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  • 1.
    Hanslik, Daniela
    et al.
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Jakobsson, Martin
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Backman, Jan
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Björck, Svante
    Lund University, Department of Geology.
    Sellén, Emma
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    O'Regan, Matthew
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Fornaciari, Eliana
    University of Padova, Department of Geosciences.
    Skog, Göran
    Lund University, Department of Geology.
    Quaternary Arctic Ocean sea ice variations and deep water isolation times2010In: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 29, no 25-26, p. 3430-3441Article in journal (Refereed)
    Abstract [en]

    A short sediment core retrieved from a local depression forming an intra basin on the Lomonosov Ridge during the Healy-Oden Trans-Arctic Expedition 2005 (HOTRAX) contains a record of the Marine Isotope Stages (MIS) 1-3 showing exceptionally high abundances of calcareous microfossils during parts of MIS 3. Based on radiocarbon dating, linear sedimentation rates of 7-9 cm/ka persist during the last deglaciation. Last Glacial Maximum (LGM) is partly characterized by a hiatus. Planktic foraminiferal abundance variations of Neogloboquadrina pachyderma sinistral and calcareous nannofossils reflect changes in Arctic Ocean summer sea ice coverage and probably inflow of subpolar North Atlantic water. Marine reservoir ages of 1400 years or more, at least during the last deglaciation, seem plausible from calibration of the radiocarbon ages using modeled reservoir corrections from previous studies in combination with the microfossil abundance record of the studied core. Paired benthic-planktic radiocarbon dated foraminiferal samples indicate a slow decrease in age difference between surface and bottom waters from the Late Glacial to the Holocene, suggesting circulation and ventilation changes.

  • 2.
    Hanslik, Daniela
    et al.
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry. Marin geovetenskap.
    Jakobsson, Martin
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry. Marin geovetenskap.
    Backmann, Jan
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry. Marin geovetenskap.
    Sellén, Emma
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry. Marin geovetenskap.
    Polyak, Leonid
    Late Pleistocene and Holocene benthic and planktonic foraminifera from the central Lomonosov Ridge2007In: First Conference on Arctic Palaeoclimate and its Extremes (APEX), 2007Conference paper (Other academic)
    Abstract [en]

    Presently available bathymetric charts show that the area between about 88°15’–89°N and 140°–180°E of the Lomonosov Ridge is characterized by a >1000 m deep depression in the ridge morphology forming a local "intra basin". During the 2005 Beringia/Healy-Oden Trans-Arctic EXpedition (HOTRAX), a detailed investigation of this part of the Lomonosov Ridge was conducted including multibeam bathymetric mapping, subbottom profiling, hydrographic measurements and sediment coring (Darby et al., 2005). The subbottom profiles reveal an expanded sediment stratigraphy in the intra basin suggesting that the area have acted as a local sediment trap with higher sediment accumulation rates compared to the 1000 m shallower ridge crest (Björk et al., in press). Core HLY0503-18JPC, investigated in this study, was retrieved at 2598 m water depth from the floor of the intra basin. The top 68 cm of this 12 m long sediment core contain abundant calcareous nanno- and microfossils. For this study, the content of benthic and planktonic foraminifera was quantified. The number of specimens per gram sediment showed several major peaks and valleys. Peak abundances of benthic and planktonic foraminifera coincide well with each other. The largest peak occurs near the base of this 68 cm long calcareous-rich sequence. All calcareous microfossils are well preserved, showing no signs of dissolution in the larger grain size fraction (>150 m). Assemblage analyses of four samples, of the size fraction >150 m, show a dominant abundance of Neogloboquadrina pachyderma (sinistral), accounting for up to 99% of the assemblage. There is no complete age model yet established for core HLY0503-18JPC, although 14C dating made on tube worms and bryozoan mats show ages of 35.200 ± 1500 (radiocarbon yrs) at 28-29 cm core depth and 32.800 ± 1500 (radiocarbon yrs) at 39 cm indicating sedimentation rates of about 1 cm/kyr. These 14C ages are in stark contrast to the nannofossil stratigraphy where the most nannofossil rich samples found between 42 and 56 cm suggest a Holocene age (Fornaciari et al., 2006) implying several times higher sedimentation rates. Additional 14C dating will be carried out on planktonic and benthic foraminifera as a next step in this study.

