Carbon emissions could change 95 per cent of surface ocean climates by 2100, threatening ecosystems: study

When it comes to protecting the ocean's ecosystems, a new study says that we're at a critical juncture point.

Up to 95 per cent of climates within the surface ocean that exist today may disappear within the next 80 years if we don't do more to curb greenhouse gas emissions, potentially having a devastating impact on ecosystems and widespread extinction, researchers say.

Researchers from Northeastern University in Massachusetts published the study last Thursday in the journal Scientific Reports. Using atmospheric carbon dioxide data, they modelled what would happen to the ocean's climates by the year 2100 under two potential climate scenarios.

"A disappearing climate is one that is common today, but will be uncommon or absent in the future, under different climate change scenarios," said lead author Katie Lotterhos, an associate professor in marine and environmental sciences, in a video interview with CTVNews.ca on Monday.

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In the first scenario — called RCP 4.5 — global emissions would peak in 2050 before decline. The UN Intergovernmental Panel on Climate Change calls this the intermediate scenario. Under RCP 4.5, the study says that 35.6 per cent of the surface ocean climates could experience "an extreme degree of global disappearance" by 2100.

But under RCP 8.5, otherwise known as the "worst case" or "business as usual" scenario, that estimate jumps to 95 per cent.

"If the projections of climate novelty and disappearance reported here are accurate, the cascading effects on marine ecosystems and communities could be substantial," the authors warn.

HOW CLIMATE CHANGE CAN AFFECT MARINE LIFE

It's more than just warmer temperatures that are threatening ocean ecosystems.

Surface ocean refers to the upper layer of the ocean that's approximately 330 feet deep. It's the part that interacts with the air the most and can absorb atmospheric carbon dioxide.

But more CO2 in the atmosphere as a result of emissions leads to more CO2 in the oceans, which can increase the acidity of the water.

"(Increased CO2 levels) basically upsets the balance of ions," said Lotterhos. "The CO2 molecules interact with the water molecules, and that results in an increase in hydrogen ions. That's what makes the water more acidic."

For certain marine species, such as oysters, snails and corals, lower pH levels can disrupt their ability to extract calcium from the sea water. These species rely on sea water calcium to form their shells.

"Under ocean acidification, it becomes harder for them to get that calcium from the seawater to make their skeletons. And once the water becomes acidic enough, it can actually dissolve the shells or skeletons," Lotterhos said.

The most extreme climate shifts would take place in areas in the tropics as well as the temperate regions in the southern hemisphere, the authors say. These areas also happen to be critical hot spots for biodiversity and coral reefs.

Some ocean species may be able to adapt to the new climates. For example, the researchers point to phytoplankton, which are able to quickly evolve and adapt to the higher levels of carbon dioxide in the ocean, given their short generation times and large population. But researchers worry that the rate of ocean climate change may be too fast for most marine species to adapt.

However, Lotterhos says her findings show that there's still time to take action and save the ocean ecosystems.

“There's quite a big difference between these different mitigation scenarios," said Lotterhos. "So, it does suggest that mitigation can have a huge effect on the degree of climate change."