The Southern Ocean is holding in a ‘burp’

Humans burp after a big meal. Heat from climate change might be released by the Southern Ocean into the atmosphere sometime in the future. This heat would cause comparable heating to anthropogenic climate change. The longer humans continue to release emissions, the more heat will be trapped in the ocean.

Bring up the heat

Heat trapped in the Southern Ocean could be “burped” up into the atmosphere and cause climate change-like effects, even after humans stop greenhouse gas emissions, according to a study published in the journal AGU Advances. This burp “originates from heat that has previously accumulated under global warming in the deep Southern Ocean, and emerges to the ocean surface via deep convection,” said the study. As a result, there could be a “renewed pulse of warming from the maritime zone, without any new CO2 entering the atmosphere,” said Daily Galaxy.

The study showed that this release would occur “after several centuries of net negative emissions levels and gradual global cooling,” and could lead to a “decadal- to centennial-scale period of warming,” said Eos. This warming would be “comparable to average historical anthropogenic warming rates.” The released heat will not be distributed evenly around the world; the effects would be “greatest and longest-lasting in the Southern Hemisphere, suggesting a greater impact on today's more vulnerable countries of the global south,” said the study. However, “while some CO2 is released, the primary impact is thermal, not chemical,” said Daily Galaxy.

Ocean on hold

Oceans act as a carbon sink, meaning they are capable of holding atmospheric carbon. The ocean will likely continue to “absorb heat well after atmospheric CO2 peaks and net-negative emissions are reached, because surface atmospheric temperatures also take their time to fall,” said Science Alert. The future Southern Ocean also has a “greatly increased capacity to absorb shortwave solar radiation, since much of the sea ice that historically reflected the heat has melted.”

The burp is attributed to two processes. These are warmer surface waters mixing with cooler layers and ventilating heat into the depths, plus the “ocean’s natural heat release pathways” are becoming less active, said Daily Galaxy. These “combined effects trap heat where it cannot easily escape, setting the stage for a delayed warming rebound.”

The potential for this “burp” “assumes a rosy climate future,” said Popular Mechanics. Unfortunately, we are a long way from being carbon negative or reaching net-zero. This is especially true as the Trump administration “openly encourages other countries (along with the U.S.) to keep burning fossil fuels.”

The study shows that “burning fossil fuels with reckless abandon for centuries will have lasting impacts long after the green revolution finally takes hold,” said Popular Mechanics. But the “sooner we can achieve this technological dream, the better our chances are for preserving a future.”