Lokacin zafi na Afirka

Lokacin zafi na Afirka (AHP; wanda aka fi sani da wasu sunaye) lokaci ne na yanayi a Afirka a lokacin ƙarshen Pleistocene da Holocene, lokacin da arewacin Afirka ya fi ruwa fiye da yau. Rufe yawancin hamadar Sahara da ciyawa, bishiyoyi da tabkuna ya haifar da canje-canje a cikin karkatawar duniya, canje-canje na ciyayi da ƙura a cikin Sahara wanda ya ƙarfafa Ruwan sama na Afirka, da kuma karuwar iskar gas. A lokacin Last Glacial Maximum da ya gabata, Sahara ya ƙunshi filayen Dune masu yawa kuma galibi ba a zaune ba. Ya fi girma fiye da yau, kuma tabkuna da koguna kamar Lake Victoria da White Nile sun bushe ko kuma a ƙananan matakan. Lokacin zafi ya fara kimanin shekaru 14,600-14,500 da suka gabata a ƙarshen taron Heinrich 1, a lokaci guda zuwa dumama Bølling-Allerød. Koguna da tabkuna kamar Tafkin Chadi sun samo asali ko fadada, kankara sun girma a Dutsen Kilimanjaro kuma Sahara ta koma baya. Manyan sauye-sauye biyu na bushewa sun faru; a lokacin Younger Dryas da gajeren taron kiloyear 8.2. Lokacin zafi na Afirka ya ƙare shekaru 6,000-5,000 da suka gabata a Lokacin yanayi na Piora Oscillation. Duk da yake wasu shaidu suna nuna ƙarshen shekaru 5,500 da suka gabata, a cikin Sahel, Arabiya da Gabashin Afirka, ƙarshen lokacin ya bayyana ya faru a matakai da yawa, kamar taron kilo 4.2.

AHP ta haifar da yaduwar zama a cikin Sahara da hamadar Larabawa, kuma tana da tasiri sosai ga al'adun Afirka, kamar haihuwar wayewar Masar ta Dā. Mutanen da ke cikin Sahara sun rayu a matsayin mafarauta da masu tarawa da shanu, awaki da tumaki. Sun bar wuraren tarihi da kayan tarihi kamar ɗaya daga cikin tsofaffin jiragen ruwa a duniya, da zane-zanen dutse kamar waɗanda ke cikin kogon masu iyo da tsaunukan Acacus. An yi la'akari da lokutan zafi na farko a Afirka bayan gano waɗannan zane-zanen dutse a cikin ɓangarorin da ba a karɓa ba na yanzu na Sahara. Lokacin da lokacin ya ƙare, mutane a hankali sun watsar da hamada don tallafawa yankuna masu aminci na ruwa, kamar Kwarin Nilu da Mesopotamiya, inda suka haifar da al'ummomi masu rikitarwa na farko.

A cikin 1850 mai bincike Heinrich Barth ya tattauna yiwuwar canjin yanayi na baya wanda ya haifar da karuwar rigar a cikin Sahara bayan gano petroglyphs a cikin Murzuq Desert,  kamar yadda Ahmed Hassanein ya yi bayan bincikensa na 1923 na hamadar Libya lokacin da ya ga hotunan dabbobin savanna a Gabal El Uweinat.  Ƙarin binciken petroglyphs ya jagoranci mai binciken hamada László Almásy don ƙirƙirar manufar Green Sahara a cikin shekarun 1930. Daga baya a cikin karni na 20, an ƙara bayar da rahoton cewa Holocene ya nuna lokacin zafi a cikin Sahara.

Ra'ayin cewa canje-canje a cikin yanayin duniya a kusa da Rana yana rinjayar ƙarfin ruwan sama ya riga ya ci gaba a 1921, kuma yayin da bayanin asali ya kasance wani ɓangare ba daidai ba, daga baya an sami shaidar da aka yadu don irin wannan sarrafawar yanayin a kan yanayi. Da farko an yi imanin cewa lokutan zafi a Afirka suna da alaƙa da matakan glacial ("ruwa ra'ayi") kafin kwanan wata na radiocarbon ya zama gama gari. Da farko a cikin shekarun 1970s, an danganta zafi ga canje-canje na precession.

 Batutuwan bincike 
Duk da yake sauye-sauyen hazo tun lokacin da aka kammala zagaye na ƙarshe, girman da lokacin canje-canjen ba su da tabbas. Dangane da yadda kuma inda ake yin ma'auni da sake ginawa, an ƙaddara kwanakin farawa daban-daban, kwanakin ƙarshe, tsawon lokaci  da matakan hazo  don lokacin zafi na Afirka.  Adadin hazo da aka sake ginawa daga bayanan paleoclimate kuma aka tsara ta hanyar ƙirar yanayi sau da yawa ba su dace da juna ba;  gabaɗaya, ƙirar Green Sahara ana ɗaukarsa matsala ga samfuran tsarin ƙasa.  Akwai ƙarin shaidu game da ƙarshen AHP fiye da farkonsa. Rushewar ruwan tafkin da Tasirin tafkin carbon ya sa ya zama da wahala a gano kwanan wata lokacin da suka bushe. Canje-canje na shuke-shuke da kansu ba lallai bane su nuna canje-canje na hazo, kamar yadda canje-canje a cikin yanayi, nau'ikan nau'ikan shuke-tsire da canje-canje wajen Amfani da ƙasa suma suna taka rawa a cikin canje-canjen shuke-finai. Isotope ratios kamar Hydrogen / deuterium rabo wanda aka yi amfani da shi don sake gina dabi'un hazo na baya kamar haka suna ƙarƙashin tasirin tasirin jiki daban-daban, wanda ke rikitar da fassarar su. Yawancin rubuce-rubuce na Holocene a gabashin Afirka sun fito ne daga ƙananan tsaunuka.

 Manazarta