(7) regional atmospheric pressure anomalies and changes in the strength and distribution of ocean currents (so-called Dynamic Sea Level Change), related in particular to the coupled ocean-atmosphere dynamics, and (6) ubiquitous land surface subsidence related in particular to extraction of groundwater and oil/gas mining and compaction of soft deltaic soils , (5) changes in the earth gravitational field, related in particular to decrease of the Greenland and Antarctic ice sheets, (4) earth crust motions - in particular the solid Earth deformation in response to mass reduction of the polar ice caps and associated water loading of the seabed, the so-called glacial isostatic adjustment (GIA) the response time scale of GIA (from decades to millennia) strongly depends on the local viscoelasticity of the earth mantle , Other phenomena can substantially influence sea levels at regional scale, inducing either sea-level rise or sea-level fall. (3) decreasing storage of surface water and groundwater on land. (2) water mass increase, which is mainly due to melting of mountain glaciers and decrease of the Greenland and Antarctic ice sheets, and (1) thermal expansion of ocean waters related to decrease of the density (also referred to as thermo-steric component of sea-level rise, related to increasing temperature), This global sea-level rise (often termed Eustatic sea-level rise) has three components: On a global scale, sea-level rise is mainly due to an increase of the water mass and water volume of the oceans. Several phenomena contribute to sea-level rise.
Figure from (SROCC, 2019) Cite error: Invalid tag The shaded areas indicate the uncertainty in the projections. Projections of possible sea-level rise for the low and high emission scenarios, RCP2.6 (blue) and RCP8.5 (red), respectively. The sea level projections of the 2021 IPCC climate report for the year 2100 are similar to the projections of the 2019 report. The high scenario can lead to a rise of up to 5 m of the global average sea level in 2300, but with great uncertainty. Two scenarios for greenhouse gas emissions are considered in this figure: (1) a "low" scenario, called RCP2.6, with strong reduction of global greenhouse gas emission, such that global warming will probably not exceed 2 oC (2) a "high" scenario, called RCP8.5, in which no measures are taken to limit greenhouse gas emissions ('business as usual').
Projections for future sea-level rise up to the year 2030 are presented in the Special IPCC Report on the Ocean and Cryosphere in a Changing Climate (SROCC, 2019), see Fig. It is almost certain that global warming due to human emissions of greenhouse gases is responsible for steepening this trend since at least a few decades. Sea-level rise is the rising trend averaged over longer periods, which is observed at many coastal stations since a few centuries. Sea levels are highly variable over periods ranging from seconds to decades. 4.1 Uncertainties related to melting of the polar ice sheets.3 Annual and decadal sea level fluctuations.
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