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  • 1. Alexanderson, Helena
    et al.
    Backman, Jan
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Cronin, Thomas M.
    Funder, Svend
    Ingólfsson, Ólafur
    Jakobsson, Martin
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Landvik, Jon Y.
    Löwemark, Ludvig
    Mangerud, Jan
    März, Christian
    Möller, Per
    O'Regan, Matthew
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Spielhagen, Robert F.
    An Arctic perspective on dating Mid-Late Pleistocene environmental history2014In: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 92, p. 9-31Article in journal (Refereed)
    Abstract [en]

    To better understand Pleistocene climatic changes in the Arctic, integrated palaeoenvironmental andpalaeoclimatic signals from a variety of marine and terrestrial geological records as well as geochronologicage control are required, not least for correlation to extra-Arctic records. In this paper we discuss,from an Arctic perspective, methods and correlation tools that are commonly used to date ArcticPleistocene marine and terrestrial events. We review the state of the art of Arctic geochronology, withfocus on factors that affect the possibility and quality of dating, and support this overview by examples ofapplication of modern dating methods to Arctic terrestrial and marine sequences.Event stratigraphy and numerical ages are important tools used in the Arctic to correlate fragmentedterrestrial records and to establish regional stratigraphic schemes. Age control is commonly provided byradiocarbon, luminescence or cosmogenic exposure ages. Arctic Ocean deep-sea sediment successionscan be correlated over large distances based on geochemical and physical property proxies for sedimentcomposition, patterns in palaeomagnetic records and, increasingly, biostratigraphic data. Many of theseproxies reveal cyclical patterns that provide a basis for astronomical tuning.Recent advances in dating technology, calibration and age modelling allow for measuring smallerquantities of material and to more precisely date previously undatable material (i.e. foraminifera for 14C,and single-grain luminescence). However, for much of the Pleistocene there are still limits to the resolutionof most dating methods. Consequently improving the accuracy and precision (analytical andgeological uncertainty) of dating methods through technological advances and better understanding ofprocesses are important tasks for the future. Another challenge is to better integrate marine andterrestrial records, which could be aided by targeting continental shelf and lake records, exploringproxies that occur in both settings, and by creating joint research networks that promote collaborationbetween marine and terrestrial geologists and modellers.

  • 2.
    Ampel, Linda
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Jakobsson, Martin
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Jakobsson, Carina
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Identifying changes in Arctic Ocean sea ice conditions north of Greenland during the Holocene2012In: APEX Sixth International Conference and Workshop: Quaternary Glacial and Climate Extremes / [ed] Ninna Immonen, Martin Jakobsson, Juha Pekka Lunkka, Kari Strand, Oulu: Oulun yliopisto , 2012, p. 32-32Conference paper (Other academic)
  • 3. Anderson, John B.
    et al.
    Conway, Howard
    Bart, Philip J.
    Witus, Alexandra E.
    Greenwood, Sarah L.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    McKay, Robert M.
    Hall, Brenda L.
    Ackert, Robert P.
    Licht, Kathy
    Jakobsson, Martin
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Stone, John O.
    Ross Sea paleo-ice sheet drainage and deglacial history during and since the LGM2014In: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 100, p. 31-54Article in journal (Refereed)
    Abstract [en]

    Onshore and offshore studies show that an expanded, grounded ice sheet occupied the Ross Sea Embayment during the Last Glacial Maximum (LGM). Results from studies of till provenance and the orientation of geomorphic features on the continental shelf show that more than half of the grounded ice sheet consisted of East Antarctic ice flowing through Transantarctic Mountain (TAM) outlet glaciers; the remainder came from West Antarctica. Terrestrial data indicate little or no thickening in the upper catchment regions in both West and East Antarctica during the LGM. In contrast, evidence from the mouths of the southern and central TAM outlet glaciers indicate surface elevations between 1000 m and 1100 m (above present-day sea level). Farther north along the western margin of the Ross Ice Sheet, surface elevations reached 720 m on Ross Island, and 400 m at Terra Nova Bay. Evidence from Marie Byrd Land at the eastern margin of the ice sheet indicates that the elevation near the present-day grounding line was more than 800 m asl, while at Siple Dome in the central Ross Embayment, the surface elevation was about 950 m asl. Farther north, evidence that the ice sheet was grounded on the middle and the outer continental shelf during the LGM implies that surface elevations had to be at least 100 m above the LGM sea level. The apparent low surface profile and implied low basal shear stress in the central and eastern embayment suggests that although the ice streams may have slowed during the LGM, they remained active. Ice-sheet retreat from the western Ross Embayment during the Holocene is constrained by marine and terrestrial data. Ages from marine sediments suggest that the grounding line had retreated from its LGM outer shelf location only a few tens of kilometer to a location south of Coulman Island by similar to 13 ka BP. The ice sheet margin was located in the vicinity of the Drygalski Ice Tongue by similar to 11 ka BP, just north of Ross Island by similar to 7.8 ka BP, and near Hatherton Glacier by similar to 6.8 ka BP. Farther south, Be-10 exposure ages from glacial erratics on nunataks near the mouths of Reedy, Scott and Beardmore Glaciers indicate thinning during the mid to late Holocene, but the grounding line did not reach its present position until 2 to 3 ka BP. Marine dates, which are almost exclusively Acid Insoluble Organic (AIO) dates, are consistently older than those derived from terrestrial data. However, even these ages indicate that the ice sheet experienced significant retreat after similar to 13 ka BP. Geomorphic features indicate that during the final stages of ice sheet retreat ice flowing through the TAM remained grounded on the shallow western margin of Ross Sea. The timing of retreat from the central Ross Sea remains unresolved; the simplest reconstruction is to assume that the grounding line here started to retreat from the continental shelf more or less in step with the retreat from the western and eastern sectors. An alternative hypothesis, which relies on the validity of radiocarbon ages from marine sediments, is that grounded ice had retreated from the outer continental shelf prior to the LGM. More reliable ages from marine sediments in the central Ross Embayment are needed to test and validate this hypothesis.

  • 4.
    Anderson, John B.
    et al.
    Rice University.
    Jakobsson, Martin
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Nitsche, Frank Oliver
    Lamont-Doherty Earth Observatory, Columbia University.
    Geomorphic expression of collapsing ice streams revealed by latest generation swath bathymetry images2011Conference paper (Other academic)
    Abstract [en]

    There is now a substantial swath bathymetry data set from Antarctica that reveals subglacial bedforms, in particular mega-scale glacial lineations, which were formed by ice streams that occupied glacial troughs during the LGM. However, with the exception of grounding zone wedges, few studies have yielded high-resolution sea floor images that show geomorphic features formed by retreating ice streams. For example, deep-tow side-scan sonar records from Ross Sea show a range of recessional features, mostly 1-3 meters high, that overprint mega-scale glacial lineations. These features were not imaged in swath bathymetry records. During the 2010 austral summer, the Swedish ice breaker Oden was used to conduct an extensive survey in the sparsely studied central trough in Pine Island Bay using the latest generation multibeam technology. The bedforms imaged in Pine Island Bay are similar to small-scale recessional features previously imaged in Ross Sea using deep-tow side-scan sonar. These include fishbone moraines and corrugated iceberg furrows, which we argue were produced daily through tidally-influenced motion of a disintegrating ice shelf. During this event a 65 km long stretch of the trough was cleared of floating ice in about 1.5 years. The break-up occurred ~12,000 cal ka BP and was likely a response to rapid sea-level rise at that time. Acquisition of more high-resolution swath bathymetry data should greatly increase our understanding of ice stream interaction with the seafloor and those factors that have influenced ice stream behavior during retreat. Future work should focus on the rugged inner shelf, were subglacial meltwater is believed to have contributed to ice stream instability.

  • 5.
    Anderson, John
    et al.
    Rice University.
    Jakobsson, Martin
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Oden Southern Ocean 0910: Cruise Report2010Report (Other academic)
  • 6. Anderson, Leif G.
    et al.
    Björk, Göran
    Holby, Ola
    Jutterström, Sara
    Mörth, Carl Magnus
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    O'Regan, Matt
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Pearce, Christof
    Stockholm University, Faculty of Science, Department of Geological Sciences. Aarhus University, Denmark.
    Semiletov, Igor
    Stranne, Christian
    Stöven, Tim
    Tanhua, Toste
    Ulfsbo, Adam
    Jakobsson, Martin
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Shelf-Basin interaction along the East Siberian Sea2017In: Ocean Science, ISSN 1812-0784, E-ISSN 1812-0792, Vol. 13, no 2, p. 349-363Article in journal (Refereed)
    Abstract [en]

    Extensive biogeochemical transformation of organic matter takes place in the shallow continental shelf seas of Siberia. This, in combination with brine production from sea-ice formation, results in cold bottom waters with relatively high salinity and nutrient concentrations, as well as low oxygen and pH levels. Data from the SWERUS-C3 expedition with icebreaker Oden, from July to September 2014, show the distribution of such nutrient-rich, cold bottom waters along the continental margin from about 140 to 180 degrees E. The water with maximum nutrient concentration, classically named the upper halocline, is absent over the Lomonosov Ridge at 140 degrees E, while it appears in the Makarov Basin at 150 degrees E and intensifies further eastwards. At the intercept between the Mendeleev Ridge and the East Siberian continental shelf slope, the nutrient maximum is still intense, but distributed across a larger depth interval. The nutrient-rich water is found here at salinities of up to similar to 34.5, i.e. in the water classically named lower halocline. East of 170 degrees E transient tracers show significantly less ventilated waters below about 150 m water depth. This likely results from a local isolation of waters over the Chukchi Abyssal Plain as the boundary current from the west is steered away from this area by the bathymetry of the Mendeleev Ridge. The water with salinities of similar to 34.5 has high nutrients and low oxygen concentrations as well as low pH, typically indicating decay of organic matter. A deficit in nitrate relative to phosphate suggests that this process partly occurs under hypoxia. We conclude that the high nutrient water with salinity similar to 34.5 are formed on the shelf slope in the Mendeleev Ridge region from interior basin water that is trapped for enough time to attain its signature through interaction with the sediment.

