Mid- to Late Holocene climate variability and the 4.2 ka BP event on the Iberian Peninsula

Schirrmacher, Julien ORCID

In light of the ongoing global warming, it is crucial to gain knowledge on the spatio-temporal manifestation on past climate events from local to supra-regional scales and their effect on ancient societies. This knowledge is needed to significantly improve local, regional, and global simulations of future climate change and its societal impacts. Following this aim, this thesis investigates the hydro-climatic and sea surface temperature variability on the Iberian Peninsula and its adjacent seas as well as its effect on ancient societies during the Mid- to Late Holocene, particularly focusing on the 4.2 ka BP event. Paleo-climatic results are based on geochemical analysis of n-alkanes and alkenones from two marine sediment cores from the Gulf of Cádiz and the Alboran Sea as well as on a compilation of various paleo-climatic proxies, also from continental archives. The results show a long-term Holocene winter drying trend on the Iberian Peninsula as well as a winter cooling trend in the Atlantic realm. Both long-term trends were superimposed by pronounced seasonal sea surface temperature and precipitation events. For example, winter cooling events in the Gulf of Cádiz correlate with ice-rafted debris discharge during Bond Event 3, in particular. Instead, sea surface temperature variations in the Alboran Sea were local phenomena and could be related to the North Atlantic Oscillation. Moreover, the North Atlantic Oscillation was a major modulator of winter precipitation variability on the southern Iberian Peninsula with a positive mode of the North Atlantic Oscillation favouring dry events during winter and an increased proportion of local-sourced summer precipitation. However, the North Atlantic Oscillation likely did not modulate the 4.2 ka BP event on the Iberian Peninsula, because this event turned out to be a series of summer dry events between 4400 and 3800 cal. BP, which were restricted to the south-east of the Iberian Peninsula. Despite of being a regional coherent event on the south-eastern Iberian Peninsula, the 4.2 ka BP event did not dramatically impact ancient societies in the area. Instead, people have been very much dependent on winter precipitation as suggested by two regional declines in settlement intensity, which were contemporaneous with winter dry events.

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Schirrmacher, Julien: Mid- to Late Holocene climate variability and the 4.2 ka BP event on the Iberian Peninsula. 2020.

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