Thanks to mineral formations found in cave systems a team of scientists reconstructed past sea … [+]
An international team of researchers reconstructed preindustrial sea levels thanks to mineral formations found in flooded caves. The results show that the impact of modern anthropogenic warming on sea-level rise will be even more extensive than previously estimated.
The team found evidence of a previously unknown 20 centimeter sea-level rise that occurred nearly 3,200 years ago when ice caps melted naturally over the course of 400 years at a rate of 0.5 millimeters per year. Otherwise, despite major climatic events like Medieval Warm Period and the Little Ice Age, the sea level remained exceptionally stable until 1900.
“The results reported in our study are alarming,” said lead author Bogdan P. Onac, geology professor at University of South Florida. “The sea-level rise since the 1900s is unprecedented when compared to the natural change in ice volumes over the last 4,000 years. This implies that if global temperatures continue to rise, sea levels could eventually reach higher levels than scientists previously estimated.”
To create the sea-level timeline, the team gathered 13 samples from eight caves along the coastline of the Mediterranean Sea. The sampled mineral deposits are rare—only forming near the coastline in cave passages that were repeatedly flooded by sea water, making them accurate markers of sea-level changes overtime.
The results were then used to calibrate a complex software at Harvard University, also used to generate sea-levels predictions under different climate scenarios.
“If humans continue to be the main driver and the temperature increases 1.5 degrees in the near future, there will be irreversible damage,” Onac said. “There will be no turning back from that point on.”
Based on ice mass loss from the Antarctic and Greenland, the average sea-level rise since 2008 is 1.43 millimeters per year, a much higher rate than 3,200 years ago.
“Even if we stop right now, sea-level will continue to rise for at least a couple of decades, if not centuries, simply because the system is warmed up.”
Models of future sea-level rise generally hover around 100 centimeters within the next 100 years. Factors like the melting rate of ice sheets and glaciers, shifting oceanic circulation patterns, water temperature, tidal range, storm surges, coastal geomorphology and land subsidence will affect local sea-level changes.
Projected sea level rise for New York. In this worst-case scenario, emissions and temperatures rise … [+]
NASA’s sea level projection tool displays possible future sea-levels under several greenhouse-gas-emission and socioeconomic scenarios. A low-emissions future limiting global warming to 1.5 degrees, a “business as usual” trajectory with emissions on their current track and a projected global warming of 2 to 4 degrees above preindustrial levels by the end of the century, and an “accelerated emissions” scenario with temperatures rising well beyond 4 degrees.
A low-emission future, for example, would occur if humanity reduces its greenhouse gas emissions, lessening the effects of climate-driven sea level change. A high-emission projection would lead to the most rapid and significant rise in sea level. Warming of over 2 degrees could be enough for Greenland’s ice sheet to melt, which would cause sea-levels to rise globally by more than 200 centimeters, TheScientist website reports.
Rising sea-levels could displace an estimated 267 million people worldwide, increase the risk for floods, cause beach erosion and habitat loss for animals and plants living on or near the shoreline.
The paper “Exceptionally stable preindustrial sea level inferred from the western Mediterranean Sea” is published in Science Advances (2022). Materials provided by the University of South Florida.
