極地氣候變化年報(bào)-2023 STATE OF POLAR CLIMATE

STATEOFPOLARCLIMATECHINESEACADEMYOFMETEOROLOGICALSCIENCESSTATESTATEOFPOLARCLIMATE2023極地氣候變化年報(bào)AssociateEditor-in-ChiefW極地氣候變化年報(bào)STATE極地氣候變化年報(bào)STATEOFPOLARCLIMATE2023NationalSatelliteMeteoroloSTATESTATEOFPOLARCLIMATE2023極地氣候變化年報(bào)Polarregionsaresensitivetoclimatechange.thisannualreport,usingvariouindicatesthattheAntarcti2023,withfrequentextremeeventsandnotableimpacTheAntarcticshowedslightlyhigherairtemperaturewithlargeeast-westregionaldifferencesandco-existenceofextremewarmandcoldevents.TheaverageannualairtemperatureovertheAntarcticais-31.86℃,slightlyhigherthanusualby0.05℃.TheaverageannualairtemperaturecontinuestoriserapidlyintheAntarcticPeninsuwiththreestationsandsevenstationsrecordingtheinhistory,respectively.Onthecontrary,theSoutheastAntarcticshowedcoldanomaliesaVictoriaLandandWilkesLandhadthecoldesttemperatureonobservationrecord.OnJuly7,theairtemperatureattheSouthPoleincreasedby40℃.Frommid-JulytotheendofAugust,mostAntarcticexperiencedfourextremecoldwaves,withtemperaturerecord.InNovember,theA23aicebergintheWeddellSeawasdetachedfromtheAntarcticiceshelf,becomingthelargesticebergintheworldwithareaof4,000km2.極地氣候變化年報(bào)STATEOFPOLARCLIMATE20231979withoveralldistributionof“warmland-coldsea”.During1979-2023,was3.4timestheglobalwarmingrate(0.18℃/decade).AnnualaverageairtemperatureoftheArcticwas-9.19℃,0.97°Chigherthanusual.Spring,summer,autumnandwinteraveragedairtemperaturewere-12.74°C,4.52°C,-7.09°C,and-21.14°C,respectively.AutumnandwinterwereobviouslywarmerinfacontinentaroundtheArcticOcean,especiallynorthernNorthernCanadaexperiencedwildfireswithpersistenceoffivemonthswithsevhightemperaturesanomaliesandlowrainfall.Thepeak極地氣候變化年報(bào)STATEOFPOLARCLIMATE2023globalattention.OnFebruary21,2023,theseaiceextent(SIE)ofAntarcticreachedanewhistoricallowof1.788×106km2,surpassingthepreviousrecordin2022.Throughoutthepastyear,theSIEofAntarctichasconsistentlyremainedasignificantlybelowhistoricalrecords.IntheArcticmarkingthefifthlowestvalueonrecord,whiletheminimumSIEwas4.23×106km2,thesixthlowestonrecord.Duetothelowseatemperaturesinspring,themeltingofArlaterthanusual,however,thehightemperaturesinsummerandautumnalsodelaprocess.極地氣候變化年報(bào)極地氣候變化年報(bào)STATEOFPOLARCLIMATE2023TheAntarcticozoneholeformedearlierandlastslongerwhiletotalArcticozonewashigherthanthehistoricalaverage.completelyuntilDecember20,duetomoreAofmaterialfromtheeruptionoftheTongavolcano.WeakenedArcticpolarvortexandwarmerstratosphericinhibitedlarge-scaleArcticozonedepletion,resultinginhightotalozmid-March2024,totalArcticozonespikedtoanear-recorPolaratmosphericgreenhousetotheglobal.In2022,annualaverageconcentrationsofcarbondioxideandsulfurhexafluorideintheAntarcticatmosph10.78ppt,respectivelywhichintheArcticatmosphereare420.40ppm,1,857.87ppb,3,334.72gasesinthepolarregionswerehigherrelativetothemin2022.SulfurhexaflandArcticatmosphereincreasedby0.38pptand0.42pptcompaincreasesofallstudyyears.