Central OC Times

An international research team, including an Earth system scientist from the University of California, Irvine, has discovered that topographical features along the sloping ocean floor significantly contribute to seawater upwelling. The study, recently published in Nature, reveals a "vigorous near-bottom upwelling" that facilitates the transition of water from denser to lighter layers at a rate of 100 meters per day.

The team conducted their research by releasing dye into a suboceanic canyon in the North Atlantic Ocean off Scotland's coast and tracking its movement. "The upwelling rates we tracked at this underwater canyon were about 10,000 times higher than the global average," said Henri Drake, UC Irvine assistant professor of Earth system science. "These findings suggest that most of the upwelling required to balance the deep ocean’s mass budget disproportionately occurs in a few turbulent hot spots like this one."

Dense water forms in polar regions as it becomes colder and saltier before sinking to the ocean’s depths where pressure increases and temperature drops. This process is crucial for regulating global climate by transferring heat and nutrients throughout the ocean. However, scientists have been puzzled by how this dense water returns to the surface—a phenomenon known as diapycnal upwelling—hindering accurate climate models.

Aboard a research vessel, scientists released dye at approximately 1,850 meters within the underwater canyon and measured its dispersion over several days using sensors moving in a yo-yo pattern. "We found that, on average, the dyed water became lighter at a rate of about a quarter of a degree Celsius per day," Drake explained. "Because warmer water is generally lighter than cold water and because light water tends to lie atop denser water, we estimate that this corresponds to a 100-meter-per-day upwelling rate."

Drake emphasized that this study provides direct evidence supporting earlier theoretical predictions about ocean circulation and mass balance. It also offers valuable insights for climate scientists aiming to understand marine mechanisms impacting global climate change.

The project included researchers from UC San Diego’s Scripps Institution of Oceanography; Massachusetts Institute of Technology; Ifremer (the French national institute for ocean science and technology); University of Exeter; Boston University; U.K.’s National Oceanography Centre; Royal Netherlands Institute for Sea Research; and Woods Hole Oceanographic Institution. The study was financially supported by the National Science Foundation and U.K.’s Natural Environment Research Council.

About UC Irvine: Founded in 1965, UC Irvine is part of the Association of American Universities and ranks among the nation’s top public universities according to U.S. News & World Report. The campus hosts more than 36,000 students across 224 degree programs and contributes significantly to local and state economies.

For further information on UC Irvine's initiatives or media access inquiries: news.uci.edu or https://news.uci.edu/media-resources.