The heat that humanity has brought to the globe after unchecked contamination does not disappear as such. The oceans on Earth have been responsible for absorbing around 90% of the excess heat produced by greenhouse gasses, acting as a massive economic compensator. However, a new modeling study conducted by GEOMAR researchers raises an alarming prospect for the future: the Australian Ocean (the body of water that surrounds Antarctica) may transfer that heat to the atmosphere in a very long time after the world has managed to reduce emissions, by using UVic v. 2.9, developed at the University of Victoria in British Columbia, Canada.
According to the research, even in a scenario of net negative emissions and a subsequent cooling of the Earth, a heat pulse originating from the depths may reappear after several years of cooling and trigger a new global heating over the course of a century at rates similar to those observed in the last 150 years.
The South Sea as an “escape valve”
After unchecked pollution, the heat that humans have brought to the world does not go away on its own. As a vast thermal buffer, the Earth’s oceans have been in charge of absorbing about 90% of the excess heat generated by greenhouse gases. The Australian Ocean, the body of water that surrounds Antarctica, may leak that heat into the atmosphere long after the globe has managed to reduce emissions, according to a new modeling study carried out by GEOMAR experts in which they used UVic v. 2.9, developed at the University of Victoria in British Columbia, Canada.
This is a concerning scenario for the future. A heat pulse from the depths could reappear after a few years of cooling and cause a new global warming over the course of a century at rates comparable to those seen in the last 150 years, even in a scenario of net negative emissions and subsequent cooling of the Earth, according to the research.
CO2 Removal
For their simulation, scientists create an idealized environment. According to this scenario, the concentration of CO2 in the atmosphere rises by 1% annually until it doubles in year 70. Following that, CO2 starts to decline at a rate of -0.1% annually, which is indicative of persistent “net negative emissions”—that is, when more CO2 is taken out of the atmosphere than is released.
What they discovered was unexpected. The model predicted a dramatic heat rise after roughly 400 years under these conditions of CO2 reduction and progressive cooling. The global average surface temperature rises by several tenths of a degree as a result of this abrupt thermal pulse, and it remains elevated for over a century.
Deep Convection as a Heat-Release mechanism
What physical process is responsible for this delayed release of heat? Deep convection is suggested by the study summary. Ocean layers are mixed during this process: warmer water that has been held at deep depths in the Southern Ocean rises to the top and interacts with the atmosphere, releasing all of the stored heat, while cold, dense surface water falls, shifting the water column.
Because the model has significant limitations, GEOMAR stresses that their work represents an idealized situation rather than an exact prediction. These include the omission of processes like ice sheet melting and the restricted geographical resolution. The important thing to remember is that ocean heat can appear over extremely long durations with delays and jumps.
Heat without CO2
Another crucial finding is that this reactivation of warming is not necessarily accompanied by a massive release of carbon into the atmosphere. According to the study, the modeled heat pulse is “largely devoid of CO2.” This is due to two main factors: changes in circulation affect heat more strongly than carbon, and seawater chemistry has the ability to “silence” CO2 loss. GEOMAR researchers confirm that the model did not simulate an identical CO2 release, so seawater chemistry retains a large portion of the dissolved carbon.
This means that the warming is driven by stored ocean heat, not by an additional spike in atmospheric CO2. In conclusion, as official sources point out, the need to reduce emissions to net zero remains “the most important step at this time.” The study reiterates the idea that “the ocean keeps the receipts.” The only way to reduce the size of this long-term thermal debt is by cutting emissions early. The heat from the deep ocean could shape the planet’s temperatures for generations.