Resolving the debate on a permanent El Niño-like state in the late Miocene: establishing equatorial Pacific conditions, driving forces and global impacts.

Informations projet

MIONIÑO

N° de convention de subvention: 796220

DOI

10.3030/796220

Projet clôturé

Date de signature de la CE 24 Avril 2018

Date de début 23 Avril 2019

Date de fin 30 Septembre 2022

Financé au titre de

• EXCELLENT SCIENCE - Marie Skłodowska-Curie Actions

Coût total

€ 183 454,80

Contribution de l’UE

€ 183 454,80

Coordonné par

UNIVERSITY COLLEGE LONDON
United Kingdom

Periodic Reporting for period 1 - MIONIÑO (Resolving the debate on a permanent El Niño-like state in the late Miocene: establishing equatorial Pacific conditions, driving forces and global impacts.)

Période du rapport: 2019-04-23 au 2021-04-22

Résumé du contexte et des objectifs généraux du projet

MIONIÑO aimed to resolve whether a permanent El Niño-like state, with warm waters spreading across the equatorial Pacific, existed during the Late Miocene. Today’s El Niño causes global climate anomalies, so past permanent El Niño-like states may have had serious, global consequences, such as widespread aridity. Late Miocene climate was similar to that predicted in IPCC projections for the year 2100. Hence, testing the existence of a Late Miocene permanent El Niño-like state may provide critical information for future climate evolution.

MIONIÑO tested the existence of a permanent El Niño-like state in the Late Miocene using geochemical microfossil records from recently recovered Western Pacific Warm Pool (WPWP) sediments and data synthesis to assess equatorial Pacific conditions, their driving forces and global impacts. MIONIÑO scientific objectives (SO) were threefold:
SO1. Examine whether a permanent El Niño-like state existed from 9.4-6.5 Ma.
SO2. Evaluate whether the transition to a La Niña-like state ~6.5 Ma was gradual or abrupt.
SO3. Assess the driving force & global climate impact of the reconstructed equatorial state.

MIONIÑOs research contributed to past and future climate change research. Resolving the debate on permanent El Niño-like conditions in the Late Miocene will discern whether warm El Niño events, as occurred in 2015/2016, become more frequent or evolve into a new mean state. Assessing causal links between permanent El Niño-like conditions and increased continental aridity will improve the models used for future climate predictions underpinning European climate mitigation and adaptation strategies. MIONIÑO can help us understand the true societal impact of more frequent or even permanent El Niño-like conditions.

Travail effectué depuis le début du projet jusqu’à la fin de la période considérée dans le rapport et principaux résultats atteints jusqu’à présent

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.

Progrès au-delà de l’état des connaissances et impact potentiel prévu (y compris l’impact socio-économique et les conséquences sociétales plus larges du projet jusqu’à présent)

MIONIÑO’s overarching goal and scientific objectives were successful and showed that in the Late Miocene, the equatorial Pacific Ocean experienced large shifts in long-term climate state, oscillating between prolonged El Niño-like and La Niña-like conditions. The foraminiferal data generated as part of MIONIÑO are the highest resolution data of their type for this time period and region. For the planktonic data, they even represent the highest resolution surface water records available for the 10-8 Ma interval of the Late Miocene.

Considering the impacts of modern El Niño and La Niña events on global precipitation patterns and industries such as fisheries and the associated global food supply, understanding the presence and consequences of prolonged late Miocene El Niño-like and La Niña-like intervals is relevant for those looking at anthropogenic climate change impacts. This relevance is increased when considering in that Late Miocene climate conditions are comparable to those predicted by IPCC projections for the year 2100. We expect MIONIÑO’s results to be of interest to Earth Scientists, climate modellers, as well as to future IPCC reports.

MIONINO logo (© Anna Joy Drury)