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Topic: Sea Level Rise

Sea Level Rise

Sea Level Rise (SLR) describes the measurable phenomenon in which the sizes of Earth’s oceans are increasing, causing them to overtake Earth’s landmasses.

In scientific literature, SLR describes the increase of collective global oceans, as opposed to various other, local, or temporary changes in sea level. SLR measurements and predictions do not necessarily imply specific regional and local impacts1,4.

There is no scientific consensus about historic SLR rates, current measures, or forecasts. However, SLR analyses with similar methods typically yield similar results. Historic analysis of pre-Industrial SLR demonstrates slow increases, around one (1) millimeter (mm) or less per year. Analyses of post-Industrial SLR rates agree on faster increases, at around one and a half (1.5) to two (2) mm per year. Analysis of contemporary SLR demonstrates accelerating trends, with rates measuring around three (3) to four (4) mm per year. NASA estimates SLR has risen around 102mm between 1993 and 2025, with a margin of error around 4mm. 100 millimeters is comparable to the width of many smartphones.

SLR is primarily measured through the analysis of tidal or satellite data. Historically, SLR was observed through tidal gauges, which record changes in the height of oceanic tides over time. In the modern era, satellites measure SLR by calculating the distance between their orbit and the oceans’ surface. The analysis of different datasets, even with the same or similar methods, can yield different SLR measurements due to sensitivities in computing and modeling1.

Glacial melt rates and the thermal expansion of oceans are the most significant contributing factors to SLR. As glaciers melt, the flow of fresh water into the oceans changes, altering their temperatures and saltiness; all of which contribute to the mass and volume of Earth’s oceans. With some controversy over degree of influence, various sciences demonstrate correlations between climate change, global warming, and SLR. As Earth warms, SLR increases.

Whatever the actual rate may be, SLR threatens coastal and low-elevation shorelands with increased tidal and nuisance flooding, ground and groundwater salinization, as well as eventual inundation and total loss. SLR is also a significant contributor to coastal erosion, with long-term implications for even higher-elevation landmasses.

©2025 ClimateLit (Zachary Dixon)

See Also: NOAA Climate.gov: Global Sea Level

References:

  • Adebisi, N., Balogun, A. L., Min, T. H., & Tella, A. (2021). Advances in estimating Sea Level Rise: A review of tide gauge, satellite altimetry and spatial data science approaches. Ocean & Coastal Management, 208, 105632.

  • Frederikse, T., Landerer, F., Caron, L., Adhikari, S., Parkes, D., Humphrey, V. W., … & Wu, Y. H. (2020). The causes of sea-level rise since 1900. Nature, 584(7821), 393-397.

  • Griggs, G., & Reguero, B. G. (2021). Coastal adaptation to climate change and sea-level rise. Water, 13(16), 2151.

  • Milne, G. A., Gehrels, W. R., Hughes, C. W., & Tamisiea, M. E. (2009). Identifying the causes of sea-level change. Nature Geoscience, 2(7), 471-478.

  • NASA (2014, September 9). Sea Level. NASA.gov. https://climate.nasa.gov/vital-signs/sea-level/?intent=121

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