The oceans are growing more stable—and stagnant—as a consequence of climate change.
Oceans are finely balanced and vulnerable to the most severe climate change effects.
When water stops pushing up and down within the entire water column, it's bad news.
As the oceans warm, they become more stable in a way scientists say will worsen climate change. If this sounds counterintuitive, remember that instability of some kinds is essential to how both wind and air circulate around the planet and affect the yearly cycles for agriculture, animal migration, and more.
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In The Guardian, researcher John Abraham explains what stability is in this context:
“In oceans, water tends to stratify, with warmer, less dense water sitting atop colder, more dense water. We refer to this as a ‘stable’ configuration. Sometimes the waters are not stable. For example, the upper waters of the ocean can suddenly become heavier. This causes the water to fall from the surface towards the ocean floor. Not only does water move up and down in the ocean, but currents flow around the world horizontally as well. It turns out these water currents have major effects on the entire ocean, as well as the weather.”
So, when the ocean is stable, that means it has settled into identifiable layers like the different colors in a Tequila Sunrise, or like the oil layer in a bottle of salad dressing. The layers have names and are studied in a couple of different ways depending on the scientists involved, whether in three or five layers or something else.
The abyssal zone, for example, is what lies against the deep (but not irregularly deep trenches) ocean floor, which in turn is called the abyssal plain.
Currents and animal populations can circulate effectively within just certain zones, in a way that seems like a miracle until you remember that humans only live in one band that basically touches the Earth’s surface only. Rainforest animals might live their entire lives in the layer above, the canopy, while birds prefer to occupy their own bands of low altitude. And we’ve all seen those days when wind is blowing one layer of clouds at a very different speed and even direction than a layer farther away.
Abraham highlights a new paper he coauthored about the warmer, more stagnant surfaces of the world’s oceans as a result of higher stability. The researchers explain:
“We find that stratification globally has increased by a substantial 5.3 [percent] in recent decades; a rate of 0.90 [percent] per decade. Most of the increase occurred in the upper 200 m of the ocean and resulted largely from temperature changes, although salinity changes play an important role locally.”
That, Abraham says, has a lot of ramifications. The less “fresh” (in the novel sense) water circulates top to bottom, the warmer the top layer grows, which in turn means it’s less nutritious, less able to absorb carbon, and more. And gravest of all, the warmer top layer accelerates its own warming.
“There is hope that we can navigate the challenges resulting from a more stable ocean—but we must start immediately,” Abraham concludes.
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