Periodic Reporting for period 3 - RISeR (Rates of Interglacial Sea-level Change, and Responses)
Reporting period: 2022-02-01 to 2023-07-31
Global sea-level rise is one of our greatest environmental challenges and is predicted to continue for hundreds of years, even if global greenhouse-gas emissions are stopped immediately. However, the range, rates and responses to sea-level rise beyond 2100 are poorly understood. Current models that project sea-level rise centuries into the future have large uncertainties because the recent observations upon which they are based, encompass too limited a range of climate variability. Therefore, it is crucial to turn to the geological record where there are large-scale changes in climate. Global temperatures during the Last Interglacial were ~1oC warmer than pre-industrial values and 3-5oC warmer at the poles (a pattern similar to that predicted in the coming centuries), and global sea level was 6-9 m higher, far above that experienced in human memory.
Through the RISeR project, we will lead a step-change advance in our understanding of the magnitude, rates and drivers of sea-level change during the Last Interglacial, to inform both global and regional sea-level projections beyond 2100. Specifically we will:
1. Develop new palaeoenvironmental reconstructions of Last Interglacial sea-level change from northwest Europe;
2. Provide the first ever chronological constraints on the timing, and therefore rates, of relative sea-level change that occurred in northwest Europe during the Last Interglacial;
3. Use state-of-the-art numerical modelling to distinguish the relative contributions of the Greenland and Antarctica ice sheets to global sea-level rise during the Last Interglacial;
4. Provide estimates of the land areas and exposed populations in northwest Europe at risk of inundation by long-term (2100+) sea-level rise, providing high-end scenarios critical for coastal-risk management practice.
These ambitious objectives will result in a state-of-the-art integrated study of the most appropriate analogue for a critical global environmental challenge; future sea-level rise.
Through the RISeR project, we will lead a step-change advance in our understanding of the magnitude, rates and drivers of sea-level change during the Last Interglacial, to inform both global and regional sea-level projections beyond 2100. Specifically we will:
1. Develop new palaeoenvironmental reconstructions of Last Interglacial sea-level change from northwest Europe;
2. Provide the first ever chronological constraints on the timing, and therefore rates, of relative sea-level change that occurred in northwest Europe during the Last Interglacial;
3. Use state-of-the-art numerical modelling to distinguish the relative contributions of the Greenland and Antarctica ice sheets to global sea-level rise during the Last Interglacial;
4. Provide estimates of the land areas and exposed populations in northwest Europe at risk of inundation by long-term (2100+) sea-level rise, providing high-end scenarios critical for coastal-risk management practice.
These ambitious objectives will result in a state-of-the-art integrated study of the most appropriate analogue for a critical global environmental challenge; future sea-level rise.
Work over the first 2.5 years of the project has focused on two elements: i) the planning for and collection of sediment cores from the North Sea from which to be able to conduct laboratory analysis; and ii) the first steps towards computational modelling of ice sheet and sea-level change in the period before and during the Last Interglacial. Geophysical datasets collected for the offshore wind industry have allowed us to map the buried landscapes in the North Sea from the last ~140,000 years, near to the modern Dutch coast. Using this information we were able to identify locations from which to collect 5 sediment cores that extend up to 40 m below the sea bed. These cores capture landscape change in the North Sea region from cold conditions to the development of peatland, which was then was flooded due to relative sea-level rise during the Last Interglacial. The cores have been photographed and under gone initial non-destructive scanning and will provide the foundation of future detailed analysis to be able to reconstruct the rate and magnitude of sea-level change. Any relative sea-level change in the North Sea over glacial-interglacial cycles is predominantly the result of melt of ice sheets adding water to the oceans, as well as land-level changes as the weight of the ice sheets is removed during retreat from their glacial maximum. The second focus therefore has been been on modelling the Eurasian ice sheet during the glacial period which preceded the Last Interglacial; and the pattern and magnitude of solid Earth response to this ice sheet loading and unloading. The primary outputs from this period have been a paper in press mapping the margin of the penultimate glacial ice sheet in the North Sea from the offshore wind geophysical datasets, and a the collection of the cores.
The first 2.5 years of the project have provided the foundations for the second half of the project which will result in beyond state-of-the-art outcomes; and therefore have not in themselves been significant breakthroughs. However, we anticipate new relative sea level reconstructions for the Last Interglacial that specifically constrain the rate of sea-level change, and in turn the rate of ice sheet melt, which will be a significant outcome from the project. This will be accompanied by beyond state-of-the-art ice sheet and solid Earth modelling by which to constrain the magnitude of ice sheet melt during the Last Interglacial. We also anticipate developing long term (2300+) sea-level rise scenarios for NW Europe based upon these results.