Geoscientists reconstruct 6.5 million years of sea level stands

January 21, 2021

TAMPA, Fla. (January 22, 2021)- The pressing concern posed by rising sea levels has created a critical need for scientists to precisely predict how quickly the oceans will rise in coming centuries. To gain insight into future ice sheet stability and sea-level rise, new research from an international team led by University of South Florida geoscientists is drawing on evidence from past interglacial periods when Earth's climate was warmer than today.

Using deposits in the caves of the Mediterranean island of Mallorca, known as phreatic overgrowths on speleothems, to reconstruct past sea level stands, the team was able to determine that the vertical extent of these unique deposits corresponds with the amplitude of the fluctuating water table, said author USF geosciences Professor Bogdan Onac. That determination now is providing scientists with a way to precisely measure past sea levels.

Working with colleagues at the University of New Mexico, University of Balearic Islands and Columbia University, the researchers' findings were published in Scientific Reports. In their project, the geosciences team documented the position and timing of sea level during key time intervals over the past 6.5 million years for which global mean sea-level estimates have been highly uncertain.

Their results contribute to the understanding of past warm periods to gain insight into the magnitude and frequency of sea level rise, which is critical for scientists' ability to forecast and make recommendations on adapting to future global warming.

The team expanded upon their research previously published in Nature, by investigating samples between 800,000 and 6.5 million years old. Using deposits from several of the Mallorcan caves and applying numerical and statistical models to estimate the corrections for glacial isostatic adjustment and long?term uplift, they translated the local sea level estimates into global mean sea level (GMSL).

Their results show that during key time events, such as Pliocene-Pleistocene Transition, when the Earth underwent a major transition from the warm climates of the Pliocene to the Pleistocene ice ages, the GMSL stood at 6.4 meters. During the beginning and the end of the Mid?Pleistocene Transition the sea level was at ?1.1 meter and 5 meters respectively.

"Overall, our results support that sea level dropped significantly after the Pliocene," said USF doctoral alum Oana Dumitru, the study's lead author who is now a postdoc at Columbia University's Lamont-Doherty Earth Observatory.

The authors also show that local sea level before and at the onset of the Messinian Salinity Crisis, a major geological event during which the Mediterranean Sea became partly to nearly dry of water, was at approximately 33 meters above present level. These estimates may offer starting points for assessing whether sea-level drawdown in the Western Mediterranean happened gradually or rapidly, the researchers said.

"Our estimates are important snapshots of sea level still stands, but additional sea level index points will be useful to yield more context for our results," the team wrote in their journal article. "By providing direct estimates of sea level using POS as robust proxies, this work advances our understanding of sea level position during several past warm periods. These results therefore contribute to efforts of studying past warm periods to gain insight into the magnitude and frequency of sea level rise."
-end-
Dumitru was joined in the research by Columbia University colleague Jacqueline Austermann; Victor J. Polyak and Yemane Asmerom of the University of New Mexico; Joan J. Fornós, Joaquin Ginés and Angel Ginés of Universitat de les Illes Balears in Mallorca, Spain.

This research is the result of a collaborative National Science Foundation (NSF) project between the University of South Florida and the University of New Mexico and part of the bilateral agreement between USF and Universitat de les Illes Balears and has been funded by NSF and the Spanish State Research Agency.

University of South Florida (USF Innovation)

Related Sea Level Articles from Brightsurf:

Sea-level rise will have complex consequences
Rising sea levels will affect coasts and human societies in complex and unpredictable ways, according to a new study that examined 12,000 years in which a large island became a cluster of smaller ones.

From sea to shining sea: new survey reveals state-level opinions on climate change
A new report analyzing state-level opinions on climate change finds the majority of Americans believe in and want action on climate change--but factors like state politics and local climate play important roles.

UM researcher proposes sea-level rise global observing system
University of Miami (UM) Rosenstiel School of Marine and Atmospheric Science researcher Shane Elipot proposes a new approach to monitoring global sea-level rise.

How much will polar ice sheets add to sea level rise?
Over 99% of terrestrial ice is bound up in the ice sheets covering Antarctic and Greenland.

Larger variability in sea level expected as Earth warms
A team of researchers from the University of Hawai'i (UH) at Mānoa School of Ocean and Earth Science and Technology (SOEST) identified a global tendency for future sea levels to become more variable as oceans warm this century due to increasing greenhouse gas emissions.

Sea-level rise could make rivers more likely to jump course
A new study shows that sea level rise will cause rivers to change course more frequently.

UCF study: Sea level rise impacts to Canaveral sea turtle nests will be substantial
The study examined loggerhead and green sea turtle nests to predict beach habitat loss at four national seashores by the year 2100.

Wetlands will keep up with sea level rise to offset climate change
Sediment accrual rates in coastal wetlands will outpace sea level rise, enabling wetlands to increase their capacity to sequester carbon, a study from the Marine Biological Laboratory, Woods Hole, shows.

How sea level rise affects birds in coastal forests
Saltwater intrusion changes coastal vegetation that provides bird habitat. Researchers found that the transition from forests to marshes along the North Carolina coast due to climate change could benefit some bird species of concern for conservation.

As sea level rises, wetlands crank up their carbon storage
Some wetlands perform better under pressure. A new Nature study revealed that when faced with sea-level rise, coastal wetlands respond by burying even more carbon in their soils.

Read More: Sea Level News and Sea Level Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.