The twilight zone of the ocean is a mysterious place. At 200-1000 meters below the surface, it's a tough place to study. That's why, during World War II, people reading sonograms from this zone were perplexed when it looked as if the ocean floor was moving up. Every day. And then back down again before dawn. In this latest installment of Sea Camp, we explore what this historical mystery has to do with the Earth's ability to cycle and store carbon in the ocean's watery depths.

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