Extreme sea levels are the joint contribution of mean sea level, tide and storm surges. The ClimEx project investigates changes in tide and storm surges over the last century, along the North Atlantic coasts. Concerning the tide, we investigated the long-term changes of the principal tidal component M₂, from 1846 to 2018 (Pineau-Guillou et al., 2021). The M₂ variations are consistent at all the stations in the North-East Atlantic. The changes started long before the 20th century and are not linear. Regarding the possible causes of the observed changes, the similarity between the North Atlantic Oscillation and M₂ variations in the North-East Atlantic suggests a possible influence of the large-scale atmospheric circulation on the tide. A possible underlying mechanism is discussed. Concerning the storm surges, we found a clear shift in the storm surge season at Brest (France), between 1950 and 2000 (Reinert et al., 2021). Extreme storm surge events occurred three weeks earlier (mid-December instead of beginning of January) in the winter 2000 than in the 1950s. Analysis of additional stations in Europe reveals a large-scale process (Roustan et al., 2022). Temporal shifts are positive (later events) in northern Europe, and negative (earlier events) in southern Europe. Such a tendency is similar to the one already reported for European river floods between 1960 and 2010 (Blöschl et al., 2017).

References

[1] Pineau-Guillou L., Lazure P. and Wöppelmann G. (2021). Large-scale changes of the semidiurnal tide along North Atlantic coasts from 1846 to 2018. Ocean Sci., 17, 17–34. https://doi.org/10.5194/os-17-17-2021

[2] Reinert M., Pineau-Guillou L., Raillard N., Chapron B. (2021). Seasonal shift in storm surges at Brest revealed by extreme value analysis. J. Geophys. Res. Oceans, 126, e2021JC017794. https://doi.org/10.1029/2021JC017794

[3] Roustan J.-B., Pineau-Guillou L., Chapron B., Raillard N., Reinert M. (2022). Shift of the storm surge season in Europe due to climate variability. Sci. Rep., 12, 8210. https://doi.org/10.1038/s41598-022-12356-5

[4] Blöschl G., Hall J., Parajka J., Perdigão R. A. P., Merz B., Arheimer B. et al. (2017). Changing climate shifts timing of European floods. Science, 357(6351), 588–590. https://doi.org/10.1126/science.aan2506

How to cite: Pineau-Guillou, L., Lazure, P., Wöppelmann, G., Roustan, J.-B., and Reinert, M.: Changes in extreme sea levels along the North Atlantic coasts, over the last century, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8186, https://doi.org/10.5194/egusphere-egu23-8186, 2023.

The monitoring of the sea level trend is important for decision-making in the near-future. For the Dutch coast, the Sea Level Monitor periodically publishes new estimates of the sea level rise trend. This observed trend, based on a selection of Dutch tide gauge stations, is used for the planning and management of our coastal defenses in the next 10-15 years. To estimate the trend in mean sea level, the influence of land subsidence, long-term tidal cycles and storm surges levels need to be removed from the observations.

In this contribution, we focus on the contribution of storm surges, that are driven by variations of atmospheric pressure and wind. We will present an updated methodology to remove the effects of these variations on the sea-level trend, which is based on monthly mean sea levels derived with a depth-averaged hydrodynamic model instead of a linear regression. A fully automated and portable workflow was developed to deploy Global Tide and Surge Model (GTSM) on a high-performance computing cluster. Leveraging recent updates of the ERA5 climate reanalysis, we extent existing GTSM simulations back to 1950 and to present-day. Based on these new simulations, we will discuss the variability in mean sea levels due to atmospheric conditions, and present how the sea-level trend changes due to the improved correction.

How to cite: Muis, S., Aleksandrova, N., Baart, F., Stolte, W., and Veentra, J.: Deployment of the global tide and surge model for estimating sea-level trends along the Dutch coast, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1252, https://doi.org/10.5194/egusphere-egu23-1252, 2023.

