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This thesis studies the potential impacts of lapse rate changes on the altitudinal thermal resource gradient in Northern England and hence of climate change on upland climate. The extreme marginality of the Pennine uplands in terms of climatic potential for plant growth is explained by reference to the maritime climate. Because the ground-based temperature lapse rate controls the altitudinal thermal resource gradient, the variation of daily temperature lapse rates by season and airflow is described, using 22 stations ranging from 8 to 847 metres above sea-level. Multiple regression models developed for each airflow in each month successfully describe surface temperature variation in most cases. Such models are used as a basis upon which to describe altitudinal variations in growing season parameters such as accumulated temperatures and frost frequency, for the present climate. Airflow scenarios, based on the regression models, describe the effects of changes in relative frequencies of airflow patterns. The altitudinal gradient in, and absolute values of, growing season parameters depend strongly on relative frequencies of Atlantic westerlies and more blocked conditions. Assuming the annual l000 dºC (degree-day) isotherm to represent the altitudinal limit to agricultural cultivation, individual annual elevations between 1801 and 1990 vary by over 300 metres. Extreme sensitivity to the circulatory pattern is also illustrated. Effects of temperature variability within airflows are at least as strong as those of mean conditions in many cases. The use of General Circulation Model output (UKHI 2 times C0(_2)) leads to strong changes in climatic potential. For example, few areas retain an annual temperature accumulation below 1000 dºC. Changes in frost parameters are also marked. Other climatic and non-climatic factors would have to be considered to predict land-use change. Preliminary analysis suggests that changes in other climatic elements (e.g. windiness or precipitation) will complement the effects of a temperature increase.

The focus of this thesis is former ice mass extent and evolution in the Wicklow Mountains, Ireland, during the Last Glacial-Interglacial Transition (LGIT; ~20-10 ka). Whilst previous research has established the existence of a local ice cap, confluent with the wider British-Irish Ice Sheet (BIIS) at the Last Glacial Maximum (LGM; ~24 ka BP), the nature of ice mass recession during the LGIT and subsequent glacier regrowth during the Younger Dryas (YD; 12.9-11.7 ka) requires evaluation. This thesis aims to produce the first regional assessment of the local palaeoglaciological record. The results of systematic geomorphological mapping, based on a combination of remote sensing and field techniques, are presented in the form of the first glacial geomorphological map of the Wicklow Mountains. The post-LGM evolution of local ice is examined based on an assessment of the geomorphological record, establishing the extent, style, and evolution of LGIT mountain glaciation during deglaciation. Using morphostratigraphic principles, two distinct phases of glaciation are recognised; (1) marginal cirque glaciation during the YD, and (2) sub-stages of more extensive topographically-restricted mountain glaciation earlier in the LGIT. A conservative approach based on an assessment of topographic setting, geomorphology, and radiation modelling indicates that the region hosted six small YD cirque glaciers. The glaciers had an average size of 0.39 km2 and covered a total area of 2.33 km2, based on their reconstruction using a combination of geomorphology and surface profile modelling. Reconstructed ELAs (Area-Altitude Balance Ratio; AABR 1.9 ± 0.81) range from 467 ± 9 m to 739 ± 8 m, with a regional average of 621 ± 9 m. Glacier-derived palaeoprecipitation calculations imply wetter conditions than at present. However, topoclimatic modelling demonstrates that local glacier mass balances were augmented by the redistribution of snow by wind and avalanching, and topographic shading, which artificially lowered ELAs. These processes were essential for marginal YD glacier initiation and survival. The style and pattern of wider LGIT ice recession is also established and identifies that local post-LGM ice did not recede and thin as one coherent ice mass. Instead, it separated into multiple topographically-controlled ice masses of different size (alpine icefield, plateau icefield, valley glaciers, and cirque glaciers) in coeval existence. Topography exerted a control on the pattern of local glacier recession and associated moraine distribution. A combination of topographic pinning points (i.e. topographic steps, lateral constriction, and tributary valley incursion), favourable slope gradients (0-15°), and changes in slope appear to have had an important influence on where moraines formed, implying an element of glacier stability at such locations. This provides further insight into non-climatic controls on moraine formation and presence/absence. This thesis delivers a more detailed understanding of post-LGM glaciation in the Wicklow Mountains. It provides clarification on the scale of YD glaciation and the impact of local topoclimatic processes on cirque glacier initiation and survival. It also provides insight into the significant role of topography in controlling retreat patterns and stability of ice masses, in response to climate amelioration throughout the wider LGIT.

The dearth of local scale data in remote high latitude areas means that regional scale data is commonly interpolated to fill the gap. These interpolations have limited accuracy due to the influence of complex topography and resultant decoupling of near-surface temperatures from regional free-air temperatures. Thus relatively little is known about how predicted regional temperature increases over the next century will likely influence local scale climates in subarctic Scandinavia. This thesis investigates local temperature variability in the incised valley area where the Kevo Subarctic Research Station (69°45'N, 27°01'E) is located. The main study area covered approximately 20km² encompassing the lake Kevojärvi and three incised valleys and an elevational range of 256m (74-330m a.s.l.). Near-surface temperature data were collected from a network of 60 temperature dataloggers for the period September 2007 to March 2012. NCEP/NCAR reanalysis data were used to reconstruct 6-hourly synoptic conditions for the study area. Lapse rates, principal component analysis and regression of surface temperatures on free-air temperatures were used to investigate present local temperature variability. The results were used to infer likely local scale temperature change assuming the strengthening westerlies and storm track predicted for the region. The data from the main network were also used to assess the representativeness of the Kevo Meteorological Station (established 1962). An additional network was set up to collect air and water temperature data from seven nearby lakes in order to validate air temperature estimations for the lakes, and to test a summer lake surface water temperature model based on air temperatures and theoretical solar radiation for remote lakes (June 2010 – September 2011). The results show a complex, highly variable temperature structure driven by the high latitude solar geometry, incised topography, variable land cover and synoptic conditions. Inversion conditions dominate temperature variability for most of the year, although with reduced influence during the polar day. Intense and persistent inversion events are a common feature of the winter months with gradients of +80°C/km not uncommon. The strongest inversion gradient was recorded at +92.4°C/km. Clear skies and low winds were the main controls of inversion formation during winter, but due to low temperatures (inhibiting convection) there was a weaker link between anticyclonic conditions and clear skies. Albedo induced steepening of lapse rates commonly gave day time lapse rates beyond -9.8°C/km (dry adiabatic) during March-May, with a peak of - 17.2°C/km measured. Diurnal temperature ranges for south facing low elevation sites were particularly large during the spring due to the daily inversion formation/destruction cycle (up to 30°C). During the ice-free period Kevojärvi had a significant influence on temperatures at low and mid elevations within the study area, resulting in a reversal of the usual day time strengthening of lapse rates. Due to its location in the valley bottom adjacent to Kevojärvi the meteorological station was not located in the most representative place in the local area (ranked 14/61), and certainly not representative of the wider area. The lake surface water temperature model showed good potential for future application. It was thought likely that predicted future synoptic changes in the region would act to inhibit inversion formation and intensity and so result in increased warming in the valley bottoms compared to the hilltops. Finally, due to the high frequency of inversion conditions and the resultant skew in temperature distributions, the reporting of lapse rates for areas such as this should be reported using median values, as mean values can be markedly different and therefore misleading.