Climatology and firn processes in the lower accumulation area of the Greenland ice sheet

82 Pages·2016·5.15 MB·English

Digital Comprehensive Summaries of Uppsala Dissertations
from the Faculty of Science and Technology 1372
Climatology and firn processes in
the lower accumulation area of the
Greenland ice sheet
CHARALAMPOS CHARALAMPIDIS
ACTA
UNIVERSITATIS
ISSN 1651-6214
UPSALIENSIS
ISBN 978-91-554-9571-8
UPPSALA
urn:nbn:se:uu:diva-284365
2016
Dissertation presented at Uppsala University to be publicly examined in Hambergsalen,
Geocentrum, Villavägen 16, Uppsala, Friday, 10 June 2016 at 10:15 for the degree of Doctor
of Philosophy. The examination will be conducted in English. Faculty examiner: Professor
Douglas Benn (University of St Andrews).
Abstract
Charalampidis, C. 2016. Climatology and firn processes in the lower accumulation area of
the Greenland ice sheet. Digital Comprehensive Summaries of Uppsala Dissertations from
the Faculty of Science and Technology 1372. 81 pp. Uppsala: Acta Universitatis Upsaliensis.
ISBN 978-91-554-9571-8.
The Greenland ice sheet is the largest Northern Hemisphere store of fresh water, and it is
responding rapidly to the warming climate. In situ observations document the changing ice
sheet properties in the lower accumulation area, Southwest Greenland. Firn densities from
1840 meters above sea level retrieved in May 2012 revealed the existence of a 5.5-meter-
thick, near-surface ice layer in response to the recent increased melt and refreezing in firn.
As a consequence, vertical meltwater percolation in the extreme summer 2012 was inefficient,
resulting in surface runoff. Meltwater percolated and refroze at six meters depth only after
the end of the melt season. This prolonged autumn refreezing under the newly accumulated
snowpack resulted in unprecedented firn warming with temperature at ten meters depth
increased by more than four degrees Celsius. Simulations confirm that meltwater reached nine
meters depth at most. The refrozen meltwater was estimated at 0.23 meters water equivalent,
amounting to 25 % of the total 2012 ablation.
A surface energy balance model was used to evaluate the seasonal and interannual variability
of all surface energy fluxes at that elevation in the years 2009 to 2013. Due to the meltwater
presence at the surface in 2012, the summer-averaged albedo was significantly reduced (0.71 in
2012; typically 0.78). A sensitivity analysis revealed that 71 % of the subsequent additional solar
radiation in 2012 was used for melt, corresponding to 36 % of the total 2012 surface lowering.
This interplay between melt and firn properties highlights that the lower accumulation area of
the Greenland ice sheet will be responding rapidly in a warming climate.
Keywords: climate change, Greenland ice sheet, accumulation area, automatic weather
stations, surface energy balance, melt–albedo feedback, surface mass budget, snow, firn,
meltwater, percolation, refreezing, runoff
Charalampos Charalampidis, , Department of Earth Sciences, LUVAL, Villav. 16, Uppsala
University, SE-75236 Uppsala, Sweden.
© Charalampos Charalampidis 2016
ISSN 1651-6214
ISBN 978-91-554-9571-8
urn:nbn:se:uu:diva-284365 (http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-284365)

