Rashin daskarewa

Deglaciation shine sauyawa daga cikakkun yanayin kankara a lokacin zamanin kankara, zuwa dumi *interglacials*, wanda ke nuna yanayin dumama na Duniya da hauhawar matakin teku saboda canji a cikin ƙanƙara na nahiyar. Don haka, yana nufin koma baya na kankara, kankara ko yashi mai daskarewa, da kuma bayyanar duniya. Raguwar cryosphere saboda ablation na iya faruwa a kowane sikelin daga duniya zuwa yanki zuwa wani glacier. Bayan Ƙarshen Glacial Maximum (kimanin shekaru 21,000 da suka gabata), an fara lalacewar ƙarshe, wanda ya kasance har zuwa farkon Holocene. A kusa da yawancin Duniya, deglaciation a cikin shekaru 100 da suka gabata yana hanzarta sakamakon Canjin yanayi, wani bangare ya haifar da canje-canje na ɗan adam ga iskar gas.

Gishiri na baya ya faru ne daga kimanin 22 ka har zuwa 11.5 ka. Wannan ya faru ne lokacin da akwai matsakaicin yanayin zafi na shekara-shekara a duniya wanda ya karu da kusan 5 ° C, wanda kuma ya kasance tare da dumama na yanki wanda ya wuce 10 ° C. Wannan kuma ya biyo bayan mai zurfi na teku da na teku mai zafi, na kimanin 1-2 ° C (zurfin teku) da 2-4 ° C (teku mai zafi). Ba wai kawai wannan dumama ya faru ba, amma kasafin kudin ruwa na duniya ya sami canje-canje masu mahimmanci kuma tsarin ruwan sama na yanki ya canza. A sakamakon duk wannan, manyan kankara na duniya, gami da waɗanda ke Eurasia, Arewacin Amurka da sassa na Antarctic sun narke. A sakamakon haka, matakan teku sun tashi kusan mita 120. Wadannan matakai ba su faru a hankali ba, kuma ba su faru ba a lokaci guda.&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;

## Tarihi
Tsarin deglaciation yana nuna rashin daidaituwa tsakanin yanayin glacial da yanayin yanayi. A sakamakon daidaitattun ma'auni a tsawon lokaci, ƙanƙara da kankara suna janyewa. Lokaci masu yawa na karuwa da raguwa na cryosphere na duniya (kamar yadda aka cire daga lura da kankara da dutse, yanayin ƙasa, tsarin ƙasa, rikodin burbushin halittu, da sauran hanyoyin kwanan wata) suna nuna yanayin cyclical na glaciology na duniya da na yanki wanda aka auna ta shekaru da ƙananan lokutan da aka sani da glacials da interglacials.  Tun daga ƙarshen lokacin glacial na ƙarshe kimanin shekaru 12,000 da suka gabata, kankara sun koma baya a kan sikelin duniya, kuma Duniya tana fuskantar lokacin zafi mai zafi wanda aka nuna kawai manyan kankara na alpine a mafi yawan latitudes tare da kankara da kankara na teku a kan sanduna. Koyaya, tun farkon Juyin Juya Halin Masana'antu, ayyukan ɗan adam sun ba da gudummawa ga saurin karuwa da kuma girman deglaciation a duniya.  

### Greenland
Binciken da aka buga a shekarar 2014 ya nuna cewa a kasa da kankara na Russell Glacier na Greenland, methanotrophs na iya zama sink na methane na halitta don tsarin halittu na subglacial, kuma yankin ya kasance aƙalla a lokacin samfurin, tushen methane na yanayi. Dangane da narkewar methane a cikin samfurori na ruwa, Greenland na iya wakiltar muhimmiyar tushen methane na duniya, kuma yana iya ba da gudummawa sosai saboda ci gaba da raguwa. Wani binciken da aka yi a shekarar 2016 ya kammala bisa ga shaidar da ta gabata, cewa a ƙasa da kankara na Greenland da Antarctica na iya kasancewa methane clathrates.

