Clumped isotopes in planktonic foraminifera: application in a multiproxy North Atlantic study

• Main Author: Umbo, Stuart
• Format: Thesis
• Language: English
• Published: 2020
• Subjects: Greenland; Mira; Labrador Sea; North Atlantic; Planktonic foraminifera
• Online Access: https://ueaeprints.uea.ac.uk/id/eprint/81490/; https://ueaeprints.uea.ac.uk/id/eprint/81490/1/Stuart%20Umbo%20PhD%20thesis%20-%20Clumped%20Isotopes%20in%20Foraminifera.pdf; https://ueaeprints.uea.ac.uk/id/eprint/81490/2/SU%20Clumped%20isotope%20calibration%20dataset.xlsx; https://ueaeprints.uea.ac.uk/id/eprint/81490/3/SU%20U1302%20compiled%20dataset.xlsx

Robust experimental protocols for the clumped isotope analysis of foraminifera are established using the University of East Anglia’s Multi-Isotopologue-Ratio-Analyser (MIRA). Key advances include sample cleaning and preparation, development of a corrective algorithm to overcome a persistent sample size effect, and optimisation of standard measurements for projection of [delta]47 values onto the absolute reference frame. A foraminifera clumped isotope temperature calibration is derived through measurement of 25 Atlantic core top samples: [delta]47=0.0314 (±0.0027)×106/T2+0.3171 (±0.0332) The calibration shows good agreement with previous studies. However, measurement uncertainty remains too large for reliable temperature reconstructions. In addition, a high-resolution, multiproxy study of North Atlantic core MD99-2251 is conducted, offering exceptional resolution through MIS 4 – 2. It shows highly variable surface temperatures with numerous cold excursions. Comparison with nearby benthic δ13C records has provided additional detail on the relationship between ice rafting and oceanic ventilation. The AMOC shows evidence of suppression following H10, H6 and H4. The new ice rafting record has provided enhanced detail on specific Heinrich Stadial events, offering improved clarity on the timing and nature of H3 and H6 — as well as showing H5a, H7a, and H7b exhibit suppressed magnitude in comparison to other Heinrich events. The onset of cooling is shown to precede ice rafting, supporting the growing body of evidence that Greenland cooling acted as a driver of ice rafting, as opposed to being a symptom of it. Finally, a new multispecies stable isotope record of core U1302 from the Labrador Sea is presented, offering improved resolution and timing restraints on the Termination II transition and MIS 5e Plateau. Short lived isotopic excursions during Termination II reveal a ‘step-like’ transition. Comparison of the isotopic signatures of epipelagic and mesopelagic foraminifera species support earlier findings of a highly ...