  • 7. Anderson, R.M.
    et al.
    Jakobsson, Martin
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Monahan, D.
    Hall, J.K.
    Montoro, H.
    Mustapha, A.A.
    General Bathymetric Chart of the Oceans (GEBCO):: A New 1:35,000,000 Scale Printed Map2005In: EOS Transactions, American Geophysical Union, v. 86(52): Fall Meet. Suppl.,, 2005, p. Abstract OS23A-1527Conference paper (Other academic)
  • 8.
    Andersson, Rina Argelia
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Jakobsson, Martin
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Meyers, Philip
    Department of Earth and Environmental Sciences, The University of Michigan, Ann Arbor, Michigan, U.S.A..
    Löwemark, Ludvig
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Johansson, Carina
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Organic matter delivery to Quaternary sediments of Amundsen Basin, central Arctic OceanManuscript (preprint) (Other academic)
    Abstract [en]

    Quaternary marine sediments retrieved from the central Arctic Ocean in a 30 cm long core, were analyzed for paleoenvironmental reconstruction. n-Alkane biomarkers combined with elemental analyses that include X-ray fluorescence (XRF) core scanning provide complementary information that suggest important influxes of terrigenous derived organic matter (OM) with depth. Changes in the variability of n-alkane-derived and elemental ratios with depth reflect the complexity of the organic carbon cycle in this region. The distributions and abundances of the long-chain n-alkanes reveal a high content of terrigenous derived components and suggest together with mathematical estimations high deliveries of the terrigenous OM in the past. XRF trace metal analyses suggest less-oxygenated bottom waters that may have allowed for better preservation conditions of OM deeper in the core.

  • 9.
    Andersson, Tommy
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Hermelin, Otto
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Skelton, Alasdair
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Jakobsson, Martin
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Bottom characterization of Lagoa das Furnas on Sao Miguel, Azores archipelago2016In: Journal of Volcanology and Geothermal Research, ISSN 0377-0273, E-ISSN 1872-6097, Vol. 321, p. 196-207Article in journal (Refereed)
    Abstract [en]

    Lagoa das Furnas is a crater lake located in an area exposed to geohazards from earthquakes and volcanic activity on the island of sao Miguel in the Azores Archipelago. Geophysical mapping of Lagoa das Furnas reveals a previously undiscovered volcanic dome. This dome is comprised largely of subaquatic pyroclastic debris of trachytic composition. Sedimentological, petrological, geochemical and geochronological studies of pyroclastic deposits from the dome link it to the historically documented Furnas 1630 eruption. The chemistry of glass and crystal fragments sampled from the dome suggests that it is comprised of more evolved magma than that of the main Furnas 1630 dome located 1400 m away. This suggests that the dome was formed during a final phase of the 1630 eruption in the Lagoa das Furnas area.

  • 10. Andrén, T.
    et al.
    Bitinas, A.
    Björck, S.
    Emelyanov, E
    Harff, J.
    Houmark-Nilelsen, M.
    Jakobsson, Martin
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Jensen, J.B.
    Jørgensen, B.B:
    Kotilainen, A.
    Knudsen, K.L.
    Lambeck, K.
    Moros, M.
    Spiess, V.
    Uscinowicz, S.
    Veski, S.
    Zelchs, Z.
    The Baltic Sea IODP project2012In: EGU General Assembly Conference Abstracts, 2012, p. 7682-7682Conference paper (Other academic)
  • 11. Arndt, Jan Erik
    et al.
    Schenke, Hans Werner
    Jakobsson, Martin
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Nitsche, Frank O.
    Buys, Gwen
    Goleby, Bruce
    Rebesco, Michele
    Bohoyo, Fernando
    Hong, Jongkuk
    Black, Jenny
    Greku, Rudolf
    Udintsev, Gleb
    Barrios, Felipe
    Reynoso-Peralta, Walter
    Taisei, Morishita
    Wigley, Rochelle
    The International Bathymetric Chart of the Southern Ocean (IBCSO) Version 1.0-A new bathymetric compilation covering circum-Antarctic waters2013In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 40, no 12, p. 3111-3117Article in journal (Refereed)
    Abstract [en]

    The International Bathymetric Chart of the Southern Ocean (IBCSO) Version 1.0 is a new digital bathymetric model (DBM) portraying the seafloor of the circum-Antarctic waters south of 60 degrees S. IBCSO is a regional mapping project of the General Bathymetric Chart of the Oceans (GEBCO). The IBCSO Version 1.0 DBM has been compiled from all available bathymetric data collectively gathered by more than 30 institutions from 15 countries. These data include multibeam and single-beam echo soundings, digitized depths from nautical charts, regional bathymetric gridded compilations, and predicted bathymetry. Specific gridding techniques were applied to compile the DBM from the bathymetric data of different origin, spatial distribution, resolution, and quality. The IBCSO Version 1.0 DBM has a resolution of 500 x 500 m, based on a polar stereographic projection, and is publicly available together with a digital chart for printing from the project website (www.ibcso.org) and at .

  • 12. Arndt, J.E.
    et al.
    Schenke, H.W.
    Barrios, F.
    Black, J.
    Buys, G.
    Jakobsson, Martin
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Nitsche, Frank
    Lamont-Doherty Earth Observatory of Columbia University.
    Rebesco, M.
    Reynoso-Peralta, W.
    Wigley, R.
    Wilson, O.
    IBCSO v1: A preview on Version 1 of the International Bathymetric Chart of the Southern Ocean2012Conference paper (Other academic)
  • 13.
    Backman, Jan
    et al.
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Jakobsson, Martin
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Frank, M.
    Sangiorini, F.
    Brinkhuis, H.
    Stickley, C.
    O´Regan, M.
    Løvlie, R.
    Pälike, H.
    Spofforth, D.
    Gattcecca, J.
    Moran, K.
    King, J.
    Heil, C.
    Age model and core-seismic integration for the Cenozoic Arctic Coring Expedition sediments from the Lomonosov Ridge2008In: Paleoceanography, Vol. 23, no PA1S03, p. PA1S03-Article in journal (Refereed)
  • 14.
    Backman, Jan
    et al.
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry. Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Jakobsson, Martin
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry. Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Frank, Martin
    Sangiorgi, F
    Brinkhuis, Henk
    Sluijs, Appy
    Stickly, Catherine
    Gattacecca, Jerome
    Age/depth relationships for the ACEX sedimentary section recovered from the Lomonosov Ridge2007Conference paper (Other (popular science, discussion, etc.))
  • 15.
    Backman, Jan
    et al.
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Jakobsson, Martin
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Rudels, B
    Moran, K
    O'Regan, M
    Moore, T
    Jokat, W
    Mayer, L.A.
    Cenozoic Depositional Regimes and the Onset of Ventilated Conditions in the Central Arctic Ocean2006In: EOS Transactions, American Geophysical Union, v. 87(52): Fall Meet. Suppl.,, 2006, p. Abstract U24A-01Conference paper (Other (popular science, discussion, etc.))
  • 16.
    Backman, Jan
    et al.
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Moran, K.
    More, T.
    King, J.
    Gattacecca, J.
    Brinkhuis, H.
    Mathiessen, J.
    Jakobsson, Martin
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Paelike, H.
    O’Regan, M.
    Frank, M.
    Kubik, P.
    Cenozoic Ridge Crest Sediments From the Central Arctic Ocean Yield cm/ka-Scale Sedimentation Rates2005In: EOS Transactions, American Geophysical Union, v. 86(52): Fall Meet. Suppl.,, 2005, p. Abstract PP51C-0607Conference paper (Other academic)
  • 17.
    Barrientos, Natalia
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Coxall, Helen
    Lear, Caroline
    O'Regan, Matt
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Mörth, Carl-Magnus
    Jakobsson, Martin
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Mg/Ca ratios in late Quaternary benthic foraminifera from the central Arctic OceanManuscript (preprint) (Other academic)
  • 18.
    Barrientos, Natalia
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Coxall, Helen
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Lear, Caroline
    Pearce, Christof
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Muschitiello, Francesco
    O'Regan, Matt
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Stranne, Christian
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    de Boer, Agatha
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Cronin, Thomas
    Semiletov, Igor
    Jakobsson, Martin
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Late Holocene variability in Arctic Ocean Pacific Water inflow through the Bering StraitManuscript (preprint) (Other academic)
  • 19.
    Barrientos, Natalia
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Jakobsson, Martin
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Mörth, Carl-Magnus
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Pearce, Christof
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Miller, Clint
    O'Regan, Matt
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Brüchert, Volker
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Johansson, Carina
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Coxall, Helen
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Post-recovery dissolution of calcareous microfossils in sediments from a highly productive Arctic marine environmentManuscript (preprint) (Other academic)
  • 20.
    Barrientos, Natalia
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Lear, Caroline H.
    Jakobsson, Martin
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Stranne, Christian
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    O'Regan, Matt
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Cronin, Thomas M.
    Gukov, Aleksandr Y.
    Coxall, Helen K.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Arctic Ocean benthic foraminifera Mg/Ca ratios and global Mg/Ca-temperature calibrations: New constraints at low temperaturesIn: Geochimica et Cosmochimica Acta, ISSN 0016-7037, E-ISSN 1872-9533Article in journal (Refereed)
    Abstract [en]