## Dalilai da sakamako
A kowane sikelin, yanayi yana tasiri ga yanayin dusar ƙanƙara da kankara a saman Duniya. A lokutan sanyi, manyan kankara na iya kaiwa zuwa Equator, yayin da a lokutan zafi fiye da yau, Duniya na iya zama cikakke ba tare da kankara ba. Wani muhimmin, wanda aka nuna, dangantaka mai kyau ta wanzu tsakanin zafin jiki da kuma yawan iskar gas kamar CO<sub>2</sub> a cikin yanayi. Babban maida hankali, bi da bi, yana da mummunar tasiri a kan girman duniya da kwanciyar hankali na cryosphere. A kan sikelin lokaci na dubban shekaru na Pleistocene glacial da kuma interglacial cycles, mai saurin farawa da narkewa shine canje-canje a cikin sigogi na orbital da ake kira Milankovitch cycles. Musamman, ƙananan insolation na lokacin rani a arewacin arewa yana ba da izinin girma na kankara, yayin da high summer insolation yana haifar da karin ablation fiye da tarin dusar ƙanƙara na hunturu.

Human activities promoting climate change, notably the extensive use of fossil fuels over the last 150 years and the resulting increase in atmospheric CO2 concentrations, are the principal cause of the more rapid retreat of alpine glaciers and continental ice sheets all across the world. For example, the West Antarctic Ice Sheet has receded significantly, and is now contributing to a positive feedback loop that threatens further deglaciation or collapse. Newly exposed areas of the Southern Ocean contain long-sequestered stores of CO2 which are now being emitted into the atmosphere and are continuing to impact glacial dynamics.

The principle of isostasy applies directly to the process of deglaciation, especially post-glacial rebound, which is one of main mechanisms through which isostasy is observed and studied. Post-glacial rebound refers to the increase in tectonic uplift activity immediately following glacial retreat. Increased rates and abundance of volcanic activity have been found in regions experiencing post-glacial rebound. If on a large enough scale, an increase in volcanic activity provides a positive feedback to the process of deglaciation as a result CO2 and methane released from volcanos.

Lokaci na deglaciation kuma yana haifar da wani ɓangare ta hanyar hanyoyin teku. Misali, katsewar ruwan sanyi mai zurfi da zurfin shiga cikin Arewacin Atlantic suna da ra'ayoyin da ke inganta ci gaba da koma baya.

Deglaciation yana tasiri a matakin teku saboda ruwan da aka riƙe a ƙasa a cikin tsari mai ƙarfi ya juya zuwa ruwa mai ruwa kuma a ƙarshe ya shiga cikin teku. Lokacin da ya gabata na tsananin deglaciation ya haifar da matsakaicin matakin teku na duniya na 1.7 mm / shekara a duk karni na 20, da 3.2 mm / shekara cikin shekaru ashirin da suka gabata, karuwa mai sauri.&nbsp;&nbsp;

Hanyoyin jiki da ke faruwa da deglaciation sun haɗa da narkewa, evaporation, sublimation, calving, da kuma matakai na aeolian kamar iska.

