The session focuses on studies that explore the physical mechanisms of sea level rise and variability, as well as the underlying drivers, across timescales ranging from paleo records to high-frequency phenomena to long-term projections, using observations and/or model simulations. Research on linkages between sea level variability, heat and freshwater content, ocean dynamics, land subsidence, ice-sheet and glacier mass loss, and terrestrial water storage is welcome. We encourage studies addressing future sea level changes, including high-end projections from rapid ice-sheet mass loss, and those assessing short-, medium-, and long-term coastal impacts and their broader implications.
Orals: Tue, 5 May, 16:15–18:00 | Room F1
Coastal Louisiana, particularly the Mississippi River Delta region, faces some of the largest rates of relative sea-level rise worldwide (>9.3 mm/yr since 1947 at Grand Isle). These large rates are dominantly driven by (nonlinear) land subsidence, but larger-scale oceanic processes in the Gulf of Mexico and the adjacent North Atlantic have also contributed to these rates, particularly over the past ~15 years. In the past, relative sea-level rise in the region has usually been approximated by means of the Grand Isle tide gauge record even though it is well known that local processes, such as subsidence and hydrologically driven processes, can vary significantly locally. Here we introduce a set of thirty-one daily tide-gauge records maintained by the U.S. Army Corps of Engineers and located throughout southern Louisiana. However, there exist several inhomogeneities within these records, including undocumented datum shifts, which necessitated the development of a homogenization framework to properly analyze trends. Given the unique issues with the dataset, particularly the spatial isolation of some tide gauges, we develop a new approach using probabilistic principal component analysis to homogenize these records in place of the traditional buddy-checking approach. Significant spatial and temporal variability in long-term sea-level trends is found in these newly homogenized records. The Lower Mississippi Delta region (also known as the Birdsfoot) stands out with the largest long-term trends on the order of 35 mm/yr, more than three times the value obtained at Grand Isle and more than twenty times the value obtained from the global average. We identify subsidence as the main driver of these changes and provide new evidence that oil and gas withdrawals have significantly contributed to them.
How to cite: Hendricks, N. and Dangendorf, S.: Tide-Gauge Data Archaeology in Coastal Louisiana Reveals Relative Sea-Level Trends Up to Twenty Times the Global Average since 1950, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14501, https://doi.org/10.5194/egusphere-egu26-14501, 2026.
Abrupt changes at decadal time scale are recurrent events in the modern climate system. Using multiple trend-change detection methods, here we report such an abrupt trend change in the early 2010s in the altimetry-based global mean sea level record, as well as in its thermal and mass components. Abrupt trend change in the mass component is mostly due to terrestrial water storage and to a lesser extent to ice sheet melting. The linear rate of rise of the global mean sea level increases abruptly from 2.9 ± 0.22 mm yr-1 over 1993-2011 to 4.1 ± 0.25 mm yr-1 over 2012-2024. Abrupt trend changes in numerous climate parameters have also been reported in the early 2010s, suggesting a more global phenomenon. Internal climate variability is likely the main driver of the early 2010s sharp change observed in sea level and components, although one cannot totally exclude any additional contribution from increased radiative forcing.
How to cite: Leclercq, L., Oelsmann, J., Cazenave, A., Passaro, M., Jevrejeva, S., Connors, S., Legeais, J.-F., Birol, F., and Abarca-del-Río, R.: Abrupt trend change in global mean sea level and its components in the early 2010s, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3430, https://doi.org/10.5194/egusphere-egu26-3430, 2026.
Africa's coastal regions, already burdened by accelerating sea level rise, faced unprecedented threats from the 2023–2024 El Niño, which triggered record surges across marine domains while compounding a long-term regional increase of 11.26 cm since 1993. Here we analyze high-resolution satellite altimetry from 1993 to 2024. Our analysis reveals how anomalous winds suppressed coastal upwelling, sparking marine heatwaves. This drove a record upper-ocean heat buildup, quadrupling prior maxima, and produced a regional surge of 8.39 cm. Steric effects accounted for over 80% of the rise in the Atlantic and Indian Oceans, with thermal expansion dominating the steric signal, while in the Mediterranean, ocean mass changes played a nearly equal role. Thermal expansion was the overwhelming driver, with steric effects accounting for over 80% of the rise in the Atlantic and Indian Oceans, while in the Mediterranean, ocean mass changes played a nearly equal role. Critically, this event’s disproportionate impact demonstrates nonlinear amplification. Record ocean stratification, more than double that of previous super El Niños, trapped surface heat, intensifying the steric response. This is magnified by a post-2008 regime shift that increased sea level trends by 71%. Consequently, El Niño events now explain 24.7% of interannual variability, underscoring their growing dominance. This dynamic creates a compound threat for Africa’s vulnerable coasts: extreme flood risks from sea level rise and land subsidence (>3 mm/year) are coupled with collapsing marine productivity, demanding urgent adaptation in low-lying deltas and Small Island Developing States.
How to cite: Kemgang Ghomsi, F. E., Stroeve, J., Crawford, A., Tamoffo, A., Mouassom, F., and Ragoasha, M.: 2023-2024 El Niño amplifies record sea level surges in African marine domains, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13655, https://doi.org/10.5194/egusphere-egu26-13655, 2026.
