Forskere kvantificerer global vulkansk CO2 -udluftning; estimere det samlede kulstof på Jorden

Vulkaner, kolliderer og spreder kontinentale og oceaniske plader, og andre fænomener genstuderet med innovative højteknologiske værktøjer, give vigtig ny indsigt i Jordens inderste virke, siger forskere.

Forbereder at opsummere og fejre det 10-årige Deep Carbon Observatory-program på National Academy of Sciences, Washington DC, 24.-26. Oktober, DCO's 500-mands reservoirer og Fluxes-team skitserede i dag flere vigtige fund, der spænder fra nutiden til milliarder af år siden; fra Jordens kerne til dens atmosfære, og i størrelse fra enkelte vulkaner til de fem kontinenter.

Blandt mange vidtrækkende fund kan skitseret og opsummeret i en række papirer, der blev offentliggjort i tidsskriftet Elementer:

• Kun to tiendedele af 1% af Jordens samlede kulstof-omkring 43, 500 gigatonn (Gt) - er over overfladen i havene, på land, og i atmosfæren. Resten er under overfladen, herunder skorpe, kappe og kerne - anslået 1,85 mia. Gt i alt
• CO ₂ udgasset til atmosfæren og havene i dag fra vulkaner og andre magmatisk aktive regioner anslås til 280 til 360 millioner tons (0,28 til 0,36 Gt) om året, herunder det, der frigives i havene fra midterhavet
• Menneskehedens årlige CO2 -udledning gennem afbrænding af fossile brændstoffer og skove, etc., er 40 til 100 gange større end alle vulkanske emissioner
• Jordens dybe kulstofcyklus gennem dyb tid afslører afbalanceret, langsigtet stabilitet af atmosfærisk CO ₂ , præget af store forstyrrelser, herunder enorm, katastrofale frigivelser af magma, der fandt sted mindst fem gange i de sidste 500 millioner år. Under disse begivenheder, enorme mængder kulstof blev forgasset, fører til en varmere atmosfære, forsurede oceaner. og masseudryddelser
• Tilsvarende en kæmpe meteorpåvirkning for 66 millioner år siden, Chicxulub -bolide -strejken på Mexicos Yucatan -halvø, frigivet mellem 425 og 1, 400 Gt CO ₂ , hurtigt opvarmet planeten og faldt sammen med massen (> 75%) udryddelse af planter og dyr - inklusive dinosaurerne. I løbet af de sidste 100 år har emissioner fra menneskeskabte aktiviteter såsom afbrænding af fossile brændstoffer har været 40 til 100 gange større end vores planets geologiske kulstofemissioner
• Et skift i sammensætningen af ​​vulkanske gasser fra ildelugtende (ligner brændte tændstikker) svovldioxid (SO2) til en gas, der er rigere på lugtfri, farveløs CO ₂ kan sniffes ud af overvågningsstationer eller droner for at advare om et udbrud - nogle gange timer, nogle gange måneder i forvejen. Udbrudssystemer med tidlig varsling med overvågning i realtid går fremad for at udnytte CO ₂ til opdagelse af SO2 -forhold, første gang anerkendt med sikkerhed i 2014

Siger DCO -forskeren Marie Edmonds fra University of Cambridge, Storbritannien:"Carbon, grundlaget for alt liv og energikilden, der er vital for menneskeheden, bevæger sig gennem denne planet fra sin kappe til atmosfæren. For at sikre en bæredygtig fremtid, det er af største betydning, at vi forstår Jordens hele kulstofcyklus. "

"Nøglen til at opklare planetens naturlige kulstofcyklus er at kvantificere, hvor meget kulstof der er, og hvor, hvor meget bevæger sig - strømmen - og hvor hurtigt, fra Deep Earth -reservoirer til overfladen og tilbage igen. "

Tilføjer kollega Tobias Fischer fra University of New Mexico, USA:"The Deep Carbon Observatory har avanceret forståelse af Jordens indre virke. Dets kollektive organ på mere end 1500 publikationer har ikke kun øget det kendte, men også fastlagt grænser for, hvad der er kendt, og måske ikke til at kende. "

"Mens vi fejrer fremskridt, vi understreger, at den dybe Jord forbliver en yderst uforudsigelig videnskabelig grænse; vi er virkelig kun begyndt at forringe de nuværende grænser for vores viden. "

Hvor meget kulstof indeholder jorden?

Forskere har længe vidst, at kulstof inde i Jorden findes som et mangfoldigt udvalg af faste stoffer, væsker, og gasser. Nogle af disse materialer involverer kombinationer af kulstof med ilt (f.eks. Kuldioxid), med jern (f.eks. karbider), med hydrogen (f.eks. kerogen, kul, råolie, og metan), og andre elementer (f.eks. silicium, svovl, og nitrogen), ud over elementært kulstof (f.eks. grafit og diamant).

Deep Carbon Observatory -forskere understreger, at kendskabet til totalt kulstof i nedre kappe og kerne stadig er spekulativt, og tallene vil helt sikkert udvikle sig i nøjagtighed, mens forskningen fortsætter. Det sagt, eksperter (især Lee et al ., 2019) anslår kulstofreservoirer på jorden som følger:

Ved tallene:Bedste aktuelle skøn, kulstof på jorden

1,85 milliarder gigatonn (1,85 x 1 milliard x 1 milliard tons):Samlet kulstof på Jorden

Sammenbrud:

• 1, 845, 000, 000 (1.845 mia.) Gt:samlet kulstof under overfladen
• 1, 500, 000, 000 (1,5 mia.) Gt:Kulstof i den nedre kappe:
• 315, 000, 000 (0,315 milliarder) Gt:Kulstof i de kontinentale og oceaniske litosfærer
• 30, 000, 000 (0,03 milliarder) Gt:Kulstof i den øvre kappe

