[Anchor]
Just as the land gets hotter every summer, the ocean is also heating up. The ocean has played a role in slowing down the pace of climate change by absorbing carbon dioxide from the atmosphere. However, a forecast has emerged that it will become increasingly difficult for the ocean to fulfill this role.
Reporter Seo Donggyun brings us this report for the year-long climate change special series, "The Signal."
[Reporter]
Sweltering heat and extreme heatwaves are not limited to the land.
Fish at aquaculture farms have died off one after another this summer, and looking at the seawater temperatures around South Korea over the past month, they were about 1.5 degrees Celsius higher than average.
The ocean's seasons usually arrive a season late, but water temperatures have already exceeded 30 degrees Celsius (86°F) in some waters, including Jeju.
The impact of high water temperatures does not stop there.
The ocean absorbs about 30 percent of the carbon dioxide emitted by humans.
However, when water warms up due to climate change, the warmed water becomes lighter, which slows down the vertical mixing movement of seawater between the upper and lower layers.
Slower circulation means that the amount of carbon dioxide dissolving into the sea surface decreases accordingly.
Carbon dioxide absorption also decreases through another pathway.
Let us look at it from the perspective of phytoplankton.
Plankton, which perform photosynthesis, survive on nutrients rising from the deep sea. When circulation weakens, nutrients decrease, and when nutrients decrease, photosynthetic activity also weakens.
Photosynthesis is, after all, the process of using light to convert carbon dioxide into nutrients and oxygen.
If photosynthesis by phytoplankton in the sea decreases, the amount of carbon dioxide absorbed from the atmosphere inevitably decreases as well.
Of course, if seawater circulation slows down, carbon dioxide that has already dissolved may remain trapped inside the ocean for a longer time.
However, the impact of the ocean failing to newly absorb carbon dioxide is greater than this trapping effect, ultimately leading to an increase in atmospheric carbon dioxide compared to now.
Overseas researchers have analyzed that if climate change and high water temperatures continue, carbon dioxide concentrations will increase by about 16 percent around the year 2500.
[Samar Khatiwala / Professor, Faculty of Core Research, Waseda University: We developed a calculation method that allows for a close analysis of the carbon cycle, and the calculation results show that by the year 2500, carbon dioxide concentrations will increase by about 16 percent, or 270 ppm.]
As carbon dioxide concentrations rise, global warming intensifies, which in turn raises the temperature of the ocean again, potentially repeating a vicious cycle that accelerates climate change.
[Video Editing: Lee Soyoung, Design: Hwang Seyeon, Producer: Kim Dogyun, Han Seungho, XR: Lee Junho, Jeon Yugeun, Choi Jaeyoung]
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