields can be observed further below. Results show that (1) large parts of the area are drained by the Glarey spring, which is used as a drinking water source, while marginal parts belong to the catchments of other springs; (2) groundwater flow towards the Glarey spring occurs in the main aquifer, parallel to stratification, while flow towards another spring crosses the entire stratigraphic sequence, consisting of about 800m of marl and limestone, along deep faults that were probably enlarged by mass movements; (3) the variability of glacial meltwater production influences the shape of the tracer breakthrough curves and, consequently, flow and transport in the aquife

State-of-the-art in studies of glacial isostatic adjustment for the British Isles: a literature review

Understanding the effects of glacial isostatic adjustment (GIA) of the British Isles is essential for the assessment of past and future sea-level trends. GIA has been extensively examined in the literature, employing different research methods and observational data types. Geological evidence from palaeo-shorelines and undisturbed sedimentary deposits has been used to reconstruct long-term relative sea-level change since the Last Glacial Maximum. This information derived from sea-level index points has been employed to inform empirical isobase models of the uplift in Scotland using trend surface and Gaussian trend surface analysis, as well as to calibrate more theory-driven GIA models that rely on Earth mantle rheology and ice sheet history. Furthermore, current short-term rates of GIA-induced crustal motion during the past few decades have been measured using different geodetic techniques, mainly continuous GPS (CGPS) and absolute gravimetry (AG). AG-measurements are generally employed to increase the accuracy of the CGPS estimates. Synthetic aperture radar interferometry (InSAR) looks promising as a relatively new technique to measure crustal uplift in the northern parts of Great Britain, where the GIA-induced vertical land deformation has its highest rate. This literature review provides an in-depth comparison and discussion of the development of these different research approaches

Mavora : development of a planning process for reconciliation of interests in wilderness

Published by Centre for Resource Management for Tussock Grasslands and Mountain Lands Institute Lincoln College, New Zealand, September 1982.The Mavora Lakes area has been a subject of regional interest and some controversy for a number of years. Geographically, the Mavora is intermediate between an acknowledged zone of preservation and a zone of land development. Historically it represents a zone of interaction between different agency interests, notably those of the New Zealand Forest Service and those of both the nature conservation and pastoral administration and development arms of the Department of Lands and Survey. Extensive pastoralism as private enterprise has yielded ground in the district to pastoral development and farm settlement. The limits to this process have tended to be set by progressive experience on the land available for farm settlement. A working plan had been drafted for the adjacent Snowdon Forest. More active management planning for lands administered separately by these two major central government agencies served to bring into sharper contrast any differences between such development proposals if they remained ineffectively co-ordinated. Meanwhile the long-valued fishery resource of the Mavora Lakes and the Mararoa River has itself commanded greater attention because of increased use by anglers and the improved road access to the area which has itself increased boating and other shoreline recreation. While discharge from the lakes in the Mararoa River is being directed down-stream into Manapouri for power production, some thought has been given to using it in part to augment the summer low flows of the Oreti to Invercargill. Different communities of interest show varying degrees of support and aversion for the different kinds of resource use outlined above. Decisions are needed to determine the optimal use of resources before any further development which may irreversibly change the resources and their character

Applicability of ERTS-1 to Montana geology

The author has identified the following significant results. Late autumn imagery provides the advantages of topographic shadow enhancement and low cloud cover. Mapping of rock units was done locally with good results for alluvium, basin fill, volcanics, inclined Paleozoic and Mesozoic beds, and host strata of bentonite beds. Folds, intrusive domes, and even dip directions were mapped where differential erosion was significant. However, mapping was not possible for belt strata, was difficult for granite, and was hindered by conifers compared to grass cover. Expansion of local mapping required geologic control and encountered significant areas unmappable from ERTS imagery. Annotation of lineaments provided much new geologic data. By extrapolating test site comparisons, it is inferred that 27 percent of some 1200 lineaments mapped from western Montana represent unknown faults. The remainder appear to be localized mainly by undiscovered faults and sets of minor faults or joints

