Canjin Ruwa na Antarctic

**Antarctic Cold Reversal** ( **ACR** ) wani yanayi ne na yanayi mai tsanani na yanayi mai zafi da sanyi na teku a fadin kudancin kudancin (> 40 ° S) tsakanin 14,700 da 13,000 shekaru kafin yanzu ( BP ) wanda ya katse sauyin yanayi na kwanan nan na deglacial (c. 18,000-11,50000 shekaru BP).   Wannan taron sanyaya an fara lura da shi sosai a cikin bayanan tushen ƙanƙara na Antarctic.     Ba da da ewa ba, shaida daga simintin ruwa da ci gaban glacial daga talakawan ƙasa (kudancin Amurka ta Kudu,        New Zealand,       da sauransu  ) da kuma sassan Oceanic  kudu da 40 ° S sun fadada yankin wannan yanayin sanyaya yanayi. ACR yana kwatanta rikitarwa na sauyin yanayi a sauye-sauye daga Pleistocene zuwa Holocene Epochs. 

Gabaɗaya, samfuran yanayi suna nuna saukowar 1.5-2 ° C  a Antarctica da sauran yankuna masu matsakaici inda sake dawo da glacial   yawanci a bayyane yake. Yanayi ya ci gaba da dumi bayan shekaru 13,000 BP kuma kankara sun nuna alamun janyewa kwatsam daga tsoffin magunguna na ACR. Har yanzu ana muhawara game da hanyoyin da ke bayan sake tsara yanayi da teku, kodayake ana ambaton karfafawar Atlantic Meridional Overturning Circulation gabaɗaya.  

## Shaidu na Stratigraphic da Glacial
Yanayin duniya a lokacin Ice Age na ƙarshe ya kai yanayin zafi mafi sanyi tsakanin c. 2,000 da 18,000 shekaru BP, yana nuna farkon ƙarshen ƙarshe na ƙarshe. Wannan canjin daga Ice Age na ƙarshe, wanda aka fi sani da deglaciation, ya kasance har zuwa c. shekaru 11,500 BP, lokacin da zafin jiki, yanayin CO2 da matakin teku suka daina ƙaruwa da sauri, kuma kankara sun kai ga matsayi mafi ƙarancin Holocene. Lokacin da aka tsara a matsayin ACR (shekaru 14,700-13,000 BP) ana nuna shi ta hanyar juyawa ko tsayawa a cikin waɗannan yanayin deglacial, watau, yanayin zafi ya sanyaya, yanayin CO2 ya tsaya, kuma kankara ya sake farfadowa. Canjin yanayi, yanayin ƙasa, da na muhalli a lokacin ACR suna da bambanci tsakanin yankuna na ƙasa waɗanda suka nuna alamun sanyaya.

### Antarctica
Ana nuna ACR a Antarctica ta hanyar ƙanƙara da aka samo daga wurare da suka bazu a duk nahiyar.[./Antarctic_Cold_Reversal#cite_note-:19-21 [1] Babban wakilin da ke bin diddigin sanyaya yanayi a cikin ƙwayoyin kankara na Antarctic sune sa hannun deuterium wanda ke nuna karkatarwa mara kyau tsakanin shekaru 14,000 da 12,500 BP. An kuma nuna cewa yawan CO2 yana raguwa a wannan lokacin a cikin waɗannan ƙwayoyin kankara.

### Kudancin Amurka
Kudancin Kudancin Amurka yana da shaidu masu kyau na sanyaya yanayi a lokacin ACR. Rubuce-rubucen Stratigraphic daga kudancin Patagonia (45 °-54 ° S) suna nuna canje-canjen muhalli da ke da alaƙa da sanyaya yanayi ko karuwar ruwan sama. Misali, bayanan pollen sun nuna tsire-tsire masu haƙuri da sanyi da tsire-shire na alpine waɗanda suka sauya zuwa tsire-tire na gandun daji bayan shekaru 12,500 BP.

### New Zealand
New Zealand tana da rubuce-rubuce da yawa waɗanda ke nuna yanayin sanyaya na shekara dubu a lokacin ACR. Rubuce-rubucen Stratigraphic daga Kudancin Alps suna bin diddigin ci gaban kankara da kuma bayyana canje-canjen gandun daji tsakanin shekaru 14,500 da 12,800 BP.   Rubuce-rubucen zafin jiki na Chironomid-inferred sun nuna raguwar zafin jiki ta lokacin rani na ~3-2 ° C.h

## Manazarta