Researchers at the University of Rochester have warned that warming oceans could trigger a hidden methane boost that speeds up climate change. According to the scientists, the oceans may be contributing to climate change in a subtle but important way that are only being recognised in recent times.
The researchers in the new study published in the journal, Proceedings of the National Academy of Sciences, shed light on how methane is produced in the open ocean.
The study team, including Thomas Weber, an associate professor in the Department of Earth and Environmental Sciences, along with graduate student, Shengyu Wang, and postdoctoral research associate, Hairong Xu, identified a process that could grow stronger as global temperatures rise.
Their findings suggest a potential feedback loop that could worsen global warming. Methane is a powerful greenhouse gas, yet scientists have long been puzzled by an unusual pattern. Surface ocean waters regularly release methane into the atmosphere, even though these waters contain plenty of oxygen.
Traditionally, methane formation has been linked to environments without oxygen, such as wetlands or deep ocean sediments. To better understand this contradiction, the research team combined global data with computer simulations.
They found that certain microbes can produce methane as they break down organic material, but only when phosphate, a key nutrient, is in short supply. “This means that phosphate scarcity is the primary control knob for methane production and emissions in the open ocean,” Weber says.
This discovery changes how scientists view methane production in marine environments. Instead of being rare, methane generation in oxygen-rich waters may occur widely in areas where phosphate levels are low. The study also highlights how climate change could influence this process in the future.
As the ocean warms, the difference in density between surface water and deeper layers increases. “Climate change is warming the ocean from the top down, increasing the density difference between surface and deep waters. “This is expected to slow the vertical mixing that carries nutrients like phosphate up from depth,” Weber says. With less mixing, fewer nutrients reach the surface.
The team’s model shows that this could leave surface waters increasingly depleted of phosphate, creating favorable conditions for methaneproducing microbes. If methane production rises, more of this gas could escape into the atmosphere.
Because methane is so effective at trapping heat, this creates the risk of a reinforcing cycle. Warmer oceans lead to higher methane emissions, which then contribute to further warming.
The research underscores how small-scale biological activity in the ocean can influence the global climate. Importantly, this feedback mechanism is not yet included in most major climate models.
As scientists work to improve predictions, accounting for processes like this may be crucial for understanding how quickly climate change will progress.
“Our work will help fill a key gap in climate predictions, which often overlook interactions between the changing environment and natural greenhouse gas sources to the atmosphere,” Weber added.
