Taron Annoxic
 Taron Annoxic | |
|---|---|
 | |
| Bayanai | |
| Ƙaramin ɓangare na | aukuwa |
Has characteristic (en)  |
anoxic waters (en) |
Wani lamari mai ban sha'awa yana kwatanta lokacin da manyan faɗuwar tekuna na duniya suka ƙare da narkar da iskar oxygen (O2), suna haifar da ruwa mai guba, euxinic (anoxic da sulfidic).[1] Ko da yake al’amuran da ba su da ƙarfi ba su faru ba na miliyoyin shekaru, tarihin ƙasa ya nuna cewa sun faru sau da yawa a baya. Abubuwan da suka faru na anxic sun zo daidai da ɓarkewar jama'a da yawa kuma wataƙila sun ba da gudummawa gare su.[2] Waɗannan ɓangarorin da yawa sun haɗa da wasu waɗanda masana ilimin yanayin ƙasa ke amfani da su azaman alamomin lokaci a cikin hulɗar rayuwa. A gefe guda kuma, akwai gadaje masu baƙar fata iri-iri daga tsakiyar Cretaceous waɗanda ke nuna abubuwan da ba su da daɗi amma ba su da alaƙa da ɓarkewar jama'a. Yawancin masana kimiyyar ƙasa sun yi imanin cewa abubuwan da ke faruwa a teku suna da alaƙa mai ƙarfi da raguwar kewayawar teku, ɗumamar yanayi, da haɓakar iskar gas. Masu bincike sun ba da shawarar haɓakar volcanism (sakin CO2) a matsayin "matsalar waje ta tsakiya don euxinia."
Ayyukan ɗan adam a zamanin Holocene, kamar sakin abubuwan gina jiki daga gonaki da najasa, suna haifar da ƙananan matattun yankuna a duniya. Masanin kimiyyar teku na Biritaniya kuma masanin yanayi Andrew Watson ya ce cikakken anoxia na teku zai dauki "dubban shekaru don bunkasa."[3]
Fage
[gyara sashe | gyara masomin]An fara gabatar da manufar taron anoxic na teku (OAE) a cikin 1976 ta Seymour Schlanger (1927 – 1990) da masanin ilimin gero Hugh Jenkyns [9] kuma ya taso ne daga binciken da aikin hako ruwa mai zurfi (DSDP) ya yi a cikin Tekun Pacific. Gano baƙar fata, mai arzikin carbon a cikin sediments na Cretaceous waɗanda suka taru a kan tudun dutsen na ƙarƙashin ruwa (misali Shatsky Rise, Manihiki Plateau), tare da shekarunsu iri ɗaya zuwa makamantansu, adibas masu tushe daga Tekun Atlantika da kuma sananniya a cikin Turai-musamman a cikin rikodin yanayin ƙasa na in ba haka ba dutsen dutsen-wanda ya mamaye Italiya. Yaɗuwa, iri da aka rubuta ba a saba gani ba, yanayin ƙarancin iskar oxygen a cikin tekunan duniya wanda ya mamaye lokuta daban-daban na lokacin yanayin ƙasa.
Binciken sedimentological na zamani na waɗannan nau'ikan ma'auni na kwayoyin halitta yawanci suna bayyana kasancewar laminations masu kyau waɗanda ba su damu da dabbobin da ke ƙasa ba, suna nuna yanayin rashin ƙarfi a kan tekun da aka yi imani da cewa ya zo daidai da ƙaramin ma'auni mai guba na hydrogen sulfide, H2S. Bugu da ƙari kuma, dalla-dalla nazarin ilimin kimiyyar halittu kwanan nan sun bayyana kasancewar kwayoyin halitta (wanda ake kira biomarkers) waɗanda ke samo daga ƙwayoyin sulfur na sulfur guda biyu da ƙwayoyin sulfur na kore-kwayoyin da ke buƙatar duka haske da free hydrogen sulfide (H2S), yana nuna cewa yanayin anoxic ya haɓaka zuwa babban hoton hoto.
