ALBERT

Description: The methods of data collection, processing, and assessment of the quality of the results ofa survey conducted at the Southern Ionian Sea off the Messinian Peninsula, Greece are presented.Data were collected by the GEBCO-Nippon Foundation Alumni Team, competing in the Shell OceanDiscovery XPRIZE, during the Final Round of the competition. Data acquisition was conductedby the means of unmanned vehicles only. The mapping system was composed of a single deepwater AUV (Autonomous Underwater Vehicle), equipped with a high-resolution synthetic aperturesonar HISAS 1032 and multibeam echosounder EM 2040, partnered with a USV (Unmanned SurfaceVessel). The USV provided positioning data as well as mapping the seafloor from the surface, usinga hull-mounted multibeam echosounder EM 304. Bathymetry and imagery data were collected for24 h and then processed for 48 h, with the extensive use of cloud technology and automatic dataprocessing. Finally, all datasets were combined to generate a 5-m resolution bathymetric surface, as an example of the deep-water mapping capabilities of the unmanned vehicles’ cooperation andtheir sensors’ integration.

Description: This study is focused on sediment cores PS72/344-1 (boxcorer) and PS72/344-3 (kastenlot) recovered from the western flank of the Southern Mendeleev Ridge during the ARKXXIII/3 (Arctic-2008) Expedition of RV ‘Polarstern’. The composite core PS 72/344 represents an undisturbed sedimentary sequence with the length of 8 m, scanned onboard for physical properties and then sampled at every 10 cm. In the present research we use various sedimentary proxies such as lithology (sediment colour and ice-rafted debris contents), physical properties (density, magnetic susceptibility, p-wave velocity, shear strength measurements), mineralogy (bulk mineralogical composition), geochemistry (total organic carbon contents, C/N ratio) and biostratigraphy (distribution of planktonic and benthic foraminifers) to reconstruct paleoceonographical conditions in the Siberian part of the Amerasian Basin during the Late Quaternary times. The age model for core PS72/344 is constrained by correlation to the stratigraphy developed for the Mendeleev Ridge (Polyak et al., 2004; Adler et al., 2009). For correlation we mainly used lithology (color cycles, IRD contents) and detrital carbonate (dolomite) contents as well as distribution of forams. According to the proposed tratigraphical framework, the PS72/344 record comprises marine isotope stages (MIS) 5 to 1. The PS72/344 proxy record demonstrates that sedimentary environments at the East Siberian Sea continental margin were strongly variable during late Quaternary times. Sedimentation patterns show that based on the proxy data we can suggest that there were three major scenarios of transportation and deposition of terrigenous material derived from the adjacent shelves, generally controlled by the extension of sea-ice cover and iceberg discharge. Using this framework of general paleoenvironmental scenarios in the studied area, we discuss the variable paleoceanographic regimes in the Arctic Ocean related to the history of glaciations in Northern Euarasia and North America during late Quaternary times (MIS 5 to present) using published data on sediment cores from the Arctic Basin. Severe ice conditions in the Arctic Ocean consistent with onsets of land-based glaciations in Northern Eurasia and North America were reconstructed for early and mid MIS 5 (two glacial/interglacial cycles), substage 5a, the MIS 5a/4 transition and MIS 2. Enhanced deposition of ice-rafted debris took place in early MIS 5, during the MIS 5a/5 transition, in MIS 4, late MIS 3. Interglacial periods correspond to MIS 5 (not enough dating points), the transitions MIS 5/5a, MIS 5a/4, MIS 3/2. The proposed age model is still preliminary that limits the paleonvironmental reconstructions and more data should be obtained during further studies.