  • 3.
    Jakobsson, Martin
    et al.
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Darby, Dennis
    Polyak, Leonid
    Eriksson, Björn
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry. Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Hanslik, Daniela
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Hell, Benjamin
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Karasti, Markus
    Löwemark, Ludvig
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Sellén, Emma
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Sjöö, Carin
    Wallin, Åsa
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Lomonosov Ridge off Greenland (LOMROG) 2007: Coring and high-resolution geophysical mapping2008Report (Other academic)
  • 4.
    Jakobsson, Martin
    et al.
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Mayer, L.A.
    Scientific Party, LOMROG
    Scientific Party, Healy
    Sellén, Emma
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Hanslik, Daniela
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Eriksson, Björn
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Löwemark, Ludvig
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Wallin, Åsa
    Glaciogenic bedforms on the Chukchi Borderland, Morris Jesup Rise and Yermak Plateau: three prolongations of the Arctic Ocean continental margin2008In: EOS Transactions, American Geophysical Union, v. 89(53): Fall Meet. Suppl.,, 2008, p. Abstract C14A-05Conference paper (Other academic)
  • 5.
    Jakobsson, Martin
    et al.
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Scientific Party, LOMROG
    Sellén, Emma
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Hanslik, Daniela
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Eriksson, Björn
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Löwemark, Ludvig
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Wallin, Åsa
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Lomonosov Ridge off Greenland 2007 (LOMROG): Geophysical mapping and coring for the Arctic glacial and sea ice history2007In: First Conference on Arctic Palaeoclimate and its Extremes (APEX): The Royal Swedish Academy of Sciences, 2007, p. March 28-29Conference paper (Other academic)
  • 6. Lovlie, R
    et al.
    Jakobsson, Martin
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Wang, Y
    Wallin, Åsa
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Sellén, Emma
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Polyak, L
    Magnetic Correlation and Chronology of Sediment-cores (HOTRAX) From the Alpha Ridge and Lomonosov Ridge: Preliminary Results and Some Questions2006In: EOS Transactions, American Geophysical Union, v. 87(52): Fall Meet. Suppl.,, 2006, p. Abstract OS53B-1109Conference paper (Other academic)
  • 7.
    O'Regan, Matthew
    et al.
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Sellén, Emma
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Jakobsson, Martin
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Predictive relationships betweenbulk density and grain size in Pleistocene sediments from the Lomonosov RidgeManuscript (preprint) (Other academic)
  • 8. Polyak, L
    et al.
    Scientific Party, HOTRAX
    Jakobsson, Martin
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Sellén, Emma
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Wallin, Åsa
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Approaches to investigating warm intervals in sedimentary records from the central Arctic Ocean based on HOTRAX'05 materials2007In: First Conference on Arctic Palaeoclimate and its Extremes (APEX): The Royal Swedish Academy of Sciences, 2007, p. March 28-29Conference paper (Other academic)
  • 9.
    Sellén, Emma
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry. Marin geovetenskap.
    Problems of stratigraphic correlation across the Arctic Ocean2007Licentiate thesis, monograph (Other academic)
    Abstract [en]

    Published articles on Arctic Ocean sedimentation rates generally falls into two categories; one suggesting mm/ka-scale sedimentation rates in the Amerasian Basin and the other cm/ka-scale rates in the Eurasian Basin. This is due to the interpretation of the first measured paleomagnetic polarity change in sediment cores as either the Brunhes-Matuyama (781 ka) reversal or as the short time magnetic excursion, Biwa II (220 ka) within the Brunhes Chron. The paleoclimatological and paleoceanographical interpretations will be greatly affected depending on which age model is applied.

