Periodic Reporting for period 4 - WARMCOASTS (Sea level and extreme waves in the Last Interglacial)
Reporting period: 2023-05-01 to 2024-10-31
The ERC StG "WARMCOASTS" project aims to enhance our understanding of the Last Interglacial period (125.000 years ago), that was characterized by a slightly warmer climate than today. During this period, global temperatures were slightly higher, resulting in smaller ice sheets and higher sea levels. The Last Interglacial serves as a "process-analog" for the potential impacts of a warmer future climate, despite being driven by different factors than the current warming trend caused by increased carbon dioxide levels. While we possess a broad understanding of the Last Interglacial climate, there are still uncertainties and debates surrounding key details. WARMCOASTS focuses on addressing three crucial open questions related to sea level and coastal changes during the Last Interglacial.
Firstly, the prevailing belief is that the sea level during this period was 6-10 meters higher than today. However, recent studies have highlighted significant uncertainties in this estimate, which must be resolved before utilizing Last Interglacial sea levels as a proxy for ice sheet melting in a warmer climate.
Secondly, there is debate about the existence of sea-level oscillations during a stable period within the Last Interglacial. Some studies propose that rapid ice-sheet melting caused these oscillations, while others reject this hypothesis. Understanding the nature and presence of these oscillations is crucial for assessing the sensitivity of ice sheets to small changes in polar temperatures.
Lastly, there is ongoing discussion regarding the occurrence of stronger sea storms/hurricanes in certain coastal regions during the Last Interglacial compared to today. Geological evidence supporting this hypothesis is limited to local contexts in the Bahamas and Bermuda, and further findings related to "stronger storms" are essential for predicting potential coastal damage under future climate conditions.
These three open questions share a common objective: advancing our knowledge of the Last Interglacial to determine the potential impacts on coastal areas as global temperatures continue to rise. WARMCOASTS is addressing these open questions through five Work Packages.
Firstly, the prevailing belief is that the sea level during this period was 6-10 meters higher than today. However, recent studies have highlighted significant uncertainties in this estimate, which must be resolved before utilizing Last Interglacial sea levels as a proxy for ice sheet melting in a warmer climate.
Secondly, there is debate about the existence of sea-level oscillations during a stable period within the Last Interglacial. Some studies propose that rapid ice-sheet melting caused these oscillations, while others reject this hypothesis. Understanding the nature and presence of these oscillations is crucial for assessing the sensitivity of ice sheets to small changes in polar temperatures.
Lastly, there is ongoing discussion regarding the occurrence of stronger sea storms/hurricanes in certain coastal regions during the Last Interglacial compared to today. Geological evidence supporting this hypothesis is limited to local contexts in the Bahamas and Bermuda, and further findings related to "stronger storms" are essential for predicting potential coastal damage under future climate conditions.
These three open questions share a common objective: advancing our knowledge of the Last Interglacial to determine the potential impacts on coastal areas as global temperatures continue to rise. WARMCOASTS is addressing these open questions through five Work Packages.
The WARMCOASTS project comprises five work packages (WPs) that collectively aim to investigate and analyze various aspects of the Last Interglacial (LIG) period.
Work Package 1 (WP1) successfully achieved the creation of a global database, called WALIS (World Atlas of Last Interglacial Shorelines). The database has been finalized and published in the open-access repository Zenodo. WALIS is composed by several regional databases, and each database is described by an accompanying paper published in a Special Issue in the journal Earth System Science Data. A database web interface was also published online and described in a manuscript in the journal "Open Research Europe". The database is being exploited, together with data from WP2, to achieve the objectives of WP3. All data and software related to WP1 are available open access.
Work Package 2 (WP2) focused on collecting new field data on Last Interglacial coastal geological sections across the Western Atlantic. Extensive field data collection was completed in Argentina, Brazil and the US East Coast, in close collaboration with local partners. Our data collection is at various stages of publication, and it will collectively encompass a transect from Patagonia (Argentina) to Virginia (USA). Additional field data related to Last Interglacial sea-level was collected in Madagascar, North Mediterranean and the Leeward Antilles (Aruba and Curacao).
Work Package 3 (WP3) aimed to analyze the data collected in WP1 and WP2 in conjunction with Dynamic Topography (DT) and Glacial Isostatic Adjustment (GIA) models to understand crustal movements affecting Last Interglacial shorelines. We participated to the refinement of DT models from the Argentinean shelf, and we worked to improve our understanding of reef isostasy processes (together with GIA and DT) in Australia. As part of this WP, we participated to the refinement of LIG peak sea-level estimates from the Bahamas, also investigating the potential source of meltwater during the LIG. This results of this work, together with data from WP1, are being exploited to explore global mean sea level patterns and source of meltwater during the LIG.
