To achieve MIONIÑO’s scientific objectives (SO1-SO3), six interwoven work packages were identified:
WP1. Project Management.
WP2. Training and Career Development.
WP3. Dissemination and Communication.
WP4. Late Miocene Stratigraphy and Astrochronology.
WP5. Reconstructing WPWP water column structure.
WP6. Presence of a permanent El Niño and the driving forces and impacts.
These work packages were designed to address four career objectives (CO1-CO4) identified to enhance the Fellow’s career. The scientific work packages WP4-6 focussed on generating high-resolution benthic and planktic foraminiferal stable isotope records from 9.4-6.0 Ma using Site U1488 samples and using this data to test the presence of permanent El Niño-like conditions, and their potential driving mechanisms and impacts.
All work packages were successful. WP1 and WP2 resulted in MIONIÑO’s effective implementation through successful project management and the Fellows training and career development. WP3 focussed on effective communication and dissemination of MIONIÑO results (see below). The main results of the scientific work packages are:
WP4: High-resolution benthic foraminiferal stable oxygen (δ18O) and carbon (δ13C) records spanning 10-6.1 Ma were generated for International Ocean Discovery Program (IODP) Site U1488 in the WPWP. This involved preparing, picking and analysing either Planulina wuellerstorfi or Cicibidoides mundulus from 1486 samples, taken after the Site U1488 splice was revised (Drury et al., 2021b, Proceedings of the IODP). The high-resolution benthic records were used to generate an astrochronology, which provided accurate age control for all MIONIÑO records. The U1488 benthic records were integrated with other improved Late Miocene stratigraphy (Westerhold, Marwan, Drury et al., Science; Drury et al., 2021a, Climate of the Past) to confirmed that the U1488 benthic record closely follows global patterns. A final publication summarising this is in preparation.
WP5: High-resolution planktonic mixed layer and thermocline foraminiferal δ18O and δ13C records spanning 9.5-6.1 Ma were generated at Site U1488. This involved picking and analysing both mixed layer Trilobatus sacculifer and thermocline Globogerina menardii from 1486 samples. The G. menardii record is awaiting final analyses, but the T. sacculifer δ13C and benthic δ13C records co-vary strongly, with the mixed layer record displaying high frequency productivity-driven variability. The T. sacculifer δ18O data becomes more negative than the benthic δ18O after 7.3 Ma. A publication summarising this is in preparation.
WP6: Using the new astrochronology and benthic δ18O record, the high-resolution U1488 mixed layer δ18O record was integrated with mixed layer δ18O data from IODP Site U1338 in the eastern equatorial Pacific. This E-W comparison resolved the Late Miocene permanent El Niño debate by showing that E-W δ18O gradients were low, e.g. El Niño-like, from 8.1 to 7.1 Ma, and were larger, e.g. La Niña-like, before 8.1 Ma and from 7.1 to 6.2 Ma (SO1). Indonesian Throughflow restriction was proposed as causing in La Niña-like conditions. Gradual tectonic changes would explain the gradual transition to La Niña-like conditions around 7.1 Ma (SO2-SO3). Finally, as MIONIÑO provide evidence that prolonged Late Miocene intervals of El Niño-like conditions existed (SO1), this likely drove long-term shifts in global precipitation patterns, and it may be the underlying cause of the variable Late Miocene aridity (SO3). A publication summarising this is in preparation.
MIONIÑO’s results were disseminated and communicated throughout in WP3. The Fellow attended and presented results at 14 conferences, workshops and meetings, and gave invited seminars and webinars. The Fellow was active on Twitter (@AstroAyJay), developed a project website and took part in a CycloPod podcast. MIONIÑO has three project-related publications (see publication section), with three further in press. The press release for the Westerhold, Marwan, Drury et al., 2020 Science paper received worldwide attention. The Fellow gave interviews for The Times and the BBC, and the story appeared in 37+ multi-lingual reports globally, including print articles in The Sun and The Times, and in the Geological Society’s Summer 2022 Geoscientist Online.