Sea-level rise (SLR) amplifies the frequency of extreme sea levels as it raises their baseline height. Projections of the frequency amplification of extremes are often computed for arbitrary future years and relative to the historical centennial event, which is not necessarily meaningful locally. Consequently, such projections may not provide salient information to adaptation planners, as they do not indicate when certain flood risk thresholds will be crossed given the current degree of local coastal flood protection.

To better support adaptation planning, we introduce a framework that extends the emerging timing perspective on sea-level rise to the frequency amplification of extreme sea levels. Moreover, by relating amplification factors to local flood protection standards estimated with the FLOPROS modelling approach, we project the timing of decreases in the local degree of protection. The sea-level rise required for such decreases is derived from extreme sea-level distributions inferred from GESLA3 observations and combined with the relative sea-level projections of the Sixth Assessment Report of the IPCC until 2150 to compute the timing of these decreases at tide gauges globally.

Our central estimates indicate that the estimated degrees of protection will be exceeded 10 times as frequently within the next 30 years (the lead time that large adaptation measures may take) at 26 & 32% of the tide gauges considered, and annually at 4 & 8%, for respectively a low & high emissions scenario (SSP1-2.6 & SSP3-7.0). Even though our results are based on estimated degrees of protection, they highlight that at several locations substantial decreases in the degree of protection may occur before large adaptation measures can be completed. Furthermore, we find that under SSP3-7.0, the same decreases in the degree of coastal protection will occur substantially faster in the future as sea-level rise accelerates. Our projection framework adds a new perspective on the frequency amplifications of extremes that may help adaptation planners to assess the available lead time and useful lifetime of protective infrastructure, given unacceptable decreases in the degree of coastal protection.

How to cite: Hermans, T., Malagón-Santos, V., Katsman, C., Jane, R., Rasmussen, D., Haasnoot, M., Garner, G., Kopp, R., Oppenheimer, M., and Slangen, A.: The Timing of Decreasing Coastal Flood Protection Due to Sea-Level Rise, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4834, https://doi.org/10.5194/egusphere-egu23-4834, 2023.

For sea-level projections along the coast of the Netherlands, ocean dynamic sea level (ODSL) is one of the most important contributors to sea-level rise in the 21^st century. The ODSL output from the latest coupled model intercomparison projects (CMIP5 and CMIP6) is used for these projections. These CMIP models overwhelmingly use ocean models with a spatial resolution of 1° and a vertical z-level coordinate. Using these CMIP models for projections does not provide a seamless connection between observations and projections, this study aims to improve on that. To do so, we use a configuration of the Regional Ocean Modelling System (ROMS) for the North Sea with a resolution of 0.25° to downscale the spatial resolution of CMIP6 models and interpolate the vertical coordinate to topography-following sigma levels to improve the projections for the Netherlands.

First, we use ROMS to reconstruct the ODSL along the coast of the Netherlands for the observational period. The regional model is forced using an atmospheric dataset constructed from ERA-interim and ERA-5 surface data and different ocean reanalysis datasets. It is not straightforward to compare the ODSL from different ocean reanalyses, as some datasets assimilate satellite altimetry data, whereas others do not. The ODSL from the reanalysis datasets that assimilate altimetry data are corrected for land ice and terrestrial water storage contributions to correct these differences.

Then, we use ROMS to obtain new projections of ODSL for the coast of the Netherlands that seamlessly connect to the estimate of ODSL from ocean reanalysis data. We extend the forcing datasets for the regional ocean model of the observational period using the anomalies of CMIP6 variables. Using this new method, we obtain improved projections along the coast of the Netherlands.

How to cite: Keizer, I., Le Bars, D., and Drijfhout, S.: Estimating ocean dynamic sea level along the coast of the Netherlands using the regional ocean modelling system (ROMS) to seamlessly connect the observational period to projections for the 21st century., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16275, https://doi.org/10.5194/egusphere-egu23-16275, 2023.