• 43, 500 Gt:samlet kulstof over overfladen - i havene, på land, and in the atmosphere (2/10ths of 1% of Earth's total carbon)
• 37, 000 Gt:Carbon in the deep ocean (85.1% of all above surface carbon)
• 3, 000 Gt:Carbon in marine sediments (6.9%)
• 2, 000 Gt:Carbon in the terrestrial biosphere (4.6%)
• 900 Gt Carbon in the surface ocean (2%)
• 590 Gt:Carbon in the atmosphere (1.4%)

Release of CO ₂ from volcanoes

Earth's total annual out-gassing of CO ₂ via volcanoes and through other geological processes such as the heating of limestone in mountain belts is newly estimated by DCO experts at roughly 300 to 400 million metric tonnes (0.3 to 0.4 Gt).

Volcanoes and volcanic regions alone outgas an estimated 280-360 million tonnes (0.28 to 0.36 Gt) of CO ₂ per year. This includes the CO ₂ contribution from active volcanic vents, from the diffuse, widespread release of CO ₂ through soils, faults, and fractures in volcanic regions, volcanic lakes, and from the mid-ocean ridge system.

In many world regions, tectonic outgassing (emissions from mountain belts and other plate boundaries), particularly in cool night temperatures, can cause dangerous levels of CO ₂ close to the ground—enough to suffocate livestock.

According to DCO researchers, with rare exceptions over millions of years the quantity of carbon released from Earth's mantle has been in relative balance with the quantity returned through the downward subduction of tectonic plates and other processes.

Carbon catastrophes

While the volume of carbon buried through subduction and what's released from volcanoes and tectonic fractures are normally in steady state, about four times over the past 500 million years this balance has been upended by the emergence of large volcanic events—1 million or more square kilometers (the area of Canada) of magma released within a timeframe of a few tens of thousands of years up to 1 million years.

These "large igneous provinces" degassed enormous volumes of carbon (estimated at up to 30, 000 Gt—equal to about 70% of the estimated 43, 500 Gt of carbon above surface today).

Carbon cycle imbalance can cause rapid global warming, changes to the silicate weathering rate, changes to the hydrologic cycle, and overall rapid habitat changes that can cause mass extinction as the Earth rebalances itself.

Similar carbon catastrophes have been caused by asteroids / meteors (bolides), such as the massive Chixculub impact in the Yucatan area of Central America 65 million years ago—an event to which extinction of the dinosaurs and most other plants and animals of the time has been attributed.

According to Australian researchers Balz Kamber and Joseph Petrus:"The Chicxulub event ... greatly disrupted the budget of climate-active gases in the atmosphere, leading to short-term abrupt cooling and medium-term strong warming."

"Dermed, some large bolide impacts are comparable to those observed in the Anthropocene in terms of rapidly disrupting the C (carbon) cycle and potentially exceeding a critical size of perturbation."

Wiring up volcanoes

DCO experts estimate that about 400 of the 1500 volcanoes active since the last Ice Age 11, 700 years ago are venting CO ₂ today. Another 670 could be producing diffuse emissions, with 102 already documented. Of these, 22 ancient volcanoes that have not erupted since Pleistocene epoch (2.5 million years ago to the Ice Age) are outgassing. Thus all volcanoes, the young and very old, may be emitting CO ₂ .

Today's CO ₂ , sulphur dioxide and hydrogen sulphide emissions rates are now quantified for many of the world's most active volcanoes thanks in part to the development of miniature, holdbar, inexpensive instruments.

And several volcanoes have been wired up with permanent gas instrument monitoring stations to obtain real time data readings, improving monitoring by governments and universities in the U.S., Italien, Costa Rica, and elsewhere. About 30 collaboratively operated gas-monitoring stations on volcanoes across five continents now exist, which continually monitor emissions.

Pioneered by scientists with DCO's DECADE (Deep Earth Carbon DEgassing) subgroup, the technologies and installations have helped revolutionize data collection within inaccessible or dangerous volcanic places. The data obtained are combined with readings from long-established ground and satellite systems.

Recent research has revealed the number of volcanoes thought to be out-gassing measurable amounts of CO ₂ today. Estimated at 150 in 2013, DECADE researchers confirm that more than 200 volcanic systems emitted measurable volumes of CO ₂ between the years 2005 and 2017. Of these, several super-regions of diffuse degassing have been documented (e.g., Yellowstone, OS., the East African Rift, Afrika, and the Technong volcanic province in China, to name a few). Diffuse degassing is now recognized as a CO ₂ source comparable to active volcanic vents.

Among the DCO's legacies:a new database (http://www.magadb.net) to capture information on CO ₂ fluxes from volcanic and non-volcanic sources around the world.

Volcanic whispers:Changes in ratio of vented SO2 to CO ₂ can forewarn of eruptions

Research at a growing number of well-monitored volcanoes worldwide has provided important new insight about the timing of eruptions relative to the composition of volcanic outgassing.

Year-round monitoring at five volcanoes revealed that the level of carbon dioxide relative to sulfur dioxide in volcanic gases systematically changes in the hours to months before an eruption. Volcanoes where such patterns have been documented include Poas (Costa Rica), Etna and Stromboli (Italy), Villarica (Chile), and Masaya (Nicaragua).

Likewise the CO ₂ to SO2 ratio changed dramatically months to years prior to large eruptions at Kilauea (Hawaii) and Redoubt Volcano (Alaska), in the U.S., suggesting that monitoring gas composition, often in invisible plumes, offers a new eruption forecasting tool that, i nogle tilfælde, precedes increases in volcano seismicity or ground deformation.