極極地氣候變化年報(bào)STATEOFPOLARCLIMATE2023STATESTATEOFPOLARCLIMATE2023極地氣候變化年報(bào)極地極地氣候變化年報(bào)STATEOFPOLARCLIMATE2023Chapter1TemperatureandAirPressure 1.1Temperature 1.1.1Antarctic 1.1.2Arctic 51.2AirPressure 91.2.1Antarctic 91.2.2Arctic Chapter2SeaIce 122.1SeaIceExtent 2.1.1Antarctic 2.1.2Arctic 2.2SeaIceConcentration 2.2.1Antarctic 2.2.2Arctic 2.3SeaIceMeltSeasonLength Chapter3AtmosphericComposition 203.1MajorGreenhouseGases 203.1.1Antarctica 203.1.2Arctic 223.2TotalOzoneinPolarRegions 253.2.1AntarcticOzoneHole 253.2.2ArcticOzoneDepletion 26MainDataSources 27Glossary 28極地氣候變化年報(bào)極地氣候變化年報(bào)ThissubsectiondiscussestheanalysisoftemperaturevariationsinAntarcticain2023usingobserva-tionaldatafromvariousAntarcticstationsandfirst-geandZhongshanStationsaresourcedfromtheChineseAcademyofMeteorologiccomefromtheReferenceAntarcticDataforEnvironmentalResearch(Met-READER)compiloftheAntarcticcontinentwas-3fortheaustralsummer(DecembertoFebruary),autu(SeptembertoNovember)were-21.92°C,-34.56°C,-38.85°C,and-31.77°C,arcticcontinentexperiencedcoldertemperaturesthanusualduringwinterandsummecreasesof0.06°Cand0.21°C,whileshowingwarmeranomaincreasesof0.53°Cand0.15°C極地氣候變化年報(bào)STATEOFPOLARCLIMATE2023Thewarminganomaliesin202continuingthepatternseenin2022,suggestingapotentialtrthatregion.Conversely,coolinganomalieswereevidesummerseason,warmanomaliesweremostprominentaroundtheAntarcticPeninsulaanditsneighbwaters.Specifically,attheAntarcticPeninsula,temperaStationwere0.75°Cand0.74°Chigherthanthelong-termaverages(refertoFigures1.1-2and1.1-3),respectively,rankingasthesecondandthirdhighestrecordedtemperatures.InauPeninsula,notablewarmingwasalsoobservedinCoatsLandandQueenMaudLand.Amongthesethree27)exhibitedthestrongestwarmanomalieswithdeviationsof3.52°C,3.44°C,and2.66°C,respectively.Additionally,intheseregions,threestationsrecordedthesecond-highestautumntemperatures(Faradayreachedthethird-highestvalues(OrcadasStation,ChangchengStation,BellingshausenStation,MarioZucchelliStation,PalmerStation,SaintMartinStation,NovolazarevskayaStation,refertoFigures1.1-1,Peninsulapersistedwithwarmerconditions.TheShowaSthighestwintertemperatureanomalyat2.65°Caboveaverage,whileBelgranoIIStation(refertoFigure1.1-28)rankedthirdwithadeviationof2.41°C.However,inspring,theAntarcticPeninsulatransitionedfromwarmanomaliestocool極地氣候變化年報(bào)STATEOFPOLARCLIMATE20231極極地氣候變化年報(bào)STATEOFPOLARCLIMATE2023極地氣候變化年報(bào)極地氣候變化年報(bào)STATEOFPOLARCLIMATE2023anomalyat3.45°Cabregionswereprimarilycausedbycoldanomaliesduringthewinterseason.VictoriaLLand,andQueenMaryLandexperiencedthemostsignificanttempbelowaverage,whereasRossIceSrankedasthesecondlowestwithdevitoFigure1.1-14)recordedthethirdlowesttemperaturFigure1.1Spatialdistributionofthe2023annualmeantemperatureanomaliesinAntarcticaandtheannualandseasonalmeantemperatureanomaliesatvariousstations(unit:°C)warmingrateof0.18°Cperdecade(Figure1.2).TheAntarcticlandtemperaturesexhibitaslightlyhigherwarmingratecomparedtoglobaltemperatures,withatrendof0.21°C/decade(Figure1.2).Additionally,significantwarmingtrendsareobservedinAntarctictespring,withwarmingratesof0.30°C/decade,0.17°C/decade,and0.36°C/decade,respectively.Howeverwinterseasonshowsalowerwarmingtrendof0.07°C/decadethatdoesnot2STATESTATEOFPOLARCLIMATE2023極地氣候變化年報(bào)Figure1.2TimeseriesofannualmeansurfacetemperatureanomaliesaveragedoverAntarcticContinent(solidredline)andglobally(solidblackline