Assessments of the global mean sea level (GMSL) budget over the satellite altimetry era (since the early 1990s) have concluded that the GMSL budget is closed within data uncertainties until 2016. However, studies have shown that since then, the sea level budget based on Argo data down to 2000 for the thermosteric contribution is no longer closed. Using an ocean reanalysis with no altimetry data assimilation, we show that accounting for deep ocean thermosteric contribution (below 2000 m, not sampled by Argo) allows the GMSL budget to be almost closed since 2016. The deep ocean contribution over 2005-2022 is estimated to 0.4 ± 0.15 mm/yr, i.e., about 10%. to the observed GMSL rise over that period. This finding reveals that deep ocean warming is gaining importance and that ocean heat uptake has now reached several regions below 2000m depth, notably the Northwestern Atlantic Ocean and areas around Antarctica.
How to cite: Cazenave, A., Yang, C., Bouih, M., Storto, A., Chen, J., Llovel, W., von Schuckmann, K., and Leclercq, L.: Evidence of increased deep ocean warming from a sea level budget approach, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3396, https://doi.org/10.5194/egusphere-egu26-3396, 2026.
The world’s coasts face the increasing risk of relative sea-level rise due to climate-induced sea-level rise and negative vertical land motion (i.e. land subsidence). The impacts of relative sea-level rise and coastal (and compound) flooding are closely related to the land’s elevation relative to sea level. Consequently, the reliability of relative sea-level rise impact and flood exposure assessment heavily relies on the correct alignment of land elevation data and sea-level information. However, this is often not the case.
Based on a systematic evaluation of the scientific literature (385 studies), we found that over 90% of contemporary sea-level rise and coastal hazard impact assessments do not apply sea-level information in addition to land elevation data and therefore fail to properly align land elevation to observed coastal sea level. From the 10% of the assessments that combined sea-level and land elevation data, 9% contain incomplete methodological documentation (rendering the study irreproducible) and/or contain flaws in vertical datum conversion and dataset combination. Less than 1% properly align sea level and land elevation and provide full methodological documentation. Our meta-analyses revealed sea-level height to be globally on average 0.3 m higher than commonly assumed, with a disproportionate impact on the Global South and differences of more than 1 m in most affected regions in the Indo-Pacific. This translates into worldwide 37% more land and up to 68% more people exposed to a 1 m relative sea-level rise. As many of the reviewed studies inform policy reports (e.g. IPCC reports), the widespread underestimation of coastal exposure may have far-reaching implications for policymaking and coastal adaptation.
Our findings reveal a community-wide methodological blind spot which calls for systemic, cross-disciplinary changes. To overcome the methodological challenges to properly align coastal land and sea-level information and prevent future errors, we provide properly combined coastal elevation information referenced to local sea level. To ensure proper data integration and reproducibility of coastal impact assessments, we also recommend to introduce author declarations and review checklists into the scientific peer-review process. These actions will raise community-wide awareness on the current blind spot, prevent future error propagation and improve transparency and reproducibility of impact studies. This will lead to improved future sea-level rise and other coastal hazard assessments and strengthen the scientific information available for policy-informing reports, like the upcoming IPCC AR7 reports.
How to cite: Seeger, K. and Minderhoud, P.: Coastal sea level higher than assumed in most sea-level rise impact assessments: Revealing a methodological blind spot, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6244, https://doi.org/10.5194/egusphere-egu26-6244, 2026.
Antarctica’s contribution to global sea-level rise is accelerating, yet projections from ice-sheet models continue to span a wide range despite sustained advances in resolution and physical realism. Using a coordinated ensemble of simulations from the H2020 European PROTECT project, we assess both the ability of six state-of-the-art ice-sheet models to reproduce observed Antarctic mass loss since the early 1990s and the extent to which present-day behaviour constrains future evolution.
Across most of the ice sheet, model agreement with observations is limited, reflecting strong sensitivity to model structure and internal dynamics rather than to external forcing alone. In sharp contrast, the Amundsen Sea sector of West Antarctica exhibits a persistent and robust relationship between modelled present-day mass-loss rates and projected sea-level contribution that extends to the end of the twenty-first century and beyond. This sector emerges as the only region where contemporary observations retain demonstrable predictive power for long-term outcomes, while elsewhere compensating processes dominate. Our results identify a fundamentally regional limit of predictability for the Antarctic Ice Sheet, highlighting where emergent constraints can meaningfully inform projections—and where uncertainty is likely irreducible with current models and observations.
How to cite: Mosbeux, C., Durand, G., Jourdain, N., Gillet-Chaulet, F., Caillet, J., Krinner, G., Nicholls, R., Amory, C., Boberg, F., Bevan, S., Berends, T., Cornford, S., Coulon, V., Edwards, T., Heiko, G., Kittel, C., Klose, A. K., Leguy, G., Lipscomb, W., and Mottram, R. and the PROTECT: On the predictability of Antarctica's contribution to sea level rise, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20445, https://doi.org/10.5194/egusphere-egu26-20445, 2026.
Current estimates of sea-level rise suggest nearly half a billion people could live on land vulnerable to temporary flooding by the end of this century, with potentially larger global populations, in addition to ecological and climatological threats, becoming more at risk in the far future when sea-level rise becomes increasingly dominated by melt from the Greenland (GrIS) and Antarctic (AIS) ice sheets. Long-term projections remain uncertain due to differences in models, process understanding and their parameterization with many simulations limited to only to 2100 or 2500 CE. Few studies have examined the multi-millennial response; those that do typically consider the GrIS or AIS alone and the focus is limited to global mean sea-level change, whereas spatial variations in sea-level and its implications for regional climate change are neglected.
