{"id":6112,"date":"2026-10-19T09:48:29","date_gmt":"2026-10-19T09:48:29","guid":{"rendered":"https:\/\/phd.hi.is\/doktorsvorn\/doktorsfyrirlestur-i-jardfraedi-david-j-harning\/"},"modified":"2026-10-19T09:48:29","modified_gmt":"2026-10-19T09:48:29","slug":"doktorsfyrirlestur-i-jardfraedi-david-j-harning","status":"publish","type":"phd_defence","link":"https:\/\/phd.hi.is\/en\/doktorsvorn\/doktorsfyrirlestur-i-jardfraedi-david-j-harning\/","title":{"rendered":"Doktorsfyrirlestur \u00ed jar\u00f0fr\u00e6\u00f0i – David J. Harning"},"content":{"rendered":"
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Doktorsefni:<\/strong>\u00a0David J. Harning<\/p>\n

Heiti ritger\u00f0ar:\u00a0<\/strong>Saga loftslags, j\u00f6kla og eldgosa \u00e1 \u00cdslandi \u00e1 N\u00fat\u00edma \u00ed lj\u00f3si ni\u00f0urst\u00f6\u00f0u ranns\u00f3kna \u00e1 Drangaj\u00f6kli og umhverfi\u00a0\u00a0(e. Refining the climate, glacier, and volcanic history of Iceland during the Holocene)<\/p>\n

Lei\u00f0beinendur: <\/strong>Dr.\u00a0\u00c1slaug Geirsd\u00f3ttir, pr\u00f3fessor vi\u00f0 Jar\u00f0v\u00edsindadeild H\u00e1sk\u00f3la \u00cdslands og dr. Gifford H. Miller, pr\u00f3fessor vi\u00f0 University of Colorado Boulder<\/p>\n

Einnig \u00ed doktorsnefnd:<\/strong><\/p>\n

Dr.Julio Sep\u00falveda, lektor vi\u00f0 INSTAAR and Department of Geological Sciences, University of Colorado Boulder<\/p>\n

Dr.Thomas M. Marchitto, d\u00f3sent vi\u00f0 INSTAAR and Department of Geological Sciences, University of Colorado Boulder<\/p>\n

Dr.Robert S. Anderson, pr\u00f3fessor vi\u00f0 INSTAAR and Department of Geological Sciences, University of Colorado Boulder<\/p>\n

Dr.Alexandra Jahn, lektor vi\u00f0 University of Colorado Boulder<\/p>\n

Ath\u00f6fn st\u00fdrir:\u00a0<\/strong>Dr. Andri Stef\u00e1nsson, pr\u00f3fessor og varadeildarforseti Jar\u00f0v\u00edsindadeildar H\u00e1sk\u00f3la \u00cdslands<\/p>\n

Um er a\u00f0 r\u00e6\u00f0a sameiginlega doktorsgr\u00e1\u00f0u me\u00f0\u00a0University of Colorado Boulder.\u00a0 V\u00f6rnin f\u00f3r fram 13.mars sl.<\/p>\n

