Holocene glacier fluctuations in the Italian Alps - Medclivar

Mediterranean Climate: from Past to Future6-9 June 2011- Lecce, ItalyHolocene glacier fluctuationsin the Italian AlpsG. Orombelli, C. Ravazzi, , R. Pini, V. MaggiDepartment of Environmental SciencesUniversity of Milano-BicoccaCNR-IDPA Milano

Some thousand glaciers are present in Italy, fromthe Maritime to the Julian Alps, with a single smallglacier in the Apennines.Canin gl.Julian AlpsClapier gl.Maritime AlpsCalderone gl.Comitato Glaciologico Italiano http://www.glaciologia.it/

Mountain glaciers, mainly composed by ice at the melting temperature,are particularly sensitive to climate changes, responding with variationsin length and volume. Since late 19th century, glacier frontal fluctuationshave been considered as proxy of climate changes. . The spectacularretreat of mountain glaciers in the last three decades is considered asthe most clear and convincing evidence of global warming.1985Recession of Morteratsch Glacier (CH) between 1985 and 20072007Source: : J. Alean, SwissEduc (www.swisseduc.chwww.swisseduc.ch) / Glaciers online (www.glacierswww.glaciers-online.netonline.net).

Holocene glacier fluctuations.Historic, stratigraphic and geomorphicevidence, producing a discontinuousrecord of glacier advance phases.Evidence of retreat phases was largelydestroyed by sub-sequentsequent advances.

Subdivisions of the HoloceneOn the base of most recent studies, the Holocenehistory of mountain glaciers in the Northern hemi-sphere can be broadly subdived in three mainperiods:- a first period (11.7 to ~ 10.2 kyr BP)corresponding to the Preboreal chronozone- a second period ( ~ 10.2 ÷ 5 kyr BP)corresponding ~ to the Boreal and Atlanticchronozones (informallyindicated as Hypsithermal)- a third period (the last ~ 5 000 years)corresponding to Subboreal-SubatlanticSubatlantic chronoz.often named Neoglaciation or Neoglacial

The first period (11.7(11.7 to ~ 10.2 kyr BP)Fluctuations of mountain glaciers during thefirst period (EarlyHolocene) ) are poorly known.Glacier advances have been reported in manymountain chains of the world (Scandinavia, Canada,Andes, , Patagonia).In the Swiss Alps the youngest moraines of the LateGlacial Egesen Stade (Egesen2, 3 & Kartell advances)are in fact Early Holocene/Preborealin age(Ivy-Ochset al., 2009).Holocene11.7Egesen StadePleistocene

10 Be weighted mean age: : 11 340 ± 370 yr12 110 ± 52011 880 ± 70011 340 ± 49010 460 ± 470In the Italian Alps moraines were recently datedby exposure ages to the latest Pleistocene - EarlyHolocene at Pian del Praiet (MaritimeAlps)(Federiciet al., 2008)

Be exposure ages for Egesen andEarly Holocene moraines(and rock glaciers) ) in the Alps10 Be(A)TyrolAustriaEngadinCHValtellinaItalyBerneseAlpsCHMaritime TyrolAlps AustriaItalyTyrolAustriaIvy-Ochs et al., 2009

NLa MareGlacierMax LIA glacierextentPeatbog at 2270 mbasal peat age:10 390 - 10 090 cal. BP0.5 kmSince ~ 10.2 kyr BP Italian glaciers were reduced to theirpresent size. Basal peat just out of LIA moraines ofLa Mare Glacier (Central Alps) dates to 10.4-10.110.1 kyr BP, sug-gesting a glacier extent comparable to the present one.

Ruitor gl.was smallerthan now10.3-1010 Kyr BPBuried peat bognear the glacierfront*2510 m a.s.l.*Basalpeat10 270 – 9 950cal yr BPmax Little Ice Ageglacier extent(1820 ?)N1 km2003

The second period (10.2 ÷ 5 kyr BP)was characterized by a generally reducedglacier activity.In many mountain chains (NorthernH.)glaciers where in a prevailing retreatedcondition and locally they entirelydisappeared.In the Italian Alps a representative sectionis present near the front of the Ruitor Glacier(Western Alps),where a peat bog buried byglacigenic sediments has been found at2510 m a.s.l.

Compressed anddeformed peattillRuitor Glaciermid 80s moraine

9 070 ±120÷ 4 945 ±6514 C yr BP~ 10 000 ÷ 5 600 cal yr BPOrombelli, , 1998The Ruitor section:calibrated 14 C ages ofcontinuous peat sediments(~10–6.7 kyr BP)and of peat clasts(6.7-5.6 kyr BP).Conditions favourable topeat formation prevailedfrom ~10 to 5.6 kyr BP.

