U of I-led underwater forest research provides rare glimpse to past climate conditions

MOSCOW, Idaho — Cypress trees found on the ocean floor 5 miles south of coastal Alabama are helping scientists from University of Idaho build climate models based on conditions 75,000 years ago.

In an article published in Climate and Atmospheric Science titled “Rapid decline and mortality of a Pleistocene-aged forest now submerged in the northern Gulf of Mexico, USA,” Associate Professor Grant Harley and his research team developed a 489-year tree-ring chronology using wood from the underwater forest.

Using core samples taken from the drowned forest, the research shows the growth and sudden death of the forest after it was submerged by intense storm activity and sea-level changes that resulted from melting glaciers. Scientists learned that the trees of the submerged forest are like trees found today in the swamps of the Lower Mississippi Delta.

“These findings allow us a rare glimpse into past climatic conditions and help us better understand the historical impact of climate change on coastal ecosystems,” Harley said.

The Pleistocene, or Ice Age, is a geological period that lasted from about 2.58 million to 11,700 years ago. This period is marked by repeated glacial cycles in which large ice sheets spread over the northern continents shaping much of the earth’s current landscape and influencing global climate. Massive pieces of glaciers broke off and drifted into the North Atlantic Ocean where they melted, releasing huge quantities of freshwater that disrupted ocean currents, cooled the climate and affected global weather patterns.

“Studying these rapid changes to earth’s climate back then will help us better understand how fast climate change might occur during this period of unprecedented warming to our planet,” Harley said.

This discovery provides a rare opportunity to study ancient ecosystems that were once terrestrial but are now submerged, offering valuable insights into past environmental conditions. The tree-ring chronology also highlights how extreme weather events, like those potentially linked to melting glaciers, could have affected coastal vegetation and contributed to large-scale mortality events, Harley said.

By combining tree-ring analysis with climate modeling, the research provides a clearer understanding of the environmental history of the southeastern U.S. coast and its ecological past, including how it may have responded to storm activity, freshwater fluxes and other climate stressors.

“This study not only adds to the field of paleoecology but also enhances our understanding of how coastal ecosystems have adapted to and been shaped by climatic events over thousands of years,” Harley said.

This project was funded to Louisiana State University by Bureau of Ocean Energy Management under award PO-0000156658. The total project funding is $54,684, of which 100% is the federal share.

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Media contact

Grant Harley
Associate Professor
Department of Earth and Spatial Sciences
208-885-0950
gharley@uidaho.edu