Antarctica’s Southern Ocean Could Unleash a 100-Year Heat ‘Burp’— And the Consequences Are Alarming!
A recent study published in AGU Advances has raised significant concerns about a potential future phenomenon in the Southern Ocean surrounding Antarctica: a thermal “burp” that could last for over a century. This event, triggered by the ocean’s massive capacity to absorb heat, may release an enormous amount of stored warmth into the atmosphere, exacerbating global warming.
The Southern Ocean’s Heat Storage: A Ticking Time Bomb?
The Southern Ocean, which encircles Antarctica, plays a crucial role in regulating the Earth’s climate by acting as a heat sink. Since the Industrial Revolution, it has absorbed more than 90% of the excess heat generated by human activities, such as the burning of fossil fuels. This vast storage capacity has allowed the ocean to buffer some of the immediate impacts of global warming. However, this heat cannot remain stored forever. Eventually, the ocean may release this accumulated warmth back into the atmosphere, potentially leading to a dramatic rise in global temperatures.
The study, published in AGU Advances, predicts that this release, referred to as a “thermal burp,” could occur under certain future climate scenarios. If humanity successfully reduces emissions and eventually removes CO2 from the atmosphere, the Earth’s global temperature could decrease. However, as the Southern Ocean cools due to these efforts, the stored heat from its deeper waters could destabilize the water column, causing a sudden release of warmth.
“At the same time, we have these warm, deeper waters,” explains Svenja Frey, an oceanography PhD student and coauthor of the study. “At some point, the water column becomes unstable, and that’s when we have the deep convection event.”
This phenomenon, though not yet fully understood, could have catastrophic effects on global temperatures, reversing any progress made through emission reduction efforts. As the ocean releases this heat, it could act as a “backfire,” undermining the cooling effects of carbon removal.
Global ocean storage of (a) heat and (b) carbon under net-positive CO2 emissions, vertically integrated, at peak atmospheric CO2 concentrations (at CO2 doubling, after 70 years of 1% per year increase); anomaly relative to preindustrial conditions in the Earth system model UVic (see Section 2.1). It illustrates that the model shows similar patterns as observations and other models, with highest concentrations of heat and carbon storage in the Southern Ocean and the north Atlantic.. Credit: AGU Advances
How CO2 Removal May Trigger a Massive Oceanic Heat Release
One of the core concerns raised by the study is how the Earth’s climate system will respond to the removal of CO2 from the atmosphere. This is a crucial question because current climate models primarily focus on emissions reduction, rather than the broader impacts of pulling carbon from the air. As Svenja Frey points out,
“The question is: How will the climate system, and specifically the ocean, react to scenarios where we remove CO2 from the atmosphere, and when we have a net global cooling effect?”
The Southern Ocean’s response is especially important due to its capacity to store both heat and carbon. While removing CO2 from the atmosphere may reduce global warming over time, the ocean’s role in storing heat means that cooling efforts might trigger the release of previously stored energy. In the scenario modeled by the researchers, as atmospheric CO2 concentrations decrease, the surface water of the Southern Ocean cools and becomes saltier due to the formation of sea ice. However, the warmer, deeper waters beneath the surface could destabilize the water column, causing a deep convection event that releases the stored heat.
This “burp” of heat could be similar in scale to the warming the planet is currently experiencing, potentially leading to a resurgence of global temperatures even after significant efforts to mitigate climate change. This underscores the complexity of managing climate change and highlights the need for a holistic approach to addressing both emissions and the ocean’s role in regulating heat.
The Southern Ocean’s Role in Earth’s Climate Dynamics
The Southern Ocean’s role in climate dynamics is often overshadowed by more well-known phenomena such as the El Niño-Southern Oscillation or the effects of the Arctic on global weather patterns. However, as the study published in AGU Advances demonstrates, the Southern Ocean is crucial in regulating both heat and carbon. It absorbs large amounts of heat from the atmosphere and plays a significant role in the planet’s overall energy balance. According to Ric Williams, an ocean and climate scientist at the University of Liverpool,
“That competition hasn’t been as prevalent over the Southern Hemisphere, because it’s this slightly more pristine atmosphere.”
The Southern Ocean’s ability to store heat stems from a combination of ocean currents that bring warmer waters south and upwelling processes that bring cold water to the surface to be warmed by solar radiation. This intricate balance has helped keep the global climate system stable, but it is also a source of potential volatility. As temperatures rise, the ocean’s capacity to absorb heat could be overwhelmed, leading to sudden and unexpected shifts in global weather patterns.
Moreover, the Southern Ocean’s relatively clean atmosphere compared to the Northern Hemisphere has made it less susceptible to the cooling effects of aerosols and pollutants. This has allowed the region to serve as a more efficient heat sink, but it also means that the ocean may be more sensitive to future changes in atmospheric composition.
The Uncertainty of Climate System Reactions
Despite the detailed modeling done in the study, one of the key takeaways is the uncertainty surrounding the Earth’s response to changes in emissions. Climate systems are highly complex, with multiple interconnected factors that can produce unexpected outcomes. As Frey emphasizes,
“The question is: How will the climate system, and specifically the ocean, react to scenarios where we remove CO2 from the atmosphere, and when we have a net global cooling effect?”
Scientists acknowledge that while models can provide insight, the true reactions of the climate system remain unknown. Removing CO2 from the atmosphere could have unintended consequences, and the “thermal burp” could be one of these surprises. The study’s authors note that the interplay between cooling the atmosphere and the Southern Ocean’s behavior remains poorly understood, and future research will be necessary to refine our predictions and strategies for managing global warming.
Given this uncertainty, it is crucial to focus not only on reducing emissions but also on carefully monitoring the ocean’s response to these efforts. The Southern Ocean, with its vast heat storage capacity, may prove to be both a valuable ally and a dangerous adversary in the fight against climate change.