    We explore the use of Mg/Ca ratios in six Arctic Ocean benthic foraminifera species as bottom water palaeothermometers and expand published Mg/Ca-temperature calibrations to the coldest bottom temperatures (<1 °C). Foraminifera were analyzed in surface sediments at 27 sites in the Chukchi Sea, East Siberian Sea, Laptev Sea, Lomonosov Ridge and Petermann Fjord. The sites span water depths of 52–1157 m and bottom water temperatures (BWT) of −1.8 to +0.9 °C. Benthic foraminifera were alive at time of collection, determined from Rose Bengal (RB) staining. Three infaunal and three epifaunal species were abundant enough for Mg/Ca analysis. As predicted by theory and empirical evidence, cold water Arctic Ocean benthic species produce low Mg/Ca ratios, the exception being the porcelaneous species Quinqueloculina arctica. Our new data provide important constraints at the cold end (<1 °C) when added to existing global datasets. The refined calibrations based on the new and published global data appear best supported for the infaunal species Nonionella labradorica (Mg/Ca = 1.325 ± 0.01 × e^(0.065 ± 0.01 × BWT), r2 = 0.9), Cassidulina neoteretis (Mg/Ca = 1.009 ± 0.02 × e^(0.042 ± 0.01 × BWT), r2 = 0.6) and Elphidium clavatum (Mg/Ca = 0.816 ± 0.06 + 0.125 ± 0.05 × BWT, r2 = 0.4). The latter is based on the new Arctic data only. This suggests that Arctic Ocean infaunal taxa are suitable for capturing at least relative and probably semi-quantitative past changes in BWT. Arctic Oridorsalis tener Mg/Ca data are combined with existing O. umbonatus Mg/Ca data from well saturated core-tops from other regions to produce a temperature calibration with minimal influence of bottom water carbonate saturation state (Mg/Ca = 1.317 ± 0.03 × e^(0.102 ± 0.01 BWT), r2 = 0.7). The same approach for Cibicidoides wuellerstorfi yields Mg/Ca = 1.043 ± 0.03 × e^(0.118 ± 0.1 BWT), r2 = 0.4. Mg/Ca ratios of the porcelaneous epifaunal species Q. arctica show a clear positive relationship between Mg/Ca and Δ[CO32−] indicating that this species is not suitable for Mg/Ca-palaeothermometry at low temperatures, but may be useful in reconstructing carbonate system parameters through time.

  • 21. Bentley, Michael J.
    et al.
    Cofaigh, Colm O.
    Anderson, John B.
    Conway, Howard
    Davies, Bethan
    Graham, Alastair G. C.
    Hillenbrand, Claus-Dieter
    Hodgson, Dominic A.
    Jamieson, Stewart S. R.
    Larter, Robert D.
    Mackintosh, Andrew
    Smith, James A.
    Verleyen, Elie
    Ackert, Robert P.
    Bart, Philip J.
    Berg, Sonja
    Brunstein, Daniel
    Canals, Miguel
    Colhoun, Eric A.
    Crosta, Xavier
    Dickens, William A.
    Domack, Eugene
    Dowdeswell, Julian A.
    Dunbar, Robert
    Ehrmann, Werner
    Evans, Jeffrey
    Favier, Vincent
    Fink, David
    Fogwill, Christopher J.
    Glasser, Neil F.
    Gohl, Karsten
    Golledge, Nicholas R.
    Goodwin, Ian
    Gore, Damian B.
    Greenwood, Sarah L.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Hall, Brenda L.
    Hall, Kevin
    Hedding, David W.
    Hein, Andrew S.
    Hocking, Emma P.
    Jakobsson, Martin
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Johnson, Joanne S.
    Jomelli, Vincent
    Jones, R. Selwyn
    Klages, Johann P.
    Kristoffersen, Yngve
    Kuhn, Gerhard
    Leventer, Amy
    Licht, Kathy
    Lilly, Katherine
    Lindow, Julia
    Livingstone, Stephen J.
    Masse, Guillaume
    McGlone, Matt S.
    McKay, Robert M.
    Melles, Martin
    Miura, Hideki
    Mulvaney, Robert
    Nel, Werner
    Nitsche, Frank O.
    O'Brien, Philip E.
    Post, Alexandra L.
    Roberts, Stephen J.
    Saunders, Krystyna M.
    Selkirk, Patricia M.
    Simms, Alexander R.
    Spiegel, Cornelia
    Stolldorf, Travis D.
    Sugden, David E.
    van der Putten, Nathalie
    van Ommen, Tas
    Verfaillie, Deborah
    Vyverman, Wim
    Wagner, Bernd
    White, Duanne A.
    Witus, Alexandra E.
    Zwartz, Dan
    A community-based geological reconstruction of Antarctic Ice Sheet deglaciation since the Last Glacial Maximum2014In: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 100, p. 1-9Article in journal (Refereed)
    Abstract [en]

    A robust understanding of Antarctic Ice Sheet deglacial history since the Last Glacial Maximum is important in order to constrain ice sheet and glacial-isostatic adjustment models, and to explore the forcing mechanisms responsible for ice sheet retreat. Such understanding can be derived from a broad range of geological and glaciological datasets and recent decades have seen an upsurge in such data gathering around the continent and Sub-Antarctic islands. Here, we report a new synthesis of those datasets, based on an accompanying series of reviews of the geological data, organised by sector. We present a series of timeslice maps for 20 ka, 15 ka, 10 ka and 5 ka, including grounding line position and ice sheet thickness changes, along with a clear assessment of levels of confidence. The reconstruction shows that the Antarctic Ice sheet did not everywhere reach the continental shelf edge at its maximum, that initial retreat was asynchronous, and that the spatial pattern of deglaciation was highly variable, particularly on the inner shelf. The deglacial reconstruction is consistent with a moderate overall excess ice volume and with a relatively small Antarctic contribution to meltwater pulse la. We discuss key areas of uncertainty both around the continent and by time interval, and we highlight potential priorities for future work. The synthesis is intended to be a resource for the modelling and glacial geological community.

  • 22. Björk, G
    et al.
    Jakobsson, Martin
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Rudels, B
    Swift, J.A.
    Anderson, L
    Darby, D.A.
    Winsor, P
    Bathymetry and deep-water exchange at the central Lomonosov ridge2006In: EOS Transactions, American Geophysical Union, v. 87(52): Fall Meet. Suppl.,, 2006, p. Abstract OS53B-1112Conference paper (Other academic)
  • 23. Björk, Göran
    et al.
    Anderson, L. G.
    Jakobsson, Martin
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Antony, D.
    Eriksson, Björn
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Eriksson, P. B.
    Hell, Benjamin
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Hjalmarsson, S.
    Janzen, T.
    Jutterström, Sara
    Linders, J.
    Löwemark, Ludvig
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Marcussen, C.
    Olsson, K. Anders
    Rudels, B.
    Sellén, Emma
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Sölvsten, M.
    Flow of Canadian basin deep water in the Western Eurasian Basin of the Arctic Ocean2010In: Deep Sea Research Part I: Oceanographic Research Papers, ISSN 0967-0637, E-ISSN 1879-0119, Vol. 57, no 4, p. 577-586Article in journal (Refereed)
    Abstract [en]

    The LOMROG 2007 expedition targeted the previously unexplored southern part of the Lomonosov Ridge north of Greenland together with a section from the Morris Jesup Rise to Gakkel Ridge. The oceanographic data show that Canadian Basin Deep Water (CBDW) passes the Lomonosov Ridge in the area of the Intra Basin close to the North Pole and then continues along the ridge towards Greenland and further along its northernmost continental slope. The CBDW is clearly evident as a salinity maximum and oxygen minimum at a depth of about 2000 m. The cross-slope sections at the Amundsen Basin side of the Lomonosov Ridge and further south at the Morris Jesup Rise show a sharp frontal structure higher up in the water column between Makarov Basin water and Amundsen Basin water. The frontal structure continues upward into the Atlantic Water up to a depth of about 300 m. The observed water mass division at levels well above the ridge crest indicates a strong topographic steering of the flow and that different water masses tend to pass the ridge guided by ridge-crossing isobaths at local topographic heights and depressions. A rough scaling analysis shows that the extremely steep and sharply turning bathymetry of the Morris Jesup Rise may force the boundary current to separate and generate deep eddies.

