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dc.contributor.advisorRasmussen, Tine Lander
dc.contributor.authorJessen, Simon Pind
dc.date.accessioned2015-07-30T11:52:05Z
dc.date.available2015-07-30T11:52:05Z
dc.date.issued2015-03-27
dc.description.abstractThe thesis builds on 11 sediment cores from c. 600 to 1900 m water depth from the continental slope west of Svalbard and one core from the Barents Sea shelf. Together, the cores cover the last 74,000 years. The primary goal was to gain a better insight in ocean circulation and glacial activity in a climatic context on glacial-interglacial and millennial time scales. The main parameters studied are ice rafted detritus (IRD) - i.e. sand grains transported out to sea by icebergs or sea ice, grain-size of sortable silt (10-63 micron), which measures the strength of bottom currents, and the magnetic susceptibility of sediments, a proxy for sediment provenance and current activity. The main findings are: - The Svalbard-Barents Sea ice sheet reached the shelf break before 24,000 years BP, when it was at its maximum size. The timing of maximum glaciation is monitored by series of mass transport deposits along the entire slope. The timing is at least 3000 years earlier than previously reconstructed. - The ice sheet was at its largest size for a relatively short time. The initial glacial retreat occurred no later than 21,000 years BP and probably started already at 24,000 years BP via a massive iceberg discharge from an active ice stream in the Storfjorden Trough south of Spitsbergen. - The millennial scale activity of the Svalbard Barents Sea ice sheet was closely linked to climate change, with a more actively calving ice sheet during warm climate intervals and a stable, probably growing ice sheet during cold climate intervals. - The bottom current strength oscillated in phase with millennial scale climate, probably reflecting changing deep water production in the Greenland Sea gyre. - Warm Atlantic water was always present on the slope, but occasionally submerged under a cover of fresh and cold Polar water.en_US
dc.description.doctoraltypeph.d.en_US
dc.description.popularabstractHadde det ikke vært for det varme Atlantisk vann i havoverflaten ville Svalbard og Nordnorges klima vært mer end 10 grader kaldere. Rytmiske variasjoner i kornstørrelsen vest for Svalbard tyder på at strømmen varierer i takt med klimaet og ikke stopper helt opp. Det meste av Svalbard-Barentshav isskjoldet lå på nåtidig havbunn, som det vestantarktiske isskjoldet idag. Isen var stabil i kaldt klima og kalvet mest i varmt klima. Aller størst var isen for 24,000 år siden. For 23,500 år siden kollapset en isstrøm og kalvet store mengder isfjell. Dette har gitt et over 1000 km langt sandspor på havbunnen. Bl. a. ut ifra slike spor har jeg sammen med min veileder, Tine Rasmussen, studert Svalbards klima- og istidshistorie. En historie preget av en robust, men varierende havstrømm og et klimafølsomt isskjold. Jeg har for det meste studert sand som er transportert med isfjell. Når isfjellene smeltet, endte sanden opp på havets bunn og således også i våre havbunnskjerner.en_US
dc.description.sponsorshipThe investigation was supported by the University of Tromsø through the Research School in Arctic Marine Geology and Geophysics (AMGG) and the Mohn Foundation to the ‘Paleo-CIRCUS’ project and by the Research Council of Norway (Centre of Excellence funding scheme, grant no. 223259/F5). Some laboratory costs were covered by grants from the national research school in climate dynamics, RESClim, and by the Amundsen Center.en_US
dc.descriptionThe papers of this thesis are not available in Munin: <br>I: Jessen, S.P., T. L. Rasmussen, T. Nielsen, and A. Solheim. 2010: 'A new Late Weichselian and Holocene marine chronology for the western Svalbard slope 30,000-0 cal years BP', available in <a href="http://dx.doi.org/10.1016/j.quascirev.2010.02.020">Quaternary Science Reviews 29, 1301-1312</a> <br>II: Jessen, S. P., and T. L. Rasmussen (submitted). 'Sortable Silt Cycles in Svalbard Slope Sediments 74-0 ka', submitted to Journal of Quaternary Science, submission no. JQS-15-0006 <br>III: Jessen, S. P., and T. L. Rasmussen: 'Ice rafting patterns on the western Svalbard slope 74-0 ka: Interplay between ice sheet activity and ocean circulation', manuscript to be submitted to Paleoceanography <br>IV: Rasmussen, T. L., E. Thomsen, M. A. Ślubowska, S. P. Jessen, A. Solheim, and N. Koç. 2007. 'Paleoceanographic evolution of the SW Svalbard margin (76°N) since 20,000 14C yr BP', available in <a href="http://dx.doi.org/10.1016/j.yqres.2006.07.002">Quaternary Research 67, 100-114</a>en_US
dc.identifier.isbn978-82-8236-172-9 (trykt) og 978-82-8236-173-6 (pdf)
dc.identifier.urihttp://hdl.handle.net/10037/7877
dc.identifier.urnURN:NBN:no-uit_munin_7478
dc.language.isoengen_US
dc.publisherUiT Norges arktiske universiteten_US
dc.publisherUiT The Arctic University of Norwayen_US
dc.rights.accessRightsopenAccess
dc.subject.courseIDDOKTOR-004en_US
dc.subjectVDP::Mathematics and natural science: 400::Geosciences: 450::Marine geology: 466en_US
dc.subjectVDP::Matematikk og Naturvitenskap: 400::Geofag: 450::Marin geologi: 466en_US
dc.titleIce rafting, Ocean circulation and Glacial activity on the western Svalbard margin 0–74 000 years BPen_US
dc.typeDoctoral thesisen_US
dc.typeDoktorgradsavhandlingen_US


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