)from1979to2023,alongwiththeirtrends(dashedlines)(unit:°C)ThetrendinAntarcticlandtemperaturechangesrevealsdistinctregionalcharacteristics,withcertainareasdisplayinghighsensitivitytoclimatechange.Forinstance,theWestAntarcticregioncontinues極地極地氣候變化年報(bào)STATEOFPOLARCLIMATE2023Figure1.3TimeseriesofannualmeantemperatureanomaliesatwarmingsitesintheWestAntarctic(a)andEastAntarctic(b)regions.Thethinsolidlinerepresentstheannualmeantemperatureanomalies,thethicksolidlinerepresentsthe11-yearrunningaverageofannualmeantemperatureanomalies,andthedashedlineindicatesthetrendinannualmeantemperatureanomalies3極極地氣候變化年報(bào)STATEOFPOLARCLIMATE2023極地氣候變化年報(bào)極地氣候變化年報(bào)STATEOFPOLARCLIMATE2023toexperiencesignificantwarming,withtheAntarcticPeninsulastandingoutasoneofthemostrapidlywarmingregionsgloballrateof0.45°Cperdecade(1947-2023,depictedbytheredlineitemperaturesintheSoutDomealsoexhibitawarmingtrend,albeitataslowerpace,withwarmingrates2023,blacklineinFigurdecade(1958-2023,blacklineinFigure1.3binotherregionsofAntarcticaarelesspronounced.ExtremeExtremeEventsIn2023,extremewarmandcoldeventsoccurredsuccessivelyinWestAntarcticaandEastAntarctica.InJuly,thecoldestmonthoftheyearinAntarctica,thetemperatureintheAntarcticPeninsularegionwasabnormallyhigh.AsignifieventwasobservedattheAmundsen-ScottStationneartheSouthPole.Thetemperatureatthisstationsoaredfrom-74°ConJuly7thto-34°ConJuly8th,withaEastAntarcticcontinentinNovembersetthehistoricallowestrecordsince1958,reaching-45.4°C.Frommid-JulytofAntarctica,fromeasternAntarcticatotheRossIceShelf,andfromWestAntarcticatotheAntarcticPeninsula.Elevenstationssetthelowesttemperatureobservationrecords,causingseveredelaysinflig(a)Theairtemperatureanomaly(relativeto1991-2020,basedonCRA-40)inJuly2023.(b)ThedailyseriesofairtemperatureatAmundsen-ScottstationinJune-July2023.(c)TheannualvariationofairtemperatureatVostokinNovemberfrom1958to2023.OnJanuary25,2023,theA81icehasanareaofapproximately1,550km2andathicknessofabout150m.InNafterstayingintheWeddellSeaformorethan40years,watersforthefirsttimeandmovedtowardstheSouthAtlantic.Theiceberghasanareaofapproximately4,000km2andaththeworldatpresen4STATESTATEOFPOLARCLIMATE2023極地氣候變化年報(bào)ThissubsectiondiscussestheanalGlobalHistoricalClimatologyNetwork-Daily(GHCN-D),theGreenlandWeatherObservationsdatasetfromtheDanishMeteorologicalInstitute,andCRA-40reacontrol.In2023,theannualaveragetemperatureintheArcticregionwas-9.19°C,whichwthelong-termaverage.Amongthem,theautumnseason(SeptembertoNovembwarmingwithatemperatureincreaseof1.87°C,reachinganaveragetemperatureof-7.09°C.Thewinterseason(DecembertoFebruary),springseasoeragetemperaturesof-21.1and0.68°Cabovethelong-ter極極地氣候變化年報(bào)STATEOFPOLARCLIMATE2023Figure1.4Spatialdistributionofthe2023annualmeantemperatureanomaliesinArcticandtheannualandseasonalmeantemperatureanomaliesatvariousstations(unit:°C)5極極地氣候變化年報(bào)STATEOFPOLARCLIMATE2023極地氣候變化年報(bào)極地氣候變化年報(bào)STATEOFPOLARCLIMATE2023In2023,themostintensewarmingintheArcticwasobservedalongthecoastsoftheBandintheCanadianArcticregion,withtemperatureincreasesexceeding2°C.AmongthestationsintheArcticregion,thesitewiththelargesttemperatureinKaraSea(refertoFigure1.4-16),withanannualaveragetemperatureof-2.4°C,whic10)reachedthesecond-highesthistoricalannualaveragetemperature.Poinca(refertoFigure1.4-3,4,and13)recordedthethird-highesthistoricalannualaveragetemperatures.Only1and12)experiencedcoolertemperatures,withdeviationsof0.5Duringthewinterof2023,thewarmingwasprimarilyconcentratedalongtheBarents-KaraSeacoast,withAmarjaama(refertoFigure1.4-16)expwinter,withtemperatures4.8°Cabovethelong-termaverage.Inthespringof2023,thewarmanomaliesweremainlyobservedintheCanadianArcticregion,withHolbech(refertoFigure1.4-7)experiencinga2.1°Ctemperatureincrease,rankingasthethirdhighesthistoricaltemperature.Addthelong-termaverage.Duringthesummerof2023,thewarminSeacoastandintheCand13)recordedtheirhighand2)hadthesecond-highesthistoricaltemperatures.Inthefallof2023,exceoftheGreenlandSeaexperiencingcoolertemperatures,allotherstationsexhibitedwarmingtrends.P1.4-7,5,and10)hadthesecond-highesthiFigure1.5TimeseriesofannualmeansurfacetemperatureanomaliesaveragedoverArctic(solidredline)andglobally(solidblackline)from1979to2023,alongwiththeirtrends(dashedlines)(unit:°C)Figure1.5),withawarmingrateof0.61°Cperdecade.Thisrateis3.4timeshrate,indicatingahighersensitivityoftheArctictoglobalw6STATESTATEOFPOLARCLIMATE2023極地氣候變化年報(bào)at0.87°Cperdecadeand0.67°Cperdecade,respectivelTherapidwarmingintheArcticprimarilyoccursovertheArratesoverland;nonetheless,theseratesstillsurpasstheglobalaveragewhileBarrowandAmdermaalongthecoastoftheBarents-KaraSeawitnessedincreasesof1.00°Cand0.90°Cperdecade,respectively.Conversely,locationslikeDaneborg,CambridgeBay,andVorkutahaveexperiencedslightlyslowerwarmingrates,withtemperatureincreasesof0.61°C,0.58°C,and0.52°Cperdecade,respectivel極地極地氣候變化年報(bào)STATEOFPOLARCLIMATE2023Figure1.6TimeseriesofannualmeantemperatureanomaliesatwarmingsitesintheArcticEurasia(a)andNorthAmerica(b)regions.Thethinsolidlinerepresentstheannualmeantemperatureanomalies,thethicksolidlinerepresentsthe11-yearrunningaverageofannualmeantemperatureanomalies,andthedashedlineindicatesthetrendinannualmeantemperatureanomalies7極地氣候變化年報(bào)極地氣候變化年報(bào)STATEOFPOLARCLIMATE2023極地極地氣候變化年報(bào)STATEOFPOLARCLIMATE2023ExtremeEventsIn2023,theaveragesurfacetemperatureofthePan-Arctic(60–90°N)fromJunetoAugustwas9.96°C,whichwasthehottestsummersince1979.UnusuallyhightemperaturesandlowrainfallinnorthernCanadacausedseveredrought,andledtorecord-breakingwildfiresinnorthwesternCanadainthesummerof2023.Thethanfivemonths,andtheburnedareareached4.16millionhectares,whichwasthelargestburnedareainthe44yearsonTheairtemperatureandprecipitationanomaly(relativeto1991–2020)inJuly2023TheGreenlandIceSheetexperiencedthewarmestsummeronrecord,withthehighestpointoftheicesheetreachingatemperaturhistoricalrecord.ThedailycumulativemeltareaoftheGreenlandIceSheetdurof2023wasthesecondlargestinthe45yearssincethestartofavailablesatelliteOnJuly20,surfacemeltingwasobservedacross67%ofthesurfaceoftheGreenlan(8.44×105km2),reachingthelargestsingle-daymeltareaoftheyear.Greenlanddailymeltsarea.8STATESTATEOFPOLARCLIMATE2023極地氣候變化年報(bào)Airpressureiskeytoconnectingthepolarclimatewiththeglobalclimacharacteristicsofthepolarpressurefieldsin2023,aswellassomeimportantciCenter,whiletheoscillationindexutilizesyear,DJF)andwinter(JunetoAugust,JJA)of2023showthattheAntarcticregionwascalelow-pressuresystems.Duringthesummer,negativeanomaliesinthegeopotentialheightfieldwereobservedovertheAntarcticcontinent,whilepositiveanothenegativeanomalyareaovertheAntarcticcontinentwasslightlylargerthanthepositiveanomaAlternatingpositiveandnegativeanomalieswereobservedaroundindicatingapronouncedzonalcirculationpattern極地極地氣候變化年報(bào)STATEOFPOLARCLIMATE2023Figure1.7500hPageopotentialheightfields(color-filledmaps)andtheiranomalies(contourmaps)foraustral(a)Summer(DJF)and(b)Winter(JJA)of2023inAntarctica.ThedataarefromCRA-40,withunitsingpmDuring1979–2023,theAntarcticOscillationindexshowedastrengwasparticularlyevidentinthesummer(0.40/10a),withminimalvariComparedto2022,thewinteranomalyshiftedfrompositivetonegative,whilethesummeranomalyre-mainedslightlystrongerthannormal,andtheannualanomalytoamoderatelypositiveanomaly9極極地氣候變化年報(bào)STATEOFPOLARCLIMATE2023極地氣候變化年報(bào)極地氣候變化年報(bào)STATEOFPOLARCLIMATE2023Figure1.8StandardizedAnomaliesofAntarcticOscillationindexduring1979–2023Inthewinterof2023,twolow-pressurecentersovertheArcticappearedinthe500hPageopotenheightfieldandweresituatedabovethenorthernregionsofEastAsiaandNorthAmerica(Figure1.9).AroundtheArcticCircleinthewinter,therewasapositiveanomalyinthegeopotentialheightfield,indicatingaweakenedArcticpolarvortex.Inthesummer,high-latituderegionspredominantlyexhibitedpositiveanomaliesinthegeopotentialhFigure1.9500hPageopotentialheightfields(color-filledmaps)andtheiranomalies(contourmaps)forboreal(a)winter(DJF)and(b)summer(JJA)of2023inArctic.ThedataarefromCRA-40,withunitsingpm(-0.70/10aforannualtrend)andintensity(-2023,theareaandintensityindicesoftheArcticpolarvortexexhibitednotablenebothwinterandsummer,indicatingaweakenedpol10STATESTATEOFPOLARCLIMATE2023極地氣候變化年報(bào)Figure1.10StandardizedanomaliesoftheNorthernHemispherepolarvortexareaindex(a)andNorthernHemispherepolarvortexstrengthindex(b)during1979–2023極地氣候變化年報(bào)STATEOFPOLARCLIMATE2023TherewerenoapparenttrendsintheArcticOscillationindex極地氣候變化年報(bào)STATEOFPOLARCLIMATE2023Figure1.11StandardizedAnomaliesofArcticOscillationindexduring1979–202311極極地氣候變化年報(bào)STATEOFPOLARCLIMATE2023極地氣候變化年報(bào)極地氣候變化年報(bào)STATEOFPOLARCLIMATE2023iceconcentrationsfromFengyun(FY)seriesmeteoseaicesurfacemelting/freezingtimedatasetprovidedbytheNationalAeronauticsoftheUnitedStates(NASA)andOceanUniversityofChina(OUC),arealsoused.TheAntarcticSIEexhibitssignificantseasonalvariability.ThefreezingperiodtypicallyspansfromApriltoSeptember,withthemeltingperiodextendingfromOctobertotheseaiceextentusuallyappearsbetweenlateFebruaryandearlyMarch.Overall,theAntarcticexperiencedextremelylowafterMay2023.ExcandFebruary25,2022(thattheSIEfromJanuarytoFebruaryandfromMaytoOctobthanthatinthesamemonthsin2017,whiletheSIEinNovemberwasofwhichwerethesecondlowestrecordgreaterthanthatin2016and2022,makingitthethirdlowestvalueoverthepast45years.Thisextremetriggeringfurtheratmosphericandecologicalresponses.Figure2.1AntarcticclimaticSIE,aswellasthemonthlyAntarcticSIEin2017,2022,and202312STATESTATEOFPOLARCLIMATE2023極地氣候變化年報(bào)Ontheinterdecadaltimescale,theAntarcticSIEhasshownatrendofaslowincreaseandthenadecreasebetween1979and2023,andthedecliningtrendhasbeenftheAntarcticSIEhassetnewrecords,withtheannualmin2023andtheannualmaximumvaluereachinganewlowfFigure2.2ThetimeseriesofAntarcticmonthlySIEanomaliesandits12-pointmovingaverage,lineartrend,andtheannualminimumSIE,theannualmaximumSIEfrom1979to2023BasedontheFengyunsatellitedata(Figure2.3),theAntarcticSIEinFebruary2023was2.66×106km2,whichwas23.63%lowerthantheclimatologicalmean(2011?2023)forthesameperiod,settingaAntarcticSIEwas17.21×106km2,whichwas8.16%smallerthantheclimatologicalmeanforthesameperiod,alsosettinganewlowrecordforalineartrendperspective,theFebruarySIEisdecreasingbyanaverageof1.04×1SeptemberSIEisdecreasingbyanaverageof1.24×105km2per極極地氣候變化年報(bào)STATEOFPOLARCLIMATE2023Figure2.3ChangesinAntarcticSIEMonitoredbytheFengyunMeteorologicalSatellites:TheanomaliesinFebruaryandSeptember2023comparedtoclimatemean(2011?2023)13極極地氣候變化年報(bào)STATEOFPOLARCLIMATE2023極地氣候變化年報(bào)極地氣候變化年報(bào)STATEOFPOLARCLIMATE2023ExtremeExtremeEventsTheAntarcticSIEin2023setnumerousnewlowrecords.First,theFebruary21,2023,AntarcticSIEof1.788×106km2setanewlowrecordfortheannualminimumAntarcticSIE,whiletheFebruary2023AntarcticSIEof1.913×106km2setanewSIEof16.956×106km2setanewrecordlowfortheannualmaximumAntarcticSIE,whiletheSeptember2023AntarcticSIEof16.801×106km2wasthesmallestSeptemberminimumrecordedinthepast45years.Inrecentyears,themeltingrateofseaiceintheAntarctichascontinuedtoaccelerate,whichhashadahugeimpactontheecologicalenvironmentoftheAntarcticandmayfurtheraffecttheglobTheArcticSIEalsoshowssignificantseasonalvariability(Figure2.4).Seaicecoverislowinthesummerandautumn,reachingitsannualminimumithemaximumSIEof2023(14.62×106km2)rankedthefifthlowestinhistory,whichwas2.01×106km2lessthanthehistoricalmaximumrecordsinceremotesensingobservationsbeganin1979comparedtothepreviousyear.Conversely,thehistoricalminimumoftheArcticSIEwasrecordedonSeptember17,2012(3.39×106km24.23×106km2,lowerthanthatinthepreviousyear.Figure2.4ArcticclimaticSIE,aswellasthemonthlyAntarcticSIEin2012,2022,and2023ThetimeseriesofmonthlyArcticSIEanomali0.04×106km2/decadefrom1979through2023,andthedownwawas12.5%/decade.No14STATESTATEOFPOLARCLIMATE2023極地氣候變化年報(bào)Figure2.5ThetimeseriesofArcticmonthlySIEanomaliesandits12-pointmovingaverage,lineartrend,andtheannualminimumSIE,theannualmaximumSIEfrom1979to2023ExtremeExtremeEventsInrecentyears,thepersistentlylowSIEintheArcticBarentsandKaraSeashascontributedtoadownwardtrendinArcticSeaiceduringthewintermonths.TheBarentsSeaSIEin2023reachedarecostudieshavelinkedthistoincreasedheattransportfromtheNorthAtlanticOcean,andmorerecentresearchhassuggestedthatatmosphericriversalsocontribute.Atmosphericriverslongwaveradiationandproducesrainfallthatcontributestothemeltingofwinterseaice.