More evidence emerges suggesting modern relative sea level (RSL) is among the lowest in several millennia. About 7000 years ago coasts were rapidly submerged beneath the sea at rates of up to 22 meters per year.
Ancient shoreline elevation evidence indicates RSL along the coasts of Central Japan has fallen ~0.82 m since the 1800s (Shishikura et al., 2023).
RSL was ~4.2 m higher than present approximately 3000 years ago and still ~2.8 m higher than present about 1500 years ago.
Image Source: Shishikura et al., 2023
From about 8000 to 6000 years ago sea level rise and warming were so rapid that coastlines retreated landward at rates of 22 m per year (Sydor et al.,, 2023). Per the charts shown in the study, there is more coastal land area above sea level today than anytime in 7000 years.
“In the period 8000–6000 yr b2k, the coastline migrated southwards (landwards), initially at a rate of up to 22 m/yr and later up to 2 m/yr. The main driving forces at that time were climate warming and rapid sea level rise.”
Image Source: Sydor et al.,, 2023
Sea levels used to be 4 m higher than today along the coasts of the Yellow Sea about 6500 years ago, or when CO2 was 265 ppm (Yang et al., 2023).
“RSL [relative sea level] increased quasi-linearly to approximately +4 m [above present sea level] 6.5 ky BP before decreasing to the current sea level (0 m) at a much slower rate.”