The Arctic Ocean turned into a key supplier of greenhouse emissions approximately 56 million years prior, amid an era of swift global heating.(Image credit: Paul Souders/Getty Images)
The Arctic Ocean once functioned as a significant origin of atmospheric greenhouse gases — and specialists caution that it could once more become one.
In holding warmth within Earth’s atmosphere, methane (CH4) is second only to carbon dioxide (CO2). Since 2020, emissions of greenhouse gases caused by humans have elevated atmospheric methane by about 10 parts per billion yearly, surpassing CO2’s increase by over twice the amount. However, the way our planet’s methane cycle will react as it keeps warming is currently unknown to scientists.
You may like
-
Methane emissions are growing below the Antarctic sea, sparking concerns about a looming climate disaster
-
An unrevealed, greatly enhanced ‘thermostat’ might trigger the Earth to overcompensate for climatic variations
-
A peatland inside the Amazon lost its capacity to soak up carbon. What are the ramifications?
The team concentrated on a duration of intense warming and acidification of the oceans that took place around 56 million years ago, identified as the Paleocene-Eocene Thermal Maximum (PETM). Resembling the global warming we’re encountering currently, the PETM is among the finest instances of a prominent climate transition resulting from disruptions in the Earth’s carbon exchange.
Past research has demonstrated by scientists that the PETM was marked by CO2 and CH4 discharges across the oceans and into the atmosphere, which imprinted distinct geochemical markers within sedimentary rocks from that period. However, even after three decades of investigation, the precise origin of these gases continues to elude scientists.
To explore the mechanics of the carbon cycle during the PETM, the experts behind this recent investigation assessed a 50-foot (15 meters) fragment of marine sediments extracted from the core of the Arctic Ocean by the Arctic Coring Expedition of the Integrated Ocean Drilling Program. Preserving the PETM warming phenomenon and its ensuing “recovery” phase, during which the climate eventually returned to stability, these sediments date back 66 million years.
The team took organic molecules from the sediments and gauged various carbon forms inside them. They cataloged the organic molecules, termed biomarkers, to determine the types of microbes that thrived on the seabed at the time of sediment deposition. They utilized the carbon forms, called isotopes, to ascertain the dietary habits of these microbes.
Commonly, methane has lighter carbon isotopes relative to CO2, implying that methane-devouring microbes yield biomarkers showcasing distinctly light carbon isotopes. The researchers monitored these biomarkers within the core samples and discovered that the prevalent methane consumers in the Arctic Ocean underwent a shift during the PETM.
Before the PETM, methane was generated deep beneath the seabed and ingested by microbes that depend on sulfate for respiration instead of oxygen, through a mechanism referred to as anaerobic oxidation of methane (AOM). However, AOM microbe biomarkers diminished during the PETM.
Currently, AOM depletes the bulk of methane inside marine sediments due to the abundance of sulfate within modern oceans. Nevertheless, it’s believed by scientists that sulfate levels were notably lower during the PETM, suggesting a constraint on the microbes’ methane consumption. The researchers posit that a substantial methane surge during the PETM might have “overwhelmed the sedimentary AOM biofilter,” which in turn caused methane release into seawater, as noted within the study.
You may like
-
Methane emissions are growing below the Antarctic sea, sparking concerns about a looming climate disaster
-
An unrevealed, greatly enhanced ‘thermostat’ might trigger the Earth to overcompensate for climatic variations
-
A peatland inside the Amazon lost its capacity to soak up carbon. What are the ramifications?
Upon methane entering the water column, indicators from the biomarkers suggested a takeover by a distinct group of microbes. Through a process known as aerobic oxidation of methane (AeOM), these microbes ingested methane through oxygen respiration.
The researchers suggest this shift could have changed the Arctic to a notable CO2 contributor subsequent to the start of PETM heating. They clarified that AOM within the sediments gives rise to the alkaline compound bicarbonate, aiding in ocean buffering and pH stabilization. However, AeOM within the water column emits CO2, which elevates warming and acidification of the seas. Also, AeOM microbes deplete O2, facilitating proliferation of other organisms with limited oxygen tolerance, which in turn devour sulfate, further depriving AOM microbes.
Might an analogous Arctic methane transition hasten current climate change? “We assess it as probable and highly plausible,” stated Bumsoo Kim, organic geochemist at NASA Johnson Space Center and primary author of the study. In an email to Live Science, Kim, who was a Texas A&M University researcher during the study, stated that the Arctic Ocean is becoming warmer and fresher, which would utilize further oxygen, thereby instigating comparable methane cycle alterations.
RELATED STORIES
—Scientists ‘reawaken’ ancient microbes from permafrost — and soon after discover they start discharging CO2
—’It was really unexpected’: 90 billion liters of meltwater forced its way via Greenland’s ice layer in an unprecedented melting occurrence
—Emerging technologies are instrumental in reestablishing Arctic sea ice
Conversely, other scientists display less conviction. Sandra Kirtland Turner, paleoclimate and paleoceanography associate professor at the University of California, Riverside, who wasn’t linked to the investigation, stated that “The factors that triggered the Arctic’s transition into a prior carbon source might not be directly comparable to the future, because the Arctic Ocean was physically more confined relative to the global ocean, and its ocean chemistry displayed notable disparities.”
Additionally, Kirtland Turner emphasized that the outcomes serve as a reminder that carbon cycle feedback mechanisms can amplify or prolong warming. She conveyed to Live Science that, “Today, carbon cycle feedback mechanisms remain inadequately restricted, with limited attention even beyond the year 2100,” which curtails our comprehension of their cumulative effects.
Aubrey ZerkleLive Science Contributor
Aubrey Zerkle is a freelance scientific writer covering subjects such as paleontology, the progression of Earth’s systems, astrobiology, and planetary science. Subsequent to securing a PhD in geosciences from Penn State University, she spent 15+ years as an academic researcher before shifting her focus towards science communication. At present, she oversees Sciworthy, a science news platform run by the non-profit Blue Marble Space.
You must confirm your public display name before commenting
Please logout and then login again, you will then be prompted to enter your display name.
LogoutRead more
Methane emissions are growing below the Antarctic sea, sparking concerns about a looming climate disaster
An unrevealed, greatly enhanced ‘thermostat’ might trigger the Earth to overcompensate for climatic variations
A peatland inside the Amazon lost its capacity to soak up carbon. What are the ramifications?
Key Atlantic current could start collapsing as early as 2055, new study finds
Massive system of rotating ocean currents in the North Atlantic is behaving strangely — and it may be reaching a tipping point
CO2 levels reach record new high, locking in more global warming
Latest in Planet Earth
Revived permafrost microbes spew CO2, scientists image ‘relativity-breaking’ illusion, and James Webb telescope spots something ‘exciting’ blasting from black hole M87*
CO2 levels reach record new high, locking in more global warming
Sourse: www.livescience.com