極地極地氣候變化年報(bào)STATEOFPOLARCLIMATE2023Figure2.6showsthedistributionsofthemonthlymeanandanomalyintheAntarcticseaiceconcentrationinFebruaryandSeptember2023,respectively.InFebruary,AntarcticseaicewasmainlydistributedintheWeddellSea,theAmundsenSeaandtheRossSea,allofwhicharethemainareasofperennialseaice.ExceptfortheseaiceconcentrationintheWeddellSea,whichwasclosetotheclimatologicalmean,theseaiceconcentratiInSeptember2023,seaicebasicallywrapsaroundtheAntarcticcontinent.TheareaofdecreasesinAntarcticseaicewasgreaterthantheareaofincreasesinAntarcticseaiceinSeptember;theseaiceconcentrationincreasedintheBellingshausenSea,theAmundsenSeaandthewesternWeddellSeaanddecreasedintheRossSea.Thema75%.TheseaiceconcentrationintheIndianOceanexhibitedlocalvariations,butthevariationwasnot15極極地氣候變化年報(bào)STATEOFPOLARCLIMATE2023極地氣候變化年報(bào)極地氣候變化年報(bào)STATEOFPOLARCLIMATE2023Figure2.62023AntarcticseaiceconcentrationanditsanomalymonitoredbytheFengyunmeteorologicalsatellites(unit:%)(a)monthlyseaiceconcentrationinFebruary2023;(b)monthlyseaiceconcentrationinSeptember2023;(c)seaiceconcentrationanomalyinFebruary2023;(d)September2023anomaly.ThesolidredlinerepresentstheaveragerangeofAntarcticseaicefrom2011to2023Figure2.7showsthemonthlymeansandanomaliesoftheArcticseaicecoSeptember2023.Arcticseaicecoverhasbeendecliningforseveraldecadiceconcentrationhasslowedinrecentyears.S2023average,wereconsistentlynegativeintheice-marginareasofthePacificsector.TheretreatofseaicewasmorepronouncedinSeptember,withnotabledeclinesobservedintheCanadianArchipelago,theBeaufortSea,theChintheBarentsSeaandpositiveintheGreenlandSeainMarch.TheanomaliesintheSeptemberweresignificantlypositive,16STATESTATEOFPOLARCLIMATE2023極地氣候變化年報(bào)Figure2.7Arcticseaiceconcentrationanditsanomaliesin2023fromFY-3seriesmeteorologicalsatellites.(a)SIConMarch.Theredlinerepresentstheaverageseaiceextentfor2011–2023(the15%seaiceconcentrationboundary).(b)Asin(a),butonSeptember.(c)SICanomalyonMarch.(d)Asin(c),butonSeptember極極地氣候變化年報(bào)STATEOFPOLARCLIMATE2023Theonsetsofmeltingandfreezingofseaicerepresentthebeginningandendofthesummermeltseason,respectively.Themeltonset(MO)referstothecontinuedpresenceofliquidwaterwithinthesnowpack,andtheicesurfacebecomesdamp.Thefreezeonset(FO)isidentifiedbyanaveragesurftemperaturebelowthemeltingpoint,thegrowthofyoungiceinopenwater,andtherefreezinglightlysnow-coveredice.TheperiodbetweentheTheArcticsurfaceMOspansfromlateMarchinice-marginareastoJuneinthecentralArctic.NotwithstandingtheadvanceoftheArcticseaicesurfaceMO,thedelayoftheFO,andthemeltseasonlengthsince1979,theMOnolongtheseaareas,whichwascloselyrelatedtothebelow-averagetemperaturesinmostoftheArcticOcApriltoAugust.Onlyinthemulti-yeariInternalvariationsinArcticseaiceMOhavebeenobservedinrecentdecades,withthemeanMO17極極地氣候變化年報(bào)STATEOFPOLARCLIMATE2023極地氣候變化年報(bào)極地氣候變化年報(bào)STATEOFPOLARCLIMATE20231advancingatarateof1.5daysperdecadefrom1thetrendwasmorepronouncedintheformerperiodthaninthelatter(Figure2.9).In2023,accordingtoobservationsbyFYsatellites,theregionalmeanMOnorthof70°Nwasearlierthanthatin2022butlaFigure2.8(a)Meltonsetand(b)Freezeonsetasaveragedfrom2011to2023.(c)Meltonsetand(d)Freezeonsetanomaliesof2023TheseaicesurfaceFOspansfrmostoftheArcticseaarea,withareasofsignificantlydelayedFOscorrespondingtoarearetreat(Fig.2.7d).ThemeanFOtrendnorthof70°NsioftheFY-3B&Dsatellites,theinter-annualvariationsareobviouTheArcticseaicemeltsealongerperiodinthefirst-yeariceareas,mdaysperdecade(Fig.2.9),sothecontinueddelayofsmoreextendedmeltseas1SincethemeltandfreezetimedatasetsprovidedbyNASAiscurrentlyupto