2023学年完整公开课版文档：lifeintheArctic

Unit2LifeintheArctic

TheintroductionofArctic

Arctic

The

Arctic

isa

polarregion

locatedatthenorthernmostpartofthe

Earth.TheArcticconsistsofthe

ArcticOcean

andpartsof

Alaska

(UnitedStates),

Canada,

Finland,

Greenland

(Denmark),

Iceland,

Norway,

Russia,andSweden.TheArcticregionconsistsofavastoceanwithaseasonallyvarying

icecover,surroundedbytreelesspermafrost.Theareacanbedefinedasnorthofthe

ArcticCircle

(66°33'N),theapproximatelimitofthe

midnightsun

andthe

polarnight.Alternatively,itcanbedefinedastheregionwheretheaveragetemperatureforthewarmestmonth(July)isbelow10

°C(50

°F);thenorthernmost

treeline

roughlyfollowsthe

isotherm

attheboundaryofthisregion.

Sociallyandpolitically,theArcticregionincludesthenorthernterritoriesoftheeightArcticstates,althoughbynaturalscience

definitionsmuchofthisterritoryisconsidered

subarctic.TheArcticregionisauniqueareaamongEarth'secosystems.TheculturesintheregionandtheArctic

indigenouspeoples

haveadaptedtoitscoldandextremeconditions.Inrecentyearstheextentoftheseaicehasdeclined.

LifeintheArcticincludesorganismslivingintheice,

zooplankton

and

phytoplankton,fishand

marinemammals,birds,landanimals,plantsandhumansocieties.

Etymology

ThewordArcticcomesfromthe

Greek

,"neartheBear,northern"andthatfromtheword,meaning

bear.Thenamereferseithertothe

constellation

UrsaMajor,the"GreatBear",whichisprominentinthenorthernportionofthe

celestialsphere,ortotheconstellation

UrsaMinor,the"LittleBear",whichcontains

Polaris,the

PoleStar,alsoknownastheNorthStar.

Climate

TheArctic'sclimateischaracterizedbycoldwintersandcoolsummers.Precipitationmostlycomesintheformofsnow.TheArctic'sannualprecipitationislow,withmostoftheareareceivinglessthan50

cm(20

in).Highwindsoftenstirupsnow,creatingtheillusionofcontinuoussnowfall.Averagewintertemperaturescanbeaslowas−40

°C(−40

°F),andthecoldestrecordedtemperatureisapproximately−68

°C(−90

°F).CoastalArcticclimatesaremoderatedbyoceanicinfluences,havinggenerallywarmertemperaturesandheaviersnowfallsthanthecolderanddrierinteriorareas.TheArcticisaffectedbycurrent

globalwarming,leadingto

Arcticseaiceshrinkage

and

Arcticmethanerelease.

Duetothepolewardmigrationoftheplanet'sisotherms(about35

mi(56

km)perdecadeduringthepast30yearsasaconsequenceofglobalwarming),theArcticregion(asdefinedbytreelineandtemperature)iscurrentlyshrinking.PerhapsthemostspectacularresultofArcticshrinkageisseaiceloss.ThereisalargevarianceinpredictionsofArcticseaiceloss,withmodelsshowingnear-completetocompletelossinSeptemberfrom2040tosometimewellbeyond2100.Abouthalfoftheanalyzedmodelsshownear-completetocompleteseaicelossinSeptemberbytheyear2100.

Plants

Arcticvegetation

iscomposedofplantssuchas

dwarfshrubs,

graminoids,

herbs,

lichens

and

mosses,whichallgrowrelativelyclosetotheground,forming

tundra.Asonemovesnorthward,theamountofwarmthavailableforplantgrowthdecreasesconsiderably.Inthenorthernmostareas,plantsareattheirmetaboliclimits,andsmalldifferencesinthetotalamountofsummerwarmthmakelargedifferencesintheamountofenergyavailableformaintenance,growthandreproduction.Coldersummertemperaturescausethesize,abundance,productivityandvarietyofplantstodecrease.TreescannotgrowintheArctic,butinitswarmestparts,shrubsarecommonandcanreach2

m(6

ft7

in)inheight;

sedges,mossesandlichenscanformthicklayers.InthecoldestpartsoftheArctic,muchofthegroundisbare;

non-vascularplants

suchaslichensandmossespredominate,alongwithafewscatteredgrassesand

forbs

(likethe

Arcticpoppy).

Animals

Herbivoresonthetundraincludethe

Arctichare,

lemming,

muskox,and

caribou.Theyarepreyedonbythe

snowyowl,Arcticfox

and

wolf.The

polarbear

isalsoapredator,thoughitpreferstohuntformarinelifefromtheice.Therearealsomany

birds

andmarinespeciesendemictothecolderregions.Otherlandanimalsinclude

wolverines,

ermines,and

Arcticgroundsquirrels.Marinemammalsinclude

seals,

walrus,andseveralspeciesof

cetacean—baleenwhales

andalso

narwhals,

killerwhales

and

belugas.Anexcellentandfamousexampleofa

ringspecies

existsandhasbeendescribedaroundthearcticcircleintheformofthe

Larus

gulls.

Naturalresources

TheArcticincludessizable

naturalresources

(oil