There is increasing awareness of the need for comprehensive information on potential future sea-level rise to inform adaptation planning and coastal decision-making. The IPCC Sixth Assessment Report (AR6) states that global mean sea level rise approaching 5 m by 2150, and more than 15 m by 2300, cannot be ruled out under high greenhouse gas emissions due to uncertainty in ice sheet processes. Moreover, local sea level rise may be further exacerbated through systematic changes in the climate system, such as a rapid weakening of the Atlantic Meridional Overturning Circulation (AMOC).

We combine the latest United Kingdom national sea-level projections (UKCP18) with recently published projections of Antarctic ice mass loss to develop a small set of physically consistent storylines of local sea-level change that extend to 2300. The storylines span the range of uncertainty assessed by AR6 and deliver continuous sea level rise information around the UK coastline. While we focus on the UK, the methods are generic and can be readily applied to other geographic locations. Further, we consider potential changes in coastal flood hazard associated with a weakening of the AMOC using dynamical downscaling and storm surge modelling of climate model projections.

How to cite: Harrison, B., Palmer, M., Allison, L., Gregory, J., Howard, T., Pardaens, A., and Tinker, J.: Towards Physically Consistent Sea Level Rise Storylines for the United Kingdom, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15655, https://doi.org/10.5194/egusphere-egu23-15655, 2023.

Regional emulation tools based on statistical relationships, such as pattern scaling, provide a computationally inexpensive way of projecting ocean dynamic sea-level change for a broad range of climate change scenarios. Such approaches usually require a careful selection of one or more predictor variables of climate change so that the statistical model is properly optimized. Even when appropriate predictors have been selected, spatiotemporal oscillations driven by internal climate variability can be a large source of model disagreement. Using pattern recognition techniques that exploit spatial covariance information can effectively reduce internal variability in simulations of ocean dynamic sea level, significantly reducing random errors in regional emulation tools. Here, we test two pattern recognition methods based on Empirical Orthogonal Functions (EOF), namely signal-to-noise maximising EOF pattern filtering and low-frequency component analysis, for their ability to reduce errors in pattern scaling of ocean dynamic sea-level change. These two methods are applied to an initial-condition large ensemble (MPI-GE), so that its externally forced signal is optimally characterized. We show that pattern filtering provides an efficient way of reducing errors compared to other conventional approaches such as a simple ensemble average. For instance, filtering only two realizations by characterising their common response to external forcing reduces the random error by almost 60%, a reduction level that is only achieved by averaging at least 12 realizations. We further investigate the applicability of both methods to single realization modelling experiments, including four CMIP5 simulations for comparison with previous regional emulation analyses. Pattern scaling leads to a varying degree of error reduction depending on the model and scenario, ranging from more than 20% to about 70% reduction in global-mean mean-squared error compared with unfiltered simulations. Our results highlight the relevance of pattern recognition methods as a means of reducing errors in regional emulation tools of ocean dynamic sea-level change, especially when one or a few realizations are available.

How to cite: Malagón-Santos, V., Slangen, A. B. A., Hermans, T. H. J., Dangendorf, S., Marcos, M., and Maher, N.: Removing Internal Variability as a Means of Improving Regional Emulation of Ocean Dynamic Sea-Level Change, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6990, https://doi.org/10.5194/egusphere-egu23-6990, 2023.

