Earth's Concealed, Potent 'Regulator' Could Overshoot Climate Adjustments

Researchers have stated that the mechanism behind the recent discoveries hinges on phosphorus’s transportation from landmasses to the seas.(Image credit: Qiang Zhang / 500px/Getty Images)

Our planet might react to the large quantities of carbon dioxide (CO2) that individuals are releasing into the environment by “overcompensating” for the instability, potentially causing the next glacial period to commence promptly, rather than being pushed back by several millennia, as initially supposed.

This is because of a newly identified “regulator” that buries substantial volumes of carbon underneath the ocean floor with such efficiency, it has the potential to negate human carbon discharges within a period of 100,000 years, according to researchers.

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With both regulators functioning concurrently, it is conceivable that the subsequent ice age could begin on schedule, as opposed to being deferred due to the consequences of climate variations, according to study co-author Andy Ridgwell, a geology professor at the University of California, Riverside, in an interview with Live Science.

The recently found regulator does not shield present-day humans from the repercussions of rising global temperatures, stated study co-author Dominik Hülse, a mathematician and biogeochemical modeler at the University of Bremen in Germany. “It doesn’t imply that we’ll be secure from global warming over the coming 100 or even 1,000 years,” he conveyed to Live Science.

Scientists have surmised for a while that Earth governs its climate across extended geological periods. Since the 1980s, researchers have theorized a process termed the silicate weathering feedback, arising when rainfall absorbs CO2 from the atmosphere and distributes it onto silicate rocks — rocks comprising minerals composed of oxygen and silicon, which account for approximately 90% of the planet’s outer layer. CO2 interacts with these rocks, dissolving them and yielding molecules that permeate into the soil, ultimately draining into the ocean. Once there, the initial CO2 transforms into limestone and chalk, effectively sealing it away for eons.

The silicate weathering feedback emulates a thermostat, because the greater the CO2 content in the atmosphere, the warmer Earth becomes, thereby intensifying the water cycle. As rainfall elevates, silicate weathering escalates, leading to a heightened transfer of CO2 into the ocean, subsequently diminishing atmospheric CO2 to standard levels.

The feedback also functions conversely. “If conditions turn excessively frigid and CO2 levels are unduly diminished, then the regulator is consuming excessively diminutive amounts of CO2 compared with a constant background discharge of CO2 from the mantle, volcanoes, and other magma attributes,” Ridgwell explained. In this circumstance, less CO2 accumulates in the ocean, and atmospheric densities gradually rise back to typical values, he noted.

Nevertheless, the silicate weathering feedback progresses gradually; it might necessitate up to 1 million years post-perturbation to equilibrate CO2 concentrations. Consequently, it cannot account for specific climatic occurrences, including Earth’s glacial and interglacial phases, marked by substantial swings in CO2 levels and temperature, transpiring roughly every 100,000 years, Ridgwell commented.

Silicate weathering is also unable to elucidate snowball Earth phenomena, which completely envelop the planet in ice, Hülse conveyed. Were silicate weathering the exclusive regulator governing Earth’s climate, its seamless balancing act would impede it from succumbing to such severe circumstances, Hülse explained.

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A secondary “regulator”

The current investigation was prompted by Hülse’s doctoral dissertation, in which he calculated the extent of organic carbon preserved in ocean sediments during prior climatic events. His results demonstrated that following episodes of heightened volcanic activity and temperature elevations, substantial volumes of organic carbon were deposited onto the seafloor. This revelation suggested a potential correlation between atmospheric CO2 concentrations and organic carbon entombment in the ocean.

“There are undeniably instances in Earth’s timeline where considerable amounts of organic carbon have been deposited,” Ridgwell acknowledged. “We’ve generally recognized that there must be additional processes transpiring [besides silicate weathering], yet incorporating it into a model is considerably more intricate.”

However, Hülse and Ridgwell addressed this challenge in the present study by merging their individual projects into a unified global climate carbon cycle model that accounted for organic carbon entombment in the seafloor. Their findings unveiled a secondary “regulator” rooted in Earth’s phosphorus cycle, commencing on land with rocks harboring minerals such as apatite, the investigators reported.

Breakdown of these rocks, initiated by rainfall, discharges phosphorus, which seeps into the earth, infiltrates streams and rivers, and subsequently enters the ocean. In that environment, phosphorus constitutes an essential nutrient for minute photosynthetic beings known as phytoplankton, which employ it to energize cellular operations. Upon the demise of phytoplankton, they submerge to the ocean’s depths, where they deposit organic carbon, phosphorus, and various nutrients.

Phytoplankton consume phosphorus to fuel cellular functions, subsequently carrying it with them to the seafloor upon their death.

In a warmer world, greater amounts of phosphorus are flushed into the ocean, causing phytoplankton to thrive, implying that increased quantities of organic carbon and phosphorus reach the ocean floor. However, warmer oceans concurrently retain diminished oxygen levels because oxygen’s solubility decreases as temperatures rise. This deoxygenation process emancipates deposited phosphorus back into the water column while simultaneously burying organic carbon within sediments.

“The exact mechanism is not entirely elucidated, but we are aware of its occurrence,” Ridgwell stated. “In previous instances where we’ve noted substantial amounts of organic carbon being entombed following a warming event, there’s exceedingly minimal phosphorus content in that material compared to typical material. If it’s not being buried, it must have been restored to the ocean.”

As phosphorus undergoes recycling, it reenters the food chain, and phytoplankton persist in proliferating as they feed on phosphorus originating from both terrestrial and oceanic sources. This triggers a phytoplankton proliferation, drawing escalating volumes of CO2 from the atmosphere and depositing heightened quantities of organic carbon onto the seafloor, thereby reducing global temperatures.

Hence, the hotter the planet becomes, the more productive the oceans transform, and the greater the carbon sequestered, resulting in climate cooling. The distinction between phosphorus and silicate weathering lies in the fact that phosphorus levels in the ocean do not recede as promptly as Earth cools, given its sustained release at the seafloor.

“The organic carbon regulator bears some resemblance to the silicate regulator, albeit with a supercharged element,” Ridgwell noted. “You ultimately accumulate an abundance of nutrients within the ocean — which are being recycled with superior efficiency — rendering their removal exceedingly challenging.”

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The phosphorus cycle ultimately recovers its equilibrium, yet the planet may “overcompensate” in the interim, instigating phenomena like snowball Earth, according to the researchers. The response of this secondary regulator to current climate shifts remains uncertain, although the ocean’s oxygen richness compared to historical levels renders a snowball Earth event improbable, they suggested.

Alternatively, the organic carbon regulator might compensate for the anticipated postponement of the ensuing ice age. Climatic alterations are disrupting Earth’s inherent cycles, and earlier studies indicate that it could postpone the subsequent glacial epoch, anticipated in approximately 11,000 years, by several decades. However, should the organic carbon regulator activate, atmospheric CO2 could revert to background densities considerably sooner, ensuring the prompt arrival of the subsequent ice age.

“Whatever delay we’ll ultimately encounter for the next ice age … contemplating this mechanism might expedite its onset,” Ridgwell stated. “One is assuredly going to commence at some juncture; the primary concern is its initiation.”

Sascha PareSocial Links NavigationStaff writer

Sascha is a staff writer based in the U.K. for Live Science. She holds a bachelor’s degree in biological sciences from the University of Southampton in England and a master’s degree in scientific communication from Imperial College London. Her work has been featured in The Guardian and the health website Zoe. Beyond her writing, she finds pleasure in tennis, bread-making, and scouting for vintage treasures in second-hand stores.

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