climate feedback loops¶

You're probably aware of climate feedback loops: for example, polar ice melting into water, which is much better at absorbing solar energy, thereby speeding up the warming.

A feedback loop you probably haven't heard about has to do with the ocean's mysterious twilight zone. In the twilight zone, sunlight can't make it through all the water, so photosynthesis is not possible. However, it's full of animal life, adapted to the dark.

Where do they get their food? Some of them eat other twilight zone animals, but the rest have to swim up! https://t.co/7xDPSNJqwH Every night, marine animals swim to the surface to eat. Because they're adapted to darkness, they can scavenge on abundant food, while predators won't be able to see them.

As the sun rises, they return to the safety of the twilight zone. This is called diel vertical migration. https://t.co/d3YMcQCmd3 So why is this important?

The stuff that they're eating is made of carbon. Carbon dioxide is pulled out of the environment by plants to make food. Normally, when animals die, the decomposition process releases carbon back into the environment as CO2. https://t.co/94BpABuvZq However, these twilight zone animals, returning daily to the depths, often die (or poop) too far down for this to happen in the normal way. Instead, much of their carbon finds its way further and further down. This is a form of carbon sequestration, trapping carbon under the sea. https://t.co/6wZXIMFkX7 Sequestration is an important part of the natural carbon cycle, preventing massive swings in atmospheric carbon.

This natural carbon sink hasn't been well-studied in the past, but we now know that it might account for 14% or more of total sequestration on the planet! https://t.co/tjDOdXydTL Considering that the massive buildup of CO2 in the atmosphere comes from human activity nudging the scales a few percentage points out of balance, 14% is huge.

And diel vertical migration is in danger because of climate change. Even subtle nudges make huge long-term differences. Many of the animals involved in this process are zooplankton. Their small size makes them very susceptible to subtle changes, like higher ocean temperatures or ocean acidification.

They're similarly subject to the whims of ocean currents, which are impacted by climate change. Surface temperature also impacts how much the water mixes, aerates, and distributes nutrients. As the water heats up, it becomes more stagnant, making it harder for living things to eat, breathe, and grow. These factors also impact the plants they feed on, which are the vital first step in this carbon sequestration. Less plant growth means less animal growth means less ocean floor poop means more carbon dioxide staying in the atmosphere. This isn't all doom and gloom though!

This massive carbon sink is damaged, but still robust. The second we stop pumping carbon into the atmosphere, this natural cycle can bounce back--if we were to actually do that right now.