Higher sea levels were due to a warmer climate, or the consequence of more water in ocean basins rather than locked up on land as ice.

In a new study, scientists assess they can now clearly separate “tectonic and climate signals in Holocene sea-level records” by precisely identifying patterns of long-term vertical land motion near coastal regions.

Meters-higher relative sea levels during the Middle Holocene have often been attributed to land uplift, or glacio-isostatic rebound – the gradual rising of the Earth’s crust as the weight of glaciers and ice sheets melted away.

This tectonic attribution precluded explanations that the sea level highstands could have been connected to a warmer climate and consequent smaller ice sheets and glaciers.

Image Source: Melnick et al., 2026

Another new study calls attention to the 1.76 m higher sea levels along the coasts of southeastern Australia 6000 years ago, falling to 0.59 m higher than today by 2000 years ago.

Australia is another region that would not be heavily impacted by glacio isostatic rebound, which again affirms these higher sea levels were linked to eustatic (climate-related) processes.

Image Source: Kennedy et al., 2026