UMary Allen
Ulwandle amanzi akhiwe ngamanzi anosawoti. Ingxenye enkulu yomhlaba imbozwe ngamanzi olwandle, angaphezu kwezingxenye ezimbili kwezintathu. Kukhona izingxenye ngazinye, kodwa zonke zixhumene. Lokhu kubizwa ngokuthi “uLwandle Lomhlaba”. Ngokuvamile ihlukaniswe izilwandle ezinhlanu.
Ngaphezu kwalokho, izingxenye zolwandle nazo zinamagama akhethekile, njengezilwandle ezihlangene namatheku. I-Mediterranean Sea iyisibonelo salokhu noma iCaribbean. ULwandle Olubomvu phakathi kweGibhithe ne-Arabia lungaphezu kolwandle oluseceleni olucishe luvaleleke ezweni lonke.
Ubuso bomhlaba ngokuyinhloko bumbozwe izilwandle: Cishe bangamaphesenti angama-71, okungukuthi cishe izingxenye ezintathu kwezine. Indawo ejulile yiseMariana Trench ePacific Ocean. Kungaba amamitha ayizinkulungwane eziyishumi nanye ukushona lapho.
Luyini ngempela ulwandle, futhi lubizwa ngani kanjalo?
Uma amanzi amaningi ezungezwe umhlabathi, akulona ulwandle kodwa iyichibi. Amanye amachibi asabizwa ngokuthi izilwandle. Lokhu kungaba nezizathu ezimbili ezahlukene.
I-Caspian Sea empeleni iyichibi likasawoti. Lokhu kusebenza futhi oLwandle Olufile. Zathola igama ngenxa yobukhulu bazo: kubantu, zazibonakala zinkulu njengolwandle.
EJalimane, kunesinye isizathu esiqondile. NgesiJalimane, sivamise ukuthi Meer ngokwengxenye yolwandle bese sithi Bheka ngokuma emanzini aphakathi nezwe. NgesiJalimane Esiphansi, noma kunjalo, kungenye indlela. Lokhu sekuthole indlela yakho olimini olujwayelekile lwesiJalimane.
Kungakho siphinde sithi “ulwandle” lolwandle: uLwandle lwaseNyakatho, uLwandle iBaltic, uLwandle oluseNingizimu, njalonjalo. Kukhona namachibi athile enyakatho yeJalimane anegama elithi “ulwandle” emagameni awo. Eyaziwa kakhulu cishe i-Steinhuder Meer e-Lower Saxony, ichibi elikhulu kunawo wonke enyakatho.
Yiziphi izilwandle ezikhona?
Ulwandle lomhlaba luvamise ukuhlukaniswa lube izilwandle ezinhlanu. Okukhulu kunawo wonke yiPacific Ocean phakathi kweMelika ne-Asia. Ibizwa nangokuthi iPacific. Olwesibili ngobukhulu yi-Atlantic Ocean noma i-Atlantic Ocean phakathi kweYurophu ne-Afrika empumalanga neMelika ngasentshonalanga. Olwesithathu ngobukhulu uLwandlekazi i-Indian phakathi kwe-Afrika, i-India ne-Australia.
Olwesine ngobukhulu yiSouthern Ocean. Lena indawo ezungeze izwekazi lase-Antarctica. Encane kunayo yonke emihlanu i-Arctic Ocean. Ilele ngaphansi kweqhwa lase-arctic futhi ifinyelela eCanada naseRussia.
Abanye abantu bakhuluma ngezilwandle eziyisikhombisa. Ngaphezu kwezilwandle ezinhlanu, zengeza izilwandle ezimbili eziseduze kwazo noma ezivame ukuhamba ngemikhumbi. Izibonelo ezivamile oLwandle iMedithera kanye neCaribbean.
Endulo, abantu babebalwa nezilwandle eziyisikhombisa. Lezi kwakuyizingxenye eziyisithupha zeMedithera njengoLwandle i-Adriatic kanye noLwandle Olumnyama. Inkathi ngayinye yayinendlela yayo yokubala. Lokhu kwakuhlobene kakhulu nokuthi yiziphi izilwandle ezaziwa nhlobo.
Kungani izilwandle zibaluleke kangaka?
Abantu abaningi bahlala eduze nolwandle: babamba izinhlanzi lapho, bamukele izivakashi noma bahamba ngomkhumbi olwandle ukuze bathuthe izimpahla. Ulwandle luqukethe izinto ezingavuthiwe ezifana nowoyela ongahluziwe, okhishwayo.
Okokugcina, ulwandle lubalulekile esimweni sezulu seplanethi yethu enguMhlaba. Ulwandle lugcina ukushisa, lukusabalalise ngemisinga, futhi lumunca namagesi abamba ukushisa njengesikhutha. Ngakho ngaphandle kwabo, besiyoba nokufudumala okwengeziwe kwembulunga yonke.
Nokho, i-carbon dioxide eningi nayo ayilungile olwandle. Emanzini olwandle, iba yi-carbonic acid. Lokhu kwenza ulwandle lube ne-asidi, okuyinto embi emizimbeni eminingi yamanzi.
Izazi zemvelo nazo zikhathazekile ngokuthi yanda udoti ophelela olwandle. Ipulasitiki ikakhulukazi incipha kancane kakhulu. Kodwa-ke, ibola ibe yizicucu ezincane kakhulu, i-microplastics. Lokhu kuvumela ukuthi igcine emizimbeni yezilwane futhi idale umonakalo lapho.
Usawoti ungena kanjani olwandle?
Akukho ndawo emhlabeni lapho kunamanzi amaningi njengasolwandle: amaphesenti angama-97. Nokho, amanzi olwandle awaphuzwa. Kwezinye ugu, kunezitshalo zokususa usawoti emanzini olwandle, okuwenza abe amanzi okuphuza.
Usawoti utholakala emadwaleni emhlabeni wonke. Ngokuphathelene nolwandle, ngokuvamile umuntu ukhuluma ngosawoti wetafula noma usawoti ovamile, esiwusebenzisa ekhishini. Usawoti wetafula uncibilika kahle kakhulu emanzini. Ngisho nemali encane ingena olwandle ngokusebenzisa imifula.
Kukhona nosawoti olwandle. Nalokho kucwila kancane emanzini. Izintaba-mlilo ezingaphansi kolwandle nazo zingakhipha usawoti. Ukuzamazama komhlaba olwandle nakho kubangela ukuba usawoti ungene emanzini.
Umjikelezo wamanzi ubangela ukuba amanzi amaningi angene olwandle. Nokho, ingalushiya kuphela ulwandle ngokuhwamuka. Usawoti awuhambisani nawo. Usawoti, kanye olwandle, uhlala khona. Lapho amanzi ehwamuka, ulwandle luba nosawoti omningi. Ngakho-ke, usawoti omncane awufani ncamashi kuzo zonke izilwandle.
Ilitha lamanzi olwandle ngokuvamile liqukethe cishe amagremu angama-35 kasawoti. Lokho kusho ukuthi isipuni esiqoqiwe nohhafu. Ngokuvamile sigcwalisa amalitha amanzi angaba ngu-150 kubhavu. Ngakho-ke kungadingeka wengeze amakhilogremu amahlanu kasawoti ukuze uthole amanzi olwandle.