    A “standard” lithostratigraphy was developed in 1980 for cores from the Alpha-Mendeleev Ridge in the Amerasian Basin. An age model was established for this lithostratigraphic model, based on the assumption that the Brunhes-Matuyama reversal boundary was correctly identified in the investigated cores. In this thesis I have tested if this “standard” lithostratigraphy is possible to apply to cores retrieved from the Lomonosov Ridge. The purpose has been to evaluate the two age model scenarios and the difference in sediment accumulation rates between the Amerasian and Eurasian Basins. The study is based on core-to-core correlations using averaged sedimentological proxies (paleomagnetism, grain size, lithostratigraphy, sediment color and foraminiferal abundance) from a selected set of Alpha Ridge cores that were used to establish the “standard” lithostratigraphic model, and the same set of published proxies for a selected set of Lomonosov Ridge cores. In addition, the coarse fraction, foraminifera abundance, and magnetic susceptibility have been analyzed for cores taken on the Alpha Ridge and the Lomonosov Ridge during the Healy-Oden Trans-Arctic Expedition (HOTRAX) in 2005.

    The results suggest that it is not possible to establish a common lithostratigraphy throughout the entire Arctic Ocean as the Amerasian Basin and the Eurasian Basin have different depositional environments. Consequently, the “standard” lithostratigraphy can only be applied to the central Amerasian Basin. The paleomagnetic polarity record, however, can be correlated between cores from the Amerasian and Eurasian Basin, indicating that the large apparent differences in sedimentation rates mainly is an artifact from different interpretations. Correlations among the HOTRAX cores using magnetic susceptibility suggest that cores from the Alpha-Mendeleev Ridge in the Amerasian Basin are possible to correlate over 550 km. Finally, grain size variations in HOTRAX core HLY0503-18JPC retrieved from a local depression in the Lomonosov Ridge can be linked to previously studied key cores from the Lomonosov Ridge crest.

  • 10.
    Sellén, Emma
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Quaternary paleoceanography of the Arctic Ocean: A study of sediment stratigraphy and physical properties2009Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    A Quaternary perspective on the paleoceanographic evolution of the central Arctic Ocean has been obtained in this PhD thesis by studying sediment cores from all of the Arctic’s major submarine ridges and plateaus. The included cores were mainly recovered during the Healy-Oden Trans-Arctic expedition in 2005 and the Lomonosov Ridge off Greenland expedition in 2007. One of the main thesis objectives is to establish whether different sediment depositional regimes prevailed in different parts of the central Arctic Ocean during the Quaternary and, if so, establish general sedimentation rates for these regimes. This was approached by dating key cores using the decay of the cosmogenic isotopes 10Be and 14C, and through stratigraphic core-to-core correlation using sediment physical properties. However, the Arctic Ocean sea ice complicated the use of 10Be for dating because a solid sea ice cover prevents the 10Be isotopes from reaching the seafloor, resulting in too old ages. Dating using 14C is also complicated due to uncertain marine reservoir age corrections in the central Arctic Ocean. The core-to-core correlations show five areas with different depositional regimes; the northern Mendeleev Ridge and Alpha Ridge, southern Mendeleev Ridge, Morris Jesup Rise, Lomonosov Ridge and Yermak Plateau, listed in the order of increasing sedimentation rates from ~0.5cm/ka to ~4.8 cm/ka. A detailed study of the relationship between sediment bulk density and grain sizes suggests a strong link between variations in clay abundance and bulk density. Grain size analysis of a Lomonosov Ridge core show that fine silt and clay dominates the interglacials, possibly due to increased suspension freezing of these size fractions into sea ice and/or nepheloid transport. Sediments younger than the marine isotope stage (MIS) 7 generally contain more coarse silt, attributed to a regime shift during the Quaternary with increased iceberg transport into the central Arctic Ocean from MIS 6 and onwards.

  • 11.
    Sellén, Emma
    et al.
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry. Marin geovetenskap.
    Jakobsson, Martin
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry. Marin geovetenskap.
    Correlating the Pleistocene sediment stratigraphy across the Arctic Ocean2008In: AGU, Fall Meeting 2008, 2008Conference paper (Other academic)
  • 12.
    Sellén, Emma
    et al.
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Jakobsson, Martin
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Pleistocene type stratigraphies from different regions of the Arctic Ocean2009In: Arctic Palaeoclimate and its EXtremes- beyond the frontier: Third International Conference and WorkshopCopenhagen, March 31st - April 3rd, 2009, 2009, p. 70-Conference paper (Refereed)
  • 13.
    Sellén, Emma
    et al.
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry. Marin geovetenskap.
    Jakobsson, Martin
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry. Marin geovetenskap.
    Backman, Jan
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry. Marin geovetenskap.
    Linking Stratigraphy on the Lomonosov Ridge With Standard Lithological Units of the Amerasian Basin, Arctic Ocean2006In: AGU Fall Meeting 2006Eos Trans. AGU, 87(52), Fall Meeting, 2006Conference paper (Other academic)
    Abstract [en]