Using the fast Earth system model CLIMBER-X, we perform idealized 50 kyr long simulations under pre-industrial CO2 concentrations, in which the GrIS, West Antarctic (WAIS), and combined GrIS+WAIS are progressively disintegrated following a realistic pattern of melt derived from previous studies. We repeat these disintegration experiments for different prescribed constant atmospheric CO2 concentrations, and target at changes in global mean near-surface temperature (ΔGMST) of 0–3 °C. Simulations start from a non-equilibrium state based on a dedicated transient simulation of the last glacial cycle with prescribed greenhouse gases and ice-load history, resulting in a present-day disequilibrium in bedrock elevation. These idealized experiments are able to quantify global and regional climate and sea-level response across varying levels of ice sheet melt and GMST change, as well as ocean thermal expansion.
First, we assess the individual impact of a GrIS+WAIS disintegration. Progressively disintegrated ice sheets leads to further warming on top of the targeted ΔGMST due to the albedo effect. However, we find that the added-up response from the individual ice sheet experiments do not reproduce the results from the GrIS+WAIS experiment, indicating the presence of nonlinear feedbacks when combined. There are significant interhemispheric differences, with regional temperatures in the added-up response from the individual ice sheet experiments differing by -13–3 °C when compared to the GrIS+WAIS experiment under pre-industrial CO2 concentrations. These numbers tend to grow as ΔGMST increases.
Second, we compare our experiments to those initialized from a pre-industrial equilibrium to assess the effect of bedrock uplift, differing spatial variations in sea-level, and coastline migration. Whereas bedrock uplift has little effect on ΔGMST, it partially compensates long-term inundation in areas like Northern Europe and Hudson Bay. Hazard maps of progressive inundation are shown for the different simulations, illustrating plausible future coastlines. A dedicated experiment with the complete disintegration of the GrIS+AIS (all ~65m) is also shown. The presented results highlight the sensitivity of regional climate and sea-level to ongoing cryospheric change, and provide a framework to assess the long-term effect of ice sheet melt in the Earth system.
How to cite: Kaufhold, C., Willeit, M., Albrecht, T., Klemann, V., and Ganopolski, A.: Changes in sea-level, regional climate, and future coastlines due to the progressive disintegration of the Greenland and West Antarctic ice sheets, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19879, https://doi.org/10.5194/egusphere-egu26-19879, 2026.
The socio-economic costs of sea level rise (SLR) are an important component of climate impact representations in integrated assessment models (IAMs). However, the representation of global or regional mean SLR and its impacts varies substantially between different IAMs; from no representation at all to the use of regionally resolved coastal impact models with more than 10,000 individual coastal segments. Current SLR impact models thereby often follow a cost-benefit analysis approach, might not represent diverse pathways of SLR impacts, or miss coastal adaptation. Especially, there is a lack of process-based models of SLR impacts with a focus on global, time-varying dynamics.
Here, we present a new modelling framework, the Feedback-based knowledge Repository for Integrated assessments of Sea level rise Impacts and Adaptation version 1.0 (FRISIAv1.0), a model designed for process-based, non-equilibrium IAMs. Its formulation for the calculation of global mean sea level rise is based on existing models, while its impact and adaptation component is a substantially modified derivation of the Coastal Impact and Adaptation Model (CIAM) for use in globally or regionally aggregated models. FRISIA follows a system dynamics approach, focusing on interconnectedness and feedback between components that is often missing in existing models. Examples of such additional connections included in FRISIA are: a reduction of local asset values and GDP per capita through the increasing storm surge damages, reduced investment in coastal zones under expected increases in exposure, and a limitation to the amount of money that can annually be spent on flood protection.
A version of FRISIA without these feedbacks approximately reproduces CIAM's results, while their integration leads to emerging new behaviour, such as a potential peak and decline in SLR-driven storm surge damages in the early 22nd century, due to economic feedbacks in the coastal zone. When coupling FRISIA to an IAM, global GDP is reduced by 1.5 - 6.2 % (17th - 83rd percentile range) under the mean SSP5-8.5 global-mean sea level rise from the IPCC's AR6 report (0.77 m by 2100) and no coastal adaptation, which is within the range reported in previous studies. We further show that the coupling of a diverse set of SLR impact streams into a process-based IAM allows the representation of a wide range of socio-economic consequences, such as effects on GDP, inflation, mortality or public debt.
As an outlook, we explore different adaptation strategies in a set of sensitivity simulations with FRISIA, focusing on the effect of delays and interruptions in flood protection investments on optimal SLR adaptation strategies. We find that both aspects can reduce the likelihood that a protect strategy (such as building a sea wall) is the optimal strategy, and we highlight the risk of a positive feedback loop of increasing SLR damage, reduced economic growth and reduced protection investments that might be triggered in some regions.
How to cite: Ramme, L., Blanz, B., Wells, C., Wong, T., Mauritzen, C., Schoenberg, W., Smith, C., and Li, C.: Feedback-based sea level rise impact modelling for integrated assessment models with FRISIAv1.0, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10322, https://doi.org/10.5194/egusphere-egu26-10322, 2026.
