Mean Sea Level Rise Research Articles

Annual mass change of the world's glaciers from 1976 to 2024 by temporal downscaling of satellite data with in situ observations

Abstract. Glaciers, distinct from the Greenland and Antarctic ice sheets, play a crucial role in Earth's climate system by affecting global sea levels, regional freshwater availability, nutrient and energy budgets, and local geohazards. Past assessments of regional to global glacier mass changes were limited in spatial coverage, temporal resolution, and/or temporal coverage. Here, we present a new observation-based dataset of glacier mass changes with global coverage and annual resolution from 1976 to 2024. We use geostatistical modeling for the temporal downscaling of decadal glacier-wide elevation change estimates derived from satellite and airborne geodetic data, with glaciological annual in situ observations. In more detail, we spatially interpolate the annual mass balance anomalies from sparse in situ observations and calibrate them to glacier-wide long-term trends from elevation change observations available for individual glaciers for varying time periods and with global glacier coverage from 2000 to 2019. We then extrapolate the results to yearly time series starting between 1915 and 1976, depending on the regional data availability, and extending to 2024. The time series are calculated separately for each of the world's glaciers and then aggregated to gridded (0.5° latitude and longitude), regional, and global estimates of annual glacier mass changes. Since 1976, Earth's glaciers have lost 9179 ± 621 Gt (187 ± 20 Gt per year) of water, contributing 25.3 ± 1.7 mm (0.5 ± 0.2 mm per year) to the global mean sea level rise. About 41 % (∼ 10 mm) of this loss occurred in the last decade, with 6 % (∼ 1.5 mm) occurring in 2023 alone, the record-breaking year of glacier mass loss. We review the strengths and limitations of our new dataset, validate and discuss related uncertainty estimates in a leave-one-out/block-out cross-validation exercise, and compare our results to earlier assessments. The annual mass change time series for individual glaciers and the derived global gridded annual mass change product are available from the World Glacier Monitoring Service (WGMS) at https://doi.org/10.5904/wgms-amce-2025-02 (Dussaillant et al., 2025).

Poleward shift of subtropical highs drives Patagonian glacier mass loss

Patagonian glaciers have been rapidly losing mass in the last two decades, but the driving processes remain poorly known. Here we use two state-of-the-art regional climate models to reconstruct long-term (1940-2023) glacier surface mass balance (SMB), i.e., the difference between precipitation accumulation, surface runoff and sublimation, at about 5 km spatial resolution, further statistically downscaled to 500 m. High-resolution SMB agrees well with in-situ observations and, combined with solid ice discharge estimates, captures recent GRACE/GRACE-FO satellite mass change. Glacier mass loss coincides with a long-term SMB decline (−0.35 Gt yr−2), primarily driven by enhanced surface runoff (+0.47 Gt yr−2) and steady precipitation. We link these trends to a poleward shift of the subtropical highs favouring warm northwesterly air advections towards Patagonia (+0.14°C dec−1 at 850 hPa). Since the 1940s, Patagonian glaciers have lost 1350 ± 449 Gt of ice, equivalent to 3.7 ± 1.2 mm of global mean sea-level rise.

Abrupt sea level rise and Earth's gradual pole shift reveal permanent hydrological regime changes in the 21st century.

Rising atmospheric and ocean temperatures have caused substantial changes in terrestrial water circulation and land surface water fluxes, such as precipitation and evapotranspiration, potentially leading to abrupt shifts in terrestrial water storage. The European Centre for Medium-Range Weather Forecasts (ECMWF) Reanalysis v5 (ERA5) soil moisture (SM) product reveals a sharp depletion during the early 21st century. During the period 2000 to 2002, soil moisture declined by approximately 1614 gigatonnes, much larger than Greenland's ice loss of about 900 gigatonnes (2002-2006). From 2003 to 2016, SM depletion continued, with an additional 1009-gigatonne loss. This depletion is supported by two independent observations of global mean sea level rise (~4.4 millimeters) and Earth's pole shift (~45 centimeters). Precipitation deficits and stable evapotranspiration likely caused this decline, and SM has not recovered as of 2021, with future recovery unlikely under present climate conditions.

