Paleoceanography 5: Chasing a Ghost

Is it possible to catch a ghost? Major ocean features like western boundary currents are fairly stable today, but millions of years ago they may have been quite different. Unfortunately, unlike living things which may leave fossils or biomarkers for scientists to find, currents have no physical remains. Scientists at Texas A&M University are working to capture a long-dead specter as they attempt to uncover the location of the Kuroshio Current millions of years ago.

Surface waters flow in a circular pattern in major ocean basins, clockwise in the Northern Hemisphere and counter clockwise in the Southern Hemisphere. Western Boundary Currents like the Kuroshio Current occur at the western edge of ocean basins. They are fast and narrow, transporting massive amounts of warm water from the equator to the poles. As the Kuroshio current flows north, it turns to the right, extending into the middle of the Pacific Ocean basin. The greatest temperature gradient with latitude in the western Pacific Ocean occurs between 38- and 40-degrees north. This gradient is associated with the Kuroshio Extension, where the current turns into the open ocean.

This diagram shows the general circulation patterns of the North and South Pacific Ocean. Boundary currents are circled; western boundary currents are found on the western edge of ocean basins, in this case off the coast of New Zealand and Japan. Image from: https://oceanservice.noaa.gov/education/tutorial_currents/04currents3.html

The Kuroshio Extension shifts north or south seasonally and over long time periods. Identifying where both the Kuorshio Current and Extension were millions of years ago is important for reconstructing past heat transport and carbon cycles in the ocean. As the Kuroshio Current flows northward and releases heat, the water cools and the solubility of CO2 increases. Therefore, regions of large temperature gradients associated with western boundary currents are where the greatest amount of CO2 enters the oceans.

This has been On the Ocean, a program made possible by the Department of Oceanography and a production of KAMU-FM on the campus of Texas A&M University in College Station. For more information and links, please go to ocean.tamu.edu and click On the Ocean.

Featured image from: Mikkel Juul Jensen/SPL/Cosmos (left) and Aphelleon/Shutterstock (right)

Script Author: James M. Fiorendino

Contributing Professor: Dr. Yige Zhang