MRS_Chapter8-proof.pdf

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1、Chapter8SeaIceMonitoringbyRemoteSensingAuthors:SteinSandvenandOlaM.Johannessen8.1INTRODUCTION8.1.1TheRoleofSeaIceintheClimateandWeatherSystemSeaiceisapartofthecryospherethatinteractscontinuouslywiththeunderlyingoceansandtheoverlayingatmosphere.Thegrowthanddecay

2、ofseaiceoccuronaseasonalcycleatthesurfaceoftheoceanathighlatitudes.Asmuchas30millionkm2oftheEarth’ssurfacecanbecoveredbyseaice.IntheNorthernHemisphere,seaiceextentfluctuateseachyearfromaminimuminSeptember,whenmostoftheiceisconfinedtothecentralArcticOcean,Greenl

3、andSeaandCanadianArchipelago,toamaximuminMarch,whentheicecoversalmosttheentireArcticOceanandmanyadjacentseas.IntheSouthernHemisphere,theannualfluctuationisevengreater,fromaminimuminFebruarytoamaxi-muminSeptemberwhentheicesurroundstheAntarcticcontinentandextends

4、equatorwardto55°–65°S(Gloersenetal.1992).Figure8-1showsanexampleofmaximumandmini-mumiceextentobtainedfrompassivemicrowavesatellitedata.Figure8-1MapsofmaximumandminimumseaiceextentandconcentrationintheArctic(top)andAntarctic(bottom)obtainedfrompassivemicrowavesa

5、tellitedatafromtheSpecialSensorMicrowaveImager(SSM/I).ThemapsarefromMarch1993(upperleftandlowerleft)andSeptember1993(upperrightandlowerright).Iceconcentrations,expressedaspercentcoverageandindicatedbythecolorbar,werecomputedfromSSM/IdatausingtheNorwegianNORSEXa

6、lgorithm.Courtesy:NERSC.2SeaIceMonitoringbyRemoteSensingThelargestvolumeofseaiceisfoundintheNorthernHemisphereinMarch,0.05millionkm3,whichisnearlytwicethemaximumseaicevolumeintheSouthernHemi-sphere.ThereasonforthisisthatthemeanthicknessofArcticseaiceisabout3m,w

7、hereasthemeanthicknessofAntarcticseaiceis1.0–1.5m.Seaiceresearchandmonitoringisimportantformanycountriesathighlatitudes,andalsothosewhooperateinAntarctica.SeaiceimposessevererestrictionsonshiptrafficintheArctic.Itisasensitiveclimateindicator,andplaysanimportant

8、roleinexplorationandexploitationofmarineresources.Seaicehasmanyrolesintheglobalclimatesystem.Itservesasaneffectiveinsulatorbetweentheoceanandtheatmosphere,restrictingexchang