    AB: Short sediment cores taken from the ice-island T3 between 1963 and 1973 were used by Clark et al. (1980) to establish a lithological classification for the Amerasian Basin in the Arctic Ocean. Over a 310 cm long stratigraphic section, synthesized from 67 cores, 13 units were recognized and labeled A to M. This lithostratigraphic model has since been applied to correlate sediment cores over large distances on the Amerasian side, i.e., between cores on the Alpha Ridge, the Northwind Ridge and the Mendeleev Ridge. The chronostratigraphy for this lithostratigraphic model was developed by the identification of the Brunhes- Matuyama paleomagnetic reversal boundary (781 ka) and the assumption of linear sedimentation rates in the synthesized lithologic model. However, recent studies have shown that this measured magnetic polarity change rather represents a short-time excursion within the Brunhes chron, implying an order of magnitude higher sedimentation rates than originally assumed. We have investigated whether it is possible to link the lithostratigraphy from the Alpha Ridge to cores taken on the Lomonosov Ridge which, in turn, have been linked to cores in the Eurasian Basin. The cores selected for this comparison were cores B-8 and B-24 from the LOREX ‘79 ice island drift expedition, core PS2185-6 from the ARK-VIII/3 expedition of 1991 and core 96/12- 1pc from the Arctic Ocean 96 expedition. Averaged sedimentary proxies (paleomagnetism, grain size, and microfossil abundance) from selected sets of T3 cores and published by Clark et al. (1980), have been used here to correlate the included Lomonosov Ridge cores. A lithostratigraphic connection between the Amerasian Basin and the Lomonosov Ridge stratigraphies was partly successfully established, although Clark's lithostratigraphic units A to M could not be recognized in the Lomonosov Ridge. Nevertheless, the established correlations clearly show that the Amerasian Basin is characterized by lower sedimentation rates when compared to the rates obtained from the Lomonosov Ridge and the Eurasian Basin , but that the Amerasian Basin rate are not as low as Clark and others previously suggested.

  • 14.
    Sellén, Emma
    et al.
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Jakobsson, Martin
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Backman, Jan
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Sedimentary regimes in Arctic’s Amerasian and Eurasian basins: Clues to differences in sedimentation rates2008In: Global and Planetary Change, ISSN 0921-8181, E-ISSN 1872-6364, Vol. 61, no 3-4, p. 275-284Article in journal (Refereed)
    Abstract [sv]

    A standard lithostratigraphic model based on cores retrieved 1963–1973 from the ice island T-3 was developed by Clark et al. (1980) for the Amerasian Basin of the Arctic Ocean. We have investigated whether or not it is possible to apply this lithostratigraphy to cores from the Lomonosov Ridge, which can be correlated to Eurasian Basin cores, for the purpose of correlating the Amerasian and Eurasian stratigraphies. Published averaged

    sedimentary proxies from a selected set of T-3 cores are used to correlate with the identical published proxies for the included Lomonosov Ridge cores. The standard lithostratigraphic classification could not be applied to the Lomonosov Ridge cores,

    which is interpreted to result from differences in sedimentary regimes in the Amerasian and Eurasian Basins. These differences also apply to the barrier between the two basins, the Lomonosov Ridge. The general sedimentation rates are three to four times lower in the Amerasian Basin than in the Eurasian Basin if the first down-core paleomagnetic inclination change is used to correlate between the two basins whereas correlation based on sediment coarse fraction suggests only two times lower rates in the Amerasian Basin.