Description: The morphometric and petrographic characteristics of the coarse-grained clasts (〉 1 cm) sampled from the sediments of the Amerasian Basin, Central Arctic Ocean, were studied. Most of the clasts are represented by dolomites (46,4%), sandstones (22,8%) and limestones (19,8%); the amount of other rocks fragments (chert, shale, igneous) is about 10%. A variety of lithological types were identified among the studied rock fragments. Limestones and dolomitic limestones often contain fragments of fauna. The majority of clasts is poorly rounded and characterized by a wide variety of shapes. More than half of the studied clasts have a size of 1-2 cm, a quarter - 2-3 cm, and larger clasts only occur in insignificant amounts. Geophysical surveys across the sampling sites showed a lack of bedrock outcrops, so the studied coarse-grained clasts are not of local origin. It is concluded that they were predominantly delivered from the Canadian Arctic Archipelago (likely from the platform area, e.g., Victoria Island), mainly due to iceberg rafting during deglaciation periods. The maximum possible contribution of the clasts from the Siberian sources is less than 23%. Distribution of the coarse-grained clasts argues for the existence of a quite stable ice drift path in the past, which is similar to the modern Beaufort Gyre.

Description: The late Pleistocene history of the Arctic comprised cyclical changes in the extension of land-based ice sheets and sea-ice cover that affected sedimentary environments in the Arctic Ocean. This PhD thesis focuses on sediment records from the Mendeleev Ridge spanning the last 200 ka. Over this time period, variable sedimentation patterns were described and possible implications for reconstruction of glacial/interglacial paleoenvironments were provided. One of the main goals of this study was to identify mineralogical and inorganic-geochemical tracers in marine sediments that could be used for discrimination of sediment provenance and consequently for reconstruction of sediment pathways. In Chapter 5 possibility of provenance discrimination based on bulk mineral composition of surface sediments is discussed. This study compares the results from two software packages, RockJock and QUAX, for quantification of mineral assemblages from the X-Ray diffraction (XRD) data. Comparison with published overviews on the mineral composition of Arctic Ocean surface sediments demonstrates that in provenance studies bulk mineral composition of sediments should be used along with other indicators for source areas. In Chapter 6 stratigraphy for 4 cores recovered along a transect at ca. 77°36’N across the Mendeleev Ridge during the ARK-XXIII/3 Expedition of RV “Polarstern” was revised using paleomagnetic parameters (inclination and paleointensity) supported by AMS 14C datings and micropaleontological evidences. Changes of sedimentary settings from the Mendeleev Ridge towards the East Siberian Sea margin were documented for the last 200 ka. As evidenced by grain-size and mineralogical data, there were several events of intensified sediment discharge at the Mendeleev Ridge possibly linked to paleoenvironmental changes in North America and Eurasia. Chapter 7 describes provenance investigations using the isotopic composition of radiogenic lead (Pb) and neodymium (Nd) of detrital fraction in core PS72/340-5 at the eastern flank of the Mendeleev Ridge. Obtained results were compared with marine surface sediment data and values for the circum-Arctic subaerial provinces. Late Quaternary sediment supply variability was analyzed using the mixing model constrained by two tracers: 207Pb/206Pb and #Nd. Our results confirm that over the last 200 ka dolomite-rich pink layers at the southern Mendeleev Ridge were deposited during events associated with intensified iceberg transport from North America. On the whole, sedimentation was mostly controlled by terrigenous input from the Chukchi and East Siberian Seas whereas sediment supply from the Laptev Sea area remained less important and relatively constant at the studied location.

