Mobile version

Mean Sea Level

As global warming occurs, a direct reaction of the climate system is the sea level rise. This rise results from seawater expansion as a response to the temperature increase and addition of water from land-ice sheets and glaciers melting. Precise monitoring of the sea level rise is made possible using altimetry satellites that help understanding climate change and its socioeconomic consequences. The Global Mean Sea Level (GMSL) has thus become a key indicator of climate change.

Data access and product information


Different satellite altimetry missions have been monitoring the GMSL successively and continuously since 1993: TOPEX/Poseidon, Jason-1, Jason-2, Jason-3 and soon, Sentinel-6 MF. These missions are called "reference missions" as they fly on a well-determined reference orbit that is unchanged since 1993. Dedicated calibration phases between the successive missions, during which the satellites fly a few second apart, help to ensure the long-term stability and precise monitoring of the sea level. In addition, a permanent control of the data quality and instrumental performances, in combination with the homogenization of the data processing and geophysical corrections , are key to produce homogeneous data that well capture the long-term evolution of the sea level.

The global sea level rise is rising, on average over the globe, by 3.5 millimeter per year. Analyzing the uncertainty of the altimetry observing system yields to construct an uncertainty envelop for the GMSL climate data record (shaded area in the figure above). The resulting uncertainty in the GMSL rise is estimated to approximately 0.4 mm/yr at the 90% confidence level.

See Ablain et al. (2019) for more details as well as the Validation page for some updates.

The reference global mean sea level (GMSL) based on data from the TopEx/Poseidon, Jason-1, Jason-2 and Jason-3 missions from January 1993 to present, after removing the annual and semi-annual signals and applying a 6-month filter. By applying the postglacial rebound correction (-0.3 mm/yr), the rise in mean sea level has thus been estimated to 3.5 mm/year with an uncertainty of 0.4 mm/yr.


Analyzing the uncertainty of the altimetry observing system yields to construct an uncertainty envelop for the GMSL climate data record (shaded area in the figure above). The resulting uncertainty in the GMSL rise is estimated to approximately 0.4 mm/yr at the 90% confidence level over period 1993-present. See Ablain et al. (2019) for more details on the methods as well as the Validation page for some figures updates.

The dashed line displayed over 1993-1998 is an estimation of the GMSL evolution after correction of the TOPEX-A instrumental drift (Cazenave WCRP 2018). It is estimated from empirical correction derived by comparing altimetry and tide-gauge sea level data (see more details in Validation). The TOPEX-A instrumental drift led to overestimate the GMSL slope during the first 6 years of the altimetry record. Accounting for this correction changes the shape of the GMSL curve, that is no more linear but quadratic, indicating that the mean sea level is accelerating during the altimetry era (1993-to present, Beckley et al. 2017, Nerem et al. 2018). Currently, this empirical correction is not applied to the AVISO GMSL dataset, wainting for the ongoing TOPEX reprocessing by CNES and NASA/JPL.


To compute the mean sea level at regional scales, auxiliary missions like SARAL/AltiKa, Envisat, ERS-1 and ERS-2 are used in addition to the reference missions. This multimission approach allow to compute the Mean Sea Level at high latitudes (higher than 66°N and S) as well as to improve the products spatial resolution. See Ssalto/DUACS webpage for the processing details.

Although the globally averaged sea level is rising over the period 1993-to present, the spatial distribution of the sea level is heterogeneous over the globe. Locally, the sea level rise can be way larger than the global average of 3.5 mm/yr. These spatial patterns are not stationary but transient features associated to heat redistribution and ocean circulation, like the ENSO events and/or the Kuroshio current, well captured by the satellite altimetry observing system.

Further information on Regional Variability and past sea level reconstructions

Regional gridded sea level trend over the period 1993-to present (in mm/year) from the multi-mission Ssalto/Duacs data. The grid resolution is of a 1/4 of a degree.

explanatory video

Altimetry satellites give observations of the sea level continuously since 1993 all over the globe. This long-term monitoring allows the scientific community to quantify the sea level rise, estimate its impact on the society and understand better its origins.

You must enable cookies in your browser preferences to save the modifications
You are using an older version of Internet Explorer, please update to take full advantage of Aviso+ features

Customize the home page

View all widgets
Reduce display
Public profile
User profile

Select/Deselect widgets

Discover AVISO+

Customizable home, reading tools, products search guide, etc.. Discover step by step the features of the new site AVISO+.

Customizable homepage

The new home page is composed of blocks called "widgets".

Rearrange the blocks with a "Click & Drop".

Hide a widget with the cross at the top right. Reset or add a widget with the "wrench" icon. The "User" and "Public" profiles offer a predefined organization.

All the modifications are automatically saved as cookies on your machine so as to enable you to have your own specific AVISO+.

Reading tools

Ease your reading by choosing the page background colour (black/white) and/or by modifying the font size.

Browsing menu and breadcrum trail

To ease your browsing through AVISO+, you can use at any time the main banner items with the interactive submenus or use the browsing menu on the left side of the screen (it is open by default). For more readiness of the page contents, you can fold and unfold the browsing menu by clicking on the tab. At any time you can know where you are thanks to the browsing menu or the breadcrum at the top of the page.

Products search guide

The first submenu of the "Data" banner item leads you to a new search form enabling you to find quickier the product that suits your needs. The list of results is updated according to your selection criteria.

AVISO+ Multimedia

The first submenu of the "Multimedia" banner item leads you to AVISO+ collections of images and videos linked to altimetry and its applications. Have a nice visit!