Investigating the spatial variability of Abrupt Cooling Events during the Lateglacial Interstadial (c. 14.7 – 12.5 ka cal BP) in Britain and Ireland using chironomids and oxygen isotopes to assess potential forcing mechanisms. / Francis, Christopher.

2022.

Research output: ThesisDoctoral Thesis

Unpublished

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  • CF Thesis with corrections

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Abstract

NW Europe will become more susceptible to abrupt cooling events (ACE) due to a reduction in the strength of the Atlantic Meridional Overturning Circulation (AMOC) caused by anthropogenic warming (IPCC, 2021). The Lateglacial Interstadial (LGIS) (~GI-1; c. 14.7-12.9 kyr ago), a relatively warm period at the end of the last glaciation, provides an excellent opportunity to study centennial-scale ACEs which are potential analogues to future ACEs. Three centennial-scale ACEs are clearly expressed in the Greenland ice core records, however, the spatial variation in magnitude of these ACEs across the British Isles and continental Europe is poorly understood due to the paucity of high-resolution well-dated records with quantified temperature reconstructions. By studying the spatial expression of ACE magnitude, potential forcing mechanisms can be assessed.

Three sites were selected to improve the spatial coverage of LGIS sites in the British Isles: Crudale Meadow (Orkney), Llangorse (Wales), and Old Buckenham Mere (East Anglia). Chironomid and oxygen-isotope analysis was conducted at a high temporal resolution (~decadal), allowing for quantitative reconstructions of past climatic temperature change, insight into seasonal temperature change and understanding of hydrological regime shifts. All three sites have robust age models based on radiocarbon dated terrestrial plant macrofossils and/or tephrochronology.

Differences in the spatiotemporal signatures in the magnitude and abruptness of the observed ACEs indicate that each ACE has a unique combination of forcing mechanisms operating at different times. The early-LGIS ACE may have primarily driven by North Sea sea-ice amplification of cooling that originated in the NW Atlantic, while the late-LGIS ACE was potentially the result of oceanic forcing from the NW and NE Atlantic. During the Mid-LGIS, numerous ACEs occurred of varying amplitude and apparent timing. This study shows the important of combining high-resolution analysis and high-precision age models in order to understand regional patterns, and potential drivers, of ACEs.
Original languageEnglish
QualificationPh.D.
Awarding Institution
Supervisors/Advisors
Award date1 Jul 2022
Publication statusUnpublished - 2022

ID: 45845091