<strong>Constraining sea level oscillations in the Last Interglacial by modeling fossil coral reefs</strong>

Presented at the INQUA conference 2023 (Rome, Italy)    Constraining sea level oscillations in the Last Interglacial by modeling fossil coral reefs Denovan Chauveau1, Alessio Rovere1, Anne-Morwenn Pastier2 1Dipartimento di Scienze Ambientali, Informatica e Statistica Università Ca’ Foscari Venezia, Italy 2Helmholtz Centre Potsdam, German Research Centre for Geosciences (GFZ), Potsdam, Germany Understanding past sea-level (SL) oscillations is essential to gauge the future patterns of SL rise, in response to warmer climate conditions. Thanks to the good preservation and dating of fossil outcrops, the Last Interglacial (LIG; ~122 ka ago) is one of the best climate analogs to study the possibility of abrupt SL changes within an interglacial. The existence and magnitude of possible intra-LIG SL oscillations is a hotly debated topic. Indeed, some LIG coastal stratigraphic sequences, especially those stemming from coral reef terraces (CRTs), are characterized by abrupt shifts in geological facies or double/multiple stepped stratigraphies, which were hitherto interpreted as proxies for abrupt SL oscillations. To investigate whether these geological formations have an eustatic origin, we focused on modeling the processes and SL scenarios that may contribute to build such reef stratigraphies. For this purpose, we used two models:  DionisosFlow software (i.e., a forward stratigraphic model) and the code of Pastier et al. (2019; Geochemistry, Geophysics, Geosystems, 20(8); i.e., a kinematic model based on reef morphology). In our work, we first calibrated the CRT morphogenesis parameters (e.g., carbonate production/reef growth; sedimentation; marine erosion; rock foundation geometry, etc.) based on global reef observations. Then, we tested different SL scenarios (e.g., a stable SL highstand, a stable SL followed by a rapid jump, a double peak SL highstand, etc.). Finally, we compared modeled and observed stratigraphies, and investigated which parameter set, processes and SL scenario are most consistent with observations of double/multiple-stepped reef stratigraphies at different sites globally. Our results highlight that the morphology of CRT sequences provides fundamental observations to unravel past SL, including the possible intra-LIG SL oscillations. </p

Modeling fossil coral reefs to constrain sea level oscillations during the Last Interglacial maximum

Presented at BeGeo conference 2023 (3-6 October, Naples, Italy).Modeling fossil coral reefs to constrain sea level oscillations during the Last Interglacial maximumDenovan Chauveau1, Alessio Rovere1, Patrick Boyden2, Nikos Georgiou1, Ciro Cerrone1, Giovanni Scardino3,4, Silas Dean11Dipartimento di Scienze Ambientali, Informatica e Statistica Università Ca’ Foscari Venezia, Italy2MARUM – Center for Marine Environmental Sciences, University of Bremen, Germany3Department of Earth and Geoenviromental Sciences, University of Bari Aldo Moro, 70125 Bari, Italy4Interdepartmental Research Center for Coastal Dynamics, University of Bari Aldo Moro, 70125 Bari, ItalyKeywords: #sealevel #coralreef #coastalgeomorphologyUnderstanding past sea-level (SL) oscillations is essential to gauge future patterns of SL rise in response to warmer climate conditions. Due to good preservation and dating of fossil outcrops, the Last Interglacial (LIG; ~122 ka ago and with a global mean SL 6-9 m above the present level) is one of the best climate analogs to study the existence of abrupt SL changes within interglacials. This, in turn, allows for the distinction between natural perturbations in SL and those due to human activity. However, the existence and magnitude of intra-LIG SL oscillations is a hotly debated topic. Some LIG coastal stratigraphic sequences, especially those stemming from coral reef terraces (CRTs), are characterized by abrupt shifts in geological facies or double/multiple stepped stratigraphies, which were hitherto interpreted as proxies for abrupt, intra-LIG SL oscillations. Here, we utilize a multi-model approach to investigate whether these geological formations have a eustatic or land motion origin. To do this, we simulate the processes and SL scenarios that may contribute to build such reef stratigraphies within two model environments: DionisosFlow software (i.e., a 3D forward stratigraphic model) and the code of Pastier et al. (2019; Geochemistry, Geophysics, Geosystems, 20(8); i.e., a kinematic model based on reef morphology). As input, we test a wide range for each CRT morphogenesis parameter (i.e., reef growth rate, marine erosion rate, rock foundation geometry, etc.) and SL scenario. We then compare modeled and observed stratigraphies, and investigate which parameter set, processes, and SL scenarios are most consistent with observations of multiple-stepped reef stratigraphies, particularly at sites in the Caribbean (Aruba, Bonaire, Yucatan and the Bahamas archipelago). Our results highlight that the morphology of CRT sequences provides fundamental observations to unravel past SL, including the possible intra-LIG SL oscillations, and that these are key to understanding the current SL rise.</p