\u00c1grip<\/strong><\/p>\n

N\u00e6mni \u00cdslands fyrir ve\u00f0urfarsbreytingum kemur fram \u00ed samfelldum ve\u00f0urathugunum og ve\u00f0urv\u00edsum og\u00a0 sk\u00fdrist a\u00f0 einhverju leyti af st\u00f6\u00f0u landsins \u00e1 skilum\u00a0 kaldra og tempra\u00f0ra sj\u00e1var- og loftmassa, sem f\u00e6rast \u00ed takt vi\u00f0 umhverfisbreytingar \u00e1 Nor\u00f0ur Atlantshafi. Samspil og \u00fer\u00f3un loftslags, j\u00f6kla og eldvirkni fyrir t\u00edma samfelldra m\u00e6linga er margslungi\u00f0 og margt er enn \u00e1 huldu um hvernig orsakasamhengi er h\u00e1tta\u00f0.\u00a0 \u00a0Mikilv\u00e6gt er a\u00f0 r\u00fdna betur \u00ed \u00feessa ferla til a\u00f0 unnt ver\u00f0i a\u00f0 b\u00e6ta sp\u00e1r um komandi umhverfis- og ve\u00f0urfarsbreytingar. \u00deessi ritger\u00f0 greinir fr\u00e1 ranns\u00f3knum \u00fear sem fj\u00f6l\u00fe\u00e6ttum greiningara\u00f0fer\u00f0um er beitt \u00ed \u00fev\u00ed skyni a\u00f0 betrumb\u00e6ta skilning okkar \u00e1 loftslagsbreytingum, \u00fatbrei\u00f0slu j\u00f6kla og myndun gj\u00f3skulaga \u00e1 \u00cdslandi \u00e1 N\u00fat\u00edma, me\u00f0 \u00e1herslu \u00e1 Vestfir\u00f0i og Drangaj\u00f6kul. N\u00e1kv\u00e6m greining \u00e1 gj\u00f3skul\u00f6gum, sem er a\u00f0 finna \u00ed seti vatna sem liggja a\u00f0 Drangaj\u00f6kli, var ger\u00f0 til a\u00f0 n\u00e1 fram \u00e1rei\u00f0anlegum aldursgreiningum \u00e1 vatnasetinu og ve\u00f0urv\u00edsum sem \u00ed \u00fev\u00ed finnast, en \u00feetta sv\u00e6\u00f0i hefur skort n\u00e1kv\u00e6mt gj\u00f3skut\u00edmatal hinga\u00f0 til. Vitnisbur\u00f0ur j\u00f6kulframr\u00e1sa (st\u00f6\u00f0uvatnaset og aldursgreiningar \u00e1 gr\u00f3\u00f0ri sem hefur komi\u00f0 \u00ed lj\u00f3s undan h\u00f6rfandi j\u00f6kli) hafa a\u00f0 geyma n\u00e1kv\u00e6m g\u00f6gn um virkni Drangaj\u00f6kuls \u00e1 N\u00fat\u00edma, studdur af ve\u00f0urv\u00edsum (TOC, d13C, C\/N og l\u00edfr\u00e6nn k\u00edsill) sem finnast \u00ed seti st\u00f6\u00f0uvatnanna. A\u00f0 auki var me\u00f0 \u00feessu verkefni \u00ed fyrsta skipti \u00e1 \u00cdslandi beitt ranns\u00f3knum \u00e1 tveimur hitastigs- og rakan\u00e6mum l\u00edfmerkjum (alkenones and branched glycerol dialkyl glycerol tetraether, GDGTs) \u00ed seti eins st\u00f6\u00f0uvatnsins og \u00ed jar\u00f0vegssni\u00f0i sem er a\u00f0 finna \u00e1 upptakasv\u00e6\u00f0i \u00feess, \u00ed \u00feeim tilgangi a\u00f0 n\u00e1 fram \u00fer\u00f3un magnbundins sumarhita \u00e1 N\u00fat\u00edma.<\/p>\n

Svipa\u00f0 og ranns\u00f3knir \u00e1 s\u00f6gu og \u00fer\u00f3un annarra \u00edslenskra j\u00f6kla gefa til kynna, benda ni\u00f0urst\u00f6\u00f0ur okkar til \u00feess a\u00f0 hl\u00fdindi \u00e1rla \u00e1 N\u00fat\u00edma (\u00e1 bilinu 2\u00b0 til 5 \u00b0 C yfir me\u00f0altali s\u00ed\u00f0ustu \u00e1ratuga) hafi leitt til h\u00f6rfunar \u00e1 forvera Drangaj\u00f6kuls. Flj\u00f3tlega eftir a\u00f0 h\u00e1marki hl\u00fdnunar var n\u00e1\u00f0, snemma \u00e1 N\u00fat\u00edma, s\u00fdna ve\u00f0urv\u00edsar \u00ed st\u00f6\u00f0uvatnaseti stigvaxandi hnignun \u00ed framlei\u00f0ni vatna\u00fe\u00f6runga og aukningu \u00ed jar\u00f0vegsrofi, sem sv\u00f6run vi\u00f0 h\u00e6gfara l\u00e6kkun sumarinngeislunar \u00e1 nor\u00f0urhveli jar\u00f0ar. Drangaj\u00f6kull mynda\u00f0ist \u00e1 n\u00fd fyrir um 2300 \u00e1rum, samhli\u00f0a \u00fev\u00ed a\u00f0 sumur t\u00f3ku a\u00f0 k\u00f3lna, og n\u00e1\u00f0i j\u00f6kullinn h\u00e1marks\u00fatbrei\u00f0slu \u00e1 litlu \u00eds\u00f6ldinni (fyrir 0,7-0,1 \u00fe\u00fasund \u00e1rum) \u00feegar hitastig sumars er tali\u00f0 hafa veri\u00f0 ~ 1 \u00b0C undir me\u00f0alhita s\u00ed\u00f0ustu \u00e1ratuga. \u00c1st\u00e6\u00f0ur kaldra fr\u00e1vika \u00e1 \u00feessu t\u00edmabili eru tengdar minni s\u00f3larvirkni, aukinni eldvirkni (b\u00e6\u00f0i sprengigosa og hraungosa) og innri breytileika ve\u00f0urkerfa \u00fear sem k\u00f3lnun var vi\u00f0haldi\u00f0 af sv\u00f6run hafs og haf\u00edss.<\/p>\n