  • 15.
    Sellén, Emma
    et al.
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry. Marin geovetenskap.
    Jakobsson, Martin
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry. Marin geovetenskap.
    Backman, Jan
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry. Marin geovetenskap.
    Hanslik, Daniela
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry. Marin geovetenskap.
    Linking stratigraphy on the Lomonosov Ridge with standard lithological units of the Amerasia Basin2007In: First Conference on Arctic Palaeoclimate and its Extremes (APEX), 2007Conference paper (Other academic)
    Abstract [en]

    A lithological classification has been established by Clark et al. (1980), based on cores primarily from the Alpha Ridge, on the Amerasian side of the Arctic Ocean. It has since been applied to correlate sediment cores over large distances, mainly in the Amerasian Basin (Alpha Ridge, Northwind Ridge and Mendeleev Ridge), but also on the Lomonosov Ridge. Over a 310 cm long stratigraphic section, synthesized from 67 cores, 13 units were recognized and named A to M by Clark et al. (1980). An age model was developed for this lithostratigraphy that relied on the identification of the Brunhes-Matuyama paleomagnetic reversal boundary (781 000 years; Lourens et al., 2004) and the assumption of a linear sedimentation rate. However, recent studies have shown that this measured magnetic polarity change represents instead a short-time excursion within the Brunhes chron. We have investigated if it is possible to infer the lithostratigraphy (Units A-M) from the Amerasian Arctic Ocean in cores from the Lomonosov Ridge that in turn have been correlated to cores in the Eurasian Basin. The cores selected for this study were B-8 and B-24 from the LOREX ‘79 ice island drift expedition (Morris et al., 1985), PS2185-6 from the Arctic’91: ARK-VIII/3 expedition with R/V Polarstern (Spielhagen et al., 1997) and 96/12-1pc from the Arctic Ocean 96 expedition with I/B Oden (Jakobsson et al., 2001). Averaged sedimentary proxies (paleomagnetism, grain size, microfossil abundance and lithostratigraphy) from a selected set of T3 cores have been published by Clark et al. (1980) and these have been used in this study to link with the same published proxies for the included Lomonosov Ridge cores. The Lomonosov Ridge cores PS 2185-6 and 96/12-1pc have previously been correlated using paleomagnetic polarity reversals and grain size (Jakobsson et al., 2001) and the lithostratigraphic units A-M were previously inferred in core B-8 by Morris et al. (1985). In our study, the lithostratigraphic units (A to M) could not be inferred in PS2185-6 or 96/12-1pc. However, correlations between the Lomonosov Ridge and Amerasian Basin T3 cores appear to be possible using paleomagnetic and grain size data. More detailed data from the Alpha Ridge sediment stratigraphy would probably enhance our first attempted correlations using these proxies. An additional correlation between the Lomonosov Ridge cores PS2185-6 and 96/12-1pc and piston core HLY0503-18JPC, retrieved from the Lomonosov Ridge during the HOTRAX expedition (2005) with USCGC Healy, has also been made. The grain size data from core HLY0503-18JPC could easily be correlated to the older cores on the Lomonosov Ridge and will hopefully be a good link to the HOTRAX cores taken on the Alpha-Mendeleev Ridge. The correlations made here, imply higher sedimentation rates on the Lomonosov Ridge than on the Alpha Ridge, but not as much higher as previously thought. By establishing a new reliable age model for the Arctic Ocean, earlier studies on Amerasian cores could be viewed from a completely different chronostratigraphic perspective.

  • 16.
    Sellén, Emma
    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, Martin
    IFM-Geomar, Leibniz Institute of Marine Sciences.
    Kubik, Peter
    Paul Scherrer Institute, ETH Zurich.
    Pleistocene variations of beryllium isotopes in central Arctic Ocean sediment cores2009In: Global and Planetary Change, ISSN 0921-8181, E-ISSN 1872-6364, Vol. 68, no 1-2, p. 38-47Article in journal (Refereed)
    Abstract [en]