The projected decay of the Antarctic Ice Sheet (AIS) over the coming centuries will lead to uplift of the Earth's surface due to Glacial Isostatic Adjustment (GIA). GIA slows down grounding line migration and therefore has a stabilizing effect on the ice sheet evolution. GIA acts on timescales of decades to centennial depending on the magnitude of the mantle viscosity. The mantle viscosity is several orders of magnitude higher in East Antarctica than in West Antarctica and varies with one order of magnitude within West Antarctica. Studies of the AIS evolution over the last glacial cycle have shown that including lateral variations of the Earth's mantle viscosity can lead to 1.5-kilometer thicker ice in West Antarctica at present day. However, current projections do not include GIA, or they use a laterally homogeneous GIA model. One study applied a uniform high mantle viscosity under East Antarctica and a uniform low mantle viscosity under West Antarctica and showed that, on longer timescales of hundreds of years, mass loss projections of Antarctica may be underestimated because spatially uniform GIA models overestimate the stabilizing effect of GIA across East Antarctica. We developed a coupled GIA - ice-sheet model using the ice-sheet model IMAU-ICE, and a 3D GIA finite element model that includes lateral mantle viscosity variations, and a seismic model to determine the patterns of the viscosity. The results of projections for two IPCC scenarios show that including lateral variations in the Earth's mantle viscosity leads to local ice thickness differences of up to 600 meters in West Antarctica  2300. The results underline and quantify the importance of including this local feedback effect in ice-sheet models when projecting the long-term sea level contribution from Antarctica.

How to cite: van Calcar, C., Bernales, J., Berends, T., van der Wal, W., and van de Wal, R.: Sensitivity of the Antarctic Ice Sheet evolution to different Earth structures using a coupled 3D GIA - ice-sheet model under different future climate scenarios, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15613, https://doi.org/10.5194/egusphere-egu23-15613, 2023.

While the understanding and modelling of relative sea level rise (SLR) due to ocean density and mass changes have greatly improved over the past few decades, SLR contributions due to vertical ground motions (VGMs) remain a major source of uncertainty. Here, VGMs relate to ground motions that have imprints of a few kilometers, as opposed to broad scale land motion such as Glacial Isostatic Adjustment (GIA). VGMs are caused by processes such as natural resource extraction or the load of anthropogenic infrastructure on recent sediment deposits or natural processes (e.g. sismotectonics, volcanism, landslide), all of which vary in space and time, and can strongly inflate SLR locally.

Here, we present a pan-European analysis of relative sea-level changes in Europe considering VGMs based on trends retrieved from the European Ground Motion Service (EGMS). EGMS allows identifying hot spots of robust subsidence along the European coastline such as the north Adriatic coast in Italy, areas such as Palavas (France), Groningen (Netherlands) and many coastal infrastructures such as dikes in La Rochelle (France) where subsidence was not documented earlier. Hence the service delineates where subsidence can have a significant impact to relative sea-level changes in coastal areas. This satisfies a major need from coastal adaptation stakeholders concerned with SLR. EGMS results are complemented and compared with VGMs estimates from permanent Global Navigation Satellite System (GNSS) network stations. The precision of the measurements is discussed: VGMs from GNSS stations derived from 4 different solutions (ULR, NGL, JPL and GFZ) allow accounting for uncertainty in trends estimation techniques. We estimate VGMs residual trends after removing the effect of the GIA from geophysical modelling, but also the effect of contemporary mass redistribution on solid Earth deformation. The results from both GNSS and EGMS suggest that the precision of ground motion velocities can be in the order of a millimetre per year.

Overall, these estimates and their uncertainty can be used to produce a new coastal pan-European relative sea-level set of projections that respond to one major user need, namely the identification of areas where sea level rise is amplified by subsidence. However two other user needs remain unachieved: the local attribution of observed sea-level changes to components with a submillimetric per year accuracy and a quantified projection of subsidence, which would at least require subsidence models.    

How to cite: Thiéblemont, R., Le Cozannet, G., Raucoules, D., Rohmer, J., Wöppelmann, G., Calkoen, F., and Nicholls, R. J.: Contribution of subsidence on relative sea level in Europe, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7227, https://doi.org/10.5194/egusphere-egu23-7227, 2023.