Global sea-level rise in the early Holocene revealed from North Sea peats

Rates of relative sea-level rise during the final stage of the last deglaciation, the early Holocene, are key to understanding future ice melt and sea-level change under a warming climate1. Data about these rates are scarce2, and this limits insight into the relative contributions of the North American and Antarctic ice sheets to global sea-level rise during the early Holocene. Here we present an early Holocene sea-level curve based on 88 sea-level data points (13.7–6.2 thousand years ago (ka)) from the North Sea (Doggerland3,4). After removing the pattern of regional glacial isostatic adjustment caused by the melting of the Eurasian Ice Sheet, the residual sea-level signal highlights two phases of accelerated sea-level rise. Meltwater sourced from the North American and Antarctic ice sheets drove these two phases, peaking around 10.3 ka and 8.3 ka with rates between 8 mm yr−1 and 9 mm yr−1. Our results also show that global mean sea-level rise between 11 ka and 3 ka amounted to 37.7 m (2σ range, 29.3–42.2 m), reconciling the mismatch that existed between estimates of global mean sea-level rise based on ice-sheet reconstructions and previously limited early Holocene sea-level data. With its broad spatiotemporal coverage, the North Sea dataset provides critical constraints on the patterns and rates of the late-stage deglaciation of the North American and Antarctic ice sheets, improving our understanding of the Earth-system response to climate change.

Estimating the sea level rise responsibility of industrial carbon producers

Abstract Global mean sea levels have risen at an accelerating rate over the past century in response, primarily to greenhouse gas emissions from the combustion of fossil fuels. We use MAGICC7, a reduced complexity climate-carbon cycle model, to quantify how emissions traced to the Carbon Majors, the world’s 122 largest fossil fuel and cement producers, from 1854–2020 contributed to present-day surface air temperature rise, and sea level rise both historically and projected through 2300. We find that emissions traced to these industrial actors have contributed 37%–58% to present day surface air temperature rise and 24%–37% to the observed global mean sea level rise to date. Critically, these emissions through 2020 are expected to contribute an additional 0.26–0.55 m of global sea level rise through 2300. We find that attribution of past emissions to projected future sea level rise is robust regardless of how emissions trajectories evolve in the coming centuries.

Emerging from the depth: preliminary clues on groundwater upsurge in the coastal city of Zliten, Libya

This study focuses on localized groundwater flooding (GWF) in Zliten, Libya. The GWF caused significant damage to approximately 200 houses, leading to the relocation of 80 families. The lack of scientifically identified reasons for this groundwater upsurge poses challenges for effective remedial actions. To investigate the flooding causes, remote sensing techniques were employed. Preliminary results showed fluctuations in groundwater storage (GWS) over the past two decades in Zliten. Notably, a sustained decrease in groundwater levels occurred from 2008 to 2012. Sea Level Rise (SLR) patterns varied across Libya’s coastline, with Zliten experiencing an estimated mean SLR of 2.8 mm/yr. Satellite-based findings suggested a consistent decline in Zliten’s water storage capacity. It is possible that (i) overuse of the aquifers has disrupted the confined aquifer, leading to a groundwater upsurge, and/or (ii) recent extensive groundwater pumping activities have placed the confined aquifer under pressure exceeding atmospheric pressure. As a result, water has surged in the wells and even the land to relieve the pressure and reached its potentiometric level. An End-Member Mixing Analysis (EMMA) of water samples from the affected areas could further validate this hypothesis by determining the contributions of surface water, groundwater, or groundwater from the confined aquifer.

Cyclone-induced storm surge flooding in the Ganges-Brahmaputra-Meghna delta under different mean-sea level rise scenarios

Bangladesh coast located in the lower part of the Ganges-Brahmaputra-Meghna delta (GBMD) regularly faces different flooding events from tidal flooding, pluvial flooding, and storm surge flooding. Cyclone-induced storm surge flooding is the most devastating flood event among all the flooding events in the GBMD in terms of human death toll and economic loss. Moreover, different climate change scenario studies suggest that the Bangladesh coast will face adverse impact from mean sea level (MSL) rise. In present study, an online wave-current coupled numerical model (Deflt3d and SWAN) is applied to the GBMD to assess cyclone-induced flooding under different mean sea level rises including 0.5 m, 1 m and 1.5 m. The model setup is calibrated and validated for Cyclone Sidr. Results show that a 1.5 m increase in MSL will cause flooding of up to 33% (11,848 sq. km) of the total coastal area of Bangladesh. Current cyclones (e.g., Cyclone Sidr) will cause more flooding in the coast in the future because of MSL rise alone. Sensitivity tests of different cyclonic parameters such the radius of maximum wind speed, maximum wind speed and landfall location in terms of cyclone-induced storm surge event are conducted by applying the model for different idealized scenarios. An increase in the cyclone maximum wind speed is more likely to increase flooded area rather than increase storm surge height at river stations in the GBMD because the protective embankments are overtopped releasing the waters into the floodplain.