  • 24. Björk, Göran
    et al.
    Jakobsson, Martin
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Assmann, Karen
    Andersson, Leif G.
    Nilsson, Johan
    Stockholm University, Faculty of Science, Department of Meteorology .
    Stranne, Christian
    Stockholm University, Faculty of Science, Department of Geological Sciences. University of New Hampshire, USA.
    Mayer, Larry
    Bathymetry and oceanic flow structure at two deep passages crossing the Lomonosov Ridge2018In: Ocean Science, ISSN 1812-0784, E-ISSN 1812-0792, Vol. 14, no 1, p. 1-13Article in journal (Refereed)
    Abstract [en]

    The Lomonosov Ridge represents a major topographical feature in the Arctic Ocean which has a large effect on the water circulation and the distribution of water properties. This study presents detailed bathymetric survey data along with hydrographic data at two deep passages across the ridge: a southern passage (80-81 degrees N), where the ridge crest meets the Siberian continental slope, and a northern passage around 84.5 degrees N. The southern channel is characterized by smooth and flat bathymetry around 1600-1700m with a sill depth slightly shallower than 1700 m. A hydrographic section across the channel reveals an eastward flow with Amundsen Basin properties in the southern part and a westward flow of Makarov Basin properties in the northern part. The northern passage includes an approximately 72 km long and 33 km wide trough which forms an intra-basin in the Lomonosov Ridge morphology (the Oden Trough). The eastern side of the Oden Trough is enclosed by a narrow and steep ridge rising 500-600m above a generally 1600m deep trough bottom. The deepest passage (the sill) is 1470m deep and located on this ridge. Hydrographic data show irregular temperature and salinity profiles indicating that water exchange occurs as midwater intrusions bringing water properties from each side of the ridge in well-defined but irregular layers. There is also morphological evidence that some rather energetic flows may occur in the vicinity of the sill. A well expressed deepening near the sill may be the result of seabed erosion by bottom currents.

  • 25. Björk, Göran
    et al.
    Jakobsson, Martin
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry. Marin geovetenskap.
    Rudels, Bert
    Swift, Jim
    Anderson, Leif
    Darby, Dennis
    Backman, Jan
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry. Marin geovetenskap.
    Winsor, Peter
    Polyak, Leonid
    Edwards, Margo
    Bathymetry and deep-water exchange across the central Lomonosov Ridge at 88°-89°N2007In: Deep-Sea Research I, Vol. 54, p. 1197-1208Article in journal (Refereed)
    Abstract [en]

    Seafloor mapping of the central Lomonosov Ridge using a multibeam echo-sounder during the Beringia/Healy–Oden Trans-Arctic Expedition (HOTRAX) 2005 shows that a channel across the ridge has a substantially shallower sill depth than the 2500m indicated in present bathymetric maps. The multibeam survey along the ridge crest shows a maximum sill depth of about 1870 m. A previously hypothesized exchange of deep water from the Amundsen Basin to the Makarov Basin in this area is not confirmed. On the contrary, evidence of a deep-water flow from the Makarov to the Amundsen Basin was observed, indicating the existence of a new pathway for Canadian Basin Deep Water toward the Atlantic Ocean. Sediment data show extensive current activity along the ridge crest and along the rim of a local Intra Basin within the ridge structure.

  • 26. Blunden, Jessica
    et al.
    Arndt, Derek S.
    Achberger, Christine
    Ackerman, Stephen A.
    Albanil, Adelina
    Alexander, P.
    Alfaro, Eric J.
    Allan, Rob
    Alves, Lincoln M.
    Amador, Jorge A.
    Ambenje, Peter
    Andrianjafinirina, Solonomenjanahary
    Antonov, John
    Aravequia, Jose A.
    Arendt, A.
    Arevalo, Juan
    Ashik, I.
    Atheru, Zachary
    Banzon, Viva
    Baringer, Molly O.
    Barreira, Sandra
    Barriopedro, David E.
    Beard, Grant
    Becker, Andreas
    Behrenfeld, Michael J.
    Bell, Gerald D.
    Benedetti, Angela
    Bernhard, Germar
    Berrisford, Paul
    Berry, David I.
    Bhatt, U.
    Bidegain, Mario
    Bindoff, Nathan
    Bissolli, Peter
    Blake, Eric S.
    Booneeady, Raj
    Bosilovich, Michael
    Box, J. E.
    Boyer, Tim
    Braathen, Geir O.
    Bromwich, David H.
    Brown, R.
    Brown, L.
    Bruhwiler, Lori
    Bulygina, Olga N.
    Burgess, D.
    Burrows, John
    Calderon, Blanca
    Camargo, Suzana J.
    Campbell, Jayaka
    Cao, Y.
    Cappelen, J.
    Carrasco, Gualberto
    Chambers, Don P.
    Chang'a, L.
    Chappell, Petra
    Chehade, Wissam
    Cheliah, Muthuvel
    Christiansen, Hanne H.
    Christy, John R.
    Ciais, Phillipe
    Coelho, Caio A. S.
    Cogley, J. G.
    Colwell, Steve
    Cross, J. N.
    Crouch, Jake
    Cunningham, Stuart A.
    Dacic, Milan
    De Jeu, Richard A. M.
    Dekaa, Francis S.
    Demircan, Mesut
    Derksen, C.
    Diamond, Howard J.
    Dlugokencky, Ed J.
    Dohan, Kathleen
    Dolman, A. Johannes
    Domingues, Catia M.
    Shenfu, Dong
    Dorigo, Wouter A.
    Drozdov, D. S.
    Duguay, Claude R.
    Dunn, Robert J. H.
    Duran-Quesada, Ana M.
    Dutton, Geoff S.
    Ehmann, Christian
    Elkins, James W.
    Euscategui, Christian
    Famiglietti, James S.
    Fan, Fang
    Fauchereau, Nicolas
    Feely, Richard A.
    Fekete, Balazs M.
    Fenimore, Chris
    Fioletov, Vitali E.
    Fogarty, Chris T.
    Fogt, Ryan L.
    Folland, Chris K.
    Foster, Michael J.
    Frajka-Williams, Eleanor
    Franz, Bryan A.
    Frith, Stacey H.
    Frolov, I.
    Ganter, Catherine
    Garzoli, Silvia
    Geai, M. -L
    Gerland, S.
    Gitau, Wilson
    Gleason, Karin L.
    Gobron, Nadine
    Goldenberg, Stanley B.
    Goni, Gustavo
    Good, Simon A.
    Gottschalck, Jonathan
    Gregg, Margarita C.
    Griffiths, Georgina
    Grooss, Jens-Uwe
    Guard, Charles 'Chip'
    Gupta, Shashi K.
    Hall, Bradley D.
    Halpert, Michael S.
    Harada, Yayoi
    Hauri, C.
    Heidinger, Andrew K.
    Heikkila, Anu
    Heim, Richard R., Jr.
    Heimbach, Patrick
    Hidalgo, Hugo G.
    Hilburn, Kyle
    Ho, Shu-peng (Ben)
    Hobbs, Will R.
    Holgate, Simon
    Hovsepyan, Anahit
    Zeng-Zhen, Hu
    Hughes, P.
    Hurst, Dale F.
    Ingvaldsen, R.
    Inness, Antje
    Jaimes, Ena
    Jakobsson, Martin
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    James, Adamu I.
    Jeffries, Martin O.
    Johns, William E.
    Johnsen, Bjorn
    Johnson, Gregory C.
    Johnson, Bryan
    Jones, Luke T.
    Jumaux, Guillaume
    Kabidi, Khadija
    Kaiser, Johannes W.
    Kamga, Andre
    Kang, Kyun-Kuk
    Kanzow, Torsten O.
    Kao, Hsun-Ying
    Keller, Linda M.
    Kennedy, John J.
    Key, J.
    Khatiwala, Samar
    Pour, H. Kheyrollah
    Kholodov, A. L.
    Khoshkam, Mahbobeh
    Kijazi, Agnes
    Kikuchi, T.
    Kim, B. -M
    Kim, S. -J
    Kimberlain, Todd B.
    Knaff, John A.
    Korshunova, Natalia N.
    Koskela, T.
    Kousky, Vernon E.
    Kramarova, Natalya
    Kratz, David P.
    Krishfield, R.
    Kruger, Andries
    Kruk, Michael C.
    Kumar, Arun
    Lagerloef, Gary S. E.
    Lakkala, K.
    Lander, Mark A.
    Landsea, Chris W.
    Lankhorst, Matthias
    Laurila, T.
    Lazzara, Matthew A.
    Lee, Craig
    Leuliette, Eric
    Levitus, Sydney
    L'Heureux, Michelle
    Lieser, Jan
    Lin, I-I
    Liu, Y. Y.
    Liu, Y.
    Hongxing, Liu
    Yanju, Liu
    Lobato-Sanchez, Rene
    Locarnini, Ricardo
    Loeb, Norman G.
    Loeng, H.
    Long, Craig S.
    Lorrey, Andrew M.
    Luhunga, P.
    Lumpkin, Rick
    Jing-Jia, Luo
    Lyman, John M.
    Macdonald, Alison M.
    Maddux, Brent C.
    Malekela, C.
    Manney, Gloria
    Marchenko, S. S.
    Marengo, Jose A.
    Marotzke, Jochem
    Marra, John J.
    Martinez-Gueingla, Rodney
    Massom, Robert A.
    Mathis, Jeremy T.
    McBride, Charlotte
    McCarthy, Gerard
    McVicar, Tim R.
    Mears, Carl
    Meier, W.
    Meinen, Christopher S.
    Menendez, Melisa
    Merrifield, Mark A.
    Mitchard, Edward
    Mitchum, Gary T.
    Montzka, Stephen A.
    Morcrette, Jean-Jacques
    Mote, Thomas
    Muehle, Jens
    Muehr, Bernhard
    Mullan, A. Brett
    Mueller, Rolf
    Nash, Eric R.
    Nerem, R. Steven
    Newlin, Michele L.
    Newman, Paul A.
    Ng'ongolo, H.
    Nieto, Juan Jose
    Nishino, S.
    Nitsche, Helga
    Noetzli, Jeannette
    Oberman, N. G.
    Obregon, Andre'
    Ogallo, Laban A.
    Oludhe, Christopher S.
    Omar, Mohamed I
    Overland, James
    Oyunjargal, Lamjav
    Parinussa, Robert M.
    Park, Geun-Ha
    Park, E-Hyung
    Parker, David
    Pasch, Richard J.
    Pascual-Ramirez, Reynaldo
    Pelto, Mauri S.
    Penalba, Olga
    Peng, L.
    Perovich, Don K.
    Pezza, Alexandre B.
    Phillips, David
    Pickart, R.
    Pinty, Bernard
    Pitts, Michael C.
    Purkey, Sarah G.
    Quegan, Shaun
    Quintana, Juan
    Rabe, B.
    Rahimzadeh, Fatemeh
    Raholijao, Nirivololona
    Raiva, I.
    Rajeevan, Madhavan
    Ramiandrisoa, Voahanginirina
    Ramos, Alexandre
    Ranivoarissoa, Sahondra
    Rayner, Nick A.
    Rayner, Darren
    Razuveav, Vyacheslav N.
    Reagan, James
    Reid, Phillip
    Renwick, James
    Revedekar, Jayashree
    Richter-Menge, Jacqueline
    Rivera, Ingrid L.
    Robinson, David A.
    Rodell, Matthew
    Romanovsky, Vladimir E.
    Ronchail, Josyane
    Rosenlof, Karen H.
    Sabine, Christopher L.
    Salvador, Mozar A.
    Sanchez-Lugo, Ahira
    Santee, Michelle L.
    Sasgen, I.
    Sawaengphokhai, P.
    Sayouri, Amal
    Scambos, Ted A.
    Schauer, U.
    Schemm, Jae
    Schlosser, P.
    Schmid, Claudia
    Schreck, Carl
    Semiletov, Igor
    Send, Uwe
    Sensoy, Serhat
    Setzer, Alberto
    Severinghaus, Jeffrey
    Shakhova, Natalia
    Sharp, M.
    Shiklomanov, Nicolai I.
    Siegel, David A.
    Silva, Viviane B. S.
    Silva, Frabricio D. S.
    Sima, Fatou
    Simeonov, Petio
    Simmonds, I.
    Simmons, Adrian
    Skansi, Maria
    Smeed, David A.
    Smethie, W. M.
    Smith, Adam B.
    Smith, Cathy
    Smith, Sharon L.
    Smith, Thomas M.
    Sokolov, V.
    Srivastava, A. K.
    Stackhouse, Paul W., Jr.
    Stammerjohn, Sharon
    Steele, M.
    Steffen, Konrad
    Steinbrecht, Wolfgang
    Stephenson, Tannecia
    Su, J.
    Svendby, T.
    Sweet, William
    Takahashi, Taro
    Tanabe, Raymond M.
    Taylor, Michael A.
    Tedesco, Marco
    Teng, William L.
    Thepaut, Jean-Noel
    Thiaw, Wassila M.
    Thoman, R.
    Thompson, Philip
    Thorne, Peter W.
    Timmermans, M. -L
    Tobin, Skie
    Toole, J.
    Trewin, Blair C.
    Trigo, Ricardo M.
    Trotman, Adrian
    Tschudi, M.
    van de Wal, Roderik S. W.
    Van der Werf, Guido R.
    Vautard, Robert
    Vazquez, J. L.
    Vieira, Goncalo
    Vincent, Lucie
    Vose, Russ S.
    Wagner, Wolfgang W.
    Wahr, John
    Walsh, J.
    Junhong, Wang
    Chunzai, Wang
    Wang, M.
    Sheng-Hung, Wang
    Lei, Wang
    Wanninkhof, Rik
    Weaver, Scott
    Weber, Mark
    Werdell, P. Jeremy
    Whitewood, Robert
    Wijffels, Susan
    Wilber, Anne C.
    Wild, J. D.
    Willett, Kate M.
    Williams, W.
    Willis, Joshua K.
    Wolken, G.
    Wong, Takmeng
    Woodgate, R.
    Worthy, D.
    Wouters, B.
    Wovrosh, Alex J.
    Yan, Xue
    Yamada, Ryuji
    Zungang, Yin
    Lisan, Yu
    Liangying, Zhang
    Peiqun, Zhang
    Lin, Zhao
    Zhao, J.
    Zhong, W.
    Ziemke, Jerry
    Zimmermann, S.
    State of the Climate in 20122013In: Bulletin of The American Meteorological Society - (BAMS), ISSN 0003-0007, E-ISSN 1520-0477, Vol. 94, no 8, p. S1-S258Article in journal (Refereed)
    Abstract [en]

