Sea-level changes in the Last Interglacial. How high, how fast?

Poster presented at the INQUA 2023 meeting in Rome A Rovere (1,6),  DD Ryan (2),  M Vacchi (2), AR Simms (3), A Dutton (4), CV Murray-Wallace (5), K Rubio Sandoval (6), D Chauveau (1), S Dean (1), P Boyden (6), N Georgiou (1), C Cerrone (1) 1. Ca' Foscari University of Venice, 2. Department of Earth Science, University of Pisa, Italy, 3. University of California, Santa Barbara, 4. Department of Geoscience, University of Wisconsin-Madison (US), 5. School of Earth, Atmospheric and Life Sciences, University of Wollongong, NSW, 6. MARUM-Center for Marine Environmental Sciences, University of Bremen The Last Interglacial (LIG, Marine Isotopic Stage 5e, 125 ka) serves as a reference for understanding a future warmer climate. Currently, researchers are examining numerous coastal relict landforms and deposits dating back to this period to gain insights into two key questions: What was the highest sea level during the LIG? Did the LIG experience rapid sea-level changes due to sudden ice sheet collapses? The WARMCOASTS project, funded by the European Research Council, aims to enhance our understanding of sea-level variations during the LIG and contribute to addressing these questions.</p

<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 the Last Interglacial notch formation in Orosei, Sardinia: A Monte Carlo approach

 Scientists typically determine past sea level through studying (i.e. elevation measurement, age determination) fossilized marine organisms and sediment deposits which were formed near the sea level. However, these indicators only offer fragmented information about sea level in time and not a continuous sea level record. As a result, scientists often consider them as markers of the highest sea level reached in the past. To overcome this, we propose an innovative method consisting of a numerical model that reconstructs the shape of erosional indicators, such as cliff indentations (i.e., tidal notches) considering various factors that influence their shape. This allows us to create a continuous record of past sea level or fill the gaps left by limited on-site measurements. Our approach provides insight into the past sea level fluctuation and could potentially have broad applications in sea level research. </p

Sea level oscillations within the Last Interglacial: insights from coral reef stratigraphic forward modelling

Poster presented at EGU General Assembly 2024 (14-19 April, Vienna, Austria).Sea level oscillations within the Last Interglacial: insights from coral reef stratigraphic forward modellingDenovan Chauveaua, Nikos Georgioua, Ciro Cerronea, Silas Deana, Anne-Morwenn Pastierb, Alessio Roverea,caDepartment of Environmental Sciences, Informatics and Statistics, Ca' Foscari University of Venice, ItalybHelmholtz Centre Potsdam, German Research Centre for Geosciences (GFZ), Potsdam, GermanycMARUM, Center for Marine Environmental Sciences, University of Bremen, GermanyUnderstanding past sea-level variations is essential to constrain future patterns of sea-level rise in response to warmer climate conditions. Due to good preservation and the possibility to use various geochemical methods to date fossil sea-level index points, the Last Interglacial (Marine Isotope Stage (MIS) 5e; 130-116 ka ago) is often regarded as one of the best climate analogs for a future slightly warmer climate. Some MIS 5e coastal stratigraphic sequences, especially fossil coral reefs in tectonically stable areas, are characterized by abrupt shifts in their geological facies or steps within the reef topography, which have been often interpreted as proxies for abrupt sea-level fluctuations within the interglacial. However, the observational evidence and magnitude of such abrupt changes are controversial. Here, we run nearly 50 thousand simulations of a 2D kinematic reef model that can reproduce reef growth and demise through time. Our aim is to investigate the parameter space, the sea-level scenarios, and the processes by which double-stepped MIS 5e fossil reefs can form. Our results show that the only sea-level history that could explain the generation of an emerged MIS 5e backstepped reef is an abrupt rise in sea level, followed by a short-term peak. Any other multiple-stepped stratigraphy can be explained by the interplay between accommodation space, marine erosion, and bedrock slope, rather than by abrupt changes in sea level.</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

<b>Mollusk shells for AAR: Dating the Quaternary shorelines along the coastline of Camarones, Chubut Providence, Argentina</b>

Argentinean Quaternary beach ridges are rich in marine fossil shells. However, the deposits lack material commonly used for the age constraint of coastal deposits, e.g., sediments for luminescence analysis or coral for U/Th analysis. To date, numerical ages have been determined by electron spin resonance and U/Th analysis of shells of the marine mollusk Ameghinomya antiqua, applications for which there are concerns due to the uptake of uranium following organism death. The amino acid racemization (AAR) geochronology method analyzes the extent of protein degradation within shells and provides an estimate of the time elapsed since the cessation of protein formation, commonly equated with the death of the organism. The application of the AAR method to mollusk shells in geochronological studies of Quaternary marine and coastal deposits is well-established, providing relative ages to stratigraphic sequences in the form of D/L values. In this study, we use samples of Ameghinomya antiqua to assess its suitability for AAR analysis in six Pleistocene field sites along the coastline of Camarones’ locality in Chubut Province, Argentina. These field sites represent beach ridges with maximum elevations ranging from ~9 to ~30 m aHT. The D/L values indicate deposits from at least two interglacial periods, consistent with previously published results, i.e., MIS 5 and MIS 11, although some discrepancies are present. The AAR results also show mixed-age deposits, indicating reworking of older deposits into younger ones. Our initial results show that AAR analysis of A. antiqua is able to discern interglacial deposits of differing ages and can be used to assess and complement ESR and U/Th results.Video presented in the EBRAM-CLAMA Congress 2023</p