Wannan fahimta ce ta baya-bayan nan,[yaushe?] wuyar warwarewa da aka dunkule a hankali tare a cikin shekaru talatin da suka gabata. Kadan daga cikin sanannun abubuwan da ake zargi da cutar anxic an danganta su ta hanyar geologically zuwa yawan samar da albarkatun mai na duniya a cikin rukunin shale na duniya a cikin rikodin yanayin ƙasa.[4]
Euxinia
[gyara sashe | gyara masomin]Duba kuma: Zagayowar Phosphorus
Abubuwan da suka faru na anxinic tare da yanayin euxinic (anoxic, sulfidic) an danganta su da matsanancin yanayi na fitar da wuta mai aman wuta. Volcanism ya ba da gudummawar haɓakar CO2 a cikin yanayi da haɓaka yanayin zafi na duniya, yana haifar da saurin zagayowar ruwa wanda ya gabatar da abubuwan gina jiki a cikin tekuna (ƙarfafa haɓaka aikin planktonic). Waɗannan matakai na iya yin aiki azaman jawo euxinia a cikin takaitattun kwanduna waɗanda ke iya haɓaka ginshiƙan ruwa. A ƙarƙashin yanayi na anoxic zuwa euxinic, phosphate na teku ba a riƙe shi a cikin laka don haka ana iya sakewa kuma a sake yin fa'ida, yana taimakawa matuƙar yawan aiki.
Makanikai
[gyara sashe | gyara masomin]Zazzabi a cikin Jurassic da Cretaceous gabaɗaya ana tsammanin sun ɗanɗana dumi, saboda haka narkar da matakan iskar oxygen a cikin teku sun yi ƙasa da na yau - yana sa anoxia ya fi sauƙi a cimma. Koyaya, ana buƙatar ƙarin ƙayyadaddun yanayi don yin bayanin ɗan gajeren lokaci (kasa da shekaru miliyan) abubuwan anoxic na teku. Hasashe biyu, da bambance-bambance a kansu, sun tabbatar da mafi dorewa.
Ɗaya daga cikin hasashe yana nuna cewa tarin abubuwan da ba su da kyau na kwayoyin halitta suna da alaƙa da ingantaccen kiyayewa a ƙarƙashin ƙuntataccen yanayi da rashin isashshen oxygen, wanda su kansu wani aiki ne na musamman na geometry na tafkin teku: irin wannan hasashe, ko da yake yana da sauƙi ga matasa da ƙananan ƙananan Cretaceous Atlantic (wanda za a iya kwatanta shi da babban yanayin da ke da alaka da Tekun Black Sea). Coeval baƙar fata shales a kan buɗaɗɗen tekun Pacific Plateaus da shiryayye tekuna a duniya
Manazarta
[gyara sashe | gyara masomin]- ↑ Timothy W. Lyons; Ariel D. Anbar; Silke Severmann; Clint Scott & Benjamin C. Gill (January 19, 2009). "Tracking Euxinia in the Ancient Ocean: A Multiproxy Perspective and Proterozoic Case Study". Annual Review of Earth and Planetary Sciences. 37 (1): 507–53. Bibcode:2009AREPS..37..507L. doi:10.1146/annurev.earth.36.031207.124233.
- ↑ Wignall, Paul B.; Richard J. Twitchett (24 May 1996). "Oceanic Anoxia and the End Permian Mass Extinction". Science. 5265. 272 (5265): 1155–1158. Bibcode:1996Sci...272.1155W. doi:10.1126/science.272.5265.1155. PMID 8662450. S2CID 35032406.
- ↑ Impact from the Deep". Scientific American. October 2006.
- ↑ What would 3 degrees mean?". Archived from the original on 19 July 2008. Retrieved 2008-07-08.
[At plus] Six degrees [i.e rise of 6 degrees Celsius] * At the end of the Permian period, 251 million years ago, up to 95% of species became extinct as a result of a super-greenhouse event, resulting in a temperature rise of six degrees, perhaps because of an even bigger methane belch that happened 200 million years later in the Eocene and also: *Five degrees of warming occurred during the Paleocene-Eocene Thermal Maximum, 55 million years ago: during that event, breadfruit trees grew on the coast of Greenland, while the Arctic Ocean saw water temperatures of 20C within 200km of the North Pole itself. There was no ice at either pole; forests were probably growing in central Antarctica. * The Eocene greenhouse event was probably caused by methane hydrates (an ice-like combination of methane and water) bursting into the atmosphere from the seabed in an immense "ocean burp", sparking a surge in global temperatures. Today vast amounts of these same methane hydrates still sit on subsea continental shelves. * The early Eocene greenhouse took at least 10,000 years to come about. Today we could accomplish the same feat in less than a century. (emphasis, links added)