Description: New sediment cores were recovered along two transects from the Canada Basin across the central Mendeleev Ridge towards the Makarov Basin and the Lomonosov Ridge in the Eurasian Arctic (northern transect along 80°30 N, southern transect along 77°30 N). Here, we present first results from Polarstern ARK-XXIII/3 expedition (Aug-Oct 2008). Based on the visual core description, Clarks standard lithological units A to M (CLARK et al. 1980) could also be clearly identified in sediment cores from the northern transect across Mendeleev Ridge. The content of sand-sized material, the prominent pink-white layers, and especially in the upper part of the records the distinct brown/beige colour cycles were considered to be the key sedimentary characteristics used for core correlation and for establishing a tentative age model. Based on this age model, the sediments recovered in cores from the southern transect are younger than Marine Isotope Stage (MIS) 8, whereas the cores from the northern transect also contain sediments probably significantly older than MIS 16. Average sedimentation rates for the time interval MIS 1 to 5 in cores from the northern transect reach values of 0.5-0.9 cm ky-1 (top Mendeleev Ridge and Canadian side), increasing to 1.9-2.4 cm ky-1 at the Makarov Basin side. Along the southern transect, sedimentation rates are significantly higher, reaching 4.2 to 〉6 cm ky-1. The most distinct pinkish intervals characterized by high numbers of dolomitic ice-rafted debris (IRD) are related to increased IRD supply due to disintegration of an extended Laurentide Ice Sheet during MIS 8 (/7), MIS 5d, and MIS 4/MIS 3. The sand-rich intervals and detrital-carbonate maxima found in the deeper part of the sediment sections from the northern transect may reflect events of IRD input due to disintegration events of the Laurentide Ice Sheet at the end of glacial MIS 8, 10, 12, and 16, a still speculative hypothesis that has to be approved by further studies. A diamicton with erosional structures at its base was identified on southern Mendeleev Ridge in water depths of 800-900 m, suggesting the impact of grounding ice masses during a glaciation older than MIS 5a. Future research of this unique new core material recovered during the Polarstern Expedition may help to answer key questions in Arctic Ocean stratigraphy/chronology to unravel the history of circum-Arctic glaciations.

Description: The Southern Ocean surrounding Antarctica is a region that is key to a range of climatic and oceanographic processes with worldwide effects, and is characterised by high biological productivity and biodiversity. Since 2013, the International Bathymetric Chart of the Southern Ocean (IBCSO) has represented the most comprehensive compilation of bathymetry for the Southern Ocean south of 60°S. Recently, the IBCSO Project has combined its efforts with the Nippon Foundation – GEBCO Seabed 2030 Project supporting the goal of mapping the world’s oceans by 2030. New datasets initiated a second version of IBCSO (IBCSO v2). This version extends to 50°S (covering approximately 2.4 times the area of seafloor of the previous version) including the gateways of the Antarctic Circumpolar Current and the Antarctic circumpolar frontal systems. Due to increased (multibeam) data coverage, IBCSO v2 significantly improves the overall representation of the Southern Ocean seafloor and resolves many submarine landforms in more detail. This makes IBCSO v2 the most authoritative seafloor map of the area south of 50°S.

Description: Dolomite-rich layers of distinct pinkish colour are used as lithostratigraphic markers in the Amerasian Basin of the Arctic Ocean. However, origin of dolomite in these sediment units has not been studied in detail. In this study, lead (Pb) and neodymium (Nd) isotope composition of detrital clay-size fraction from different lithofacies were investigated in core PS72/340-5 recovered at the eastern flank of the Mendeleev Ridge. Prior to the geochemical analyses, grain-size distribution was analyzed in order to minimize the grain-size effect on the provenance signature. For provenance discrimination, results of isotope measurements were compared with marine surface sediment data and values for the circum-Arctic subaerial provinces. Late Quaternary sediment supply variability was analyzed using the mixing model constrained by two tracers: 207Pb/206Pb and e-Nd. Variations of sediment isotopic composition are inferred to result from mixing of volcanic and plutonic components. Usage of Pb isotopic ratios alone does not allow distinction between these two types of sources. Results confirm that over the last estimated ca. 200 ka dolomite-rich pink layers at the Mendeleev Ridge were deposited during events probably associated with intensified iceberg transport from North America. In general, however, sedimentation was mostly controlled by terrigenous input from the Chukchi and East Siberian Seas, whereas sediment supply from the Laptev Sea area remained less important and relatively constant at the studied location.