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44.ObtainingFreshwaterfromicebergs
Theconceptofobtainingfreshwaterfromicebergsthataretowedtopopulatedareasandaridregionsoftheworldwasoncetreatedasajokemoreappropriatetocartoonsthanreallife. Butnowitisbeingconsideredquiteseriouslybymanynations, especiallysincescientistshavewarnedthatthehumanracewilloutgrowitsfreshwatersupplyfasterthanitrunsoutoffood.
Glaciersareapossiblesourceoffreshwaterthathasbeenoverlookeduntilrecently. Three-quartersoftheEarth'sfreshwatersupplyisstilltiedupinglacialice, areservoirofuntappedfreshwatersoimmensethatitcouldsustainalltheriversoftheworldfor 1,000 years. Floatingontheoceanseveryyearare 7,659 trillionmetrictonsoficeencasedin 10000 icebergsthatbreakawayfromthepolaricecaps, morethanninetypercentofthemfromAntarctica.
Hugeglaciersthatstretchovertheshallowcontinentalshelfgivebirthtoicebergsthroughouttheyear. Icebergsarenotlikeseaice, whichisformedwhentheseaitselffreezes, rather, theyareformedentirelyonland, breakingoffwhenglaciersspreadoverthesea. Astheydriftawayfromthepolarregion, icebergssometimesmovemysteriouslyinadirectionoppositetothewind, pulledbysubsurfacecurrents. Becausetheymeltmoreslowlythansmallerpiecesofice, icebergshavebeenknowntodriftasfarnorthas 35 degreessouthoftheequatorintheAtlanticOcean. Tocorralthemandsteerthemtopartsoftheworldwheretheyareneededwouldnotbetoodifficult.
Thedifficultyarisesinothertechnicalmatters, suchasthepreventionofrapidmeltinginwarmerclimatesandthefunnelingoffreshwatertoshoreingreatvolume. Buteveniftheicebergslosthalfoftheirvolumeintowing, thewatertheycouldprovidewouldbefarcheaperthanthatproducedbydesalinization, orremovingsaltfromwater.