Tsinkaye na shekaru da yawa na Atlantic

Atlantic Multidecadal Oscillation (AMO), wanda aka fi sani da Atlantic Multideudal Variability (AMV),  shine bambancin da aka yi la'akari da yanayin zafin jiki na teku (SST) na Tekun Atlantika ta Arewa a kan shekarun da suka gabata. 

Duk da yake akwai wasu goyon baya ga wannan yanayin a cikin samfuran da kuma abubuwan lura na tarihi, akwai jayayya game da girman, da kuma ko yana da lokaci na al'ada kuma ana iya rarraba shi azaman oscillation. Har ila yau, akwai tattaunawa game da danganta canjin zafin jiki na teku zuwa abubuwan halitta ko abubuwan da suka haifar da mutum, musamman a yankunan Atlantic masu zafi da ke da muhimmanci ga ci gaban guguwa. Har ila yau, ana haɗa oscillation na Atlantic tare da sauye-sauye a cikin aikin guguwa, tsarin ruwan sama da ƙarfi, da canje-canje a cikin yawan kifi.

 Ma'anar da tarihi 
Shaida game da sauye-sauyen yanayi da yawa da ke tsakiyar Arewacin Atlantic ya fara fitowa a cikin aikin 1980s na Folland da abokan aiki, wanda aka gani a Fig. 2.d.A. Wannan oscillation shine kawai abin da Schlesinger da Ramankutty suka mayar da hankali a cikin 1994,  amma ainihin kalmar Atlantic Multidecadal Oscillation (AMO) Michael Mann ne ya kirkireshi a cikin wata hira ta tarho ta 2000 tare da Richard Kerr,  kamar yadda Mann ya ba da labarin, shafi na 30 a cikin The Hockey Stick and the Climate Wars: Dispatches from the Front Lines (2012). 

Ana bayyana siginar AMO yawanci daga alamu na bambancin SST a Arewacin Atlantic da zarar an cire kowane layi. Wannan lalacewa an yi niyya ne don cire tasirin iskar gas mai zafi ta duniya daga binciken. Koyaya, idan siginar dumama ta duniya ba ta da layi a lokaci (watau ba kawai karuwar layi ba), bambance-bambance a cikin siginar tilas zai shiga cikin ma'anar AMO. Sakamakon haka, alaƙa da lissafin AMO na iya rufe tasirin dumamar yanayi, kamar yadda Mann, Steinman da Miller suka nuna,  wanda kuma ke ba da cikakken tarihin ci gaban kimiyya.

 Alamar AMO 
An ba da shawarar hanyoyi da yawa don cire yanayin duniya da tasirin El Niño-Southern Oscillation (ENSO) a kan SST na Arewacin Atlantic. Trenberth da Shea, suna zaton cewa tasirin tilasta duniya a kan Arewacin Atlantic yayi kama da teku ta duniya, sun cire duniya (60 ° N-60 ° S) ma'anar SST daga Arewacin Atlantic don samun sabuntawa na AMO.

Ting et al. duk da haka suna jayayya cewa tsarin SST da aka tilasta ba daidai ba ne a duniya; sun raba bambancin da aka tilastawa da na ciki ta amfani da sigina zuwa hayaniya yana kara girman nazarin EOF.Mingfang, Ting; Yochanan Kushnir; Richard Seager; Cuihua Li (2009). "Forced and Internal Twentieth-Century SST Trends in the North Atlantic". Journal of Climate. 22 (6): 1469–1481. Bibcode:2009JCli...22.1469T. doi:10.1175/2008JCLI2561.1. S2CID 17753758.

Van Oldenborgh et al. sun sami alamar AMO yayin da SST ya kai matsakaici a kan matsanancin wurare masu zafi na Arewacin Atlantic (don cire tasirin ENSO wanda ya fi girma a latitude na wurare masu zafi) minus koma baya a kan matsakaicin zafin jiki na duniya.

Guan da Nigam sun cire yanayin duniya da ba a tsaya ba da kuma bambancin yanayi na Pacific kafin su yi amfani da nazarin EOF ga ragowar SST na Arewacin Atlantic.

Alamar da ta lalace ta layi ta nuna cewa anomaly na SST na Arewacin Atlantic a ƙarshen karni na ashirin an raba shi daidai tsakanin ɓangaren tilasta waje da bambancin da aka samar a ciki, kuma cewa mafi girma na yanzu yayi kama da tsakiyar karni na asirin; akasin haka sauran hanyoyin suna nuna cewa babban ɓangare na anomaly na Arewacin Atlantika a ƙarshen karni nke ashirin an tilasta shi a waje.

Frajka-Williams et al. 2017 sun nuna cewa canje-canje na baya-bayan nan a cikin sanyaya na subpolar gyre, yanayin zafi a cikin subtropics da sanyi anomalies a kan wurare masu zafi, sun kara rarrabawar sararin samaniya na gradient na meridional a cikin yanayin zafi na teku, wanda AMO Index bai kama ba.Eleanor Frajka-Williams; Claudie Beaulieu; Aurelie Duchez (2017). "Emerging negative Atlantic Multidecadal Oscillation index in spite of warm subtropics". Scientific Reports. 7 (1): 11224. Bibcode:2017NatSR...711224F. doi:10.1038/s41598-017-11046-x. PMC 5593924. PMID 28894211.

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