    For the first time in serveral years, the El Nino-Southern Oscillation did not dominate regional climate conditions around the globe. A weak La Ni a dissipated to ENSOneutral conditions by spring, and while El Nino appeared to be emerging during summer, this phase never fully developed as sea surface temperatures in the eastern conditions. Nevertheless, other large-scale climate patterns and extreme weather events impacted various regions during the year. A negative phase of the Arctic Oscillation from mid-January to early February contributed to frigid conditions in parts of northern Africa, eastern Europe, and western Asia. A lack of rain during the 2012 wet season led to the worst drought in at least the past three decades for northeastern Brazil. Central North America also experienced one of its most severe droughts on record. The Caribbean observed a very wet dry season and it was the Sahel's wettest rainy season in 50 years. Overall, the 2012 average temperature across global land and ocean surfaces ranked among the 10 warmest years on record. The global land surface temperature alone was also among the 10 warmest on record. In the upper atmosphere, the average stratospheric temperature was record or near-record cold, depending on the dataset. After a 30-year warming trend from 1970 to 1999 for global sea surface temperatures, the period 2000-12 had little further trend. This may be linked to the prevalence of La Ni a-like conditions during the 21st century. Heat content in the upper 700 m of the ocean remained near record high levels in 2012. Net increases from 2011 to 2012 were observed at 700-m to 2000-m depth and even in the abyssal ocean below. Following sharp decreases in to the effects of La Ni a, sea levels rebounded to reach records highs in 2012. The increased hydrological cycle seen in recent years continued, with more evaporation in drier locations and more precipitation in rainy areas. In a pattern that has held since 2004, salty areas of the ocean surfaces and subsurfaces were anomalously salty on average, while fresher areas were anomalously fresh. Global tropical cyclone activity during 2012 was near average, with a total of 84 storms compared with the 1981-2010 average of 89. Similar to 2010 and 2011, the North Atlantic was the only hurricane basin that experienced above-normal activity. In this basin, Sandy brought devastation to Cuba and parts of the eastern North American seaboard. All other basins experienced either near-or below-normal tropical cyclone activity. Only three tropical cyclones reached Category 5 intensity-all in Bopha became the only storm in the historical record to produce winds greater than 130 kt south of 7 N. It was also the costliest storm to affect the Philippines and killed more than 1000 residents. Minimum Arctic sea ice extent in September and Northern Hemisphere snow cover extent in June both reached new record lows. June snow cover extent is now declining at a faster rate (-17.6% per decade) than September sea ice extent (-13.0% per decade). Permafrost temperatures reached record high values in northernmost Alaska. A new melt extent record occurred on 11-12 July on the Greenland ice sheet; 97% of the ice sheet showed some form of melt, four times greater than the average melt for this time of year. The climate in Antarctica was relatively stable overall. The largest maximum sea ice extent since records begain in 1978 was observed in September 2012. In the stratosphere, warm air led to the second smallest ozone hole in the past two decades. Even so, the springtime ozone layer above Antarctica likely will not return to its early 1980s state until about 2060. Following a slight decline associated with the global 2 emissions from fossil fuel combustion and cement production reached a record 9.5 +/- 0.5 Pg C in 2011 and a new record of 9.7 +/- 0.5 Pg C is estimated for 2012. Atmospheric CO2 concentrations increased by 2.1 ppm in 2012, to 392.6 ppm. In spring 2012, 2 concentration exceeded 400 ppm at 7 of the 13 Arctic observation sites. Globally, other greenhouse gases including methane and nitrous oxide also continued to rise in concentration and the combined effect now represents a 32% increase in radiative forcing over a 1990 baseline. Concentrations of most ozone depleting substances continued to fall.

