The research about the ocean’s “twilight zone” and its impact on climate change was published recently in the journal Nature Communications. This study involved researchers from institutions including the University of Exeter and Cardiff University, and it highlights a potential 20-40% decline in twilight zone life by the end of this century due to climate change.
Additionally, detailed reports and further studies on the twilight zone’s role in climate and carbon sequestration have been published by the Woods Hole Oceanographic Institution through their Ocean Twilight Zone (OTZ) project
The ocean’s “twilight zone,” or mesopelagic zone, lies between roughly 200 and 1,000 meters deep, where little light penetrates. This zone teems with diverse marine life and plays a critical role in regulating Earth’s climate by sequestering carbon from the atmosphere into the deep ocean, acting as a buffer that slows climate change. It transports organic carbon from surface waters down to depth, where it is stored for hundreds to thousands of years, thus mitigating atmospheric CO2 levels.
Research shows the twilight zone contains the largest quantity of fish stocks by weight in the ocean (up to 95%) and recycles about 80% of organic material descending from upper layers, making it vital for oceanic food webs and the global carbon cycle. The ocean overall contains roughly 50 times more carbon than the atmosphere, and the twilight zone contributes significantly to this carbon storage.
However, the twilight zone is vulnerable to climate change impacts. Warming ocean temperatures disrupt this delicate system by increasing water stratification, altering ocean currents, and reducing the sinking of organic matter that feeds twilight zone life, leading to reduced food and oxygen availability at depth.
Studies analyzing past warm periods on Earth indicate that warming could cause a 20-40% reduction in twilight zone life by the end of this century. In high-emissions scenarios, much of this life could be lost within 50 to 150 years, with no recovery for millennia.
Loss of twilight zone life would diminish its crucial carbon sequestration role, likely causing atmospheric CO2 levels to rise faster and intensifying climate change effects. This underscores the urgency for better scientific understanding and protective marine policies targeting this vast yet understudied mid-ocean region.