Sea-level rise (SLR) information and scenarios have improved greatly over the last few decades. This includes spatially explicit online tools which facilitate access for coastal risk and adaptation users. There is also a greater need to provide guidance on the use of this information including the median and extreme projections. In addition to SLR science aspects this also requires consideration of the user perspective and the diverse decisions that are using SLR information. Some would argue that the user perspective and needs are the starting point for such analysis. Key user issues include risk tolerance and timescale of the decision. Co-production of appropriate SLR information among practitioners, policymakers and SLR scientists will support well-informed choices concerning the appropriate SLR information and its application in coastal adaptation and practise. This is a key step in mainstreaming SLR adaptation to a routine, operational activity which is a priority as SLR accelerates. SLR projections around the median are increasingly well understood and consistent across sources, with growing confidence in the methods used to develop them. However, less likely high-end SLR responses remain uncertain, mainly reflecting knowledge gaps and quantitative uncertainties in the Greenland/Antarctic ice sheet components of SLR. Consideration of this information, where appropriate, is important to understand the range of risks and avoid maladaptation. Despite this uncertainty, many decisions on maintenance, upgrade and new adaptation actions need to be made today or in the near future before we expect this uncertainty to be significantly addressed. There is a danger of both under- and over-preparing for these tail risks. Different approaches to tackling decisions under uncertainty will be considered. Taking an adaptive (or multi-step) approach has many benefits implying a learning approach to adaptation and the need to assess the evolution of SLR over time in addition to projections. The implications for sea-level and associated ice sheet science will be considered.
How to cite: Nicholls, R., Lowe, J., Hinkel, J., and Hanson, S.: Sea-level rise scenarios and information to support effective risk assessment and adaptation planning, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20690, https://doi.org/10.5194/egusphere-egu26-20690, 2026.
Posters on site: Tue, 5 May, 10:45–12:30 | Hall X5
Most of the outer Norwegian arctic coastline is experiencing relative sea-level (RSL) rise despite being near-field areas with ongoing vertical land uplift due to glacioisostatic adjustment. However, due to a lack of pre-instrumental RSL-data over the last millennium, the transition from falling to rising RSL is not well constrained in time and space.
In this project we have reconstructed the past 500 years of RSL-history of the Vesterålen archipelago in northern Norway. We have analyzed salt-marsh sediments using preserved agglutinated foraminifera as proxy evidence of local RSL- change. Our data bridges the gap between the instrumental record and previous palaeo-RSL reconstructions and provides new insights into the recent sea-level history of the region.
Here, we will present our modeled RSL-curve and highlight our main results regarding when the transition from sea-level regression to the current sea-level transgression occurred, and the magnitude of post-industrial sea-level rise in the region.
How to cite: Lilienthal, O. E., Vasskog, K., and Nixon, F. C.: Documenting the transition from late Holocene relative sea-level fall to observed modern rise in Vesterålen, Northern Norway, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3382, https://doi.org/10.5194/egusphere-egu26-3382, 2026.
Regional sea-level change in the semi-enclosed Baltic Sea is strongly influenced by atmospheric forcing and wind-driven redistribution of water masses, leading to significant spatial variability in absolute sea level trends across the different sub-basins. This study focusses on absolute sea level trends in the Baltic Sea using satellite gridded sea level anomalies (0.0625º) from the European Seas Gridded L4 product provided by the E.U. Copernicus Marine Service (https://doi.org/10.48670/moi-00141). The daily time series (from January 1993 to the end of December 2023) are first deseasoned by removing the average annual cycle at each point. Then robust linear trends are estimated at each grid point by computing median slopes. In contrast to ordinary least-squares slopes characterising linear trends in the mean, these median slopes are calculated by minimising the mean absolute deviation of a linear trend model from the observations instead of the mean quadratic deviation, which makes them more robust to outliers and sensitive to the typical tendency of changes rather than to large deviations. Uncertainty is computed assuming non-independence by the Huber sandwich robust estimator for the covariance matrix.
The derived median slopes are in general higher than ordinary linear trends in the mean, except in the northern and easternmost areas of the Baltic. In the Bay of Bothnia ordinary linear trends and median trends are very similar, while in the eastern end of the Gulf of Finland median trends are similar or even slightly lower than ordinary linear trends. In the remaining areas, median trends are significantly larger than ordinary linear trends, the largest difference occurring in the Bothnian Sea. Coastal areas exhibit trends that differ from those in the adjacent basins. In the Gulf of Finland, median trends are higher than ordinary linear trends along the Finnish coast, whereas along the Roslagen coast (northern Stockholm Archipelago) the two slope estimates are in good agreement. Along the southern coastline of the Bothnian Sea, median sea-level trends reach the highest values, exceeding 6 mm/year.
The present study is financed within the scope of the Recovery and Resilience Mechanism (MRR) of the European Union (EU), framed in the Next Generation EU, for the period 2021 - 2026, within project NewSpacePortugal, with reference 11.
How to cite: Barbosa, S. and Donner, R.: Robust trends in Baltic sea level from satellite altimetry observations, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17399, https://doi.org/10.5194/egusphere-egu26-17399, 2026.
Oceanic nonlinearities drive random intrinsic sea level variations over the global ocean, which locally compete with forced sea level variations that are paced by atmospheric and astronomical drivers. This study utilizes a global ocean/sea-ice 50-member ensemble simulation to characterize the sea level mean seasonal cycle (computed over 1993-2015) and partition its forced and intrinsic components. The model faithfully represents many features of the observed sea level mean seasonal cycle. We show that the mean seasonal cycle of sea level is most stochastic in the Southern Ocean, in western boundary currents, and along +/-20° latitudes, and remains partly random up to 10°x10° scales in these regions. Forced and intrinsic components mostly have a steric origin but with deeper signals involved for the intrinsic term. Our study thus demonstrates that ocean nonlinearities give a marked stochastic flavor to the sea level seasonal cycle averaged over 23 years and illustrates the usefulness of eddying ocean ensemble simulations for adequately interpreting observations.