  • 27. Chauhan, T.
    et al.
    Rasmussen, T. L.
    Noormets, R.
    Jakobsson, Martin
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Hogan, K. A.
    Glacial history and paleoceanography of the southern Yermak Plateausince 132 ka BP2014In: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 92, p. 155-169Article in journal (Refereed)
    Abstract [en]

    The southern Yermak Plateau (YP) is situated at the entrance to the Arctic Ocean in the narrow MarginalIce Zone (MIZ) between the Polar and Arctic Fronts, north-west of Svalbard. A gravity core JM10-02GChas been analysed in order to reconstruct paleoceanographic conditions and the movement of the seaice margin as well as the glacier ice conditions of the SvalbardeBarents Sea Ice Sheet (SBIS) during theLast InterglacialeGlacial cycle. The distribution of planktic and benthic foraminifera, planktic and benthicoxygen and carbon isotopes and variations in ice-rafted debris (IRD) has been investigated. The sedimentcore covers the time interval from the Marine Isotope Stage (MIS) 6/5e transition (Termination II, c.132 ka BP) to the early Holocene. During Termination II (TII), the SBIS retreated and the sea ice marginwas in distal position whereas during MIS 5 to MIS 4 the sea ice margin was close to the core site. Severalcore intervals interpreted as representing MIS 5e, MIS 5c, MIS 5a, MIS 3 and MIS 1 were barren ofcalcareous microfossils whereas the intervals representing MIS 4 and MIS 2 were characterised by highproductivity (HP) of planktic and benthic foraminifera. These “glacial” HP zones were associated with theopen water conditions resulting from the advection of Atlantic Water (AW) and retreat of the sea icemargin. The barren zones during MIS 5, MIS 3 and MIS 1 resulted from the proximity of the sea icemargin whereas during MIS 2 the likely cause was an advance of the SBIS.

  • 28.
    Chi Fru, Ernest
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences. Swedish Museum of Natural History, Sweden.
    Arvestal, Emma
    Callac, Nolwenn
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    El Albani, Abderrazak
    Kilias, Stephanos
    Argyraki, Ariadne
    Jakobsson, Martin
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Arsenic stress after the Proterozoic glaciations2015In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 5, article id 17789Article in journal (Refereed)
    Abstract [en]

    Protection against arsenic damage in organisms positioned deep in the tree of life points to early evolutionary sensitization. Here, marine sedimentary records reveal a Proterozoic arsenic concentration patterned to glacial-interglacial ages. The low glacial and high interglacial sedimentary arsenic concentrations, suggest deteriorating habitable marine conditions may have coincided with atmospheric oxygen decline after similar to 2.1 billion years ago. A similar intensification of near continental margin sedimentary arsenic levels after the Cryogenian glaciations is also associated with amplified continental weathering. However, interpreted atmospheric oxygen increase at this time, suggests that the marine biosphere had widely adapted to the reorganization of global marine elemental cycles by glaciations. Such a glacially induced biogeochemical bridge would have produced physiologically robust communities that enabled increased oxygenation of the ocean-atmosphere system and the radiation of the complex Ediacaran-Cambrian life.

  • 29. Chiu, Pin-Yao
    et al.
    Chao, Weng-Si
    Gyllencreutz, Richard
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Jakobsson, Martin
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Li, Hong-Chun
    Löwemark, Ludvig
    O'Regan, Matt
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    New constraints on Arctic Ocean Mn stratigraphy from radiocarbon dating on planktonic foraminifera2017In: Quaternary International, ISSN 1040-6182, E-ISSN 1873-4553, Vol. 447, p. 13-26Article in journal (Refereed)
    Abstract [en]

    Variations in the abundance of manganese (Mn) in Arctic Ocean sediments are used as a tool to identify glacial and interglacial periods. This study aims to provide new insight into the applicability of Mn as a stratigraphic tool in the topmost sediment and to investigate the occurrence of Mn peaks in sediments within the range of radiocarbon dating. In combination with variations in ice-rafted debris (IRD), radiocarbon dating is used to better constrain the stratigraphic occurrence of Mn peaks, and the synchroneity between multiple records, especially during the late glacial and the Holocene. We find that a hiatus spanning MIS 2 is widely observed in most of our cores, resulting in a merging of Mn peaks of Holocene age and the later part of MIS 3. The Holocene Mn peak is usually high amplitude but short, while the MIS 3 Mn peak has a lower amplitude and is protracted. Where preserved, MIS 2 sediments form a 2-3 cm thick layer characterized by a light color, low Mn content, sparse IRD and low foraminiferal abundance. IRD variations provide a powerful tool to identify the boundary of the Holocene and late MIS 3 in cores with a MIS 2 hiatus. Because the IRD content displays a general increment from the start of MIS 3, and both the Holocene and MIS 2 show small IRD variations, the end of MIS 3 can be pinpointed to the point of decrease in IRD. The hiatus of MIS 2 is widely observed in our cores, suggesting extensive persistent sea ice coverage during the peak of the last glacial cycle, with sharply reduced sedimentation throughout the Arctic Ocean. Identifying similar events during previous glacial periods may be an important step towards constructing longer and more accurate chronologies for Arctic Ocean sediments.

  • 30. Christian, Marcussen
    et al.
    Jakobsson, Martin
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry. Marin geovetenskap.
    Lomonosov Ridge off Greenland (LOMROG) 20072007In: EOS Transactions: American Geophysical Union, v. 88(52), 2007, p. Abstract OS41C-03Conference paper (Other academic)
  • 31. Colleoni, F.
    et al.
    Krinner, G.
    Jakobsson, Martin
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Glaciation and Deglaciation Dynamics of Marine Isotope Stage 6 (160 - 140 kyrs BP):: Land - Ice - Atmosphere Feedbacks2008In: EOS Transactions, American Geophysical Union, v. 89(53): Fall Meet. Suppl., 2008, p. Abstract PP13C-1455Conference paper (Other academic)
  • 32.
    Colleoni, Florence
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences. Joseph Fourier University, France.
    Krinner, G.
    Jakobsson, Martin
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    The role of an Arctic ice shelf in the climate of the last glacial maximum of MIS 6 (140 ka)2010In: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 29, no 25-26, p. 3590-3597Article in journal (Refereed)
    Abstract [en]

    During the last decade, Arctic icebreaker and nuclear submarine expeditions have revealed large-scale Pleistocene glacial erosion on the Lomonosov Ridge, Chukchi Borderland and along the Northern Alaskan margin indicating that the glacial Arctic Ocean hosted large Antarctic-style ice shelves. Dating of sediment cores indicates that the most extensive and deepest ice grounding occurred during Marine Isotope Stage (MIS) 6. The precise extents of Pleistocene ice shelves in the Arctic Ocean are unknown but seem comparable to present existing Antarctic ice shelves. How would an Antarctic-style ice shelf in the MIS 6 Arctic Ocean influence the Northern Hemisphere climate? Could it have impacted on the surface mass balance (SMB) of the MIS 6 Eurasian ice sheet and contributed to its large southward extent? We use an Atmospheric General Circulation Model (AGCM) to investigate the climatic impacts of both a limited MIS 6 ice shelf covering portions of the Canada Basin and a fully ice shelf covered Arctic Ocean. The AGCM results show that both ice shelves cause a temperature cooling of about 3 °C over the Arctic Ocean mainly due to the combined effect of ice elevation and isolation from the underlying ocean heat fluxes stopping the snow cover from melting during summer. The calculated SMB of the ice shelves are positive. The ice front horizontal velocity of the Canada Basin ice shelf is estimated to ≈ 1 km yr−1 which is comparable to the recent measurements of the Ross ice shelf, Antarctica. The existence of a large continuous ice shelf covering the entire Arctic Ocean would imply a mean annual velocity of icebergs of ≈12 km yr−1 through the Fram Strait. Our modeling results show that both ice shelf configurations could be viable under the MIS 6 climatic conditions. However, the cooling caused by these ice shelves only affects the Arctic margins of the continental ice sheets and is not strong enough to significantly influence the surface mass balance of the entire MIS 6 Eurasian ice sheet.

  • 33.
    Colleoni, Florence
    et al.
    Joseph Fourier University, France.
    Krinner, Gerhard
    Joseph Fourier University, France.
    Jakobsson, Martin
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Peyaud, Vincent
    Joseph Fourier University, France.
    Ritz, Catherine
    Joseph Fourier University, France.
    Influence of regional factors on the surface mass balance of the large Eurasian ice sheet during the peak Saalian (140 kyrs BP)2009In: Global and Planetary Change, ISSN 0921-8181, E-ISSN 1872-6364, Vol. 68, no 1-2, p. 132-148Article in journal (Refereed)
    Abstract [en]

    Recent geologically-based reconstructions of the Eurasian ice sheet show that during the peak Saalian (≈ 140 kya) the ice sheet was larger over Eurasia than during the Last Glacial Maximum (LGM) at ≈ 21 kya. To address this problem we use the LMDZ4 atmospheric general circulation model to evaluate the impact on the Saalian ice sheet's surface mass balance (SMB) from proglacial lakes, dust deposition on snow, vegetation and sea surface temperatures (SST) since geological records suggest that these environmental parameters were different during the two glacial periods. Seven model simulations have been carried out. Dust deposition decreases the mean SMB by intensifying surface melt during summer while proglacial lakes cool the summer climate and reduce surface melt on the ice sheet. A simulation including both proglacial lakes and dust shows that the presence of the former parameter reduces the impact of the latter, in particular, during summer. A switch from needle-leaf to tundra vegetation affects the regional climate but not enough to significantly influence the SMB of the nearby ice margin. However, a steady-state vegetation in equilibrium with the climate should be computed to improve the boundary conditions for further evaluations of the vegetation impact on the ice sheet's SMB. Finally, changes of the SST broadly affect the regional climate with significant consequences for the SMB.

