Exceptionally stable preindustrial sea level inferred from the western Mediterranean Sea

Abstract

An accurate record of preindustrial (pre-1900 CE) sea level is necessary to contextualize modern global mean sea level (GMSL) rise with respect to natural variability. Precisely dated phreatic overgrowths on speleothems (POS) provide detailed rates of Late Holocene sea-level rise in Mallorca. Statistical analysis indicates that sea level rose locally by 0.12 to 0.31 m (95% confidence) from 3.26 to 2.84 thousand years (ka) ago (2σ) and remained within 0.08 m (95% confidence) of preindustrial levels from 2.84 ka to 1900 CE. This sea-level history is consistent with glacial isostatic adjustment models adopting relatively weak upper mantle viscosities of ~10 20 Pa s. There is virtual certainty (>0.999 probability) that the average GMSL rise since 1900 CE has exceeded even the high average rate of sea-level rise between 3.26 and 2.84 ka inferred from the POS record. We conclude that modern GMSL rise is anomalous relative to any natural variability in ice volumes over the past 4000 years.

The Anthropocene within the Geological Time Scale: a response to fundamental questions

“…Effects to date include: substantial ongoing loss of the world's glaciers (Rounce et al, 2023) with a corresponding rise in the snow/tree lines and release of stored contaminants (Schmid et al, 2011); increased erosion (Rose et al, 2011;Syvitski et al, 2022) and fluvial sediment flux (Li et al, 2021;Syvitski et al, 2022); and sea-level rise accelerating to 4.4 mm/yr during 2012-2022 (WMO, 2022; cf. the extreme Late Holocene stability described by Onac et al, 2022) and now thought certain to exceed 2 m in coming centuries (Vernimmen and Hoojier, 2023). The opportunity to preserve the West Antarctic Ice Sheet from collapse, for instance, has probably already passed (Naughten et al, 2023).…”

Characterization of phreatic overgrowths on speleothems precipitated in the northern Adriatic during a sea-level stillstand at ca. 2.8 ka

“…Sea-level studies based on phreatic overgrowths on speleothems (POS) have been conducted since the early 1970s (Ginés and Ginés, 1974). Unlike the submerged speleothems and biogenic encrustations, POS allow precise sea-level reconstructions (Vesica et al, 2000;Tuccimei et al, 2010;Polyak et al, 2018;Onac et al, 2022). POS are secondary depositional structures (carbonate encrustations) that precipitate in coastal caves at the water table around pre-existing vadose speleothems in favorable geochemical conditions (Ginés et al, 1981;Fornós et al, 2002).…”

“…POS also have been identified and described in Bermuda (Harmon et al, 1978) and Mexico (Jenson et al, 2018). So far, POS-based research has contributed greatly to the study of sea level, in particular to precisely characterize the Late Pleistocene highstands, and to improve the glacial isostatic adjustments for the western Mediterranean (Tuccimei et al, 2012;Polyak et al, 2018;Onac et al, 2022). However, some POS that formed during the Late Holocene (Tuccimei et al, 2010(Tuccimei et al, , 2011Miklavič et al, 2018) and, during the last 2800 years in particular, show sea-level stability throughout that period (Onac et al, 2022).…”

Driving processes of relative sea-level change in the Adriatic during the past two millennia: From local tectonic movements in the Dubrovnik archipelago (Jakljan and Šipan islands) to global mean sea level contributions (Central Mediterranean)

“…Therefore, to improve understanding of the magnitudes, rates, and driving processes of RSL change at all scales (local, regional and global) and in different geomorphological and geological contexts, there is a need for diverse kinds of RSL proxy records (e.g. Morhange and Marriner, 2015;Khan et al, 2019;Dean et al, 2019;Onac et al, 2022) which can provide robust high-resolution RSL reconstructions.…”