Sea-level rise along the North Atlantic coasts since 1900

The global mean sea-level rise is today well quantified: 1.4 ± 0.1 mm yr^-1 over 1901-1993 (based on tide gauge records) and 3.0 ± 0.2 mm y^-1 over 1993-2010 (based on satellite altimetry data). However, this rise is not uniform and large departures from the global mean sea-level trend are observed. Given that over 750 million people are living in the low-elevation coastal zone and because sea-level will continue to rise due to climate change, it is crucial to obtain reliable trends at local and regional scale, to design appropriate adaptation policies for the future. In this study, we investigated the North Atlantic sea-level rise over the 20th century along the coasts using tide gauges and climate model outputs from the Coupled Model Intercomparison Project 6 (CMIP6) framework. As climate models do not account for land ice melt, the contribution of ice sheets (Greenland and Antarctica), mountain glaciers and land water storage were added a posteriori. Climate models provide gridded data with a relatively coarse resolution (~1°); whether they correctly simulate sea-level rise at a given point in space is still an open question. We explored the ability of climate models to correctly reproduce the 20th century sea-level trends at the nearest points to tide gauge locations in the North Atlantic ocean over 1900-2014. Based on a multi-member ensemble approach from CMIP6 model outputs, we determine both the externally forced (ensemble mean) and internal variability contribution (ensemble spread) to historical sea-level changes. We showed that the internal variability is higher on the west side of the North Atlantic basin than on the east side.