A Learning Experience

A winter cruise meant to offer students opportunities to gain at-sea expedition experience satisfied a science goal as well this winter.

An expedition to the Indian Ocean made the first detailed measurements of a key oceanographic phenomenon, an outcome that might not have been possible without an innovative University of California funding program to support ship-based research.

The UC Ship Funds program, which emphasizes student teaching aboard research expeditions, along with the National Science Foundation, supported studies on Scripps Institution of Oceanography at UC San Diego’s research vessel Roger Revelle.

Scripps physical oceanographers Jennifer MacKinnon, Robert Pinkel and Shaun Johnston led a search for giant undersea waves. Like surface waves people see on the beach, so-called internal ocean waves also crest and break under the sea surface. Some can reach the size of 10-story buildings.

During the cruise, the researchers focused on an area of the Indian Ocean known as the Southwest Indian Ridge, one of the areas on the planet where tectonic plates are spreading apart. In addition to addressing a dearth of data about internal waves in this region, the researchers surmised that the Southwest Indian Ridge’s jagged topography might result in an array of interesting internal wave phenomena.

They were correct. With instruments that measured water velocity, the researchers believe they captured the first close look at internal waves and internal mixing inside a 6-kilometer (3.7-mile) deep area called the Atlantis II Fracture Zone. Their data include information on how cooler, bottom waters intricately mix with warmer waters as they flow between the Southern and Indian Oceans.

“Higher up in the water column, we observed a series of internal tidal beams crisscrossing the water column, bouncing between ridge tops and the surface,” said MacKinnon.

With the newly obtained data, Pinkel and graduate students Oliver Sun and San Nguyen will be studying the pathways of wave energy emitted from the tidal beams. Sun and Nguyen were among four students who were able to take part in the cruise thanks to UC Ship Funds.

Results from the cruise, which concluded Jan. 30, will help scientists understand how currents flow around the planet and especially through the under-sampled Indian Ocean region. The data may also help scientists better understand the earth’s climate system by adding details to computer models of how heat and dissolved greenhouse gases are mixed into the deep ocean.

“What we’ve learned from this cruise and others before it is that ocean mixing is enormously different from place to place and time to time,” said MacKinnon. “The more places we look, the more we see different sorts of things causing mixing and the more inhomogeneous it all seems.”

For Bruce Appelgate, associate director for Ship Operations and Marine Technical Support, the cruise was the latest example of how funding sources such as UC Ship Funds can deliver unique opportunities for research and teaching. Since 1995 UC Ship Funds have supported an average of 57 days at sea per year on cruises ranging from single-day trips off San Diego to 21-day expeditions from foreign ports.

“Oceanographic research vessels are enormously expensive to operate, and the competition among researchers for external funding is fierce. Scripps has historically recognized the importance of enabling our researchers’ and students’ access to the sea,” said Appelgate. “Our UC Ship Funds allow us to continue this tradition by supporting teaching and research at sea aboard Scripps vessels.”

-- Mario C. Aguilera