North Pacific waters are acidifying more rapidly below the surface
Posted on August 14, 2025 by Marcie Grabowski

Carbon dioxide in the atmosphere enters the ocean at the surface and has been increasing the acidity of Pacific waters since the beginning of the industrial revolution over 200 years ago. A new study, led by University of Hawai‘i at Mānoa oceanographers, revealed that the ocean is acidifying even more rapidly below the surface in the open waters of the North Pacific near Hawai‘i. Their discovery was published recently in the Journal of Geophysical Research: Oceans.

“Ocean acidification has far‐reaching consequences for ocean biology and the global climate,” said Lucie Knor, lead author of the study and postdoctoral researcher in the UH Mānoa School of Ocean and Earth Science and Technology (SOEST). “We expected some indicators of ocean acidification to be changing more rapidly below the surface, because that was what some global studies have previously discovered, but we were very surprised that this was true for every single ocean acidification indicator.”

Knor and co-authors analyzed a 35‐year record of ocean carbon measurements made by the Hawai’i Ocean Time-series program throughout the entire water column–from the surface to nearly three miles deep–at the open ocean field site 60 miles north of O‘ahu, Hawai‘i, Station ALOHA.

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“Deeper waters are already naturally quite acidic in the North Pacific, so quickly increasing acidity could negatively impact plankton species and other organisms that live below the surface,” said Knor. “In the long run, these changes in ocean chemistry also make it harder for the ocean to keep taking up more CO₂ from the atmosphere.”

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