  • 34. Colleoni, Florence
    et al.
    Krinner, Gerhard
    Jakobsson, Martin
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry. Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Svendsen, John-Inge
    Peyaud, J.I.
    Ritz, Catherine
    Simulation of the Late Saalian (140 ka BP) climate in Eurasia: Conditions for the existence of an2007Conference paper (Other academic)
  • 35.
    Colleoni, Florence
    et al.
    Joseph Fourier University, France.
    Krinner, Gerhard
    Joseph Fourier University, France.
    Jaobsson, Martin
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Sensitivity of the Late Saalian (140 kyrs BP) and LGM (21 kyrs BP) Eurasian ice sheet surface mass balance to vegetation feedbacks2009In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 36, article id L08704Article in journal (Refereed)
    Abstract [en]

    This work uses an atmospheric general circulation model (AGCM) asynchronously coupled to an equilibrium vegetation model to investigate whether vegetation feedbacks could be one of the reasons why the Late Saalian ice sheet (140 kyrs BP) in Eurasia was substantially larger than the Last Glacial Maximum (LGM, 21 kyrs BP) Eurasian ice sheet. The modeled vegetation changes induce a regional cooling for the Late Saalian while they cause a slight regional warming for LGM. As a result, ablation along the margins of the Late Saalian ice sheet is significantly reduced, leading to an increased surface mass balance, while there are no significant mass balance changes observed from vegetation feedbacks at LGM.

  • 36.
    Colleoni, Florence
    et al.
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Liakka, Johan
    Stockholm University, Faculty of Science, Department of Meteorology .
    Krinner, Gehrard
    Laboratoire de Glaciologie et Géophysique de l'Environnement - Grenoble (France).
    Jakobsson, Martin
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Masina, Simona
    Centro Euro-Mediterraneao per i Cambiamenti Climatici.
    Peyaud, Vincent
    Laboratoire de Glaciologie et Géophysique de l'Environnement - Grenoble (France).
    The Late Saalian surface ocean (140 ka): sensitivity of the Late Saalian Eurasian ice sheet to sea surface conditionsManuscript (preprint) (Other academic)
    Abstract [en]

    This work focuses on the Late Saalian (140 ka) and LGM (21 ka) Eurasian ice sheets surface mass balance (SMB) sensitivity to changes in sea surface temperatures (SST). Since no global Late Saalian SST compilations exist, we test the sensitivity of the Late Saalian climate using an AGCM forced with two data-based LGM SST reconstructions. Furthermore, an attempt to reconstruct the Late Saalian SST is performed using an AGCM coupled to a mixed-layer ocean. The resulting Late Saalian SST are cooler than the LGM SST in the Northern Hemisphere and warmer in the Southern. The winter sea ice extends to 40◦ N in both North Atlantic and Pacific oceans. Changes in SST affect the SMB of the Eurasian ice sheet during both glaciations although the Late Saalian ice sheet is less sensitive to the prescribed SST changes than the LGM.

  • 37.
    Colleoni, Florence
    et al.
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Liakka, Johan
    Stockholm University, Faculty of Science, Department of Meteorology .
    Krinner, Gerhard
    Laboratoire de Glaciologie et Géophysique de l'Environnement - Grenoble (France).
    Jakobsson, Martin
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    The Late Saalian period (160 - 140 ka): insight on an unusual glaciationManuscript (preprint) (Other academic)
    Abstract [en]

    This work focuses on the climate evolution over the Late Saalian period (160 - 140 ka) over Eurasia. At this time, the Eurasian ice sheet was larger and higher than during the Last Glacial Maximum. June insolation over the high latitudes presents a large fluctuation over this period: two glacial minima toward 160 and 140 ka and a large insolation peak toward 150 ka. From the geological evidence chronology, it seems clear that the large Eurasian ice sheet already reached its maximum extent at 160 ka. To understand how this ice sheet could survive the 150 ka June insolation maximum, we use several numerical models to simulate the evolution of the vegetation cover, the surface ocean temperatures and finally the evolution of the Late Saalian climate over the three time slices 140, 150 and 160 ka. Results show that the Late Saalian climate variations are dominated by orbital forcings, responding to a large eccentricity enhancing the precession effect especially at 140 ka. From 160 to 150 ka, the surface ocean exhibits open water conditions in the North At- lantic during summer while sea surface temperature at 140 ka are clearly colder with a large sea ice extent reaching 40◦ N in both the North Atlantic and the North Pacific. This corresponds to a milder climate before 140 ka inducing a larger positive surface mass balance despite the 150 ka insolation peak because of larger precipitation rates. On the contrary, the drastic cooling caused by the astronomical forcing at 140 ka leads to a drier climate cancelling ablation and reducing the accumulation over the ice sheet.

  • 38.
    Colleoni, Florence
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences. Joseph Fourier University, France.
    Liakka, Johan
    Stockholm University, Faculty of Science, Department of Meteorology .
    Krinner, Gerhard
    Jakobsson, Martin
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Masina, Simona
    Peyaud, Vincent
    The sensitivity of the Late Saalian (140 ka) and LGM (21 ka) Eurasian ice sheets to sea surface conditions2011In: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 37, no 3-4, p. 531-553Article in journal (Refereed)
    Abstract [en]

    This work focuses on the Late Saalian (140 ka) Eurasian ice sheets’ surface mass balance (SMB) sensitivity to changes in sea surface temperatures (SST). An Atmospheric General Circulation Model (AGCM), forced with two preexisting Last Glacial Maximum (LGM, 21 ka) SST reconstructions, is used to compute climate at 140 and 21 ka (reference glaciation). Contrary to the LGM, the ablation almost stopped at 140 ka due to the climatic cooling effect from the large ice sheet topography. Late Saalian SST are simulated using an AGCM coupled with a mixed layer ocean. Compared to the LGM, these 140 ka SST show an inter-hemispheric asymmetry caused by the larger ice-albedo feedback, cooling climate. The resulting Late Saalian ice sheet SMB is smaller due to the extensive simulated sea ice reducing the precipitation. In conclusion, SST are important for the stability and growth of the Late Saalian Eurasian ice sheet.

  • 39. Cronin, T. M.
    et al.
    Dwyer, G. S.
    Farmer, J.
    Bauch, H. A.
    Spielhagen, R. F.
    Jakobsson, Martin
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Nilsson, Johan
    Stockholm University, Faculty of Science, Department of Meteorology .
    Briggs, W. M., Jr.
    Stepanova, A.
    Deep Arctic Ocean warming during the last glacial cycle2012In: Nature Geoscience, ISSN 1752-0894, E-ISSN 1752-0908, Vol. 5, no 9, p. 631-634Article in journal (Refereed)
    Abstract [en]

    In the Arctic Ocean, the cold and relatively fresh water beneath the sea ice is separated from the underlying warmer and saltier Atlantic Layer by a halocline. Ongoing sea ice loss and warming in the Arctic Ocean(1-7) have demonstrated the instability of the halocline, with implications for further sea ice loss. The stability of the halocline through past climate variations(8-10) is unclear. Here we estimate intermediate water temperatures over the past 50,000 years from the Mg/Ca and Sr/Ca values of ostracods from 31 Arctic sediment cores. From about 50 to 11 kyr ago, the central Arctic Basin from 1,000 to 2,500 m was occupied by a water mass we call Glacial Arctic Intermediate Water. This water mass was 1-2 degrees C warmer than modern Arctic Intermediate Water, with temperatures peaking during or just before millennial-scale Heinrich cold events and the Younger Dryas cold interval. We use numerical modelling to show that the intermediate depth warming could result from the expected decrease in the flux of fresh water to the Arctic Ocean during glacial conditions, which would cause the halocline to deepen and push the warm Atlantic Layer into intermediate depths. Although not modelled, the reduced formation of cold, deep waters due to the exposure of the Arctic continental shelf could also contribute to the intermediate depth warming.

  • 40. Cronin, T. M.
    et al.
    Gemery, L.
    Briggs, W. M.
    Jakobsson, Martin
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Polyak, L.
    Brouwers, E. M.
    Quaternary Sea-ice history in the Arctic Ocean based on a new Ostracode sea-ice proxy2010In: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 29, no 25-26, p. 3415-3429Article in journal (Refereed)
    Abstract [en]

    Paleo-sea-ice history in the Arctic Ocean was reconstructed using the sea-ice dwelling ostracode Acetabulastoma arcticum from late Quaternary sediments from the Mendeleyev, Lomonosov, and Gakkel Ridges, the Morris Jesup Rise and the Yermak Plateau. Results suggest intermittently high levels of perennial sea ice in the central Arctic Ocean during Marine Isotope Stage (MIS) 3 (25–45 ka), minimal sea ice during the last deglacial (16–11 ka) and early Holocene thermal maximum (11–5 ka) and increasing sea ice during the mid-to-late Holocene (5–0 ka). Sediment core records from the Iceland and Rockall Plateaus show that perennial sea ice existed in these regions only during glacial intervals MIS 2, 4, and 6. These results show that sea ice exhibits complex temporal and spatial variability during different climatic regimes and that the development of modern perennial sea ice may be a relatively recent phenomenon.