A Prioritization Framework for Adaptation Responses for Climate Change-Induced Erosion in Island Beaches—Cases from the Aegean Islands, Greece

This contribution presents a new approach for assessing/ranking the vulnerability of beaches to mean and extreme sea level rise at regional (island) scales. It combines socio-economic information with beach erosion projections from morphodynamic models to rank beach vulnerability in a structured, ‘holistic’ manner. It involves the collation of various beach geo-spatial environmental and socio-economic data, which are then combined with erosion projections under different climatic scenarios. A Strengths–Weaknesses–Opportunities–Threats (SWOT) framework is employed for the indicator selection, and multi-criteria methods (Analytical Hierarchy Process—AHP, Technique for Order of Preference by Similarity to Ideal Solution—TOPSIS, Preference Ranking Organization Method for Enrichment Evaluations—PROMETHEE II) are then used to optimize indicator weights and rank beach vulnerability. Framework implementation in Lesvos and Kos has shown that there will be significant effects of the mean and (particularly) of the extreme sea levels on the carrying capacity and the capability of the beaches to buffer backshore assets, in the absence of appropriate adaptation measures. As the proposed approach relies on widely available information on many of the socio-economic indicators required to assess the beach’s significance/criticality, it can provide a reproducible and transferable methodology that can be applied at different locations and spatial scales.

Ice flow dynamics of the northwestern Laurentide Ice Sheet during the last deglaciation

Abstract. Reconstructions of palaeo-ice-stream activity provide insight into the processes governing ice stream evolution over millennial timescales. The northwestern sector of the Laurentide Ice Sheet experienced a period of rapid retreat driven by warming during the Bølling–Allerød (14.7–12.9 ka) that may have contributed significantly to global mean sea level rise during this time. Therefore, the northwestern Laurentide Ice Sheet provides an opportunity to investigate ice sheet dynamics during a phase of rapid ice sheet retreat. Here, we classify coherent groups of ice-flow-parallel lineations into 326 flowsets and then categorise them as ice stream, deglacial, inferred deglacial or event flowsets. Combined with ice-marginal landforms and a new ice margin chronology (Dalton et al., 2023), we present the first reconstruction of ice flow dynamics of the northwestern Laurentide Ice Sheet at 500-year time steps through the last deglaciation (17.5–10.5 ka). At the local Last Glacial Maximum (17.5 ka), the ice stream network was dominated by large, marine-terminating ice streams (> 1000 km long) that were fed by the Cordilleran–Laurentide ice saddle to the south and the Keewatin Dome to the east. As the ice margin retreated onshore, the drainage network was characterised by shorter, land-terminating ice streams (< 200 km long), with the exception of the Bear Lake and Great Slave Lake ice streams (∼ 600 km long) that terminated in large glacial lakes. Rapid reorganisation of the ice drainage network, from predominantly northerly ice flow to westerly ice flow, occurred over ∼ 2000 years, coinciding with a period of rapid ice sheet surface lowering in the ice saddle region. We note a peak in ice stream activity during the Bølling–Allerød that we suggest is a result of increased ablation and a steepening of the ice surface slope in ice stream onset zones and the increase in driving stresses that contributed to rapid ice drawdown. The subsequent cessation of ice stream activity by the end of the Bølling–Allerød was a result of ice drawdown lowering the ice surface profile, reducing driving stresses and leading to widespread ice stream shutdown.

Advanced Studies in Breakwaters and Coastal Protection

Globally, mean sea level rise has been accelerating, populations living in coastal zones have been gradually growing, including in low-lying coasts, and the demands for deeper harbors have been quickly increasing to accommodate the future deeper-draft vessels that are being bought online by shipping companies [...]

