New study on changing sea levels

Aug 11, 2021

A new study of shorelines in the Bahamas may change estimates of past sea levels. Here, some of the authors survey coastal rocks on the archipelago’s Crooked Island formed when sea levels were higher. Photo: Blake Dyer

One of the current mysteries of climate science surrounds the widely accepted evidence that during the planet’s most recent past natural warm period, about 128,000 to 117,000 years ago, global sea levels peaked as high as 6 to 9 meters higher than today. And, during that so-called last interglacial, temperatures were just 1or 2 degrees Celsius warmer than those of preindustrial times—marks we may surpass by century’s end, if not sooner. Such a deluge could have been produced only by collapses of the Greenland and/or Antarctic ice sheets. If that happens now, it will drown much of the human world. Yet, at least so far, models of future sea level rise generally hover around a meter or so within the next 100 years.

In a new study, a team at Columbia University’s Lamont-Doherty Earth Observatory (USA) and MARUM believes they have an answer: They say that researchers examining signs of past sea levels along various coasts may have failed to accurately correct for long-term ups and downs of the land itself. Based on newly sophisticated measurements made across the Bahamas along with new methods of analyzing data, the researchers produced lower—though still daunting—estimates for the last interglacial. They say seas peaked at least 1.2 meters higher than today—roughly in line with most current models for the next 100 years of so. However, they say, levels could have been higher. An unlikely upper limit, they say, is 5.3 meters. The study appears this week in the Proceedings of the National Academy of Sciences (PNAS).

Original publication:

Blake Dyer, Jacqueline Austermann, William J. D’Andrea, Roger C. Creel, Michael R. Sandstrom, Miranda Cashman, Alessio Rovere, and Maureen E. Raymo: Sea-level trends across The Bahamas constrain peak last interglacial ice melt. PNAS 2021. DOI: https://doi.org/10.1073/pnas.2026839118

Press release Lamont-Doherty Earth Observatory