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List of papers
Thisthesisisbasedonthefollowingpapers,whicharereferredtointhetext
bytheirRomannumerals.
I Citterio,M.,D.vanAs,A.P.Ahlstrøm,M.L.Andersen,S.B.
Andersen,J.E.Box,C.Charalampidis,W.T.Colgan,R.S.Fausto,S.
Nielsen,andM.Veicherts(2015). Automaticweatherstationsforbasic
andappliedglaciologicalresearch. Geol. Surv. DenmarkGreenland
Bull. 33,69–72.
II Charalampidis,C.andD.vanAs(2015). Observedmelt-season
snow-packevolutionontheGreenlandicesheet. Geol. Surv. Denmark
GreenlandBull. 33,65–68.
III Charalampidis,C.,D.vanAs,J.E.Box,M.R.vandenBroeke,W.T.
Colgan,S.H.Doyle,A.L.Hubbard,M.MacFerrin,H.Machguth,and
C.J.P.P.Smeets(2015). Changingsurface–atmosphereenergy
exchangeandrefreezingcapacityoftheloweraccumulationarea,West
Greenland. TheCryosphere9(6),2163–2181.
IV Machguth,H.,M.MacFerrin,D.vanAs,J.E.Box,C.
Charalampidis,W.T.Colgan,R.S.Fausto,H.A.J.Meijer,E.
Mosley-Thompson,andR.S.W.vandeWal(2016). Greenland
meltwaterstorageinfirnlimitedbynear-surfaceiceformation. Nat.
Clim. Change6(4),390–393.
V Charalampidis,C.,D.vanAs,W.T.Colgan,R.S.Fausto,M.
MacFerrin,andH.Machguth(2016). Thermaltracingofretained
meltwaterintheloweraccumulationareaoftheSouthwestern
Greenlandicesheet. Ann. Glaciol. 57(72),n/a–n/a.
VI Charalampidis,C.,D.vanAs,P.L.Langen,R.S.Fausto,B.
Vandecrux,andJ.E.Box(inreview). Regionalclimatemodel
performanceinGreenlandfirnderivedfrominsituobservations. Geol.
Surv. DenmarkGreenlandBull.
Reprintsweremadewithpermissionfromthepublishers.
Copyrights. PaperI,II,VI:(cid:2)c DeNationaleGeologiskeUndersøgelserfor
DanmarkogGrønland(GEUS)2015–2016.
PaperIII:(cid:2)c Authors2015(CreativeCommonsAttribution3.0License).
PaperIV:(cid:2)c NaturePublishingGroup2016.
PaperV:(cid:2)c Authors2016(CreativeCommonsAttribution4.0License).
Co-authorships. ThecontributiontoPaperIwastheinvolvementinthe
development,maintenanceandestablishmentofautomaticweatherstations
ontheGreenlandicesheet,aswellasthediscussionandassistanceduringthe
compositionofthemanuscript.
ThecontributiontoPaperIVwastheparticipationinthefieldcampaignsthat
collectedthedata,theperformanceofpartofthedataanalysis,the
continuousdiscussionoftheresults,andfurtherdevelopmentoftheanalysis.
Support. TheoutlinedresearchwasconductedattheGeologicalSurveyof
DenmarkandGreenland(GEUS)inCopenhagen,Denmark,andisa
contributiontotheNordicCentreofExcellenceSVALI,“Stabilityand
VariationsofArcticLandIce”,fundedbytheNordicTop-levelResearch
Initiative(TRI).Thisresearchbuildsupondatagatheredandresultsobtained
withintheGreenlandAnalogueProject(GAP).Themeasurementswere
collectedduringtheSnowProcessesintheLowerAccumulationZone
(SPLAZ)campaignin2012,andtheArcticCircleTraversecampaignsin
2013and2015(ACT-13,ACT-15).
ThisworkiswithintheframeworkoftheProgrammeforMonitoringofthe
GreenlandIceSheet(PROMICE),launchedandfundedbytheDanish
EnergyAgency(Energistyrelsen)undertheDanishMinistryofEnergy,
UtilitiesandClimate,andwithintheDanishCooperationforEnvironmentin
theArctic(DANCEA).
Relevant papers
Contributionsrelatedtothiswork,butnotpartofthethesisarereferredtoin
thetextbytheirGreeknumerals:
α(cid:3) VanAs,D.,R.S.Fausto,W.T.Colgan,J.E.Box,andthePROMICE
projectteam(incl. C.Charalampidis)(2013). Darkeningofthe
Greenlandicesheetduetothemelt–albedofeedbackobservedatthe
PROMICEweatherstations. Geol. Surv. DenmarkGreenlandBull. 28,
69–72.
β(cid:3) VanAs,D.,R.S.Fausto,K.Steffen,andthePROMICEprojectteam
(incl. C.Charalampidis)(2014). Katabaticwindsandpiteraqstorms:
observationsfromtheGreenlandicesheet. Geol. Surv. Denmark
GreenlandBull. 31,83–86.
γ(cid:3) Fausto,R.S.,D.vanAs,J.A.Antoft,J.E.Box,W.T.Colgan,andthe
PROMICEprojectteam(incl. C.Charalampidis)(2015). Greenland
icesheetmeltareafromMODIS(2000–2014). Geol. Surv. Denmark
GreenlandBull. 33,57–60.
δ(cid:3) VanAs,D.,R.S.Fausto,J.Cappelen,H.Machguth,R.S.W.vande
Wal,R.J.Braithwaite,andthePROMICEprojectteam(incl. C.
Charalampidis)(inpress). PlacingGreenlandicesheetablation
observationsinamulti-decadalcontext. Geol. Surv. Denmark
GreenlandBull.
Coverofprintedversion. CombinationofLandsatLookimagery(“Natural
Color”foricesheetandwater,and“Thermal”forlandsurface)ofthewider
areaofManiitsoq(Sukkertoppen),about100kmsouthofKangerlussuaq
(SøndreStrømfjord). ThedatawereacquiredbyLandsat7on14August
1999(sceneidentifier: LE70060141999226EDC00),andareavailablefrom
theU.S.GeologicalSurvey.
Inuitportrait. ScanoforiginalartarchivedintheGEUSglaciologylibrary.