Present State and Prospects of Ice Sheet and Glacier Modelling

Since the late 1970s, numerical modelling has become established as an important technique for the understanding of ice sheet and glacier dynamics, and several models have been developed over the years. Ice sheet models are particularly relevant for predicting the possible response of ice sheets to climate change. Recent observations suggest that ice dynamics could play a crucial role for the contribution of ice sheets to future sea level rise under global warming conditions, and the need for further research into the matter was explicitly stated in the Fourth Assessment Report (AR4) of the United Nations Intergovernmental Panel on Climate Change (IPCC). In this paper, we review the state of the art and current problems of ice sheet and glacier modelling. An outline of the underlying theory is given, and crucial processes (basal sliding, calving, interaction with the solid Earth) are discussed. We summarise recent progress in the development of ice sheet and glacier system models and their coupling to climate models, and point out directions for future wor

Holocene Reconstruction of the West Greenland Current and the Greenland Ice Sheet Margin Near Disko Bay Using Foraminiferal Assemblages

The Greenland Ice Sheet (GIS) is currently thinning and retreating. One of the focal points for present research on the GIS retreat is Jakobshavn Isbrae, the largest ice stream on Greenland’s West coast, which is retreating today at least in part from ocean subsurface warming (Holland et al., 2008). Jakobshavn is located in Disko Bay, which receives warm Atlantic water from the West Greenland Current (WGC). In this thesis we present multi-proxy data from four marine sediment cores that help constrain the timing of ice retreat from the continental shelf and identify the marine conditions that accompanied retreat. Cores were taken in a transect from the outer shelf to near the mouth of the isfjord and basal dates give minimum ages of retreat from the shelf, bay sill, and near shore of 11.4, 11.1, and 9.4 cal kyr BP. Foraminiferal assemblages and IRD counts from these cores indicate that after rapid retreat of the GIS the region experience cold conditions. Atlantic waters, via the WGC were first felt in the bay sometime between 9 and 8.5 cal. kyr BP. A possible strengthening of the WGC is seen on the shelf at approximately 7.0 cal. kyr BP. A dramatic rise in calcareous fauna from 6.2 – 3.5 cal. kyr BP in all cores indicates a significant shift in the strength of the WGC, with warm, Atlantic associated fauna gradually increasing and peaking at 4.5 cal. kyr BP. This coincides with the believed retreat of Jakobshavn Isbrae behind its present margin (Weidick et al.,1990), suggesting that subsurface warming may have played a part in the ice stream’s retreat in the past. The region returns to colder conditions by 3.0 cal. kyr BP, indicating a late onset of neoglacial cooling

Gazing at the Solar System: Capturing the Evolution of Dunes, Faults, Volcanoes, and Ice from Space

Gazing imaging holds promise for improved understanding of surface characteristics and processes of Earth and solar system bodies. Evolution of earthquake fault zones, migration of sand dunes, and retreat of ice masses can be understood by observing changing features over time. To gaze or stare means to look steadily, intently, and with fixed attention, offering the ability to probe the characteristics of a target deeply, allowing retrieval of 3D structure and changes on fine and coarse scales. Observing surface reflectance and 3D structure from multiple perspectives allows for a more complete view of a surface than conventional remote imaging. A gaze from low Earth orbit (LEO) could last several minutes allowing for video capture of dynamic processes. Repeat passes enable monitoring time scales of days to years. Numerous vantage points are available during a gaze (Figure 1). Features in the scene are projected into each image frame enabling the recovery of dense 3D structure. The recovery is robust to errors in the spacecraft position and attitude knowledge, because features are from different perspectives. The combination of a varying look angle and the solar illumination allows recovering texture and reflectance properties and permits the separation of atmospheric effects. Applications are numerous and diverse, including, for example, glacier and ice sheet flux, sand dune migration, geohazards from earthquakes, volcanoes, landslides, rivers and floods, animal migrations, ecosystem changes, geysers on Enceladus, or ice structure on Europa. The Keck Institute for Space Studies (KISS) hosted a workshop in June of 2014 to explore opportunities and challenges of gazing imaging. The goals of the workshop were to develop and discuss the broad scientific questions that can be addressed using spaceborne gazing, specific types of targets and applications, the resolution and spectral bands needed to achieve the science objectives, and possible instrument configurations for future missions. The workshop participants found that gazing imaging offers the ability to measure morphology, composition, and reflectance simultaneously and to measure their variability over time. Gazing imaging can be applied to better understand the consequences of climate change and natural hazards processes, through the study of continuous and episodic processes in both domains