  • 41. Cronin, Thomas M.
    et al.
    O'Regan, Matt
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Pearce, Christof
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Gemery, Laura
    Toomey, Michael
    Semiletov, Igor
    Jakobsson, Martin
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Deglacial sea level history of the East Siberian Sea and Chukchi Sea margins2017In: Climate of the Past, ISSN 1814-9324, E-ISSN 1814-9332, Vol. 13, no 9, p. 1097-1110Article in journal (Refereed)
    Abstract [en]

    Deglacial (12.8-10.7 ka) sea level history on the East Siberian continental shelf and upper continental slope was reconstructed using new geophysical records and sediment cores taken during Leg 2 of the 2014 SWERUS-C3 expedition. The focus of this study is two cores from Herald Canyon, piston core SWERUS-L2-4-PC1 (4-PC1) and multicore SWERUS-L2-4-MC1 (4-MC1), and a gravity core from an East Siberian Sea transect, SWERUS-L2-20-GC1 (20GC1). Cores 4-PC1 and 20-GC were taken at 120 and 115m of modern water depth, respectively, only a few meters above the global last glacial maximum (LGM; similar to 24 kiloannum or ka) minimum sea level of similar to 125-130 meters below sea level (m b.s.l.). Using calibrated radiocarbon ages mainly on molluscs for chronology and the ecology of benthic foraminifera and ostracode species to estimate paleodepths, the data reveal a dominance of river-proximal species during the early part of the Younger Dryas event (YD, Greenland Stadial GS-1) followed by a rise in river-intermediate species in the late Younger Dryas or the early Holocene (Preboreal) period. A rapid relative sea level rise beginning at roughly 11.4 to 10.8 ka (similar to 400 cm of core depth) is indicated by a sharp faunal change and unconformity or condensed zone of sedimentation. Regional sea level at this time was about 108m b.s.l. at the 4-PC1 site and 102m b.s.l. at 20-GC1. Regional sea level near the end of the YD was up to 42-47m lower than predicted by geophysical models corrected for glacio-isostatic adjustment. This discrepancy could be explained by delayed isostatic adjustment caused by a greater volume and/or geo-graphical extent of glacial-age land ice and/or ice shelves in the western Arctic Ocean and adjacent Siberian land areas.

  • 42.
    Darby A., Dennis
    et al.
    Old Dominion University.
    Myers, Wesley B.
    Old Dominion University.
    Jakobsson, Martin
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Rigor, Ignatius
    University of Washington.
    Modern dirty sea ice characteristics and sources: The role of anchor ice2011In: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 116, no C09008Article in journal (Refereed)
    Abstract [en]

    Extensive dirty ice patches with up to 7 kg m−2 sediment concentrations in layers of up to 10 cm thickness were encountered in 2005 and 2007 in numerous areas across the central Arctic. The Fe grain fingerprint determination of sources for these sampled dirty ice floes indicated both Russian and Canadian sources, with the latter dominating. The presence of benthic shells and sea weeds along with thick layers (2–10 cm) of sediment covering 5–10 m2 indicates an anchor ice entrainment origin as opposed to suspension freezing for some of these floes. The anchor ice origin might explain the dominance of Canadian sources where only narrow flaw leads occur that would not favor suspension freezing as an entrainment process. Expandable clays, commonly used as an indicator of a Kara Sea origin for dirty sea ice, are present in moderately high percentages (>20%) in many circum-Arctic source areas, including the Arctic coasts of North America. Some differences between the Russian and the North American coastal areas are found in clay mineral abundance, primarily the much higher abundance of chlorite in North America and the northern Barents Sea as opposed to the rest of the Russian Arctic. However, sea ice clay mineralogy matched many source areas, making it difficult to use as a provenance tool by itself. The bulk mineralogy (clay and non-clay) does not match specific sources possibly due to reworking of the sediment in dirty floes through summer melting or the failure to characterize all possible source areas.

  • 43. Darby, D.A.
    et al.
    Jakobsson, Martin
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    HOTRAX’05 Cores Provide New Hope for a Pan-Arctic Stratigraphic and Paleoclimatic framework for IPY projects2005In: ICARP II, Copenhagen: Denmark 2005, 2005Conference paper (Other academic)
  • 44. Darby, D.A.
    et al.
    Jakobsson, Martin
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Polyak, L.
    Trans-Arctic Coring Expedition Results2005In: EOS Transactions, American Geophysical Union, v. 86(52): Fall Meet. Suppl.,, 2005, p. Abstract PP33A-1559Conference paper (Other academic)
  • 45. Darby, D.A.
    et al.
    Jakobsson, Martin
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Rigor, I
    New Insights in Sea Ice Drift Based on Dirty Ice Samples Collected in 2005 by the HOTRAX Expedition2006In: EOS Transactions, American Geophysical Union, v. 87(52): Fall Meet. Suppl.,, 2006, p. Abstract OS53B-1099Conference paper (Other academic)
  • 46. Darby, D.A.
    et al.
    Ortiz, J.D.
    Polyak, L.
    Lund, S.
    Jakobsson, Martin
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Woodgate, R.A.
    Shelf and Slope Sedimentation in the Arctic Ocean:: Comparison of the Alaskan Margin with Deep-Sea Sediments; Drift Deposits and the Role of Sea Ice2008In: EOS Transactions, American Geophysical Union, v. 89(53): Fall Meet. Suppl., 2008, p. Abstract OS51A-1217Conference paper (Other academic)
  • 47. Darby, Dennis
    et al.
    Jakobsson, Martin
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry. Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Rigor, Ignatius
    New insights in sea ice drift based on dirty ice samples collected in 2005 by the HOTRAX expedition2007Conference paper (Other academic)
  • 48.
    Darby, Dennis
    et al.
    Old Dominion University.
    Ortiz, Joe
    Polyak, Leonid
    Ohio State University.
    Lund, S
    Jakobsson, Martin
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Woodgate, R.A.
    The role of currents and sea ice in both slowly deposited central Arctic and rapidly deposited Chukchi-Alaskan margin sediments2009In: Global and Planetary Change, ISSN 0921-8181, E-ISSN 1872-6364, Global and Planetary Change, Vol. 68, no 1-2, p. 58-72Article in journal (Refereed)
    Abstract [en]

    A study of three long cores from the outer shelf and continental slope north of Alaska in the Arctic Ocean indicate that localized drift deposits occur here with sedimentation rates of more than 1.5 m/kyr during the Holocene. Currents in this area average about 5–20 cm/s but can reach 100 cm/s and these velocities transport the sediment found in these cores primarily as intermittent suspended load. These high accumulation sediments form levee-like deposits associated with margins of canyons cutting across the shelf and slope. Unlike most textural investigations of Arctic sediment that focus on the coarser ice-rafted detritus (IRD), this paper focuses on the > 95% of the sediment, which is finer than 45 μm. The mean size of this fraction varies between 6 and 15 μm in Holocene sediments from the Chukchi–Alaskan shelf and slope with the higher values closer to shore. Analysis of detailed size distributions of these Holocene deposits are compared to 34 sediment samples collected from sea ice across the Arctic Ocean and to Holocene sediment from central Arctic Ocean cores and indicate that similar textural parameters occur in all of these sediments. Principal components of these size distributions indicate that sea ice is an important link between the shelves and the central Arctic. Factor scores indicate nearly identical components in the clay and fine silt size fractions but very different components in the coarse silt for sea ice sediment and central Arctic ridge sediments compared to shelf and continental slope deposits. Sea ice must contribute to sedimentation in both of these Arctic regions, but bottom currents dominate in the slope region, forming drift deposits.

  • 49.
    Darby, Dennis
    et al.
    Old Dominion University.
    Polyak, Leonid
    Ohio State University.
    Jakobsson, Martin
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Initial Results of HOTRAX Address a Wide Range of Arctic Paleoclimate Issues2009In: PAGES Newsletter, ISSN 1563-0803, Vol. 17, no 1, p. 18-19Article in journal (Other (popular science, discussion, etc.))
  • 50.
    Darby, Dennis
    et al.
    Old Dominion University.
    Polyak, Leonid
    Ohio State University.
    Jakobsson, Martin
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    The 2005 HOTRAX Expedition to the Arctic Ocean2009In: Global and Planetary Change, ISSN 0921-8181, E-ISSN 1872-6364, Vol. 68, no 1-2, p. 1-4Article in journal (Refereed)
    Abstract [en]

    The Healy–Oden Trans-Arctic Expedition (HOTRAX'05) recovered 29 long piston cores and associated multicores along a transect from the Alaskan margin across the central Arctic Ocean to the northern Svalbard margin. The initial results focus on the age and stratigraphy of these cores using a variety of approaches including radiocarbon, paleomagnetic and other chronostratigraphic methods as well as detailed correlations of proxy records. High sedimentation cores from probable drift deposits are described from the shelf and continental slope north of Alaska. Provenance and sedimentary processes in these deposits include both currents and sea-ice rafting. Much lower sedimentation rates in the central Arctic Ocean show geographic variability consistent with the patterns of expected sediment distribution by ice and, to a smaller extent, subsurface currents. Insights into the Upper Quaternary stratigraphy and depositional history are provided in two papers on a core from the Mendeleev Ridge with sedimentation rates relatively elevated for this region. To compliment the results from the HOTRAX cores, two papers are included dealing with the stratigraphy and sedimentary processes on the Chukchi shelf and a modeling study addressing why the Marine Isotopic Stage 6 (ca. 140 ka) glaciation was substantially more extensive in the Arctic than the Last Glacial Maximum.

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