The third period: : the last 5000 yearsThis period is often referred to as Neoglaciation(Porter & Denton 1967) since it was characterized bya general reactivation/reappearancereappearance of mountainglaciers.Several phases of advance (and retreat)punctuated this period, culminating around 5000,3800, 3100, 2500, 1400, 900, 650, 350 and 150years b2k(Wanneret al. 2008)In the Italian Alps there is evidence of the start ofthe Neoglaciation at the Miage and Niederjochglaciers at about 5 000 ys BP.

Miagelateral moraineCombal outwash plainMiage morainicamphithetre1332-1172 BP5029-4575 BPThe “Lake” Combal plain dammed by the right lateral moraineof the Miage Gl. . (Mont BLanc) ) and by the small Miageamphiteatre. . The lake was first formed by an advance blockingthe valley before ~ 4.8 kyr BP (Deline& Orombelli, 2005) .

Niederjoch/Giogo Basso Gl.(Baroni & Orombelli, 1995)Ötzi(~ 5200 cal BP)The mummified corpse of theiceman rested directly on bedrock,suggesting that, after death, itbecame buried in snow on ice-freeground ~ 5.2 kyr BP and since thenremained continuously preservedin cold ice, frozen to bedrock at theupper edge of the Giogo Basso Gl.(EasternAlps).At about 5.2 kyr BP, for an abrupt climate change, GiogoBasso glacier started to re-form near the Tisa Pass in itsupper accumulation basin.

advancingre-formingCalderone glacierabsentIn the Apennines the CalderoneGlacier, possibly still presentduring the Late Glacial, disappea-red in the Early Holocene, , andre-formedat 4.5-4.34.3 kyr BP(Giraudiet al., 2011)possiblypresent

Two Mid-Neoglacialadvance phases are recorded in theItalian Alps at 3 - 2.5 kyr Bp and in the early Middle AgesVII – IX centuries ADForni Glacier (Ortles(Ortles-Cevedale Group),reached a frontalposition a few metresdownvalley of thesub-sequentsequent max.LIA moraine, around3 - 2.7 kyr BPMid-Neoglacialadvance3 - 2.7 kys BPMax LIA ~ 1859

The Little Ice Age in the Italian AlpsThe Little Ice Age (LIA) moraines are ubiquitous andwell preserved at the forefield of the Italian glaciers,where they generally represent their Holocene max.advance. They date mainly to the last major phaseof advance in the XIX century.TrioletPré de BarLittle Ice Age moraines

(d’Osterwald 1826)Triolet and Pré de Bar glaciers in 1820

The Little Ice Age in the AlpsThree main advance phasesoccurred in the Alps duringthe Little Ice Age, as shown bythe Great Aletsch glacier:1360-139013901600-165016501820-6034502005Holzhauser, Magny & Zumbuhl, , 2005

Earlier phases of the LIA in the Italian Alps are recorded byhistoric documents of the Ruitor floods. When in an advancedposition, the Ruitor Glacier dammed a lake, which producedrepeated outburst floods, damaging La Thuile & Aosta valleys.Ruitor delta-moraine(Favre,, 1864)The ice-dammedlake of Ruitor (La Thuile)in 1862Ruitor glacial ouburst floods:1284 ?1371 ÷ 1470 ?1594, 1595, 1596,1597,15981630, 1640, 1646, 1679, 168017511864LIA maxextentRuitor LakeRuitorGl.

The Little Ice Age in the Italian AlpsA few moraines/advanceadvance phases have been dated tothe first decades of the XVII century ( Miage, Lys,VerraVerra),but the best documented part of the LIA is in the first halfof the XIX century.In the Western Alps many glaciers reached their maximumextent in 1818-18201820. After a retreat in the 1830s a secondlargest advance occurred in 1845-18601860.In the Central Alps the Forni glacier reached its maximumsize in 1859.Since the second half of the XIX century the Italian glacierswere retreating, with only minor re-advancephases around1890-9595, 1920-2525 and 1965–19851985, reaching more and moreretreated positions.

The retreat of Forni Glacier, Valtellina,in the last centuryPhoto Folladori~ 18901998

Holocene fluctuations of Italian glaciers compared toadvance/retreatphases on the Northern side of the AlpsBrenvaLysCalderoneForniLysCalderoneCalderoneMiage“Iceman”LIAGöschener 2Göschener 1Ruitor peat“Neoglacial Neoglacial”LateMidEarly5Val ViolaMaritime Alps~10.211.7glacier friendlyglacier hostileclimatic conditionsconditions Ivy-Ochs et al. 2009

Val Savaranche (Gran Paradiso)remnants of glaciers nested inside 19 th century morainesThe Italian glaciers in the AnthropoceneThank you for your attentionCNR IRPI – Torino - 2000