| dc.description.abstracteng | The polar regions are important components of the Earth's climate system, as these areas are the main sources of fresh water on Earth. Any conflicts in that system can affect people's lives in different ways. Numerous studies show that global air temperature has increased, and it can lead to a global sea level rise due to polar ice-sheet mass loss. An increase in sea level in polar regions not only provides evidence of climate change, but also acts as a complex feedback mechanism between the Earth system components. This feedback can be used to predict what can happen in the future at different spatial and temporal resolutions. The ice core is an important climate archive that can help us to understand past climate conditions and we can use this information to predict future climate change using Earth climate modelling. There are numerous methods to investigate information from the ice core, Dielectric Profiling (DEP) recoded along the ice core is one such methods. Dielectric Profiling (DEP) is related to the impurity content of the ice core, such as acidity, salt, and ammonia concentrations or impurities caused by a volcanic event.
In this dissertation, I focus on measuring and processing the recorded permittivity and conductivity of DEP data and then use the data in different aspects of glaciology and paleoclimatology. This study investigates different ice core data, including The East GReenland Ice-core Project (EGRIP) as a first ice core from the upper region of the North-East-Greenland Ice Stream (NEGIS), the North Greenland Eemian (NEEM) ice core with the oldest reconstructed record from a folded core, and the North Greenland Ice Core Project (NGRIP) with the oldest undisturbed record in Greenland.
This dissertation established a first chronology of the EGRIP ice core over the Holocene and late last glacial period. The depth–age relationship of an ice core plays a key role in assessing the past Earth climate system. After field measurement in Greenland and processing the data set, I rely on DEP data and electrical conductivity measurements (ECM) and tephra records for the synchronization between the EGRIP, NEEM, and NGRIP ice cores. The synchronization was mainly of volcanic events and common patterns of DEP and ECM peaks. The timescale was transferred to the EGRIP ice core from the annual-layer-counted Greenland Ice Core Chronology 2005 (GICC05) timescale from the NGRIP core. This new timescale for the EGRIP is named GICC05-EGRIP-1.
Second, this dissertation investigates the internal architecture of the Greenland ice sheet by linking numerical forward modelling on the dielectric profile of ice cores and data derived from multi-channel ultra-wideband radar systems from the airborne survey. The modelling results have very good agreement with radio-echo sounding measurements. It was found that the internal reflections are mainly due to conductivity changes, and the across–-flow concentrated fabric in the deeper part of drill site (e.g., EGRIP ). Also, this study provides the possibility to determine ages for the reflectors, which can be considered as isochrone, and extend the dating from the drill site regions along the radar lines over large parts of northern Greenland.
Third, this dissertation evaluates extreme climate after the massive eruption of 'Alaska's Okmok volcano and its effect on human lives. In this way, unpublished DEP data from NGRIP2 and NEEM ice have been processed for the synchronization between ice cores. This volcano was evaluated based on the DEP, ECM, volcanic tephra data, and climate proxy records in six Arctic ice cores. The Earth system model simulations indicate that temperatures in Mediterranean regions were 7°C below normal during the two-year period after this massive eruption. The global cooling due to that eruption affected the lives of people in the late Roman Republic in 43 and 42 BC. | de |