The full chain of events by which ocean bio-geochemical changes, triggered by man-made greenhouse gas emissions, may cascade through marine habitats and organisms, penetrating to the deep ocean and eventually influencing humans was described by a study.
Previous analyses have focused mainly on ocean warming and acidification, considerably underestimating the biological and social consequences of climate change.
Factoring in predictable synergistic changes such as the depletion of dissolved oxygen in seawater and a decline in productivity of ocean ecosystems, the new study shows that no corner of the world ocean will be untouched by climate change by 2100.
"When you look at the world ocean, there are few places that will be free of changes; most will suffer the simultaneous effects of warming, acidification, and reductions in oxygen and productivity," lead author Camilo Mora, assistant professor at the Department of Geography in the College of Social Sciences at the University of Hawai'i at Manoa (UH Manoa), said.
"The consequences of these co-occurring changes are massive-everything from species survival, to abundance, to range size, to body size, to species richness, to ecosystem functioning are affected by changes in ocean biogeochemistry," Mora said.
The human ramifications of these changes are likely to be massive and disruptive. Food chains, fishing, and tourism could all be impacted.
The study shows that some 470 to 870 million of the world's poorest people rely on the ocean for food, jobs, and revenues, and live in countries where ocean goods and services could be compromised by multiple ocean biogeochemical changes.
The researchers used the most recent and robust models of projected climate change developed for the Fifth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC) to inform their analysis.
They discovered that most of the world's ocean surface will be simultaneously impacted by varying intensities of ocean warming, acidification, oxygen depletion, or shortfalls in productivity.
Only a very small fraction of the oceans, mostly in polar regions, will face the opposing effects of increases in oxygen or productivity, and nowhere will there be cooling or pH increase.
The study is set to be published in the scientific journal PLOS Biology.