Work Package 4 (WP4) focused on using stratigraphic forward models to investigate intra-interglacial sea-level oscillations during the LIG. Dionisos FLOW model was tested using the study case of Madagascar, and work is ongoing to utilize this model in the ABC islands (Aruba, Bonaire, and Curacao) in the Southern Caribbean, where field data has been gathered to calibrate reef stratigraphic forward models. Further modeling work, using a simpler stratigraphic model, saw the completion of an ensemble of 50,000 2D kinematic reef models simulating coral reef growth. The results of this work show that the only sea-level history that could explain the generation of an emerged MIS 5e backstepped (i.e. double) reef is a first sea-level peak followed by an abrupt rise in sea level and a second short-term peak. Any other multiple-stepped stratigraphy can be explained by the interplay between reef growth, marine erosion, and bedrock slope. We also developed a model to replicate the formation of tidal notches under different sea-level scenarios, and obtained that, depending on the boundary conditions chosen, either synchronized or out-of-sync ice-volume shifts in Antarctic and Greenland ice sheets can reproduce the notch morphology.
Work Package 5 (WP5) aimed to identify and study landforms and deposits indicating wave intensity during the Last Interglacial. Fieldwork was carried out on a boulder ridge in Cape Verde to assess its suitability as a proxy for LIG storms, but its attribution to the LIG is uncertain. Hydrodynamic and coastal models are being employed to analyze beach ridge records from Argentina and Florida. We participated to a community effort to explore potential storm surge changes in the LIG with an hydrodynamic model coupled with a paleoclimate model reproducing LIG wind and pressure patterns.
Work Package 1 (WP1) successfully achieved the creation of a global database, called WALIS (World Atlas of Last Interglacial Shorelines). The database has been finalized and published in the open-access repository Zenodo. WALIS is composed by several regional databases, and each database is described by an accompanying paper published in a Special Issue in the journal Earth System Science Data. A database web interface was also published online and described in a manuscript in the journal "Open Research Europe". The database is being exploited, together with data from WP2, to achieve the objectives of WP3. All data and software related to WP1 are available open access.
Work Package 2 (WP2) focused on collecting new field data on Last Interglacial coastal geological sections across the Western Atlantic. Extensive field data collection was completed in Argentina, Brazil and the US East Coast, in close collaboration with local partners. Our data collection is at various stages of publication, and it will collectively encompass a transect from Patagonia (Argentina) to Virginia (USA). Additional field data related to Last Interglacial sea-level was collected in Madagascar, North Mediterranean and the Leeward Antilles (Aruba and Curacao).
Work Package 3 (WP3) aimed to analyze the data collected in WP1 and WP2 in conjunction with Dynamic Topography (DT) and Glacial Isostatic Adjustment (GIA) models to understand crustal movements affecting Last Interglacial shorelines. We participated to the refinement of DT models from the Argentinean shelf, and we worked to improve our understanding of reef isostasy processes (together with GIA and DT) in Australia. As part of this WP, we participated to the refinement of LIG peak sea-level estimates from the Bahamas, also investigating the potential source of meltwater during the LIG. This results of this work, together with data from WP1, are being exploited to explore global mean sea level patterns and source of meltwater during the LIG.
Work Package 4 (WP4) focused on using stratigraphic forward models to investigate intra-interglacial sea-level oscillations during the LIG. Dionisos FLOW model was tested using the study case of Madagascar, and work is ongoing to utilize this model in the ABC islands (Aruba, Bonaire, and Curacao) in the Southern Caribbean, where field data has been gathered to calibrate reef stratigraphic forward models. Further modeling work, using a simpler stratigraphic model, saw the completion of an ensemble of 50,000 2D kinematic reef models simulating coral reef growth. The results of this work show that the only sea-level history that could explain the generation of an emerged MIS 5e backstepped (i.e. double) reef is a first sea-level peak followed by an abrupt rise in sea level and a second short-term peak. Any other multiple-stepped stratigraphy can be explained by the interplay between reef growth, marine erosion, and bedrock slope. We also developed a model to replicate the formation of tidal notches under different sea-level scenarios, and obtained that, depending on the boundary conditions chosen, either synchronized or out-of-sync ice-volume shifts in Antarctic and Greenland ice sheets can reproduce the notch morphology.
Work Package 5 (WP5) aimed to identify and study landforms and deposits indicating wave intensity during the Last Interglacial. Fieldwork was carried out on a boulder ridge in Cape Verde to assess its suitability as a proxy for LIG storms, but its attribution to the LIG is uncertain. Hydrodynamic and coastal models are being employed to analyze beach ridge records from Argentina and Florida. We participated to a community effort to explore potential storm surge changes in the LIG with an hydrodynamic model coupled with a paleoclimate model reproducing LIG wind and pressure patterns.
Overall, the project has made significant progress in achieving its goals across multiple work packages, resulting in valuable datasets, publications, and ongoing research activities. WALIS is arguably the most extensive compilation of Last Interglacial sea-level index points to date. The data insertion interface we built for WALIS has no equals in the paleo sea-level community. Thanks to the support provided by PAGES (the Past Global Changes project), WALIS has been updated to include Holocene sea-level data, following existing Holocene database templates and best practices. The number of sea-level data points included in WALIS has surpassed those included in previous global compilations. Furthermore, WALIS is not static, and it will remain open to both new contributions and corrections of existing records as new data becomes available. The data collected in the context of WP2 encompasses a very wide goegraphic span, and is a solid base to gather new insights on sea-level peak during the LIG, as it is being done in WP3. The models adopted in WP4 and WP5, benchmarked with field data, are producing new insights on sea-level oscillations and wave intensity during the LIG.