Hitastigs- og rakan\u00e6ma l\u00edfmerki\u00f0 GDGT var a\u00f0 auki rannsaka\u00f0 \u00ed tveimur \u00f6\u00f0rum umhverfum; \u00ed jar\u00f0vegssni\u00f0i fr\u00e1 N\u00fat\u00edma \u00e1 h\u00e1lendi \u00cdslands, og \u00ed sj\u00e1varsetkjarna sem tekinn var af landgrunninu fyrir nor\u00f0an \u00cdsland.\u00a0 Fyrir sj\u00e1varsetskjarnann var a\u00f0 auki \u00fer\u00f3a\u00f0ur \u00edslenskur GDGT-hitastigskvar\u00f0i, sem byggir \u00e1 yfirbor\u00f0ss\u00fdnum teknum af sj\u00e1varbotninum og s\u00fdna ni\u00f0urst\u00f6\u00f0ur m\u00f6guleika \u00e1 a\u00f0 n\u00e1 fram minni \u00f3vissu (\u00b10.4\u00b0C) me\u00f0 sl\u00edkri sta\u00f0bundinni kv\u00f6r\u00f0un samanbori\u00f0 vi\u00f0 hnattr\u00e6na kv\u00f6r\u00f0un (\u00b14,0\u00b0C). Sta\u00f0bundin kv\u00f6r\u00f0un er s\u00e9rstaklega mikilv\u00e6g fyrir sv\u00e6\u00f0i eins og \u00cdsland, \u00fear sem hitastigstengsl GDGT v\u00edkur fr\u00e1 heildar l\u00ednulegri fylgni hnattr\u00e6nna kvar\u00f0a (\u00fe.e. k\u00f6ld og heit sv\u00e6\u00f0i). \u00de\u00f3 k\u00f3lnun \u00e1 litlu \u00eds\u00f6ldinni endurspeglist greinilega \u00ed h\u00e1marksst\u00e6r\u00f0 Drangaj\u00f6kuls og e\u00f0lisr\u00e6num ve\u00f0urv\u00edsum, kemur k\u00f3lnun Litlu \u00edsaldarinnar ekki sk\u00fdrt fram \u00ed hitastigsn\u00e6ma l\u00edfmerkinu (GDGT) \u00ed \u00feeim \u00feremur umhverfum sem h\u00e9r eru til umfj\u00f6llunar (vatnaseti, jar\u00f0vegi og sj\u00e1varseti). \u00cd fyrstu tveim tilfellunum, (\u00fe.e. vatnaseti og jar\u00f0vegssni\u00f0i), er l\u00edklegasta \u00e1st\u00e6\u00f0an rof \u00e1 eldri jar\u00f0vegi fr\u00e1 hl\u00fdrri t\u00edma (\u00fe.e eldri jar\u00f0vegur hefur foki\u00f0 yfir yngri jar\u00f0veg og \u00ed st\u00f6\u00f0uvatni\u00f0 \u00e1 h\u00e1marki litlu \u00edsaldar), n\u00e6ringarefni og GDGT hafa blandast yngra efni a\u00f0 einhverju leyti og gefa \u00fev\u00ed til kynna hl\u00fdrra hitastig en var \u00ed raun \u00e1 litlu \u00eds\u00f6ldinni. \u00cd sj\u00e1varsetinu benda l\u00edfmerkin til \u00feess a\u00f0 \u00feykkur og samfelldur haf\u00eds hafi myndast \u00e1 h\u00e1marki litlu \u00edsaldarinnar og n\u00e1\u00f0 a\u00f0 einangra sj\u00f3 undir yfirbor\u00f0inu og \u00feannig komi\u00f0 \u00ed veg fyrir hitastreymi fr\u00e1 undirl\u00f6gum sj\u00e1var til andr\u00famsloftsins. \u00deessi ritger\u00f0 b\u00e6tir vi\u00f0 n\u00fdjum og \u00edtarlegum ni\u00f0urst\u00f6\u00f0um sem eru mikilv\u00e6gar fyrir ger\u00f0 l\u00edkana sem mi\u00f0a a\u00f0 \u00fev\u00ed a\u00f0 sp\u00e1 fyrir um \u00fer\u00f3un loftslags og hugsanlegar breytingar \u00e1 n\u00e6stu \u00f6ldum.<\/p>\n

