Light-absorbing snow impurity concentrations measured on Northwest Greenland ice sheet in 2011 and 2012

Light-absorbingsnowimpuritiesofelementalcarbon�(EC),�organiccarbon�(OC),�andmineraldusthave� beenmeasuredatthreelocationsatelevationsfrom�1,469�to�1,992�monAugust�1,�2011,�andatthesite� SIGMA-A�(78�N,�68�W,�elevation�1,490�m)�onthenorthwestGreenlandicesheet�(GrIS)�duringtheperiod� fromJune�28�toJuly�12,�2012.　AtSIGMA-A,�aremarkablesnowsurfaceloweringtogetherwithsnow� meltingwasobservedduringtheobservationperiodin�2012,�whenarecordsurfacemeltingeventoccurred� overtheGrIS.� Theconcentrationsinthesurfacewere� 0.9,� 3.8,� and� 107�ppbwforEC,� OC,� anddust,� respectively,�atthebeginningoftheperiod,�whichincreasedto�4.9,�17.2,�and�1327�ppbwforEC,�OC,�anddust,� respectively,�attheend.　TheECanddustconcentrationswereremarkablyhigherthanthoseatthethree� locationsin�2011�andtherecentmeasurementsatSummit.　However,�ourmeasurementsforECandOC� couldbeunderestimatedbecausearecentstudyindicatesthatthecollectionefficiencyofaquartzfiber