Periodic Reporting for period 4 - OceaNice (Paleoceanography of the Ice-proximal Southern Ocean during Past Warm Climates)
Période du rapport: 2023-08-01 au 2024-07-31
OceaNice addressed the role ocean conditions around Antarctica had on past fluctuations in size of the Antarctic ice sheet. It focused on key past warm time intervals: The Pleistocene (1-0 Myr), the Pliocene (3.5-3 Myrs ago) and the mid-Miocene (17-14 Myrs ago). Oceanice groundtruthed the use of organic-walled dinoflagellate cyst assemblages to reconstruct past paleoenvironmental conditions: sea ice, sea surface temperature and nutrients/upwelling by augmenting surface sediment sample datasets and developing transfer functions to translate fossil dinocyst assemblages to past surface ocean conditions in an accurate, quantitative way. It then applies these tools together with biomarker proxies for SST to Pleistocene glacial-interglacial fluctuations, notably to investigate the latitudinal migration of ocean frontal systems. It further applies these proxies to Pliocene and Miocene sedimentary records, to investigate past surface ocean conditions. In conclusion, OceaNice met its main aim to develop and test the use of fossil dinoflagellate cysts for reconstruction of past ocean surface temperature, nutrients, sea ice and salinity conditions, even in a quantitative way. We have used these tools to provide a long-term history of the latitudinal position of ocean fronts throughout the Neogene, and this provides the much-needed context of ocean structure that can be tied to reconstructed dynamics of the Antarctic ice sheet. In doing so, we collaborated with ice sheet modelers who could demonstrate that the Miocene might not have had such strong increase in ice volume, but a change in geometry, whereby the icesheets reduced in height but extended in surface area, thereby advancing towards the coast. The project further targeted high-resolution reconstructions of ocean change in the Pleistocene and Pliocene, with some unexpected results: the magnitude of northward migration of fronts in the Indian Ocean during Pleistocene glacial maxima, and during glacial-interglacial transition prior to the mid-Piacenzian warm period. The most recent result from OceaNice targeted a surprising geologic question of the find of iceberg-rafted debris offshore an island in the Scotia Sea, in the Late Eocene, 3 million years prior to the onset of Antarctic glaciation. We demonstrate with particle trace experiments in a late Eocene ocean model that this island was in the middle of the track of icebergs out of the WEddell Sea, and that that ocean was cold enough to have mid-sized icebergs survive the ocean track to the island. This demonstrates the likelyhood that Late Eocene Antarctica was indeed already glaciated with marine terminated tongues that generated ice bergs, and puts Late Eocene Climate as well as the onset of Antarctic glaciation into a new perspective. Quite a bit of research results are still in the pipeline, expanding on the application of the new dinocyst-based proxy for ocean conditions.
Work performed in WP1:
1. Antarctic-proximal surface sediment sample compilation of dinoflagellate cysts. This project is completed with the publication of Thole et al., 2023
2. dinocyst-and biomarker-based reconstruction of the subtropical front latitudinal migrations around Tasmania. Data is complete, and writing of paper is still in progress. This paper demonstrates the use of dinocysts to reconstruct past migrations of frontal systems.
3. late Pleistocene paleoceanographic conditions offshore Sabrina coast, Antarctica. Data will be implemented in a multi-disciplinary paper that awaits some further analyses by collaborators
4. Compilation of Southern Ocean sea surface temperature reconstructions of MIS 10-12. All data gathered, paper almost submitted.
5. Reconstructing latitudinal SST gradients at MIS4-6. Paper by first author Ai is published in Nature Communications, with PI and Thole as co-authors. A spinoff of this project received additional funding from the NWO open science fund, in which all SST data from MIS 6–4 of the Southern Ocean will be compiled. Work is ongoing
6. Quantitative oceanographic reconstructions using modern dinocyst assemblages as training set. PD3 Schobben designed a shiny app OceanExplorer in this project, which is published. the transfer function work is currently expanded in a follow-up project, and shows promise.
Work performed in WP2:
1. Neogene paleoceanographic evolution of the Subtropical Front (ODP Site 1168).
Long-term Neogene evolution of the STF SSTs is published in Hou et al., 2022 Climate of the Past.
Long-term Neogene dinoflagellate cyst assemblage data and clumped-isotope-based deep-sea temperature and ice volume record published in Hou et al., 2023 Nature Communications.
High-resolution Oceanographic reconstruction across M2 glaciation and mid-Piacenzian warm period is published in Hou et al., 2025 Climate of the past.
2. Latitudinal migrations of the subtropical front at the Agulhas Plateau during the Pliocene (IODP Site U1475).
Paper led by PhD Hou is at its final stages of preparation. It contains an unprecedented high-resolution SST record across the mid-Piacenzian and reports the Agulhas Leakage trends throughout the Pliocene.
3. PhD Suning Hou received a doctoral degree from Utrecht University in 2024.
Work performed in WP3:
For WP3, the first project tracing ice bergs in the Eocene high-resolution model progresses is completed with the publication of the work by Elbertsen et al., 2025. First paper on the oceanographic consequences of the evolution of the Tasmanian Gateway and Drake Passage is now published (Sauermilch et al., 2023) with PD2 as PI.