How to cite: Donatelli, C., Ponte, R. M., Penduff, T., Zhao, M., and Llovel, W.: Intrinsic ocean variability partly randomizes the mean seasonal cycle of sea level , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4116, https://doi.org/10.5194/egusphere-egu26-4116, 2026.
Patterns of sea level rise (SLR) and surface warming are tightly coupled, though strong S/N in SLR makes it ideal for identifying forced responses. While climate model ensembles provide an estimate of the forced SLR pattern, standard-resolution models poorly resolve key components of the coupled climate response, including ocean eddies and atmospheric and oceanic fronts. The importance of these small-scale features to regional SLR trends constitutes a major uncertainty in current simulations. Here, the improvements provided through high-resolution (HR) modeling are demonstrated using the recently released MESACLIP experiment, a 10-member ensemble spanning 1920-2100 that is unique for its HR atmospheric (0.25º) and oceanic (0.1º) components. Through comparison with standard-resolution simulations, including a nominal 1º version of the model used in MESACLIP, a fundamental alteration in both the pattern and magnitude of forced regional SLR in the MESACLIP simulations is demonstrated. Agreement between 30-year simulated trends and satellite altimetry is greatly improved and altimeter-era emergence of a La Niña-like forced response is identified in the Pacific and Southern Oceans. These findings suggest that forcing contributes significantly to the ongoing La Niña-like changes in the Pacific ocean and that significant improvements in forced climate change patterns, including those in regional SLR, can be realized through HR climate model ensembles.
How to cite: Fasullo, J. and Nerem, S.: High-Resolution Modeling Confirms a La Niña-like Forced Sea Level Response in CESM, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21975, https://doi.org/10.5194/egusphere-egu26-21975, 2026.
The Southern Ocean (SO) plays a crucial role in the global climate system by absorbing heat and carbon dioxide from the atmosphere. Understanding sea level changes and associated physical processes in the SO can provide valuable insights into how the ocean contributes to regulating Earth’s climate. Ocean dynamical processes are crucial for redistributing ocean heat and mass, thereby significantly influencing sea level change in the SO and globally. Here we investigate the mechanisms of thermal and ocean mass (ocean bottom pressure, OBP) variations, which are two important components of sea level variability. Observations show that since the 1950s, the subsurface South Hemishphere has been rapidly warming in the south and cooling in the north. A theoretical analysis and ocean model perturbation experiments indicates that the subsurface cooling is mainly attributed to pure heaving caused by wind stress change. In the SO, OBP variations explain most of large-scale sea level variations at seasonal-to-decadal time scales. Regional OBP variations are mainly driven by surface wind and regulated by the bottom topography. Strong OBP signals are located in the deep basins where closed planetary vorticity isolines present. At interannual time scales, OBP patterns in the SO are closely associated with El Niño-Southern Oscillation and Southern Annular Mode, which can indicate interannual variability of Antarctic Circumpolar Current transport to a great extent.
How to cite: Cheng, X.: Ocean dynamical processes underlying sea-level change and variabilityin the Southern Ocean, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4577, https://doi.org/10.5194/egusphere-egu26-4577, 2026.
Sea level is rising globally, threatening the world coastlines. In this context, it is of paramount importance to understand the physical mechanisms driving spatiotemporal coastal sea-level changes. The adaptation of the coastal sea level to seawater density changes in the open ocean remains, for example, rather poorly understood. The present talk is a contribution towards this understanding. In the flat-bottomed open ocean, density horizontal gradients yield alone the presence of geostrophic baroclinic circulation and spatial variations in steric sea level. At the margins of oceanic basins, the situation is very different. The presence of continental slopes is a vorticity barrier hindering baroclinic geostrophic transport towards the coast and accumulation or removal of water there. In addition, the steric sea level vanishes at the coast where the seafloor depth is zero. In the low-frequency limit, how coastal sea level can be impacted by open ocean density spatiotemporal changes is hence non-trivial and must involve ageostrophic mechanisms. Here, we show that seawater density gradients generate large along-slope currents because of the Joint Effect of Baroclinicity and Relief (JEBAR). The latter currents are slowed down by bottom friction, which in the process transmits the sea level – originally of open ocean and steric origin – to the coast as manometric changes. The framework used is the Arrested Topographic Wave theory extended to a baroclinic ocean.
How to cite: Diabaté, S. T., Fraser, N., and McCarthy, G.: Mediation of sea level from the open ocean to the coast, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13445, https://doi.org/10.5194/egusphere-egu26-13445, 2026.
Closing the global sea-level budget is a central goal of climate research, as failing to do so could indicate that some components are not properly assessed. Yet achieving agreement between the measured total sea-level rise and the sum of its contributions does not necessarily reflect consistency among the individual components. In this study, we compile and compare published estimates from the past two decades for ice-sheet and glacier mass balance, land water storage, and steric expansion, and complement them with mass‑change trends from GRACE-derived products.
For each component, we find a substantial spread among published estimates, often larger than the reported uncertainties. These discrepancies persist even in reconciled or community-based products, particularly in regions with limited observational coverage and where different methodologies, models, or datasets are used. This is especially visible for land water storage and ice-sheet mass balance, and in the last decade also for steric expansion.
These findings suggest that the closure of the sea-level budget can mask compensating errors among its components. Rather than undermining confidence, the aim of our work is to identify where efforts should focus in order to reduce uncertainties and strengthen future assessments of global sea-level change.
