Ruwa mai zurfi na Arewacin Atlantic

Ruwa mai zurfi na Arewacin Atlantic (NADW) ruwa ne mai zurfi wanda aka kafa a Tekun Atlantika ta Arewa. Yankin thermohaline (wanda aka bayyana daidai a matsayin yaduwar juyawa) na tekun duniya ya haɗa da kwararar ruwan zafi daga kudancin kudancin zuwa Arewacin Atlantic. Ruwa da ke gudana zuwa arewa ya canza ta hanyar evaporation da gauraya da sauran ruwa, wanda ke haifar da karuwar salinity. Lokacin da wannan ruwa ya kai Arewacin Atlantic, yana sanyaya kuma ya nutse ta hanyar convection, saboda raguwar zafin jiki da karuwar salinity wanda ke haifar da karuwar yawa. NADW shine fitowar wannan zurfin zurfi, wanda za'a iya gano shi ta hanyar babban salinity, babban abun ciki na oxygen, mafi ƙarancin abinci mai gina jiki, babban 14/12,  da chlorofluorocarbons (CFCs). 

CFCs abubuwa ne na ɗan adam waɗanda ke shiga saman teku daga musayar gas tare da yanayi. Wannan abun da ke ciki na musamman yana ba da damar gano hanyarsa yayin da yake haɗuwa da Circumpolar Deep Water (CDW), wanda hakan ya cika zurfin Tekun Indiya da wani ɓangare na Kudancin Pacific. NADW da kafa shi yana da mahimmanci ga yaduwar juyawa ta Atlantic (AMOC), wanda ke da alhakin jigilar ruwa mai yawa, zafi, gishiri, carbon, abubuwan gina jiki da sauran abubuwa daga Tropical Atlantic zuwa Mid da High Latitude Atlantic.

A cikin samfurin belin conveyor na zagayawar thermohaline na teku na duniya, nutsewar NADW tana jan ruwan Arewacin Atlantic zuwa arewa. Koyaya, wannan kusan tabbas sauƙaƙewar ainihin dangantakar da ke tsakanin kafa NADW da ƙarfin Gulf Stream / Arewacin Atlantic.

 Halitta da tushe 
NADW wani nau'i ne mai rikitarwa na ruwa da yawa wanda aka kafa ta hanyar zurfin convection da cikawar ruwa a fadin Greenland-Iceland-Scotland Ridge . 
Yankin da ke sama an kafa su ne ta hanyar zurfin bude teku a lokacin hunturu. Labrador Sea Water (LSW), wanda aka kafa a cikin Labrador Ocean, na iya kaiwa zurfin 2000 m yayin da ruwa mai yawa ya nutse ƙasa. Classical Labrador Sea Water (CLSW) samarwa ya dogara da preconditioning na ruwa a cikin Labrador Tekun daga shekarar da ta gabata da kuma ƙarfin Arewacin Atlantic oscillation (NAO). 

A lokacin kyakkyawan NAO, yanayin yana nan don guguwar hunturu mai ƙarfi don bunkasa. Wadannan guguwa suna sabunta ruwa na sama, kuma iskarsu tana kara yawan kwararar cyclonic, wanda ke ba da damar ruwa mai yawa ya nutse. A sakamakon haka, zafin jiki, salinity, da yawa sun bambanta kowace shekara. A wasu shekaru waɗannan yanayin ba su wanzu ba kuma ba a kafa CLSW ba. CLSW yana da yanayin zafin jiki na 3 ° C, salinity na 34.88 psu, da kuma yawan 34.66.Smethie, William M.; Fine, Rana A.; Putzka, Alfred; Jones, E. Peter (2000). "Tracing the flow of North Atlantic Deep Water using chlorofluorocarbons". Journal of Geophysical Research: Oceans. 105 (C6): 14297–14323. Bibcode:2000JGR...10514297S. doi:10.1029/1999JC900274. 

Wani bangare na LSW shine Upper Labrador Sea Water (ULSW). ULSW siffofi a ƙananan ƙananan CLSW kuma yana da matsakaicin CFC tsakanin 1200 da 1500 m a cikin subtropical North Atlantic. Eddies na sanyi kasa saline ULSW suna da irin wannan yawa na ruwan gishiri mai zafi da gudana tare da DWBC, amma kula da manyan CFCs. ULSW eddies suna lalacewa da sauri yayin da suke haɗuwa a gefe tare da wannan ruwan gishiri mai zafi.Smethie, William M.; Fine, Rana A.; Putzka, Alfred; Jones, E. Peter (2000). "Tracing the flow of North Atlantic Deep Water using chlorofluorocarbons". Journal of Geophysical Research: Oceans. 105 (C6): 14297–14323. Bibcode:2000JGR...10514297S. doi:10.1029/1999JC900274.

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