1. Antarctic-proximal surface sediment sample compilation of dinoflagellate cysts. This project is completed with the publication of Thole et al., 2023
2. dinocyst-and biomarker-based reconstruction of the subtropical front latitudinal migrations around Tasmania. Data is complete, and writing of paper is still in progress. This paper demonstrates the use of dinocysts to reconstruct past migrations of frontal systems.
3. late Pleistocene paleoceanographic conditions offshore Sabrina coast, Antarctica. Data will be implemented in a multi-disciplinary paper that awaits some further analyses by collaborators
4. Compilation of Southern Ocean sea surface temperature reconstructions of MIS 10-12. All data gathered, paper almost submitted.
5. Reconstructing latitudinal SST gradients at MIS4-6. Paper by first author Ai is published in Nature Communications, with PI and Thole as co-authors. A spinoff of this project received additional funding from the NWO open science fund, in which all SST data from MIS 6–4 of the Southern Ocean will be compiled. Work is ongoing
6. Quantitative oceanographic reconstructions using modern dinocyst assemblages as training set. PD3 Schobben designed a shiny app OceanExplorer in this project, which is published. the transfer function work is currently expanded in a follow-up project, and shows promise.
Work performed in WP2:
1. Neogene paleoceanographic evolution of the Subtropical Front (ODP Site 1168).
Long-term Neogene evolution of the STF SSTs is published in Hou et al., 2022 Climate of the Past.
Long-term Neogene dinoflagellate cyst assemblage data and clumped-isotope-based deep-sea temperature and ice volume record published in Hou et al., 2023 Nature Communications.
High-resolution Oceanographic reconstruction across M2 glaciation and mid-Piacenzian warm period is published in Hou et al., 2025 Climate of the past.
2. Latitudinal migrations of the subtropical front at the Agulhas Plateau during the Pliocene (IODP Site U1475).
Paper led by PhD Hou is at its final stages of preparation. It contains an unprecedented high-resolution SST record across the mid-Piacenzian and reports the Agulhas Leakage trends throughout the Pliocene.
3. PhD Suning Hou received a doctoral degree from Utrecht University in 2024.
Work performed in WP3:
For WP3, the first project tracing ice bergs in the Eocene high-resolution model progresses is completed with the publication of the work by Elbertsen et al., 2025. First paper on the oceanographic consequences of the evolution of the Tasmanian Gateway and Drake Passage is now published (Sauermilch et al., 2023) with PD2 as PI.
Completed:
1. New compilation of surface sediment dinocyst assemblages demonstrating the strong relationship between dinocyst assemblages and surface ocean conditions (SST, nutrients, sea ice). Demonstration of an improved tool to reconstruct past conditions in the Southern Ocean
2. Application of this proxy to Pleistocene glacial-interglacial cycles (both ice-proximal and subtropical front)
3. Novel way of reconstructing Pleistocene frontal system change using paired latitudinally dispersed biomarker records
4. Evolution of the Neogene subtropical front at Tasmania, applies proxies under 1 and 2 to protray how the "gateway to the Southern Ocean" established, in context of ice-proximal conditions.
5. mid-Miocene evolution of bottom water temperatures at the subtropical front using clumped isotope geochemistry
6. mid-Pliocene evolution of the Agulhas system, showing how conditions changed in the agulhas oceanographic system, with profound implications for the transport of salt to the N Atlantic Ocean
7. Reconstruction of the paleoceanographic consequences of the widening of the Tasmanian Gateway.
8. Evaluation of late Eocene iceberg drift patterns using high-resolution ocean modelling and lagrangian iceberg tracing.
Expected beyond the end of the project:
1. Development of an open-source transfer function that uses surface sediment dinocyst assemblages as training set and quantifies past SST, sea ice conditions and nutrients. Work on this is ongoign in newly funded research projects
2. Quantification of oceanographic conditions (SST, nutrients, sea ice) for the Pleistocene Southern Ocean across MIS 4-6 and MIS 12-10. Work on this is ongoing in newly funded projects
1. New compilation of surface sediment dinocyst assemblages demonstrating the strong relationship between dinocyst assemblages and surface ocean conditions (SST, nutrients, sea ice). Demonstration of an improved tool to reconstruct past conditions in the Southern Ocean
2. Application of this proxy to Pleistocene glacial-interglacial cycles (both ice-proximal and subtropical front)
3. Novel way of reconstructing Pleistocene frontal system change using paired latitudinally dispersed biomarker records
4. Evolution of the Neogene subtropical front at Tasmania, applies proxies under 1 and 2 to protray how the "gateway to the Southern Ocean" established, in context of ice-proximal conditions.
5. mid-Miocene evolution of bottom water temperatures at the subtropical front using clumped isotope geochemistry
6. mid-Pliocene evolution of the Agulhas system, showing how conditions changed in the agulhas oceanographic system, with profound implications for the transport of salt to the N Atlantic Ocean
7. Reconstruction of the paleoceanographic consequences of the widening of the Tasmanian Gateway.
8. Evaluation of late Eocene iceberg drift patterns using high-resolution ocean modelling and lagrangian iceberg tracing.
Expected beyond the end of the project:
1. Development of an open-source transfer function that uses surface sediment dinocyst assemblages as training set and quantifies past SST, sea ice conditions and nutrients. Work on this is ongoign in newly funded research projects
2. Quantification of oceanographic conditions (SST, nutrients, sea ice) for the Pleistocene Southern Ocean across MIS 4-6 and MIS 12-10. Work on this is ongoing in newly funded projects