Scorching heat waves are not just a land phenomenon.
This summer, farmed fish have died en masse, and a look at sea surface temperatures around South Korea over the past month shows they were about 1.5°C (35°F) higher than usual.
Although the ocean's seasons typically lag behind by one season, water temperatures have already exceeded 30°C (86°F) in some waters, including off Jeju Island.
The impact of high water temperatures goes beyond this.
The oceans absorb about 30% of the carbon dioxide emitted by humans.
However, as climate change warms the water, warmer water becomes lighter, slowing down the vertical mixing of seawater.
Slower circulation means that the amount of carbon dioxide dissolving into the ocean surface decreases accordingly.
Carbon dioxide absorption also declines through another pathway.
Let us look at it from the perspective of phytoplankton.
Plankton, which perform photosynthesis, feed on nutrients rising from the deep sea. When circulation weakens, nutrients decrease, and fewer nutrients lead to a weaker photosynthetic process.
Photosynthesis is the process of using light to convert carbon dioxide into nutrients and oxygen.
If photosynthesis by marine phytoplankton declines, the amount of carbon dioxide absorbed from the atmosphere inevitably decreases as well.
Of course, slower seawater circulation can mean that carbon dioxide already dissolved remains trapped in the ocean longer.
However, the effect of the ocean failing to newly absorb carbon outweighs this trapping effect, ultimately leading to a greater increase in atmospheric carbon dioxide than now.
Overseas researchers analyzed that if climate change and high water temperatures continue, carbon dioxide concentrations could rise by about 16% by around the year 2500.
[Samar Khatiwala / Professor, Faculty of Liberal Arts and Sciences, Waseda University: We developed a calculation method that allows us to closely analyze the carbon cycle, and the calculations showed that by the year 2500, carbon dioxide concentrations would increase by about 16%, or 270 ppm.]
Higher carbon dioxide concentrations intensify global warming, which in turn raises ocean temperatures again, potentially repeating a vicious cycle that accelerates climate change.
(Reported by Seo Dong-gyun | Produced by Lee Se-young | Video by Lee So-young | Graphics by Hwang Se-yeon | Producer: Kim Do-gyun, Han Seung-ho | XR: Lee Jun-ho, Jeon Yu-geun, Choi Jae-young | Produced by SBS Digital News)
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