Testing climate synchronicity between Scotland and Romania since the last glacial maximum

• Main Author: Gheorghiu, Delia Mihaela
• Format: Thesis
• Language: English
• Published: 2012
• Subjects: GB Physical geography; GE Environmental Sciences; Ice cap; Ice Sheet; North Atlantic
• Online Access: http://theses.gla.ac.uk/3362/; http://theses.gla.ac.uk/3362/1/2012GheorghiudPhD.pdf; https://eleanor.lib.gla.ac.uk/record=b2934163

This thesis develops a chronology of ice retreat in the Monadhliath Mountains (Scotland) and Rodna Mountains (Romania) during the late Pleistocene using glacial geomorphology and surface exposure dating with cosmogenic 10Be. In the Monadhliath Mountains, 10Be exposure ages indicate deglaciation of the Last Devensian ice sheet at 15.1 ka (n = 2). Boulders from moraines in three Monadhliath cirques yielded exposure ages between 11.8 ka and 9.8 ka (470 – 600 m), suggesting that a Late Glacial readvance occurred during the Younger Dryas stadial (n = 9). The limited extent of these YD glaciers in the Monadhliath Mountains is explained in terms of the drier climate experienced by the eastern part of the Central Highland ice cap, but also in terms of local factors such as topography and snow blow. The resulting glacial reconstruction largely confirms that a SW to NE precipitation gradient dominated Scotland during the Younger Dryas. In the Romanian Carpathians, located at the southern periphery of the NW European ice sheet, there was only limited coverage of ice, mostly at higher elevations in the form of mountain glaciers. Field evidence suggests that during the last local maximum glaciation ice reached lower elevations than previously suggested in the Rodna Mountains. Glacially transported boulders were abandoned at 37.2 – 26.6 ka (n = 4) at an elevation of ~900 m. Glacial erratics and bedrock samples (n = 27) provide a consistent chronology for deglaciation during the Lateglacial, suggesting that ice retreated towards higher ground between 18.3 – 13.2 ka (1100 – 1800 m altitude). Final deglaciation took place at 12.5 - 11.2 ka (n = 9). These new chronologies are compared to other climate archives in Europe and the climatic oscillations recorded in the North Atlantic region. This analysis increases our understanding of past atmospheric circulation across Europe, and gives insights into the climatic forcing mechanisms during the last maximum extent of ice sheets and glaciers. During the last glacial episodes, the pattern of climate cooling from the western high latitudes towards the eastern mid latitudes was complicated, triggering different responses in local climates that appear to have been out of phase with the broader north-western European trend. Located in the NW Europe, Scotland was influenced by the wetter and colder conditions from the Atlantic which led to the expansion of the British Ice sheet during the global Last Glacial Maximum (LGM). However, smaller ice masses located further southwards and south-eastwards of the European ice sheet responded faster to the climatic oscillations in the North Atlantic region. During the LGM, the southward repositioning of the Polar Front and the presence of the ice sheet changed the atmospheric circulation across Europe. There was limited supply of moisture to the Rodna Mountains, especially because of blocking by the eastern Siberian high pressure system, and the glaciers experienced a slow retreat in a very cold and dry environment. However, a more synchronous Younger Dryas is likely to have occurred due to a more northern position of the Polar Front. This allowed for stronger wet and cold westerly winds to reach most of Europe at the same time.