Sea-level rise integrates the responses of several components (ocean thermal expansion, mass loss from glaciers and ice sheets, terrestrial water storage). Before the satellite era, global sea-level reconstructions depend on tide-gauge records and ocean observations. However, the available global mean sea level (GMSL) reconstructions using different methods indicate a spread in sea-level trend over 1900-2008 (1.3~2.0 mm yr^-1). With the improved understanding of the causes of sea-level change, here we update the original Church and White (2011) reconstruction by using the latest observations, taking the time-evolving sea-level fingerprint, sterodynamic sea level (SDSL) climate change pattern and local vertical land motion (VLM) into account. The updated trend of GMSL of 1.6 ± 0.2 mm yr^-1 (90% confidence level) over 1900-2019 is consistent with the sum of contributions of 1.5 ± 0.2 mm yr^-1, slightly lower than 1.8 ± 0.2 mm yr^-1 from original reconstruction. The lower trend from the updated reconstruction is mainly due to including residual VLM correction. The trends at tide gauge locations from updated reconstruction agree better with the tide gauge observations, with comparable mean trend of 1.7 mm yr^-1 (standard deviation; STD of 2.0 mm yr^-1) from observation and 1.7 mm yr^-1 (STD of 1.2 mm yr^-1) from the updated reconstruction. The inclusion of sea-level fingerprint and SDSL climate change pattern are the dominant contributors for improved reconstruction skill on regional scales at tide gauge locations. This update leads to GMSL solution that are consistent with other reconstructions in terms of long-term trend and 30-year running rate.

How to cite: Wang, J., Church, J. C., Zhang, X., and Chen, X.: Updating sea-level reconstruction since 1900, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10639, https://doi.org/10.5194/egusphere-egu23-10639, 2023.

Satellite altimeters have measured the global mean and regional patterns of sea level change since 1993 with impressive detail and precision. While the global mean rate of sea level rise has been studied extensively and is readily linked to global water budgets, the regional patterns (or deviations from the global mean) are subject to diverse physical mechanisms that span the gauntlet of internal climate dynamics, and models suggest a nuanced relationship to radiative forcing (greenhouse gases, aerosols, etc.). To date, little attempt has been made to synthesize the regional patterns of sea level change across the global ocean with a common diagnostic framework. Here we combine oceanic and atmospheric observations and leverage ensembles of a state-of-the-art global climate model to unravel the mechanisms governing the basin-scale patterns of sea level change around the world ocean. By applying some bedrock principles of physical oceanography and coupled dynamics, we find a leading role for wind forcing—Ekman and Sverdrup dynamics together yield faithful reproductions of the large-scale structure of sea level change from the tropics to the midlatitudes. We argue that the global pattern of sea level rise since 1993 is set, to leading order, by changes in the wind-driven ocean circulation and their influence on sea surface height via ocean heat divergence. Importantly, wind-driven needn’t be synonymous with internal variability—indeed, much of the observed global pattern is recovered by global climate models subject to historical anthropogenic forcings, and single-forcing experiments enable further insight into which forcings are responsible for which regional phenomena. As we move forward into the uncertain future, a better understanding of the causes of regional rates of sea level rise, including distinguishing which features are driven by human activities versus modes of natural variability—or both, is critical for the successful adaptation of humanity and its infrastructure to a rapidly changing climate.

How to cite: Nerem, R. S., Karnauskas, K., Fasullo, J., and Hamlington, B.: Unraveling Regional Patterns of Sea Level Change over the Altimeter Era, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9831, https://doi.org/10.5194/egusphere-egu23-9831, 2023.

Sea level change is not uniform around the globe. We focus on regional sea level change in the East China Sea (ECS), a Western Pacific marginal sea of 770.000 km², with a densely populated and economically important coastal area. Several challenges arise when investigating past and current sea level change and budgets in this region.