Determination of Mean Sea Level from 1980 to 2018 using tidal observation data, Bonny Primary Port, Nigeria

Mean Sea Level (MSL) is the average height of the sea for all stages of tide over 19 years; and it is obtained through tidal analysis. This research work aims at determination and assessment of the MSL for the Bonny port. Tidal data of 1980, 1994 and 2018 years of observation were employed using the Least Squares Adjustment method with MATLAB programming codes for data processing. The results of the monthly analysis were compared and subjected to statistical analysis (Mean, standard deviation, t-test and Analysis of variance (ANOVA). The difference between the computed 1980 yearly mean and that of 1994 is 3.0 mm; while that of 1994 and 2018 is 5.1 mm. The yearly variation for 1980 to 1994 is (3.0/14) mm = 0.20 mm; and for 1994 to 2018 is (5.1/24) mm = 0.21 mm. The variation for 1980 to 2018 is (0.20-0.21) mm. The results show gradual rise in MSL for the period of 1980 to 2018 as further explained by the month and the year variables. Therefore, it can be concluded that there is a gradual rise in sea level of about 0.01 mm for the period of study in Bonny which does not take into consideration the subsidence phenomenon. Although, the rate is low, however, the results suggest that the relative sea level could be much higher because there is a lot of fluid extraction.

Land conversions not climate effects are the dominant indirect consequence of sun-driven CO2 capture, conversion, and sequestration

Abstract Groundwater is crucial to sustaining coastal freshwater needs. About 32 million people in the coastal USA rely on groundwater as their primary water source. With rapidly growing coastal communities and increasing demands for fresh groundwater, understanding controls of continental-scale coastal groundwater salinity is critical. To investigate what hydrogeological factors (e.g., topography, hydraulic conductivity) control coastal saline groundwater at continental scales, we have simulated variable-density groundwater flow across North America with the newly developed Global Gradient-based Groundwater Model with variable Densities (G3M-D). The simulation results suggest that under a steady climate and pre-development conditions (i.e., steady 30-year mean groundwater recharge, no withdrawals nor sea level rise) saline groundwater is present in 18.6% of North America's coastal zone, defined as up to 100 km inland and up to 100 m above mean sea level. We find that the coastal zone is particularly vulnerable to containing saline groundwater at low hydraulic gradients (<10-4) and large hydraulic conductivities (>10-2 m day-1). To analyze model parameter sensitivities, i.e., which parameters control the resulting distribution of saline groundwater, we utilize the inherent spatial model variability. We find that hydraulic gradient, topographic gradient, hydraulic conductivity, and aquifer depth are important controls in different places. However, no factor controls coastal groundwater salinization alone, suggesting that parameter interactions are important. Using G³M-D based on G3M, a model that previous work found to be strongly controlled by topography, we find no controlling influence of recharge variability on the saline groundwater distribution in North America. Despite a likely overestimation of saline interface movement, the model required 492 000 years to reach a near-steady state, indicating that the saline groundwater distribution in North America has likely been evolving since before the end of the last ice age, approximately 20 000 years ago.

Why is the Earth System Oscillating at a 6-Year Period?

Abstract A 6-year cycle has long been recognized to influence the Earth’s rotation, the internal magnetic field and motions in the fluid Earth’s core. Recent observations have revealed that a 6-year cycle also affects the angular momentum of the atmosphere and several climatic parameters, including global mean sea level rise, precipitation, land hydrology, Arctic surface temperature, ocean heat content and natural climate modes. In this review, we first present observational evidences supporting the existence of a 6-year cycle in the Earth system, from its deep interior to the climate system. We then explore potential links between the Earth’s core, mantle and atmosphere that might explain the observations, and investigate various mechanisms that could drive the observed 6-year oscillation throughout the whole Earth system.

Análise multitemporal do uso e cobertura da terra na Reserva Extrativista Marinha da Baía do Iguape - Recôncavo Baiano

This study aimed to analyze land use and land cover dynamics at the Iguape Bay Marine Extractive Reserve (RESEX) employing Landsat images from 1986, 1994, 2003, 2017 and 2022. The Iguape Bay RESEX covers the municipalities of Cachoeira, São Félix and Maragogipe, located in the Bahian Recôncavo region. The employed methodological procedures comprised a bibliographic research, geographic database organization in a GIS environment, data tabulation, digital image processing and map production. Land use and land cover mapping was carried out by the vectorization method. Mapping accuracy encompassing global and Kappa index accuracies was above 90%. Mangrove area expansion by 1.8 km 2 , agricultural class reduction and increase in dense Atlantic Rainforest remnants were noted at the Iguape Bay RESEX over the last 36 years (1986 to 2022). In this context, multitemporal land use and land cover analyses become paramount, as they allow for furthering knowledge on targets exposed to the probable impacts of rising mean sea levels, contributing to REEX coastal planning and management and the formulation of public policies aimed at local fishing communities.

