冰山获得淡水(Obtaining Fresh water from icebergs)

theconceptofobtainingfreshwaterfromicebergsthataretowedtopopulatedareasandaridregionsoftheworldwasoncetreatedasajokemoreappropriatetocartoonsthanreallife.butnowitisbeingconsideredquiteseriouslybymanynations,especiallysincescientistshavewarnedthatthehumanracewilloutgrowitsfreshwatersupplyfasterthanitrunsoutoffood.

glaciersareapossiblesourceoffreshwaterthathasbeenoverlookeduntilrecently.three-quartersoftheearthsfreshwatersupplyisstilltiedupinglacialice,areservoirofuntappedfreshwatersoimmensethatitcouldsustainalltheriversoftheworldfor1,000years.floatingontheoceanseveryyearare7,659trillionmetrictonsoficeencasedin10000icebergsthatbreakawayfromthepolaricecaps,morethanninetypercentofthemfromantarctica.

hugeglaciersthatstretchovertheshallowcontinentalshelfgivebirthtoicebergsthroughouttheyear.icebergsarenotlikeseaice,whichisformedwhentheseaitselffreezes,rather,theyareformedentirelyonland,breakingoffwhenglaciersspreadoverthesea.astheydriftawayfromthepolarregion,icebergssometimesmovemysteriouslyinadirectionoppositetothewind,pulledbysubsurfacecurrents.becausetheymeltmoreslowlythansmallerpiecesofice,icebergshavebeenknowntodriftasfarnorthas35degreessouthoftheequatorintheatlanticocean.tocorralthemandsteerthemtopartsoftheworldwheretheyareneededwouldnotbetoodifficult.

thedifficultyarisesinothertechnicalmatters,suchasthepreventionofrapidmeltinginwarmerclimatesandthefunnelingoffreshwatertoshoreingreatvolume.buteveniftheicebergslosthalfoftheirvolumeintowing,thewatertheycouldprovidewouldbefarcheaperthanthatproducedbydesalinization,orremovingsaltfromwater.