    Neogene marine sediments can be dated via decay of the cosmogenic radionuclide 10Be. Two cores from theAlpha and Mendeleev Ridges in the Arctic Ocean have been analyzed for seawater-derived beryllium (Be)isotopes in order to date the sediments and to calculate sedimentation rates. The decrease of 10Be concentrationin the cores was used to calculate first order sedimentation rates. To eliminate the dilution effect of berylliumcaused by short-term changes in sedimentation rate and grain size, the 10Be concentrationswere normalized tothe terrigenous stable isotope 9Be determined in the same sample aliquot. The measured 10Be concentrationsyield low average sedimentation rates for the Alpha and Mendeleev Ridges of 2.3 mm ka−1 and 2.7 mm ka−1,respectively. Sedimentation rates calculated from the 10Be/9Be ratios result in similarly low values, rangingfrom 0.2 to 6.8 mm ka−1 for the Alpha Ridge core and from 1.9 to 6.9 mm ka−1 for the Mendeleev Ridge core.However, amino acid racemization dating for the past 150 ka of a core adjacent to the Mendeleev Ridge corestudied here indicates significantly higher sedimentation rates than calculated from the downcore decreaseof 10Be and 10Be/9Be. If such higher rates also prevailed at the locations of our cores, for which there isbiostratigraphic evidence, either the supply of 10Be was much lower than assumed or that of 9Be was muchhigher. This could imply that the signature of the deepwaters in this part of the Arctic Ocean compared to todaywas largely different for most of the past approximately one million years with a significantly lower 10Be/9Beratio. Our study also addresses the variability of beryllium isotopes in sediment cores across the Arctic Oceanthrough a comparison of previously published results. Calculated 10Be fluxes reveal low values in the AmerasianBasin and highest values in the Eurasian Basin, near the Fram Strait. The decrease of Be isotopes in the twostudied Amerasian Basin cores may thus have been caused by environmental factors such as significantlyreduced inflow of Atlantic waters in the past, reduced input of 10Be and/or increased input of 9Be from theshelves, combined with a more efficient sea ice shielding in this part of the Arctic Ocean.

  • 17.
    Sellén, Emma
    et al.
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry. Marin geovetenskap.
    Jakobsson, Martin
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry. Marin geovetenskap.
    Kubik, Peter
    Frank, Martin
    Beryllium Isotope Dating of Sediment Cores From the Alpha Ridge, Arctic Ocean2007In: Eos, Trans. AGU, 88(52), Fall Meeting, 2007Conference paper (Other academic)
    Abstract [en]

    AB: Poor preservation of biogenic calcium carbonate and biosilica in Arctic Ocean sediments has led to large problems regarding the establishment of a reliable chronostratigraphy. There are currently two differing sedimentation rate scenarios proposed for the Arctic Ocean. The first suggests sedimentation rates on the order of mm/ka and is based on cores from the Amerasian Basin, whereas the second suggests sedimentation rates on the order of cm/ka mainly derived from Eurasian Basin cores. Here we present dating results from cores HLY0503-09JPC and HLY0503-14JPC retrieved from the Alpha Ridge during the Healy-Oden Trans-Arctic Expedition 2005 (HOTRAX). These cores have been analyzed for seawater-derived beryllium (Be) isotopes in order to establish a chronostratigraphy. The isotopes 10Be and 9Be were extracted simultaneously from sample aliquots by using a leaching procedure. The decrease of 10Be concentration (half-life = 1.51 Million years) with depth in core provides first order sedimentation rates for the sampled cores. To eliminate the dilution effect of beryllium caused by short-term changes in sedimentation rate and grain size variability, the 10Be concentration was normalized to the stable isotope 9Be. The preliminary results show low downcore 10Be concentrations in both cores from the Alpha Ridge. Plotting 10Be against depth suggests an average sedimentation rate of ~2.9 mm/ka for core HLY0503-09JPC and ~2.3 mm/ka for HLY0503- 14JPC. The calculated 10Be/9Be ratios point to even lower average sedimentation rates of ~1.9 mm/ka for core HLY0503-09JPC and ~1.6 mm/ka for HLY0503-14JPC. However, core HLY0503-14JPC shows a pronounced variability of the 10Be concentration as well as for the 10Be/9Be ratio, which results in a large uncertainty of the calculated sedimentation rates. The 10Be concentrations for this core will be compared with the grain size record in order to reduce the scatter of the data. The preliminary beryllium isotope chronostratigraphy supports lower sedimentation rates in the Amerasian Basin compared to the Eurasian Basin. A long-term solid sea ice cover in the Beaufort Gyre may explain the low 10Be concentrations, but does not explain the calculated low sedimentation rates.