Increased sea level rise accelerates carbon sequestration in a macro-tidal salt marsh.

Increased sea level rise accelerates carbon sequestration in a macro-tidal salt marsh.

Vertical land motion is underestimated in sea-level projections from the Oka estuary, northern Spain

Coastal populations are susceptible to relative sea-level (RSL) rise and accurate local projections are necessary for coastal adaptation. Local RSL rise may deviate from global mean sea-level rise because of processes such as geoid change, glacial isostatic adjustment (GIA), and vertical land motion (VLM). Amongst all factors, the VLM is often inadequately estimated. Here, we estimated the VLM for the Oka estuary, northern Spain and compared it to the VLM component of sea-level projections in the Intergovernmental Panel on Climate Change (IPCC) Sixth Assessment Report (AR6) and the Spanish National Climate Change Adaptation Plan (NCCAP). To estimate VLM, we updated Holocene RSL data from the Atlantic coast of Europe and compared it with two 3D GIA models. Both models fit well with RSL data except in the Oka estuary. We derived a VLM rate of − 0.88 ± 0.03 mm/yr for the Oka estuary using the residuals of GIA misfits. Comparable VLM rates of − 0.85 ± 0.14 mm/yr and − 0.80 ± 0.32 mm/yr are estimated based on a nearby Global Navigation Satellite Systems station and differenced altimetry-tide gauge technique, respectively. Incorporating the updated late Holocene estimate of VLM in IPCC AR6 RSL projections under a moderate emissions scenario increased the rate of RSL rise by 15% by 2030, 11% by 2050, and 9% by 2150 compared to the original IPCC AR6 projections, and also increased the magnitude of RSL rise by over 40% by 2035 and 2090 compared with projections from the Spanish NCCAP. Our study demonstrates the importance of accurate VLM estimates for local sea-level projections.

Steric Sea Level Rise and Relationships with Model Drift and Water Mass Representation in GFDL CM4 and ESM4

Abstract Density-driven steric seawater changes are a leading-order contributor to global mean sea level rise. However, intermodel differences in the magnitude and spatial patterns of steric sea level rise exist at regional scales and often emerge during the spinup and preindustrial control integrations of climate models. Steric sea level results from an eddy-permitting climate model, GFDL CM4, are compared with a lower-resolution counterpart, GFDL-ESM4. The results from both models are examined through basin-scale heat budgets and watermass analysis, and we compare the patterns of ocean heat uptake, redistribution, and sea level differ in ocean-only [i.e., Ocean Model Intercomparison Project (OMIP)] and coupled climate configurations. After correcting for model drift, both GFDL CM4 and GFDL-ESM4 simulate nearly equivalent ocean heat content change and global sea level rise during the historical period. However, the GFDL CM4 model exhibits as much as a 40% increase in surface ocean heat uptake in the Southern Ocean and subsequent increases in horizontal export to other ocean basins after bias correction. The results suggest regional differences in the processes governing Southern Ocean heat export, such as the formation of Antarctic Intermediate Water (AAIW), Subpolar Mode Water (SPMW), and gyre transport between the two models, and that sea level changes in these models cannot be fully bias-corrected. Since the process-level differences between the two models are evident in the preindustrial control simulations of both models, these results suggest that the control simulations are important for identifying and correcting sea level–related model biases.

