Periodic Reporting for period 4 - RISeR (Rates of Interglacial Sea-level Change, and Responses)
Reporting period: 2023-08-01 to 2025-01-31
Global sea-level rise is one of the most significant environmental challenges of the coming centuries, and it will continue long after greenhouse-gas emissions are reduced. However, predictions beyond 2100 remain highly uncertain because modern observations capture only a narrow window of climate variability. To improve long-term projections, it is essential to study periods in Earth’s past when temperatures and ice-sheet responses resembled those expected in the near future. The Last Interglacial is the most relevant such period: global temperatures were around 1°C above pre-industrial levels, polar regions were 3–5°C warmer (a pattern similar to that predicted in the coming centuries), and global sea level was 6–9 m higher.
The RISeR project set out to deliver a step change in understanding the magnitude, rates, and drivers of sea-level rise during the Last Interglacial, with the goal of informing long-term (2100+) coastal-risk assessments. The project aimed to:
1. Reconstruct Last Interglacial sea-level change in northwest Europe;
2. Provide the first chronological constraints on the timing and rates of relative sea-level change in this region;
3. Use advanced numerical modelling to determine how ice-sheet collapse in Greenland and Antarctica contributed to global sea-level rise;
4. Produce long-term sea-level rise scenarios for northwest Europe relevant to future coastal planning.
These objectives enabled an integrated reconstruction–modelling approach to understand one of the best natural analogues for future sea-level rise.
The RISeR project set out to deliver a step change in understanding the magnitude, rates, and drivers of sea-level rise during the Last Interglacial, with the goal of informing long-term (2100+) coastal-risk assessments. The project aimed to:
1. Reconstruct Last Interglacial sea-level change in northwest Europe;
2. Provide the first chronological constraints on the timing and rates of relative sea-level change in this region;
3. Use advanced numerical modelling to determine how ice-sheet collapse in Greenland and Antarctica contributed to global sea-level rise;
4. Produce long-term sea-level rise scenarios for northwest Europe relevant to future coastal planning.
These objectives enabled an integrated reconstruction–modelling approach to understand one of the best natural analogues for future sea-level rise.
Over the course of the project, we combined new geological data, innovative analyses, and state-of-the-art modelling to produce the most complete reconstruction of Last Interglacial sea-level change for northwest Europe to date. We made extensive use of offshore geophysical datasets acquired for the wind-energy sector, allowing us to map buried landscapes and former coastlines across the North Sea. These data were critical for identifying optimal coring locations and for reconstructing environmental change over the last ~140,000 years.
Five sediment cores up to 40 m long were collected from the Dutch sector of the North Sea. These cores captured the transition from cold, terrestrial conditions to widespread peat formation and subsequent flooding driven by Last Interglacial sea-level rise. Each core underwent high-resolution scanning, sedimentary analysis, and microfossil and geochemical investigation, providing robust indicators of both the magnitude and rates of relative sea-level rise. These data formed the foundation for several scientific advances, including new chronological constraints using luminescence dating and multiproxy palaeoenvironmental reconstruction.
Parallel to the geological analyses, we developed new ice-sheet and Earth-deformation models for the Eurasian Ice Sheet and its forebulge response. These improved the accuracy of relative sea-level corrections and provided a clearer separation of global ice-volume change from local land-level adjustments. The project also contributed to international datasets and modelling frameworks, including high-resolution sea-level databases and updated glacial isostatic adjustment models.
Key outputs included:
1. A new map of the penultimate glaciation margin in the North Sea;
2. The first temporally constrained reconstruction of Last Interglacial sea-level rise in northwest Europe;
3. New assessments of ice-sheet sensitivity and melt contributions during the Last Interglacial;
4. Improved methods for combining geophysical data, sediment cores, and chronological techniques;
5. Open-access datasets and model code supporting wider community use.
Collectively, the work significantly strengthened the empirical basis for understanding ice-sheet behaviour during warm periods and provided critical constraints needed for long-term sea-level projections.
Five sediment cores up to 40 m long were collected from the Dutch sector of the North Sea. These cores captured the transition from cold, terrestrial conditions to widespread peat formation and subsequent flooding driven by Last Interglacial sea-level rise. Each core underwent high-resolution scanning, sedimentary analysis, and microfossil and geochemical investigation, providing robust indicators of both the magnitude and rates of relative sea-level rise. These data formed the foundation for several scientific advances, including new chronological constraints using luminescence dating and multiproxy palaeoenvironmental reconstruction.
Parallel to the geological analyses, we developed new ice-sheet and Earth-deformation models for the Eurasian Ice Sheet and its forebulge response. These improved the accuracy of relative sea-level corrections and provided a clearer separation of global ice-volume change from local land-level adjustments. The project also contributed to international datasets and modelling frameworks, including high-resolution sea-level databases and updated glacial isostatic adjustment models.
Key outputs included:
1. A new map of the penultimate glaciation margin in the North Sea;
2. The first temporally constrained reconstruction of Last Interglacial sea-level rise in northwest Europe;
3. New assessments of ice-sheet sensitivity and melt contributions during the Last Interglacial;
4. Improved methods for combining geophysical data, sediment cores, and chronological techniques;
5. Open-access datasets and model code supporting wider community use.
Collectively, the work significantly strengthened the empirical basis for understanding ice-sheet behaviour during warm periods and provided critical constraints needed for long-term sea-level projections.
RISeR delivered several advances that moved the field beyond the previous state of the art. The integration of industrial geophysical surveys with academic sedimentological and chronological techniques produced a new class of high-resolution reconstructions for the North Sea basin. Novel luminescence dating approaches provided unexpectedly precise estimates of the timing and pace of early Last Interglacial marine inundation, allowing the first quantification of sea-level rise rates for this region. The project also advanced knowledge of solid-Earth deformation during major ice-sheet transitions, improving the reliability of regional sea-level reconstructions.
Modelling work produced refined estimates of melt contributions from Greenland and Antarctica and improved understanding of how ice sheets responded to sustained warming. These advances directly support long-term sea-level projection efforts. The project’s methodological innovations, including multiproxy coring strategies, geomorphological mapping, and chronological integration, have already been adopted by other groups and represent a substantial transfer of knowledge and capability.
Although some findings aligned with expectations, others were surprising, including evidence for faster-than-expected early Last Interglacial sea-level rise and a more complex pattern of landscape flooding in the North Sea than previously recognised. Together, these results contribute significantly to the scientific basis for assessing future high-end sea-level scenarios in northwest Europe and beyond.
Modelling work produced refined estimates of melt contributions from Greenland and Antarctica and improved understanding of how ice sheets responded to sustained warming. These advances directly support long-term sea-level projection efforts. The project’s methodological innovations, including multiproxy coring strategies, geomorphological mapping, and chronological integration, have already been adopted by other groups and represent a substantial transfer of knowledge and capability.
Although some findings aligned with expectations, others were surprising, including evidence for faster-than-expected early Last Interglacial sea-level rise and a more complex pattern of landscape flooding in the North Sea than previously recognised. Together, these results contribute significantly to the scientific basis for assessing future high-end sea-level scenarios in northwest Europe and beyond.