Ocean mass change is observed by GRACE(-FO). However, one needs to account for hydrological signals leaking from land into the ocean, as well as for sediment discharge from rivers. Steric contributions are usually measured by Argo floats, but from the shallow inner shelf of the ECS only few data are available. Thus, ocean reanalyses should be handled with caution. Total sea level change from altimetry can be compared to tide gauge data, but gauges are sparsely distributed in the ECS area and only few stations are co-located with GNSS to account for vertical land motion.

In this contribution, we analyze and compare different data products to better understand regional sea level change and its contributors. Time series of ECS- averaged levels (total from altimetry, mass from GRACE and GRACE-FO and steric from ORAS5 reanalysis) are computed and compared in terms of trend, seasonal amplitudes and correlations. Additionally, spatial patterns are investigated, revealing that the shallow coastal regions, vast continental shelf areas and deep sea areas show distinct characteristic behaviors of sea level change. Altimetry and tide gauge data show a correlation of higher than 70% for 11 of 13 available records. Finally, we compare the individual data sets to results of a joint sea level inversion framework (Uebbing, 2022).

How to cite: Strohmenger, C., Liu, Z., Uebbing, B., Kusche, J., Reißner, L., Shen, Y., Feng, W., and Chen, Q.: Investigating the sea level budget in the East China Sea, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3929, https://doi.org/10.5194/egusphere-egu23-3929, 2023.

Tide-gauge records along the U.S. West Coast since the mid-1920’s show large ENSO-correlated sea-level variability and a below-average linear trend relative to the global mean over the past three decades. On weekly and longer timescales, sea-level variations in the region are primarily steric, reflecting variations in coastal ocean temperatures rather than that of mass. Previous research into sea-level variability in the region identified coastally-trapped waves forced by nonlocal winds as the main source of long-lasting sea-level variability. Here we offer a rigorous quantification of the contributions of wind-stress and buoyancy forcing anomalies across the entire Pacific Basin on the U.S. West Coast Sea level using a global data-constrained ocean and sea-ice model of the Estimating the Circulation and Climate of the Ocean (ECCO) consortium. Causal relationships are quantified using the model’s adjoint and mechanisms are elucidated via perturbation experiments.

By convolving the adjoint sensitivities with atmosphere forcing anomalies we find that long-term (>1 week) sea level variations along the U.S. West Coast are almost entirely due to wind-stress anomalies while buoyancy anomalies, in contrast, contribute virtually nothing. Interestingly, the wind stress anomalies that contribute to sea level variations in the region come from two sectors: i) a coastally-confined region from 0-45N and ii) and the open-ocean Pacific equatorial waveguide (roughly -/+ 10 degrees latitude). Wind stress anomalies in the coastally-confined sector induce coastally-trapped waves which propagate poleward, depress the thermocline, reduce upwelling/air-sea heat loss and, thereby, lead to positive ocean temperature / steric height anomalies. Zonal wind stress anomalies in the equatorial waveguide induce eastward-propagating equatorial Kelvin waves, some energy of which is converted to coastally-trapped waves upon reaching continent, which lead to positive steric height anomalies following the same causal chain.

This study highlights the benefits of applying the complimentary tools of adjoint-based convolution and perturbation experiments to explain the origin of regional sea-level anomalies.

How to cite: Fenty, I., Wang, O., and Fukumori, I.: Causal Mechanisms of Sea Level Variations along the U.S. West Coast, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10695, https://doi.org/10.5194/egusphere-egu23-10695, 2023.

The shelf northwest of Europe is home to subinertial fluctuations in sea level, whose peak-to-peak amplitude reach several tens of centimetres. These weekly-to-monthly shelf-wide sea-level variations feature at the coast, and therefore understanding their drivers is of prime importance for coastal adaptation. These sea-level changes have been previously hypothesized to reflect the strength of the European slope current (Chafik et al., 2017), a wind and density driven quasi-barotropic circulation lying in the region of the 500 to 1000 m isobaths (Huthnance & Gould, 1989). This interpretation has however not yet been validated by in-situ observations.

