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hubie [soylentnews.org] writes:

International collaboration highlights significant findings in climate change study [unm.edu]:

An international team of scientists has developed an accurate record of preindustrial sea level utilizing precisely dated phreatic overgrowths on speleothems that provide a detailed history of Late Holocene sea-level change in Mallorca, Spain, an island in the western Mediterranean Sea. The results provide an unprecedented picture of sea level over the past 4,000 years, putting the preindustrial and modern global mean sea level (GMSL) histories in context.

[...] The absolute position of relative sea level is determined from uranium-series ages obtained on phreatic overgrowth on speleothem (POS) samples. The POS grow precisely at the seawater-air interface and are thus accurate indicators of sea level during any growth period. In this study the Late Holocene (the past 4,000 years) sea-level estimates are based on 136 new, precise uranium-series dates of 13 POS samples obtained from eight caves along the southern and eastern coastline of Mallorca.

[...] "Getting a precise measure of sea level has been a challenge. We were lucky enough to get this amazing set of samples that span the full 4,000 years," said Asmerom. "The data showed that sea level was remarkably stable for most of the 4000 years, except for a sudden jump of about 0.25 meters between 2,830 and 3,200 years before present.

"We show that modern GMSL rise is anomalous relative to any natural variability over the past 4,000 years, including the rise at ~3000 years ago. The current rate of sea-level rise is about six times higher compared to the rate during the jump 3,000 years ago, and is likely driven by greenhouse gas warming."

The team found that sea level rose locally by 0.12 to 0.31 meters during the timeframe of 3.26 to 2.84 thousand years ago and remained within 0.08 m of preindustrial levels from 2.84 thousand years ago to the year 1900 CE (Common Era). This sea-level history is consistent with glacial isostatic adjustment models adopting relatively weak upper mantle viscosities. There is virtual certainty from this research that the average GMSL rise since 1900 CE has exceeded even the high average rate of natural sea-level rise ~3,000 years ago inferred from the speleothem record.

"One of the biggest obvious unknowns about the future is how much global real-estate we are going to lose to global warming and how fast it could happen," This has existential implications for many island nations, in addition to the significant increase in tidal floodings and saltwater incursion into coastal aquifers and estuaries. Nearly 40 percent of the world population lives within 100 km of a coast", said Asmerom.

Journal Reference:
Bogdan P. Onac, Jerry X. MitrovicaJoaquín Ginés, Yemane Asmerom, et al., Exceptionally stable preindustrial sea level inferred from the western Mediterranean Sea [open], Sci Adv, 8, 26, 2022. DOI: 10.1126/sciadv.abm6185 [doi.org]

Original Submission