Timing and origin of recent regional ice-mass loss in Greenland

Abstract

Within thelastdecade,theGreenlandicesheet(GrIS)anditssurroundingshaveexperiencedrecord high surfacetemperatures(Mote,2007; Box etal.,2010), icesheetmeltextent(Fettweisetal.,2011) and record-lowsummersea-iceextent(Nghiemetal.,2007). Usingthreeindependentdatasets,we derive,forthefirsttime,consistentice-masstrendsandtemporalvariationswithinsevenmajor drainagebasinsfromgravityfieldsfromtheGravityRecoveryandClimateExperiment(GRACE; Tapley et al.,2004), surface-icevelocitiesfromInteferometricSyntheticApertureRadar(InSAR; Rignot and Kanagaratnam,2006) togetherwithoutputoftheregionalatmosphericclimatemodelling(RACMO2/ GR; Ettema etal.,2009),andsurface-elevationchangesfromtheIce,cloudandlandelevationsatellite (ICESat; Sørensenetal.,2011). Weshowthatchangingicedischarge(D),surfacemeltingand subsequentrun-off(M/R)andprecipitation(P)allcontribute,inacomplexandregionallyvariable interplay,totheincreasinglynegativemassbalanceoftheGrISobservedwithinthelastdecade. InterannualvariabilityinPalongthenorthwestandwestcoastsoftheGrISlargelyexplainsthe apparentregionalmasslossincreaseduring2002–2010,andobscuresincreasingM/RandDsincethe 1990s.Inwinter2002/2003and2008/2009,accumulationanomaliesintheeastandsoutheast temporarilyoutweighedthelossesbyM/RandDthatprevailedduring2003–2008,andaftersummer 2010.Overall,forallbasinsoftheGrIS,thedecadalvariabilityofanomaliesinP,M/RandDbetween 1958 and2010(w.r.t.1961–1990)wassignificantlyexceededbytheregionaltrendsobservedduring the GRACEperiod(2002–2011).