Spatial and temporal Arctic Ocean depositional regimes: a key to the evolution of ice drift and current patterns

Abstract

a b s t r a c tSediment 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.

New insights on Arctic Quaternary climate variability from palaeo-records and numerical modelling

“…Clark, 1970) to the Brunhes/Matuyama boundary, which has a present inferred age of 780 ka (Lourens et al, 2004). Sellén et al (2010) point to the recent study of Channell and Xuan (2009), which shows that inclinations in Arctic Ocean cores may, in fact, not at all be related to the "real" established and dated paleomagnetic reversals and/or shorter duration magnetic excursions. Instead paleoceanographic conditions on a basin-wide scale in combination with relatively low sedimentation rates may have generated near bottom environments where oxidation processes caused titano-magnetities to transform into titano-maghematites and, during this diagenetic change, acquire a chemical remnant magnetization that is partially self reversed ).…”

“…Perhaps the most conspicuous of these markers is the first encountered prominent paleomagnetic inclination change, which occurs in the stratigraphy in all cores, from the southern part of the Mendeleev Ridge, across the Arctic Ocean and the Lomonosov Ridge to the Morris Jesup Rise. This inclination change occurs towards the end of MIS 7 according to the established chronostratigraphy by Sellén et al (2010), but was ascribed earlier (e.g. Clark, 1970) to the Brunhes/Matuyama boundary, which has a present inferred age of 780 ka (Lourens et al, 2004).…”

“…1). The first by Sellén et al (2010) is based on cores retrieved during the Healy-Oden Trans-Arctic Expedition (HOTRAX) 2005 and the Lomonosov Ridge off Greenland Expedition (LOMROG) 2007 (Fig. 1).…”

“…Instead paleoceanographic conditions on a basin-wide scale in combination with relatively low sedimentation rates may have generated near bottom environments where oxidation processes caused titano-magnetities to transform into titano-maghematites and, during this diagenetic change, acquire a chemical remnant magnetization that is partially self reversed ). This implies that even if the first prominent down-core inclination change does not represent one of the proper excursions, it may be a useful paleoceanographic marker, which according Sellén et al (2010) occurs in MIS 7.…”

“…This may be linked to the presence of extensive ice shelves Jakobsson et al, 2010) and overall cold oceanographic conditions during glacial periods preventing melt out and delivery of sediments. However, Sellén et al (2010) show in their study on spatial and temporal sediment depositional regimes in the Arctic Ocean that the MIS 6 glacial period, the period when the most extensive ice shelf is proposed to have existed , is particularly characterized by a prominent increase in coarse grain (>63 mm) material. Such an increase in coarse grains is also found in some regions for the subsequent glaciations.…”