Acidity of coastal waters antarctica It could double by the end of this centuryThe survival of whales, penguins and hundreds of other species living in the Southern Ocean is threatened, according to research recently published by the University of Colorado Boulder (USA).
Scientists predict that by 2100, the upper 200 meters of the ocean, where most marine life lives, could see an increase in acidity of more than 100% compared to levels recorded in the 1990s. Nature Communication.
“The findings are critical to our understanding of the future evolution of marine ecosystem health,” said Nicole Lovenduski, co-author of the paper and interim director of the CU Boulder Institute for Arctic and Alpine Research (INSTAAR).
Oceans play an important role as a buffer against climate change, absorbing almost 30% of CO2 released Worldwide. But as more CO2 dissolves in the oceans, seawater becomes more acidic.
“Anthropogenic CO2 emissions are at the heart of ocean acidification,” said Cara Nissen, first author of the paper and INSTAAR research scientist.
The Southern Ocean surrounding Antarctica is particularly susceptible to acidificationThis is partly because cold water tends to absorb more CO2. The region’s ocean currents also contribute to relatively acidic water conditions.
Using a computer model, Nissen, Lovenduski and their team simulated how Southern Ocean seawater would change in the 21st century and found that it would become more acidic by 2100, and that the situation would be dire indeed if the world fails to reduce emissions.
Both the surface and bottom of the ocean
“This isn’t just the upper layer of the ocean. The entire water column of the Southern Ocean coast, including its lower partcan be subject to severe acidification,” Nissen said.
The team then investigated the situation privately. marine protected areas (MPAs) From Antarctica. In order to protect biodiversity, human activities such as fishing are limited in these regions.
There are currently two MPAs in the Southern Ocean, covering approximately 12% of the region’s water.
In recent years, scientists have proposed the designation of three more MPAs that would cover approximately 60% of the Southern Ocean.
The team’s model showed: Both existing and proposed Marine Protected Areas will be subject to significant acidification by the end of the century.
For example, assuming higher emissions, the average acidity of water in the Ross Sea region (the world’s largest MPA at the northern tip of Antarctica) would increase by 104% from 1990 to 2100 levels. In a medium emissions scenario, the water would still become 43% more acidic.
“I was surprised how severe ocean acidification could be in these coastal waters,” Nissen said.
Phytoplankton is in danger
Previous studies have shown that Phytoplankton, a group of algae that forms the basis of the marine food web, grows more slowly or dies when water becomes too acidic.
Likewise, acidic water weakens the shells of creatures such as snails and sea urchins.
These changes could alter the food web and ultimately affects top predators, e.g. whales and penguins.
The Weddell Sea is one of three proposed MPAs located off the coast of the Antarctic Peninsula. Nissen states that scientists believe in this region. Weddell Sea may serve as climate change refuge for organismsThe main reason for this is that this region has the highest sea ice cover in Antarctica.
Ice protects the ocean from warming and prevents seawater below from absorbing CO2 from the air, thus reducing the rate of acidification. Additionally, there has been very little human activity in the area to date.
However, models and simulations carried out by experts reveal the following: As the planet continues to warm, sea ice will melt and the Weddell Sea region will experience acidification Like other Marine Protected Areas in medium to high emissions scenarios, but with slightly more delayed progress.
“The result shows that The Weddell Sea region should be given high priority as a protected areaNissen stated.
“As a scientist who often studies the open ocean, I tend to think of Antarctic coastal zones as a conduit for climate signals to reach the global deep ocean. This study reminded me that changing Antarctic coastal zones can lead to rapid changes,” Lovenduski said. aforementioned. .
The study suggests that the world can only prevent severe acidification of the Southern Ocean in a lowest emissions scenario in which society rapidly and aggressively reduces CO2 emissions.
Reference work: https://www.nature.com/articles/s41467-023-44438-x
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