Paleoclimate Scientist Udara Amarathunga on an International Ocean Discovery Program to the Gibraltar Strait

Dec. 28, 2023
Researchers standing before their cruise ship about to depart from Amsterdam.

The Expedition 401 crew before departing from Amsterdam on December 12, 2023. Udara Amarathunga is in the back row, fourth from right.

Udara Amarathunga, Harry H. Hess Postdoctoral Research Fellow

Udara Amarathunga, Harry H. Hess Postdoctoral Research Fellow.

FOR IMMEDIATE RELEASE: Today, the exchange of the waters between the Mediterranean Sea and the Atlantic Ocean collide through a single gateway in the Gibraltar Strait. Approximately eight million years ago there were two other gateways: one in northern Morocco and the other through southern Spain. These connections narrowed and then closed, restricting exchange and causing the Mediterranean sea to fall by hundreds of meters. As a result, these waters became so salty that a layer of salt crystals more than 1000 meters thick, called the “salt giant,” formed at the bottom of its sea floor.

Around five million years ago, severe flooding reconnected the Atlantic with the Mediterranean, terminating salt giant formation and transforming the Mediterranean into the current marine system. This set of events impacted global climate both, by changing ocean chemistry, and its movement patterns. It may have led to a major episode of cooling the planet and creating permanent Arctic glaciers. The secrets of what happened during this period are preserved in the sediments in-and-on either side of the fossilized gateways.


Gibraltar Strait with four marked locations in red.

Off-shore (IODP) and on-shore (ICDP) scientific drilling sites of sediment planned for the IMMAGE project.



On December 12, 2023, the International Ocean Discovery Program (IODP) Expedition 401 departed from Amsterdam to begin a two-month scientific journey to the Gibraltar Strait. Its mission is to uncover these climate secrets buried beneath hundreds of meters of water and rock. Onboard will be Harry Hess postdoctoral research fellow and paleoclimate scientist Udara Amarathunga. He will be collaborating with the Daniel Sigman Research Laboratory at Princeton remotely throughout the expedition. Udara specifically will be using the nitrogen isotopes in foraminifera to reconstruct changes in the flow between the open ocean and the Mediterranean.

The overall objective of the International Ocean Discovery Program (IODP) Expedition 401 is to better understand the exchange between the Mediterranean and the Atlantic Ocean during the most dynamic period of its evolution as a gateway.

The expedition is conducted by the JOIDES Resolution Science Operator (JRSO) as part of the IODP. The IODP is a multidecadal, international research program supported by 22 nations, with the goal of exploring Earth's history and structure recorded in seafloor sediments and rocks and monitoring sub-seafloor environments. This first land-to-sea drilling project is led by Co-Chief Scientists Rachel Flecker (University of Bristol, UK) and Emmanuelle Ducassou (University of Bordeaux, France). It is an expedition that forms part of the larger IMMAGE Project, the first land-to-sea drilling project [acquisition of data across the shoreline to investigate the interconnected global Earth system], representing a collaboration between the International Ocean Discovery Program (IODP) and the International Continental Scientific Drilling Program (ICDP).

JOIDES Resolution provides personalized ship-to-shore live broadcasts

Throughout the expedition, the JOIDES Resolution can provide personalized ship-to-shore live broadcasts to school, community, and museum groups, the media and the general public. There's an opportunity for a ship-to-shore session for any group interested (online 40-minutes tour + QA session)

To book a session, you can reach an outreach officer on board, with this link:
Contact [email protected] for more information. 

Contact / Interviews / Images:

Erin Winick Anthony and Kellan Moss
Expedition 401 Onboard Outreach Officers
Email: [email protected]

Carol Cotterill
Assistant Director, Education and Outreach
US Science Support Program

Email: [email protected]

Trevor Williams
Expedition 401 Project Manager
JOIDES Resolution Science Operator

Email: [email protected] OR [email protected]

Related links:

About the expedition
IODP JRSO • Expeditions • Mediterranean Atlantic Gateway Exchange

About the research program

Live Video events with the JOIDES Resolution

Expedition webpage
(Expedition 401 is the off-shore component of the land-to-sea IMMAGE drilling project)

Join the crew and Science team on board the JOIDES Resolution

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