Using data from single-point current-meters and acoustic Doppler current profilers moored west of France, Ireland and Scotland, we show that the common mode of northwest European sea-level changes covaries with along-isobath currents on the shelf and on the upper part of the slope (< 400 m of water depth). However, the pattern of variability is different in the slope current and further off-shelf, , with the correlations between shelf sea levels and in-situ currents decreasing moving down-slope (> 400m of water depth).  We discuss whether or not the relationship between European sea levels and shelf and slope currents emerges from momentum balance associated with the slope current existence (joint effect of winds, baroclinicity and bathymetry). We also discuss the relevance for coastal sea levels and associated coastal vulnerability.

Chafik, L., Nilsen, J. E. Ø., & Dangendorf, S. (2017). Impact of North Atlantic teleconnection patterns on Northern European sea level. Journal of Marine Science and Engineering, 5(3), 43.

Huthnance, J. M., & Gould, W. J. (1989). On the northeast Atlantic slope current. In Poleward flows along eastern ocean boundaries (pp. 76-81). Springer, New York, NY.

How to cite: Diabaté, S. T., Fraser, N. J., and McCarthy, G. D.: Wind-driven currents and sea-level variability of the northwest European shelf, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15625, https://doi.org/10.5194/egusphere-egu23-15625, 2023.

It is now well established that sea level rise is not uniform and presents large deviations from its global mean trend. 
Indeed, some regions such as the western Pacific ocean or the Indian ocean experience a linear rise 3 times larger than the global mean sea level trend since 1993 (Cazenave and Llovel, 2010; Llovel and Lee, 2015).
Superimposed to the long-term trend, the interannual variability may enhance or reduce sea level change over a shorter time period (few months). It is well known that these variations are linked to the interannual variability of the steric sea level driven by natural modes of climate variability such as El Nino Southern Oscillation (in the tropical Pacific ocean) and the Indian Ocean Dipole (in the north Indian ocean, Llovel et al., 2010). Therefore, investigating the mechanisms of interannual variability of steric sea level appears to be highly relevant for understanding processes at play in regional sea level variability. 

In this work, we investigate the local sources and sinks of interannual steric sea level variability using the ECCOv4 (Estimating the Circulation and Climate of the Ocean, Forget et al., 2015) state estimate over 1993-2014. We find that the variability is, in almost all regions, sustained by interannual fluctuating winds via Ekman transport and damped by both interannual variations of the net heat flux from the atmosphere and by the rectification effect of subannual oceanic circulation. 

This method allows not only the identification of the physical process at play in the interannual steric sea level variability, but also if the latter is a source or a sink of the interannual steric sea level variability. This method presents evident advantages especially to assess the reliability of coupled climate models used to predict future sea level changes.

How to cite: Hochet, A., Llovel, W., Sévellec, F., and Huck, T.: Sources and sinks of interannual steric sea level variability, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12782, https://doi.org/10.5194/egusphere-egu23-12782, 2023.

Recent advances in satellite and in-situ measurements have enabled the monitoring of GMSL budget components and provided insights into ocean effects on the Earth’s energy imbalance and hydrology. The global mean sea level rise slowed over the 2000s, which coincides with a global warming hiatus period, but has accelerated again since 2011. This decadal fluctuation in GMSL rise can be attributed to climate-related fluctuation in ocean heat and mass change. Sea level and Earth’s energy budget results demonstrate that the decadal climate variability has resulted in ocean mass loss and decreased ocean heat uptake, slowing the GMSL rise rate during the 2000s. After ~2011, the climate-driven fluctuations of ocean mass, heat, and GMSL rise rate were reversed. This result highlights the importance of natural variability in understanding the ongoing sea-level rise.

How to cite: Cha, H., Moon, J.-H., Kim, T., and Song, Y. T.: The drivers of decadal fluctuation in the global mean sea level rise, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5189, https://doi.org/10.5194/egusphere-egu23-5189, 2023.