How to cite: Barletta, V. R., Bordoni, A., and Khan, S. A.: Review of Sea-Level Budget Components and Their Consistency in the Recent Literature, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13410, https://doi.org/10.5194/egusphere-egu26-13410, 2026.
Sea level rise is a key indicator of climate change and a major driver of coastal flooding and erosion. Reliable assessment of long-term sea level trends requires high-quality, internally consistent observations that account for instrumental changes and vertical land motion. In this study, we present the reprocessing of long-term tide gauge records around the Korean Peninsula to generate Level-2 (L2) delayed-mode sea level height data and assess recent multi-decadal sea level rise from a climate change perspective. Historical tide gauge observations from 21 coastal stations were reprocessed from the beginning of measurements to December 2024 using a comprehensive quality control framework. The reprocessing procedure includes station history investigation, residual comparison, relative sea level difference analysis with neighboring stations, and scientific interpolation of missing or abnormal data. To accurately quantify long-term sea level variability, vertical land motion associated with coastal structures and ground subsidence was evaluated using precise leveling surveys, GNSS-derived vertical displacement, and satellite-based SAR imagery, and applied as corrections to the sea level records. As a result, consistent hourly L2-quality sea level datasets with observation periods exceeding 30 years were reconstructed. Using the reprocessed datasets, sea level rise rates along the Korean coast were estimated. Over the past 36 years, mean sea level has risen at an average rate of 3.17 mm yr⁻¹, corresponding to an increase of approximately 11.5 cm. Regional variability is evident: rise rates of 3.06–3.6 mm yr⁻¹ are observed along the west and east coasts, while the south coast exhibits relatively lower rates of 2.6–3.4 mm yr⁻¹. Decadal analysis for the last 30 years (1995–2004, 2005–2014, and 2015–2024) reveals temporal and regional variations in sea level rise, with periods of acceleration and deceleration depending on coastal region. The reconstructed L2 sea level datasets provide a robust observational basis for climate change assessment, coastal hazard analysis, and ocean–climate interaction studies. The L2 data will be publicly released via the Korea Hydrographic and Oceanographic Agency in the first half of this year, supporting reproducible and policy-relevant sea level research.
How to cite: Jeong, K.-Y., Kim, H., Ham, H., Lee, H.-Y., Gu, B.-H., Seo, G.-H., and Cho, Y.-K.: Multi-Decadal Sea Level Rise along the Korean Coasts Based on L2-Quality Reprocessed Tide Gauge Observations, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8862, https://doi.org/10.5194/egusphere-egu26-8862, 2026.
This study presents long-term projections of global and regional sea level changes over the next one million years using a conceptual global sea level model, and evaluates the corresponding shoreline variations around the Korean Peninsula. The global ice-volume variations over the past one million years were first simulated using a conceptual global ice-volume model, and the modeled results show a strong correlation with proxy-based global sea level reconstructions, with correlation coefficients of –0.78 for the past 800 kyr and –0.81 for the past 500 kyr, confirming the model’s long-term reproducibility. Future simulations applying five Shared Socioeconomic Pathway (SSP) greenhouse gas scenarios indicate that under low-emission scenarios (SSP1–2.6 and SSP2–4.5), the next glacial inception is expected to occur approximately 50–60 kyr from the present. In contrast, under high-emission scenarios (SSP3–7.0 and SSP5–8.5), the onset of the next glaciation is delayed until 120–170 kyr in the future. Notably, the SSP5–8.5 scenario projects an exceptionally prolonged interglacial period lasting over 100 kyr, with a global mean sea-level rise of up to 24 m that persists for an extended duration. Based on these results, the future shoreline configurations around the Korean Peninsula were reconstructed. Depending on the scenario, global sea level is projected to rise by approximately 12–21 m within the next millennium, resulting in a marked inland retreat of coastlines, particularly along the western and southern coasts of Korea, including the Hwanghae and Chungcheong regions. After 50 kyr, certain scenarios show coastal expansion due to sea-level fall, while after 100 kyr, the progression toward the next glacial maximum leads to a complete exposure of the Yellow Sea basin.
How to cite: Kim, J.-H., Jun, S.-Y., Park, T., Park, W., Park, K., Han, Y., Jang, K., and Han, C.: Long-term Prediction of Sea-Level Changes around the Korean Peninsula over the Next One Million Years using a Conceptual Global Sea-Level Model, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6572, https://doi.org/10.5194/egusphere-egu26-6572, 2026.
Projections of future sea-level rise are critical for informing adaptation planning and risk assessments. However, physical modelling frameworks, due to significant computational requirements, lack the flexibility required for rapid analysis and exploration of the latest global emission scenarios. Data-driven and statistical sea-level emulators can fill this requirement and continue to calibrate themselves to the latest large physical modelling experiments, such as ISMIP, and literature evidence which is published in slower-time - while providing new insights derived from observational constraints and combinations of multiple lines of evidence. Here, we present multi-century sea-level projections using an enhanced version of the ProFSea sea-level emulator tool, and quantify human exposure under high and low-likelihood ice-sheet processes. Due to the flexibility, performance and probabilistic structure of the model, we can explore a large suite of scenarios as well as their observationally constrained counterparts, identify dominant sources of model and process uncertainty, and go further in our analysis to determine human-relevant impacts for vulnerable regions around the world. In addition, we push the emulator out-of-sample to explore its behaviour under idealised very-high emission and overshoot scenarios - a potentially critical limitation of non-physically based emulators.