Impacts of Sea Level Rise on Danish Coastal Wetlands – a GIS-based Analysis

Intergovernmental Panel on Climate Change (IPCC) scenarios run by an ensemble of models developed by the Coupled Model Intercomparison Project (CMIP) projects an average sea level rise (SLRs) of 0.6 to 1.2 m for the low and high emission scenarios (SSP1-1.9, SSP5-8.5), during the next century (IPCC 2021). The coastal zone will experience an increase in the flooding of terrestrial habitats and the depth of marine productive areas, with potential negative consequences for these ecosystems. The coast in Denmark is highly modified due to anthropogenic uses. Dikes, dams, and other coastal infrastructure are widespread, causing a coastal squeeze that prevents natural coastal development and inland migration of coastlines. We performed a national-scale analysis on the impacts of mean sea level rise (MSLR) in 2070 and 2120, and a 1 in 10-year storm surge water level (10SS) in 2120 MSLR for the Danish coast. Our study shows extensive permanent flooding of coastal habitats (~14%), whereas only 1.6% of urban areas will be flooded. Finally, very large agricultural areas (~191,000 ha) will be frequently flooded by 10SS if no extra protective measures are planned. With the present coastal protection structures, key habitats will be affected by permanent flooding or coastal squeeze while even larger extents will be subjected to intermittent marine flooding. About 45% (199 km2) of all Danish coastal wetlands will be permanently flooded by 2120, while areas occupied by forest, lakes and freshwater wetlands will be more frequently flooded by marine water. This study highlights the importance of including coastal habitats as dynamic elements in climate adaptation plans. Conservation and restoration of key habitats such as coastal wetlands should be prioritized in management plans. If Denmark does not change its current priorities, it may face the complete loss of coastal wetlands habitat in the 22nd century.

Dynamic projections of extreme sea levels for western Europe based on ocean and wind-wave modelling

Abstract. Extreme sea levels (ESLs) are a major threat for low-lying coastal zones. Climate-change-induced sea level rise (SLR) will increase the frequency of ESLs. In this study, ocean and wind-wave regional simulations are used to produce dynamic projections of ESLs along the western European coastlines. Through a consistent modelling approach, the different contributions to ESLs, such as tides, storm surges, waves, and regionalized mean SLR, as well as most of their non-linear interactions, are included. This study aims at assessing the impact of dynamically simulating future changes in ESL drivers compared to a static approach that does not consider the impact of climate change on ESL distribution. Projected changes in ESLs are analysed using non-stationary extreme value analyses over the whole 1970–2100 period under the SSP5-8.5 and SSP1-2.6 scenarios. The impact of simulating dynamic changes in extremes is found to be statistically significant in the Mediterranean Sea, with differences in the decennial return level of up to +20 % compared to the static approach. This is attributed to the refined mean SLR simulated by the regional ocean general circulation model. In other parts of our region, we observed compensating projected changes between coastal ESL drivers, along with differences in timing among these drivers. This results in future changes in ESLs being primarily driven by mean SLR from the global climate model used as boundary conditions, with coastal contributions having a second-order effect, in line with previous research.

A probabilistic approach to combine sea level rise, tide and storm surge into representative return periods of extreme total water levels: Application to the Portuguese coastal areas

Coastal hazard and vulnerability assessments in the context of climate change usually rely on the estimation of total water levels (TWLs) through a deterministic approach, consisting on the simple summation of its components: mean or median sea level rise projections, maximum tide values, and extreme storm surge projections based on return periods (usually of 100 years). However, such methodology yields TWLs compatible with return periods much greater than the commonly used ones in hazard, vulnerability and risk assessments, occasionally by more than one order of magnitude (thousands of years). Deterministic approaches also neglect uncertainties in TWL components, or other sources of variability, as random variables with known probability density functions. Here, we present, validate, evaluate and apply a methodology to provide a numerical solution for the estimation of representative return periods of extreme TWLs, for any coastal area, to which the three cumulative density functions of SLR, tide and storm surge are given. The use of representative TWLs is crucial for accurate hydrodynamical modelling of coastal flooding, both along inland waters and coastlines facing the open ocean, as well as to coastal vulnerability and risk assessments. Using two dynamic ensembles, the projected 4-, 25- and 100-year representative TWL return periods are estimated across five vulnerable areas along the Portuguese coastline and compared with deterministic TWLs. Our results show that the methodology can accurately reproduce the observed TWL distributions and return values associated with extreme events, these being generally lower than the deterministic ones, undergoing, nevertheless, greater changes towards the end of the 21st century. We provide a baseline for future studies to delve into more accurate and realistic translation of physical, anthropogenic-driven climate change effects into socioeconomic impacts along the coastal areas.