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Future sea-level rise poses an existential threat for many river deltas, yet quantifying the effect of sea-level changes on these coastal landforms remains a challenge. Sea-level changes have been slow compared to other coastal processes during the instrumental record, such that our knowledge comes primarily from models, experiments, and the geologic record. Here we review the current state of science on river delta response to sea-level change, including models and observations from the Holocene until 2300 CE. We report on improvements in the detection and modeling of past and future regional sea-level change, including a better understanding of the underlying processes and sources of uncertainty. We also see significant improvements in morphodynamic delta models. Still, substantial uncertainties remain, notably on present and future subsidence rates in and near deltas. Observations of delta submergence and land loss due to modern sea-level rise also remain elusive, posing major challenges to model validation. ▪ There are large differences in the initiation time and subsequent delta progradation during the Holocene, likely from different sea-level and sediment supply histories. ▪ Modern deltas are larger and will face faster sea-level rise than during their Holocene growth, making them susceptible to forced transgression. ▪ Regional sea-level projections have been much improved in the past decade and now also isolate dominant sources of uncertainty, such as the Antarctic ice sheet. ▪ Vertical land motion in deltas can be the dominant source of relative sea-level change and the dominant source of uncertainty; limited observations complicate projections. ▪ River deltas globally might lose 5% (∼35,000 km 2 ) of their surface area by 2100 and 50% by 2300 due to relative sea-level rise under a high-emission scenario. Expected final online publication date for the Annual Review of Earth and Planetary Sciences, Volume 51 is May 2023. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.
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Progress and future directions in constraining uncertainties in sea-level projections using observations
Coastal planning, mitigation and adaptation efforts rely on credible sea-level projections generated by physical models. However, the large uncertainties in these projections pose a challenge for policymakers. Here we provide an overview of the main sources of uncertainty in model projections of sea-level change on multi-decadal to centennial timescales and we offer perspectives on the use of observations to narrow uncertainties. We propose several directions for future research, including improvements in emerging emulation techniques, more systematic quantification of uncertainty structure within both observations and models, lengthening observational records of processes, and expanding collaborations across physical and social sciences. Advancements in these areas are urgently needed, as the next phase of the Intergovernmental Panel on Climate Change assessment cycle gets underway.
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- Award ID(s):
- 2103754
- PAR ID:
- 10694964
- Author(s) / Creator(s):
- ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; more »
- Publisher / Repository:
- Springer Nature
- Date Published:
- Journal Name:
- Nature Climate Change
- Volume:
- 15
- Issue:
- 10
- ISSN:
- 1758-678X
- Page Range / eLocation ID:
- 1039 to 1051
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
-
Accepted Manuscript
- Journal Article:
- https://doi.org/10.1038/s41558-025-02437-4