## Rashin daskarewa na Laurentide Ice Sheet
A cikin Pleistocene Epoch, Laurentide Ice Sheet ya bazu a manyan yankuna na arewacin Arewacin Amurka, tare da fiye da murabba'in kilomita 5,000,000 na ɗaukar hoto. Yankin kankara na Laurentide yana da zurfin ƙafa 10,000 a wasu yankuna, kuma ya kai kudu har zuwa 37 ° N. Dyke et al sun shirya taswirar girman Laurentide Ice Sheet a lokacin deglaciation. Hanyoyin deglaciation suna motsawa ta hanyoyi daban-daban, tare da babban direba yana canzawa a cikin hasken rana mai shigowa, ko insolation, a Arewacin Hemisphere. Amma, kamar yadda ba duk hauhawar rana ba a duk lokacin da ya haifar da deglaciation, zuwa yawan kankara na yanzu da muke gani a yau. Wannan yana haifar da kammalawa daban, wanda ke nuna cewa akwai yiwuwar ƙofar yanayi, dangane da kankara da ke janyewa, kuma a ƙarshe ya ɓace. Kamar yadda Laurentide ya kasance mafi girman kankara a Arewacin Hemisphere, an gudanar da bincike mai yawa game da bacewarsa, fitar da samfuran ma'aunin makamashi, samfuran yaduwar yanayi-teku, da samfuran daidaitawar makamashi. Wadannan binciken sun kammala cewa Laurentide ice sheet ya gabatar da daidaitattun ma'auni na surface a lokacin kusan dukkanin deglaciation, wanda ke nuna cewa asarar taro a duk lokacin deglacization ya kasance fiye da yiwuwar saboda fitarwa mai ƙarfi. Ba har sai farkon Holocene ba lokacin da ma'aunin farfajiyar ya canza ya zama mara kyau. Wannan canji zuwa ma'auni mara kyau ya nuna cewa raguwar ƙasa ta zama direba wanda ya haifar da asarar yawan kankara a cikin kankara na Laurentide. An kammala cewa Laurentide ice sheet kawai ya fara nuna halaye da alamu na deglaciation bayan tilasta radiative da kuma yanayin zafi na rani ya fara tashi a farkon Holocene.

## Sakamakon deglaciation na kankara Laurentide
Lokacin da kankara ta Laurentide ta ci gaba ta hanyar aiwatar da deglaciation, ta haifar da sabbin wurare da yawa kuma tana da tasirin ƙasa daban-daban. Na farko kuma mafi mahimmanci, yayin da manyan kankara suka narke, akwai babban adadin ruwan da ya narke. Yawan ruwan da ya narke ya haifar da siffofi da yawa, gami da tabkuna na ruwan sha, wanda zai iya zama mai girma. Ba wai kawai akwai ruwan da ya narke wanda ya samar da tabkuna ba, akwai kuma hadari da ya hura a kan ruwan sha na ciki. Wadannan guguwa sun haifar da raƙuman ruwa masu karfi don lalata bakin kankara. Da zarar an fallasa dutsen kankara, saboda hauhawar matakan teku da rushewar da raƙuman ruwa suka haifar, an raba kankara kuma an zubar da su. Manyan tabkuna sun zama ruwan dare, amma haka kuma ƙananan tabkuna, marasa zurfi, masu ɗan gajeren lokaci. Wannan bayyanar da ɓacewar ƙananan tabkuna masu zurfi sun rinjayi yawancin tsire-tsire, yaduwa da bambancin da muke gani a yau. Tafkunan sun yi aiki a matsayin shingen shuka ƙaura, amma lokacin da waɗannan tabkuna suka bushe, tsire-tsire na iya ƙaura da yaduwa sosai.

## Rashin daskarewa na ƙarshe
 

Tsakanin ƙarshen ƙarshen Glacial na ƙarshe zuwa farkon Holocene (kimanin 19k-11k shekaru da suka wuce), yana nuna canje-canje a cikin adadin iskar gas da kuma na meridional jujjuyawar wurare dabam dabam na Atlantic (AMOC), lokacin da matakin teku ya tashi da mita 80.  Bugu da ƙari, ƙaƙƙarfan raguwa na ƙarshe yana da alamar CO  bugun jini guda uku,  da kuma bayanan fashewar volcanic sun nuna cewa volcanism na ƙasa ya karu a duniya da sau biyu zuwa shida sama da matakan baya tsakanin 12 ka da 7 ka. 