Ongoing Multi-method Investigations of Last Interglacial Sea Level

Presented at the "X Young Geomorphologists’ Day, III IAG International Young Geomorphologists’ Meeting & IAG Southern Europe Webinar – Venice 1-2 March 2024"Silas Dean1, Denovan Chauveau1, Ciro Cerrone1, Nikos Georgiou1, D.D.Ryan2, Karla Rubio Sandoval3, Alessio Rovere11Department of Environmental Sciences, Informatics and Statistics, Ca’ Foscari University of Venice, Italy2Department of Earth Sciences, University of Pisa, Italy3MARUM - Center for Marine Environmental Sciences, University of Bremen, Bremen, GermanyKeywords: Sea level change, climate change, last interglacial, MIS 5e, reef modelling, storm eventsThe Last Interglacial (LIG, Marine Isotope Stage 5e, ~125 ka) is a process analogue for a future warmer climate. Thousands of coastal relic landforms and deposits dating back to this period are studied today to obtain insights on pressing questions such as: What was the peak LIG sea level? Was the highstand characterised by single or multiple peaks? Were rapid sea-level changes triggered by sudden ice sheet collapses? The WARMCOASTS project has already compiled a large database of LIG sea-level proxies in the World Atlas of Last Interglacial Shorelines (WALIS), and investigation is also continuing using a number of methods including coral reef stratigraphic forward modelling, storm event and wave modelling, and field surveys for sea-level indicators in South and North America and the Caribbean. The results of this ongoing research may help refine our understanding of ice sheets and sea levels under warmer climate conditionsReferencesChauveau, D., Georgiou, N., Cerrone, C., Dean, S., & Rovere, A. (2024). Sea-level oscillations within the Last Interglacial: insights from coral reef stratigraphic forward modelling. https://doi.org/10.31223/X59T1VGowan, E. J., Rovere, A., Ryan, D. D., Richiano, S., Montes, A., Pappalardo, M., & Aguirre, M. L. (2020). Last interglacial (MIS 5e) sea-level proxies in southeastern South America. Earth System Science Data Discussions, 2020, 1-40.Pastier, A. M., Husson, L., Pedoja, K., Bézos, A., Authemayou, C., Arias‐Ruiz, C., & Cahyarini, S. Y. (2019). Genesis and architecture of sequences of Quaternary coral reef terraces: Insights from numerical models. Geochemistry, Geophysics, Geosystems, 20(8), 4248-4272.Rubio-Sandoval, K., Rovere, A., Cerrone, C., Stocchi, P., Lorscheid, T., Felis, T., ... & Ryan, D. D. (2021). A review of last interglacial sea-level proxies in the western Atlantic and southwestern Caribbean, from Brazil to Honduras. Earth System Science Data, 13(10), 4819-4845.Rovere, A., Ryan, D. D., Vacchi, M., Dutton, A., Simms, A. R., & Murray-Wallace, C. V. (2022). The world atlas of last interglacial shorelines (version 1.0). Earth System Science Data Discussions, 2022, 1-37.</p