How to cite: Weeks, J., Munday, G., Steinert, N. J., Khatri, H., Palmer, M., Gohar, L., and Perks, R.: Multi-century sea-level projections and human impacts under the indicative ScenarioMIP-CMIP7 forcings, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18937, https://doi.org/10.5194/egusphere-egu26-18937, 2026.
Simplified sea level modelling approaches are developed to efficiently explore future sea level rise and associated uncertainties. Sea level emulators (SLEs) are mostly calibrated against the responses of process-based complex models, they can be run on multi-century timescales and feed into regionalisation efforts, integrated assessment and coastal risk modelling. Here, we introduce the Sea Level Emulator Intercomparison Project (SLEIP) to systematically assess available sea level emulators and identify future research needs to maximise the utility of this modelling approach. SLEIP covers 13 datasets from the participating models BRICK (with DOECLIM and SNEASY climate forcing), FACTS (7 individual emulator workflows), FRISIA, MAGICC, ProFSea and SURFER. All of the participating SLEs produce projections out to the year 2300 for the main sea level drivers thermal expansion, glacier mass loss, Greenland and Antarctic ice sheet mass loss, and land water storage. Participating SLEs differ in whether and how they account for low-confidence, high-impact processes of poorly known likelihood, such as marine ice-cliff instability (MICI). The SLE components with the largest response range are the Greenland and Antarctic ice sheet, with the Antarctic ice sheet becoming the most uncertain sea level driver in 2300. With identical MAGICC climate forcing input, 2300 median global mean sea level rise estimates range from 0.46 m to 1.71 m (outer 17th-83rd percentile range: 0.32-3.20 m) under very low emissions (SSP1-1.9), 0.67 m to 2.01 m (0.47-3.56 m) under low emissions (SSP1-2.6), 1.64 m to 4.07 m (1.15-10.53 m) under moderate emissions (SSP2-4.5), 2.35 m to 9.33 m (1.68-14.39 m) under high emissions (SSP3-7.0), and 2.44 m to 11.16 m (1.74-15.79 m) under very high emissions (SSP5-8.5), all relative to 1995-2014. SLEIP also allows investigating the sea level response under overshoot. Under the overshoot scenario SSP5-3.4-OS (peak GMT: 2.3 °C, 2100 GMT: 1.9 °C), median projections range from 0.45 m to 0.86 m (0.36-1.31 m) in 2100 and 0.80 m to 2.30 m (0.56-9.82 m) in 2300.
How to cite: Nauels, A., Möller, T., Couplet, V., Kopp, R. E., Kumar, P., Mengel, M., Munday, G., Nicholls, Z. R. J., Palmer, M. D., Ramme, L., Slangen, A. B. A., Smith, C., Weeks, J. H., and Wong, T. E.: Assessing emulated multi-century global mean sea level projections - the Sea Level Emulator Intercomparison Project (SLEIP), EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6946, https://doi.org/10.5194/egusphere-egu26-6946, 2026.
Accurate modelling of monsoon and storm surge heights is crucial for effective coastal and climate resilience management in Singapore. Despite advances in climate modeling and hydrodynamic simulations, systematic biases remain a challenge, often resulting in under- or overestimation of extreme events and coastal hazards. Bias correction is crucial to improve the accuracy of projections. This study explores the application of several bias-adjustment techniques—mean bias correction, variance scaling, and quantile mapping—to improve the accuracy of monsoon and storm surge projections along Singapore’s coastlines. Mean bias correction adjusts the model output to match the observed mean better, whereas variance scaling further refines the distribution by adjusting the model output variance to match the observed variance. Quantile mapping provides a comprehensive approach by modifying the entire distribution of model outputs to match the observed distribution, creating a mapping between the model's Cumulative Distribution Function (CDF) and the observed CDF, which improves the simulation of both median and extreme values. In this study, outputs from the Delft3D FM hydrodynamic model, driven by atmospheric forcings from the Singapore Variable Resolution – Regional Climate Model (SINGV-RCM), which employs six global climate models (GCMs) from the CMIP6 climate projections, were compared with observed data at multiple tide gauge stations in the region. We applied these bias-correction methods individually to historical simulations (1984-2014) and in combination to project future monsoon and storm surge heights (2015-2100). The corrected projections are evaluated through statistical metrics and comparison with historical observations, demonstrating significant improvements in model accuracy and reliability. Our results highlight that quantile mapping provides the most comprehensive bias correction, capturing the full distribution of extreme events, while mean bias correction and variance scaling offer simpler, computationally efficient alternatives.
How to cite: Samsami, F., Tkalich, P., Dandapat, S., and Xu, H.: Enhancing Coastal Hazard Projections in Singapore: Application of Bias Correction Techniques for Monsoon and Storm Surge Modeling, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2657, https://doi.org/10.5194/egusphere-egu26-2657, 2026.
Extreme sea levels (ESLs) pose severe flood risks to coastal communities. Climate change is amplifying these risks as sea level rise (SLR) will increase the probability of given baseline ESL events. This will challenge coastal design standards relying on fixed return periods, as this assumption becomes obsolete under rapidly changing climate conditions. This study evaluates how future SLR will transform ESL return periods and compress the windows for adaptation along the German Bight at the North Sea coast.