Tsakanin kimanin 19ka, ƙarshen Ƙarshen Glacial Maximum (ko LGM) zuwa 11ka, wanda shine farkon Holocene, tsarin yanayi ya sami canji mai yawa. Yawancin wannan canjin yana faruwa ne da sauri, yayin da duniya ke hulɗa da ƙarshen zamanin kankara na ƙarshe. Canje-canje a cikin hasken rana shine babban dalilin wannan Canjin yanayi na duniya, kamar yadda wannan ke da alaƙa da wasu canje-canje da yawa a duniya, daga canjin kankara, zuwa maida hankali ga iskar gas mai ɗorewa, da sauran abubuwan da suka haifar da martani daban-daban, a duniya da yanki. Ba wai kawai kankara da iskar gas da ke fuskantar canji ba, har ma da wannan, akwai canjin yanayi na kwatsam, da kuma abubuwan da suka faru da sauri, da kuma hauhawar matakin teku. Rugujewar kankara, tare da hauhawar matakan teku ba su faru ba har sai bayan 11ka. Duk da haka, duniya ta isa lokacin da take tsakanin ƙanƙara a yanzu, inda yanayi yake da daidaituwa kuma yana da kwanciyar hankali, kuma yawan iskar gas yana nuna kusa da matakan masana'antu. Wannan bayanan duk yana samuwa ne saboda karatu da bayanin da aka tattara daga bayanan wakilai, duka daga ƙasa da teku, wanda ke kwatanta tsarin duniya na canje-canje a cikin yanayi yayin da yake cikin lokacin Deglaciation. 

A lokacin Ƙarshe na Glacial Maximum (LGM), an sami ƙaramar ƙarancin yanayi na Carbon Dioxide ( CO  ), wanda aka yi imani da shi sakamakon babban abun ciki na carbon a cikin zurfin teku, ta hanyar rarrabuwa tsakanin Tekun Kudancin. Waɗannan zurfin zurfin tekun Kudancin Tekun sun ƙunshi mafi ƙarancin δ13C, wanda sakamakon haka ya haifar da kasancewa wurin da mafi girman yawa, da mafi yawan abun ciki na gishiri a lokacin LGM. Fitar da irin wannan nau'in carbon da aka ƙera ƙila ya kasance sakamakon kai tsaye na zurfin tekun Kudancin teku, wanda ke motsa shi ta hanyar haɓakar iska mai ƙarfi, da ja da baya na kankara, waɗanda ke da alaƙa kai tsaye da ɗumamar Antarctic, sannan kuma ya zo daidai da abubuwan sanyi, Tsoho da Matashi Dryas, a arewa. 

A duk faɗin LGM a Arewacin Amurka, gabas ta cika da gandun daji masu jure sanyi, yayin da kudu maso gabas da arewa maso yammacin Amurka suka ci gaba da gandun dajin da aka rufe a yau, wanda ke nuna cewa a lokacin LGM yanayin zafi ya fi sanyi kuma yanayin gaba ɗaya ya fi bushewa fiye da waɗanda muke fuskanta a yau. Har ila yau, akwai alamar cewa kudu maso yammacin Amurka ya fi ruwan sama a lokacin LGM idan aka kwatanta da yau, kamar yadda akwai gandun daji, inda a yau muke ganin hamada da hamada. A cikin Amurka, bambancin tsire-tsire gabaɗaya yana nuna faɗuwar yanayin zafi na (aƙalla 5 ° C), sauyawa na waƙoƙin guguwa na yamma zuwa kudu, da kuma yanayin zafi mai zurfi.

## Yanayin ƙasa
 
Yawancin siffofi da ake gani a yau sun bambanta da karfi mai karfi a lokacin, ko nan da nan bayan, deglaciation. Rarraba irin waɗannan siffofin ƙasa yana taimakawa wajen sanar da fahimtar yanayin glacial da lokutan geologic na baya. Nazarin yanayin da aka fallasa na iya sanar da fahimtar halin yanzu da kuma makomar kusa yayin da kankara a duk faɗin duniya ke komawa baya a halin yanzu na canjin yanayi. Gabaɗaya, wuraren da aka lalata kwanan nan ba su da kwanciyar hankali kuma za su matsa zuwa daidaituwa.

Samfurin yanayin ƙasa na yau da kullun wanda ya haifar da deglaciation, ko kuma ya haifar da tsarin geomorphic na gaba bayan fallasawa saboda deglaciations:

* Moraine
* Esker
* Kettle
* Kame
* Drumlin
* Thermokarst
* Kwarin Ramin Ramin
* Tafkin da ke gaba
* Tashar karkashin dusar ƙanƙara

## Manazarta