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

GB Physical geography;GE Environmental Sciences

Gheorghiu, Delia Mihaela ; Fabel, Derek

University:University of Glasgow

Department:School of Geographical and Earth Sciences

关键词: Last Glacial Maximum, Younger Dryas, Devensian glaciation, surface exposure dating, geomorphology, Monadhliath Mountains, Rodna Mountains, Scotland, Romania.;   

Others  :  http://theses.gla.ac.uk/3362/1/2012GheorghiudPhD.pdf

来源: University of Glasgow

【 摘 要 】

This thesis develops a chronology of ice retreat in the Monadhliath Mountains (Scotland)and Rodna Mountains (Romania) during the late Pleistocene using glacial geomorphologyand surface exposure dating with cosmogenic 10Be.In the Monadhliath Mountains, 10Be exposure ages indicate deglaciation of the LastDevensian ice sheet at 15.1 ka (n = 2). Boulders from moraines in three Monadhliathcirques yielded exposure ages between 11.8 ka and 9.8 ka (470 – 600 m), suggesting that aLate Glacial readvance occurred during the Younger Dryas stadial (n = 9). The limitedextent of these YD glaciers in the Monadhliath Mountains is explained in terms of the drierclimate experienced by the eastern part of the Central Highland ice cap, but also in termsof local factors such as topography and snow blow. The resulting glacial reconstructionlargely confirms that a SW to NE precipitation gradient dominated Scotland during theYounger Dryas.In the Romanian Carpathians, located at the southern periphery of the NW European icesheet, there was only limited coverage of ice, mostly at higher elevations in the form ofmountain glaciers. Field evidence suggests that during the last local maximum glaciationice reached lower elevations than previously suggested in the Rodna Mountains. Glaciallytransported 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 fordeglaciation during the Lateglacial, suggesting that ice retreated towards higher groundbetween 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 climaticoscillations recorded in the North Atlantic region. This analysis increases ourunderstanding of past atmospheric circulation across Europe, and gives insights into theclimatic 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 highlatitudes towards the eastern mid latitudes was complicated, triggering different responsesin local climates that appear to have been out of phase with the broader north-westernEuropean trend. Located in the NW Europe, Scotland was influenced by the wetter andcolder conditions from the Atlantic which led to the expansion of the British Ice sheetduring the global Last Glacial Maximum (LGM). However, smaller ice masses locatedfurther southwards and south-eastwards of the European ice sheet responded faster to theclimatic oscillations in the North Atlantic region. During the LGM, the southwardrepositioning of the Polar Front and the presence of the ice sheet changed the atmosphericcirculation across Europe. There was limited supply of moisture to the Rodna Mountains,especially because of blocking by the eastern Siberian high pressure system, and theglaciers experienced a slow retreat in a very cold and dry environment. However, a moresynchronous Younger Dryas is likely to have occurred due to a more northern position ofthe Polar Front. This allowed for stronger wet and cold westerly winds to reach most ofEurope at the same time.