  • 18.
    Sellén, Emma
    et al.
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry. Marin geovetenskap.
    Jakobsson, Martin
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry. Marin geovetenskap.
    Kubik, Peter
    Frank, Martin
    Beryllium isotope variations in sediment cores from the Alpha Ridge, Arctic Ocean2008In: Arctic Palaeoclimate and its Extremes (APEX): second international conference and workshop, 2008, p. 92-Conference paper (Other academic)
    Abstract [en]

    The Healy-Oden Trans-Arctic Expedition 2005 (HOTRAX) recovered cores along a transect across the Arctic Ocean. Here we present results from measurements of seawater-derived beryllium isotopes in cores HLY0503-09JPC and HLY0503-14JPC from the Alpha-Mendeleev Ridge. The intention of measuring beryllium (Be) isotopes is to establish a chronostratigraphy as the decrease of 10Be concentration (half-life = 1.51 Million years) with depth in the cores may provide first order sedimentation rates. The isotopes 10Be and 9Be were extracted simultaneously from sample aliquots by using a leaching procedure. To eliminate the dilution effect of beryllium caused by short-term changes in sedimentation rate and grain size variability, the 10Be concentration was normalized to the stable isotope 9Be. The results show low downcore 10Be concentrations and subsequently sedimentation rates on the order of mm/ka in both cores from the Alpha Ridge. However, we note two indications suggesting that our calculated sedimentation rates from the beryllium results may not be valid and requires further analysis: 1) the decrease of 10Be down core does not follow a well defined trend; 2) a comparison with preliminary results from nannofossil studies of cores HLY0503-14JPC and HLY0503-08JPC located nearby HLY0503-09JPC indicates much higher sedimentation rates than we obtained from the 10Be data (Backman and Fornaciari pers. comm.). The pronounced decrease of 10Be with core depth may imply a stronger effect of sea ice shielding of atmospheric inputs, whereas the 9Be increase with depth may point to a stronger continental input of 9Be.

  • 19.
    Sellén, Emma
    et al.
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry. Marin geovetenskap.
    Jakobsson, Martin
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry. Marin geovetenskap.
    Kubik, Peter W.
    Frank, Martin
    Beryllium isotope concentrations in sediment cores from Arctic Ocean2008In: IGC, Oslo 2008, 2008Conference paper (Other academic)
  • 20.
    Sellén, Emma
    et al.
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    O'Regan, Matthew
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Grain size distributions and ice-rafting in thecentral Arctic Ocean – a million year perspectiveManuscript (preprint) (Other academic)
  • 21.
    Sellén, Emma
    et al.
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    O'Regan, Matthew
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Jakobsson, Martin
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Spatial and temporal ArcticOcean depositional regimes: a key to the evolution of ice and current patterns2010In: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 29, no 25-26, p. 3644-3664Article in journal (Refereed)
    Abstract [en]

    Sediment physical properties measured in cores from all the major ridges and plateaus in the central Arctic Ocean were studied in order to analyze the spatial and temporal consistency of sediment depositional regimes during the Quaternary. In total, six physiographically distinct areas are outlined. In five of these, cores can be correlated over large distances through characteristic patterns in sediment physical properties. These areas are (1) the southern Mendeleev Ridge, (2) the northern Mendeleev Ridge and Alpha Ridge, (3) the Lomonosov Ridge, (4) the Morris Jesup Rise and (5) the Yermak Plateau. Averaged downhole patterns in magnetic susceptibility, bulk density and lithostratigraphy were compiled to establish a composite stratigraphy for each area. In the sixth physiographic area, the Chukchi Borderland, repeated ice-grounding during recent glacial periods complicates the stratigraphy and prevents the compilation of a composite stratigraphy using the studied material. By utilizing published age models for the studied cores we are able to show that the northern Mendeleev Ridge and Alpha Ridge have the lowest average late Quaternary sedimentation rates, while intermediate sedimentation rates prevail on the southern Mendeleev Ridge and the Morris Jesup Rise. The second highest sedimentation rate is observed on the Lomonosov Ridge, whereas the average sedimentation rate on the Yermak Plateau is more than twice as high. The close correlation of physical properties within each area suggests uniform variations in sediment transport through time, at least throughout the later part of the Quaternary. The unique stratigraphic characteristics within each area is the product of similar past depositional regimes and are key for furthering our understanding of the evolution of ice drift and current patterns in the central Arctic Ocean.

1 - 21 of 21
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