Tsakiyar Eocene Yanayin yanayi mafi kyau

Tsakiya Eocene Climatic Optimum (MECO), wanda kuma ake kira Tsakiyar Tsakiyar Yammacin Eocene   wani lokaci ne na yanayi mai dumi wanda ya faru a lokacin Bartonian, daga kusan 40.5 zuwa 40.0 Ma.  Ya nuna sanannen canji na yanayin sanyaya na duniya wanda ya nuna tsakiyar da Ƙarshen Eocene.

 Tsawon lokaci 
Tsawon lokacin da MECO ya ɗauka ana jayayya, kodayake an san cewa ya kasance daga kusan 40.5 zuwa 40.0 Ma. Dangane da wuri da hanyar, an kiyasta tsawon lokacin taron a 300, 500, 600, da 750 kyr.

 Yanayi 
MECO ya kasance dai-dai a duniya kuma an lura da shi a cikin jerin ruwa da na ƙasa. matsakaicin yanayin zafi na duniya a lokacin MECO ya kasance kusan 23.1 ° C. A cikin Tekun Tethys, an kiyasta Yanayin zafi na teku (SSTs) a 32-36 °C. Yanayin ruwa daga abin da ke yanzu Liguria ya tashi da kimanin 4-6 ° C, yayin da tekuna daga kudu maso yammacin Balkanatolia suka warma da 2-5 ° C. Arewa maso yammacin Atlantic ya sami karuwar 3 ° C a yanayin zafi na teku. A kudu maso yammacin Pacific, SSTs sun tashi daga matsakaicin kimanin 22 ° C zuwa 28 ° C. Yanayin zafi mai zurfi na teku ya kasance kusan 9 ° C a saman MECO. A kan shelf mai zurfi a kusa da tsibirin Seymour, yanayin zafi ya warts da ~5 ° C. Yankin Arewacin Amurka ya fi dumi, da 9 ° C daga 23 ° C ± 3 ° C zuwa 32 ° C ± 4 ° C a saman MECO, sannan ya biyo bayan raguwar 11 ° C bayan MECO.

A Yammacin Arewacin Amurka, tabkuna sun zama maras gishiri. Pyrenees ya zama mai zafi da bushewa. Arewa maso tsakiyar Turkiyya, sannan wani ɓangare na Balkanatolia, yana da rigar da dumi. An yi tunanin cewa nahiyar Asiya ta fuskanci matsanancin bushewa a lokacin MECO, kodayake bincike na baya-bayan nan ya nuna cewa wannan ya faru ne bayan MECO.

Yanayin yanayi na nahiyar ya karu tare da hauhawar yanayin zafi. Ayyukan halittu na ruwa sun tashi yayin da ingantaccen zagaye na ruwa ya ba da ƙarin abubuwan gina jiki ga teku. An rubuta eutrophication mai zurfi daga Tethys,  Arewacin Atlantic,  Kudancin Atlantic,  da Kudancin Tekun.

Ragewar abun ciki na iskar oxygen na teku ya faru a lokacin MECO a cikin Tethys Ocean .   Yanayin Dysoxic a cikin Tethys ya kasance kusan 400-500 kyr bisa ga binciken geochemical na shafin Alano a arewa maso gabashin Italiya. Shaida daga Kudancin Tekun ya nuna zurfin ruwa deoxygenation da aka bunkasa a wannan yankin ruwa ma. Yawan binnewar carbon na kwayoyin halitta ya tashi a cikin waɗannan ruwan da ba su da iskar oxygen, wanda zai iya aiki a matsayin mummunan ra'ayi wanda ya taimaka wajen dawo da yanayin zafi na duniya zuwa yanayin su na MECO bayan dumama ya ƙare. Koyaya, deoxygenation ba ya ko'ina a duniya; Shafukan Kudancin Atlantic kamar Kudancin Tekun Bincike Shafin 702 ba su nuna wata shaida game da kowane canji zuwa yanayin dysoxic ba. Ingantaccen tsari na glauconites a wasu sassan da aka yi nazari a fadin MECO an yi imanin a wani bangare yana nuna raguwar abun ciki na iskar oxygen, kamar yadda wannan ya kawar da motsi na baƙin ƙarfe da ikon da za a haɗa shi don yin glauconite.

Akwai shaida yaduwar teku da ke faruwa a lokacin MECO ta hanyar manyan raguwa a cikin tarin carbonate a cikin teku a zurfin fiye da kilomita uku. Acidification ya shafi dukkan ginshiƙan ruwa, ya kai har zuwa yankin abyssal.

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