The paleoglaciology of the Tibetan Plateau is still largely unexplored, despite its importance for regional and global climate reconstructions. In this thesis a comprehensive glacial geological record is presented from an extensive part of the northeastern Tibetan Plateau centred on the Bayan Har Shan. Glacial reconstructions for this region range from restricted mountain glaciers through the intermediate-size regional-scale Huang He ice sheet to a plateau-scale Tibetan ice sheet. To provide a robust basis for glacial reconstructions, this thesis provides conclusions based on two principle methods, remote sensing and field studies. The remote sensing of a 90 m resolution digital elevation model and 15- and 30 m resolution satellite imagery renders a detailed data set with complete spatial coverage of large- and medium-scale glacial landforms, and large-scale plateau geomorphology. Observations from fieldwork campaigns add detailed point information for the distribution of glacial deposits. Geomorphological glacial traces such as glacial valleys, glacial lineations, marginal moraines, meltwater channels, and hummocky terrain occur frequently in elevated mountain areas, indicating former alpine-style glaciations. Glacial deposits in the form of till, erratic boulders, and glaciofluvial sediments are common in areas with mapped glacial landforms, but also beyond, in areas lacking large-scale glacial landforms. For extensive plateau areas in-between formerly glaciated mountain blocks, there is a striking absence of glacial landforms and sediments, indicating that these areas, perhaps, never were ice covered. Interestingly, glacial deposits occur further away from the mountain blocks than the large- and medium-scale glacial landforms, indicating insignificant erosion beneath the maximum ice covers close to their margins. The large-scale geomorphology of the northeastern Tibetan Plateau is characterised by a low-relief plateau surface with glacial valleys in elevated mountain blocks and marginal steep V-shaped valleys. This geographical distribution indicates a dominance of glacial erosion in the elevated mountain areas and a dominance of fluvial erosion along the steep plateau margins, dissecting a relict plateau surface. The outline of the relict plateau surface mimics the proposed outline of the Huang He ice sheet, suggesting that the inferred ice sheet may represent a misinterpreted relict surface with scattered glacial traces. In conclusion, the glacial geology examined in the Bayan Har Shan region is consistent with paleo-glaciers of varying extent restricted to elevated mountain areas. Even though extensive icefields/ice caps were centred on discrete mountain areas, there is no indication that these ice masses merged but rather that they were separated from each other by unglaciated plateau areas. The presented glacial geological record will be used in further studies towards a robust paleoglaciological reconstruction for the northeastern Tibetan Plateau.

Global warming, with pronounced increases toward the poles and high latitudes, has impacts on alpine vegetation. If snow patterns change in response to global warming, snow parameters are predictors of interest in alpine plant species distribution and traits modeling because snow is known to strongly control the local growing conditions of alpine plants. Also, with technical advances some environmental variables can be produced using remote sensing instead of using field measurements. In this thesis, I investigate the role of snow persistence and wintertime snow depth in ecological modeling of alpine vegetation, derived from a mixture of satellite data and field data. The possibilities of using predictor data derived from remote sensing versus field measurements is also investigated in species modeling, with Landsat derived Land Surface Temperature and topography-based Wetness Index in comparison to punctual field measurements of temperature and soil moisture. Species presence, coverage and heights were collected in alpine Vindelfjällen from 90 plots of 1 m2, covering a range of 900-1450 m.a.s.l. and at varying distances to snow patches. A total of 186 models were generated for 10 species, with varying response variables and predictor combinations. The effect snow patches had was species specific. Snow parameters were statistically significant in half of the species distribution models (mostly snow persistence). Most species’ traits were best estimated not using snow parameters. Both temperature and soil moisture collected in the field can be replaced by corresponding predictors generated through remote sensing to create functioning models, which are also better at predicting species distribution and traits.

There has been confirmation in the last two decades, through instrumental measurements onboard satellites, that the 'solar constant' does, as has long been hypothesized, vary. While there is no consensus as to the best method for estimating past variations in solar output, it seems likely that over the last 500 years, the sun has played a role in the changing climate. However, there is little evidence to suggest that changes in irradiance are having a large impact on the current warming trend. A complementary approach of empirical and model-based analysis is used to determine if the climate effects of an estimated change in solar irradiance were significant in the pre-industrial era and what climate patterns emerge in response to reduced solar forcing at that time. Also investigated is the modification of solar-induced climate patterns by a hitherto underrepresented forcing - changes in Earth's orbit - and how solar and orbital forcing compare to that of increasing atmospheric greenhouse gas concentration. Finally a brief analysis of the effects of a Maunder Minimum-like solar irradiance on a climate forced by doubled CO2 is undertaken. Clear evidence is established herein for the ability of relatively small changes in solar irradiance to impact the global climate. Both at the century scale and at shorter periodicities, the variability of the solar 'constant' is influential in defining the global mean climate and more importantly, the regional characterization of that climate. Influencing the preferred mode of decadal variability, such as North Atlantic Oscillation, solar variability alters the mean climate for northern Europe and the North Atlantic region. The global response for temperature is found to be near-linear, while precipitation is more complex. Excitation of important feedbacks, such as sea-ice, plays an important role in determining the resulting pattern of response and ensures that even a much smaller forcing (solar variability) can exert a similar fingerprint to that of a larger forcing (greenhouse gases). Orbital forcing, typically excluded from model experiments for the decadal-to-centennial scale, is found to provide important modification of regional response and may be critical for determining a more accurate 'forecast' for future climate.

This study was designed with the overriding goal of improving our understanding of the nature, causes, and impacts of past climatic conditions in the High Arctic and to evaluate the potential impacts of future climatic warming. Specifically, the focus of this project was centered on Upper and Lower Murray Lakes (81° 21' N, 69° 32' W) on northern Ellesmere Island, Nunavut, Canada. Sediment cores were collected from each of the lakes in order to reconstruct past climate and environmental variability and space-borne synthetic aperture radar (SAR) data were used to evaluate recent variability in the ice cover of these lakes. The climatic setting and physical characteristics of Lower Murray Lake has led to the formation and preservation of annually laminated sediments (varves). Varve deposition began ca. 5200 calendar years BP and continued through 2004 AD, providing an annual record of sediment accumulation spanning the past 5200+ years. Annual mass accumulation was correlated to regional July temperatures providing a means of quantitatively evaluating past temperature changes in the region. The temperature reconstruction suggests that recent temperatures are ∼2.6°C higher than minimum temperatures observed during the Little Ice Age, maximum temperatures during the past 5200 years exceeded modern values by ∼0.6°C, and that minimum temperatures observed approximately 2900 varve years BC were ∼3.5°C colder than recent conditions. SAR observations of the ice cover Upper and Lower Murray Lake were used to assess the potential effects of past and future temperatures on lake-ice conditions. Under current climatic conditions the lakes average several weeks of ice-free conditions in August and early September, although in some years a continuous ice cover persists throughout the year. The relationship between summer temperature and ice melt at the lakes suggests that recent warming in the High Arctic has forced the lakes across a threshold from a state of perennial ice cover to seasonal melting. Projected future warming will significantly increase the duration of ice free conditions on Upper and Lower Murray Lakes. Ice-out is predicted to occur between 6 and 28 days earlier for every 1°C of warming.

No description available.

No description available.

No description available.

No description available.

No description available.

No description available.