Universität zu Köln

Schaffernicht, Erik Jan (2018). Linkage between Dust Cycle and European Loess in the Last Glacial Maximum Determined by Atmospheric Model Simulations. PhD thesis, Universität zu Köln.

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Abstract

The Last Glacial Maximum (LGM) is a turning point of the Earth’s climate and the human dispersal. Yet, the then prevailing atmosphere dynamics over Europe and the North Atlantic as well as the mineral dust cycle in Europe are not well understood. This dissertation improves understanding the LGM climate and its dust cycle. Based on global climate simulations, it compares the LGM climatologies, jet stream, Circulation Weather Types (CWTs), and Combined Empirical Orthogonal Functions (CEOFs) with their present analogues. The dust cycle was reconstructed for Europe based on statistic dynamic downscaling using CWT frequency-conform regional Weather Research and Forecasting Model (WRF) simulations for the LGM. Proxies and reanalyses served to evaluate all simulations; among them a comprehensive compilation of loess-based reconstructed mass accumulation rates for the LGM. By comparing the simulated LGM depositions with these rates,linkage was established between the LGM dust cycle and the present loess. For the North Atlantic and Europe, the CEOFs suggest a lower LGM than present climate variability. The jet stream was narrower and partly more than 10 m/s faster there. Possible subsequent jet stream paths ran over and along the Nordic Seas, eastwards along the onset of the Central German Uplands or over the Mediterranean. The North Atlantic Oscillation (NAO) was 50% stronger combined with a 6° wider (westward) Azores High. The latitude-deviating LGM temperatures indicate that the North Atlantic Current extended up to Norway. Precipitation reduced by more than 150 mm/yr over the proglacial European areas; including a reduction of more than 300 mm/yr over the North Sea Basin. Near the EIS coast, periods of precipitation and temperatures that ranged below their climatological average synchronized with above-average precipitation periods over the Azores; both likely correlating with a below-average NAO. Similarly, stronger EIS High periods correlated with reduced precipitation and temperatures in western and central Europe. Combined with strong dry northeast sector winds, they favored erosion along the proglacial areas. Consistently, more frequent southerlies, cyclones, and east sector winds occurred in central and eastern Europe. This agrees with katabatic winds and the EIS-induced blocking that shifted the storm tracks southward. In contrast to the present westerlies, east sector winds (36%) and cyclones (22%) dominated central Europe. The east sector winds dominated the dust transport from the proglacial EIS areas to central Europe. In particular over western Europe, cyclones and strong — yet rare — west sector winds contributed in addition to the dust transport. Most dust was emitted from the Alps-, Black Sea- and EIS-bounded area. Its emissions culminated in proglacial central Europe with peaks of more than 100 kg m^(−2) yr^(−1) . The LGM dust plumes mainly ran westwards along the EIS margin. The highest aeolian depositions covered West Poland, the German Bight, and the North German Plain (between 1 and 100 kg m^(–2) yr^(–1) ). The significance of the east sector winds for the LGM is corroborated by the consistency of the simulated depositions and the mass accumulation rates reconstructed from more than 70 distinct loess sites across Europe.

Item Type:	Thesis (PhD thesis)
Creators:	Creators Email ORCID ORCID Put Code Schaffernicht, Erik Jan UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-90365
Date:	22 November 2018
Language:	English
Faculty:	Faculty of Mathematics and Natural Sciences
Divisions:	Faculty of Mathematics and Natural Sciences > Department of Geosciences > Institute for Geophysics and Meteorology
Subjects:	Natural sciences and mathematics Physics Earth sciences
Uncontrolled Keywords:	Keywords Language Mineral dust cycle English Last Glacial Maximum English Europe English Weather Research and Forecasting Model English WRF English Loess English Climate Proxies English Circulation Weather Types English Combined Empirical Orthogonal Functions English Principal Component Analysis English Statistic dynamic downscaling English MPI-ESM-P English Regional climate simulations English Max Plank Institute Earth System Model Paleo English Paleoclimate Modelling Intercomparison Project Phase 3 English Our Way to Europe English Collaborative Research Centre 806 English Sonderforschungsbereich 806 German
Date of oral exam:	24 July 2018
Referee:	Name Academic Title Shao, Yaping Prof. Dr. Pinto, Joaquim Prof. Dr.
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/9036