In recent decades, the Earth’s seas have been rising at a rate of under 0.8 mm/year (8 cm per century) according to estimations of the sum of contributions to sea level rise. In contrast, sea levels rose at rates of more than 40 mm/year ~10,000 years ago.
Relative sea level rise can be calculated using observations from the sum of contributing sources: 1) terrestrial water storage, 2) thermal expansion (warming), and 3) glacier and ice sheet melt.
As the above image illustrates, the peer-reviewed scientific literature suggests the total contribution to sea level rise for recent decades can be calculated as about 0.8 mm/yr, or 8 cm (~3 inches) per century.
- Terrestrial water storage: -0.55 to -0.71 mm/yr (Chao et al., 2008, Reager et al., 2016)
- Thermal expansion: 0.64 mm/yr (Llovel et al., 2014)
- Glacier and ice sheet melt: 0.76 mm/yr (Frederikse et al., 2018)
In contrast, results from a new paper (Nirgi et al., 2019) suggest Baltic sea levels were as much as 10 m higher than they are now about 7,300 years ago; regional seas had risen by about 21 to 22 m between 10,800 and 10,300 years ago, which is 4.3 m per century (43 mm/yr).
Image Source: Nirgi et al., 2019
To put this sea level rise rate (40+ mm/yr) into perspective, shorelines retreated at rates of 40 m per year and 75 cm per week (Donoghue, 2011) earlier in the Holocene.
Image Source: Donoghue, 2011
For other regions, sea levels naturally rose at rates of 6 meters per century (60 mm/yr) at the end of the last glacial maximum (Zecchin et al., 2015).
Image Source: Zecchin et al., 2015
These explosive sea level rise rates were not just local or regional in scope, but hemispheric (at least).
About 14,500 years ago, the Northern Hemisphere warmed up by 4°C to 5°C within a span of “just a few decades” as sea levels subsequently rose 12 to 22 m in less than 340 years (Ivanovic et al., 2017).
That’s 3.5 to 6.5 m per century, or 35 to 65 mm/yr for the Northern Hemisphere.
This abrupt change occurred without significant changes in atmospheric CO2 concentrations, undercutting attempts to link CO2 concentration changes to abrupt climate change in the paleoclimate record.