\u00a0Um doktorsefni\u00f0<\/strong><\/p>\n

David J. Harning f\u00e6ddist \u00e1ri\u00f0 1991 og \u00f3lst uppi \u00ed New Hampshire, Bandar\u00edkjunum. Hann lauk B.Sc. pr\u00f3fi \u00ed jar\u00f0fr\u00e6\u00f0i fr\u00e1 Bates College (Maine).\u00a0 Lokaverkefni hans fjalla\u00f0i um loftslagsbreytingar \u00e1 seinni hluta n\u00famt\u00edma og bygg\u00f0i \u00e1 vettvangsvinnu og jar\u00f0efnafr\u00e6\u00f0ilegum greiningum \u00e1 vatnaseti \u00e1 N\u00fdja Sj\u00e1landi. Hann h\u00f3f sameiginlegt doktorsn\u00e1m vi\u00f0 H\u00e1sk\u00f3la \u00cdslands og H\u00e1sk\u00f3lann \u00ed Colorado Boulder hausti\u00f0 2015.\u00a0<\/p>\n

Vi\u00f0bur\u00f0ur \u00e1 facebook<\/a><\/p>\n<\/div><\/div>","protected":false},"featured_media":1926,"template":"","meta":{"site-sidebar-layout":"default","site-content-layout":"","ast-site-content-layout":"default","site-content-style":"default","site-sidebar-style":"default","ast-global-header-display":"","ast-banner-title-visibility":"","ast-main-header-display":"","ast-hfb-above-header-display":"","ast-hfb-below-header-display":"","ast-hfb-mobile-header-display":"","site-post-title":"","ast-breadcrumbs-content":"","ast-featured-img":"","footer-sml-layout":"","ast-disable-related-posts":"","theme-transparent-header-meta":"","adv-header-id-meta":"","stick-header-meta":"","header-above-stick-meta":"","header-main-stick-meta":"","header-below-stick-meta":"","astra-migrate-meta-layouts":"default","ast-page-background-enabled":"default","ast-page-background-meta":{"desktop":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"ast-content-background-meta":{"desktop":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"_phd_date_start":"2019-04-02T14:00:00+00:00","_phd_date_end":"2019-04-02T15:30:00+00:00","_phd_location":"A\u00f0albygging H\u00e1t\u00ed\u00f0arsalur","_phd_admission":"Allir velkomnir","_phd_thesis_title":"Saga loftslags, j\u00f6kla og eldgosa \u00e1 \u00cdslandi \u00e1 N\u00fat\u00edma \u00ed lj\u00f3si ni\u00f0urst\u00f6\u00f0u ranns\u00f3kna \u00e1 Drangaj\u00f6kli og umhverfi (e. Refining the climate, glacier, and volcanic history of Iceland during the Holocene)","_phd_source_url":"https:\/\/gamli.hi.is\/vidburdir\/doktorsfyrirlestur_i_jardfraedi_david_j_harning","_phd_source_node_id":"316053","_phd_source_type":"vidburdir","_phd_member_id":538,"footnotes":""},"phd_school":[113,93],"phd_discipline":[115],"class_list":["post-6112","phd_defence","type-phd_defence","status-publish","has-post-thumbnail","hentry","phd_school-jardvisindadeild","phd_school-verkfraedi-og-natturuvisindasvid","phd_discipline-phd-i-jardfraedi"],"_links":{"self":[{"href":"https:\/\/phd.hi.is\/en\/wp-json\/wp\/v2\/phd_defence\/6112","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/phd.hi.is\/en\/wp-json\/wp\/v2\/phd_defence"}],"about":[{"href":"https:\/\/phd.hi.is\/en\/wp-json\/wp\/v2\/types\/phd_defence"}],"version-history":[{"count":0,"href":"https:\/\/phd.hi.is\/en\/wp-json\/wp\/v2\/phd_defence\/6112\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/phd.hi.is\/en\/wp-json\/wp\/v2\/media\/1926"}],"wp:attachment":[{"href":"https:\/\/phd.hi.is\/en\/wp-json\/wp\/v2\/media?parent=6112"}],"wp:term":[{"taxonomy":"phd_school","embeddable":true,"href":"https:\/\/phd.hi.is\/en\/wp-json\/wp\/v2\/phd_school?post=6112"},{"taxonomy":"phd_discipline","embeddable":true,"href":"https:\/\/phd.hi.is\/en\/wp-json\/wp\/v2\/phd_discipline?post=6112"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}