Using data from the coastDat-2 hindcast – a high-resolution dataset of water levels and waves for the North Sea region – we performed statistical analyses to derive return curves for regional ESLs, linking return heights to their corresponding return periods. These return curves were then combined with sea level projections from the Sixth Assessment Report (AR6) of the Intergovernmental Panel on Climate Change (IPCC) under various global warming scenarios. From this integrated analysis, we calculated two key metrics: amplification factors (AFs) and timings. The AFs quantify how much more probable a baseline event will become under future SLR conditions, whereas the timings describe the available timeframe before a specific amplification threshold is exceeded, providing valuable information about windows for adaptation planning.
Our results demonstrate that AFs across the study region increase substantially with higher warming levels, dramatically raising the probability of baseline ESL events becoming commonplace. Timings also shrink considerably under rising temperatures, highlighting the accelerating urgency for proactive adaptation measures. Importantly, we also identified significant regional variability in how coastal locations respond to SLR. Locations with lower baseline ESL return heights – associated with smaller tidal ranges and lower water level variability – experience larger amplification sooner. At these sites, a 100-year ESL event could become a 10-year event (AF = 10) within only a few decades under high warming levels, whereas this threshold will be exceeded much later elsewhere. This spatial heterogeneity emphasizes that effective adaptation strategies must be tailored to the local response to SLR rather than applying uniform, coast-wide approaches.
For practical adaptation planning, AF thresholds can be translated directly into required intervention frequencies. Establishing widely accepted thresholds is crucial for implementation: lower AF thresholds better manage residual flood risk but compress adaptation windows, potentially necessitating a paradigm shift from occasional adjustments to continuous adaptation.
How to cite: Jordan, C., Schlurmann, T., Scheiber, L., Goseberg, N., and David, C. G.: Priorities in coastal protection due to extreme sea levels under sea level rise, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11299, https://doi.org/10.5194/egusphere-egu26-11299, 2026.
Global warming leads to sea level rise (SLR), and coastal zones will have to adapt to avoid extensive impacts on people and capital. Possible adaptation strategies can be broadly categorized into no (only autonomous) adaptation, adaptation via retreat from the coast, and protection construction or other forms of accommodation to rising sea levels. Cost-benefit analysis often suggests retreat as the “optimal” strategy for the majority of the (rural) coastline, whereas protection is typically suggested for coastal zones with relatively high population or capital densities.
Here, we use the new FRISIA modelling tool to explore the effect that delays in adaptation and interruptions in flood protection investments can have on what the optimal SLR adaptation strategy is. We thereby define optimality not just by a single metric that combines several quantities, but look at monetary costs, people affected and flood fatalities separately, thereby offering more insights and avoiding the difficult weighting of people and capital.
Sensitivity experiments indicate that delaying the start year of adaptation via retreat or protection reduces the likelihood that protection is the optimal strategy in favour of retreat, especially when considering people rather than monetary impacts. This is mostly because protection construction takes longer and might be imperfect due to limitations in money availability in regions with low population and capital density.
Accounting for interruptions in flood protection investments reduces the likelihood that protection remains the optimal adaptation strategy, particularly in coastal zones that are close to the affordability threshold for building protection. We demonstrate that a reinforcing feedback loop, whereby increasing SLR-induced damage depresses economic growth and thereby places further constraints on protection investments, can be triggered in regions with low population and capital density. Our results further indicate a heightened risk of escalating damages in regions with intermediate population and capital density. In these areas, conventional cost–benefit analysis may still identify protection as the preferred strategy, yet this outcome is highly sensitive to interruptions or constraints in investment, rendering these regions especially vulnerable to adverse development pathways.
How to cite: Ramme, L., Schoenberg, W., Blanz, B., Mauritzen, C., Wells, C., and Li, C.: The Impact of Delays and Interruptions on Optimal Sea-Level Rise Adaptation under Uncertainty, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10482, https://doi.org/10.5194/egusphere-egu26-10482, 2026.
Posters virtual: Fri, 8 May, 14:00–18:00 | vPoster spot 4
EGU26-4120 | ECS | Posters virtual | VPS7
Seasonal and Interannual Variability of Tide-Gauge Records along the Angolan Coast for the period 2015 – 2020Fri, 08 May, 14:57–15:00 (CEST) vPoster spot 4
Tide-gauge observations are among the most reliable sources for assessing sea-level variability and its seasonal and temporal changes in coastal regions. This study analyzes sea-level records obtained from tide gauges along the Angolan coast for the period 2015–2020, with the objective of characterizing the seasonal and interannual variability of tides. The methodology included quality control and pre-processing of hourly and monthly sea-level data, removal of non-tidal signals, harmonic tidal analysis, and the assessment of seasonal variability and its statistical significance. Despite limitations related to data gaps, limited temporal resolution, and the lack of complementary oceanographic data, the results reveal pronounced seasonal and interannual variability in sea level. This variability reflects the combined influence of tidal dynamics, regional ocean circulation, wind forcing, and climate-related processes. The analysis highlights the importance of continuous and homogeneous tide-gauge records along the Angolan coast for improving the detection and interpretation of sea-level variability. The findings contribute to coastal monitoring efforts and provide relevant information for coastal management, risk assessment, and the development of adaptation strategies in the context of sea-level change.
Keywords: Sea level variability, Tide-gauge observations, Seasonal and interannual variability, Angolan coast.
How to cite: Guilherme, F., Neves, M., and Lamas, L.: Seasonal and Interannual Variability of Tide-Gauge Records along the Angolan Coast for the period 2015 – 2020 , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4120, https://doi.org/10.5194/egusphere-egu26-4120, 2026.
