University of Hawai`i: Corals record 1,000 years of climate variability

Climate change alters the globe in many ways, and new research by the University of Hawai`i shows that even the deep ocean is changed fundamentally.

(Image: Samples of Hawaiian gold coral Kulamanamana haumeaae, which can live for thousands of years, were collected during a HURL Pisces V submersible dive. The submersible’s robotic arm is visible in the picture. The image is the cover shot on the current issue [Jan. 2, 2014] of the journal Nature. Credit: UH Hawaii Undersea Research Laboratory, DSRV Pisces Pilot Max Cremer.)

The chemical processes in the North Pacific around Hawai`i are showing signs of significant alteration—a change that appears clearly associated with climate change, according to a new paper in Nature.

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The Hawaii Undersea Research Laboratory (HURL) at the University of Hawaii-Manoa School of Ocean and Earth Science and Technology (SOEST), working with researchers from the Lawrence Livermore National Laboratory (LLNL) and the University of California-Santa Cruz analyzed deep-sea corals gathered near the Hawaiian Islands using the HURL Pisces V submersible.

By studying the skeletal layers of the slow-growing and very old corals, they were able to assess changes in the nitrogen levels in the ocean. The researchers were able to track changes in the ocean food web over the past 1,000 years from their studies of the ancient corals.

For most of that 1,000 years, the levels bounced around by a small amount. Then, as the Industrial Revolution began changing the makeup of the atmosphere and the Little Ice Age came to an end, the levels changed.

The research showed that nitrogen fixation—the process by which living things take up nitrogen from the atmosphere or water—has increased by roughly 20 percent in the North Pacific over the past roughly 150 years. And it found that the increase is still going on.

"This...has very significant implications about how we understand, and perhaps, can better predict effects of global warming in the Pacific, but also likely in other subtropical regions," Tom Guilderson of LLNL said.

Citation: Increasing subtropical North Pacific Ocean nitrogen fixation since the Little Ice Age. Owen A. Sherwood, Thomas P. Guilderson, Fabian C. Batista, John T. Schiff and Matthew D. McCarthy. Nature, doi:10.1038/nature12784

© Jan TenBruggencate 2014