Multiproxy investigation of the last 2,000 years BP marine paleoenvironmental record along the western Spitsbergen margin

A reconstruction of the last 2,000 years BP of environmental and oceanographic changes on the western margin of Spitsbergen was performed using a multidisciplinary approach including the fossil assemblages of diatoms, planktic and benthic foraminifera and calcareous nannofossils and the use of geochemistry (X-ray fluorescence spectroscopy, X-ray diffraction). We identified two warm periods (2,000–1,600 years BP and 1,300–700 years BP) that were associated with the Roman Warm Period and the Medieval Warm Period that alternate with colder oceanic conditions and sea ice coverage occurred during the Dark Ages (1,600–1,300 years BP) and the beginning of the Little Ice Age. During the Medieval Warm Period the occurrence of ice-rafted debris and Aulocoseira spp., a specific diatom genus commonly associated with continental freshwater, suggests significant runoff of meltwaters from local glaciers

Paleontological and sedimentological evidences in the Holocenic sedimentary record of the Bellsund Drift (Svalbard – Arctic)

The Arctic region represents a sensitive area to climatic variations. The Bellsund Drift is located in the Fram Strait area, between Greenland and Svalbard, and represents the only deep connection to the Arctic Ocean. In this strait occurs the interaction of two water masses, the warm Atlantic Water (AW) and the cold Arctic water (ArW). This interaction produces an important heat and mass exchange with the Arctic Ocean, influencing the climate in the entire Arctic region. During the EUROFLEETS-2 Cruise PREPARED on board the R/V G.O. Sars, June 2014, a Calypso piston core GS191-01PC (1647 m water depth), was collected in the Bellsund Drift area. The core contains a highresolution depositional sedimentary record of the last 20 kyr (Lucchi et al., 2014). For this work, we focused on the expanded Holocene sequence (more than 5 m-thick), defined using the age model constructed by Caricchi et al. (2019). Our study is based on the benthic and planktic foraminifera and grain size analysis. The millennial record of the Bellsund Drift indicates a progressive increase of the water temperature, due to the incoming of the warm Atlantic water and the decreasing extension of sea-ice, which retreat by melting, producing cold superficial water masses facilitating the incoming of the AW into the entire water column. The IRD input during the end of the Upper Pleistocene indicates diffuse sea-ice and cold conditions. Higher productivity and warmer conditions characterised the Early Holocene. A shift from warm to colder conditions occurred during the Mid Holocene, affecting the ocean productivity. The Late Holocene showed the prevalence of surface cold-water conditions related to the sea ice melting, determined by increased AW heat inflow to the Arctic

Paleoenviromental changes during the last 2 ka BP in the Eastern Side of Fram Strait.

Polar regions regulate the climate through the heat exchange between ocean and atmosphere, the sea ice formation or melting, and bottom water formation. Lately, the scientific community has been focusing on the study of the last 2000 years. This interval gives information about climate natural variability versus change induced by human activity. Moreover, the studies of environmental changes recorded in this period offer the possibility to understand how our climate may evolve in the near future. This study is focused on the last 2 ka BP and has the aim to understand the paleoenvironmental variations in the eastern side of Fram Strait, through multidisciplinary micropaleontological and sedimentological analyses, focussing on the diatom assemblages. Two long Calypso cores GS191-01 PC (19.68 m) and GS191-02 PC (17.37 m) were collected on the Bellsund and Isfjorden Drift, during the expedition of RV G.O. Sars (5th–15th June 2014), in the framework of the project Eurofleets-2 PREPARED. Here we present the study of the first 80 cm for core GS191-01PC and the first 18 cm for core GS191-02 PC corresponding to the last 2 ka years BP. The investigated sedimentary sequence is dominated by muddy, bioturbated sediments with very rare/sparse IRD (Ice Rafted Debris). The Diatom assemblage was analysed every 2-cm, corresponding to a resolution of 30 years for GS191-01PC and at every 1-cm in core GS191-02PC, corresponding to a resolution of 126 year. On the basis of the age model proposed by Caricchi et al. (2019), the multi-proxy analyses on the diatoms and foraminifera assemblages, and sedimentological data, allowed us to distinguish in the record four different climatic periods indicated as Units. Unit A (2000 - 1500 cal yr BP) is the older, and indicates relatively warm conditions, suggesting the influence of warm water with a cooling period between between 1800 to 1700 cal yr BP, characterized by increased sea ice coverage and the presence of cold water masses. In unit B (1500 - 1300 cal yr BP) is period of cooler conditions compared with the previous one, and it is characterized by the presence of extended sea ice and a minor inflow of the warm water. Unit C (1300- 700 cal yr BP) records a warming surface water with presence of freshwater of continentally origin. Unit C ends with the worsening of climatic conditions characterized by a progressive cooling. Unit D (700 cal yr BP to recent) represents a cooling period characterized by extended sea ice coverage and an increased distribution of cold-water taxa

Preliminary results of a micropaleontological study of a sediment core collected on the Bellsund Drift (Svalbard): the last 10 ka.

Diatoms are one of the major phytoplankton groups blooming in cold and nutrient-rich regions. They are sensitive to minute changes in environmental parameters (e.g. temperature, salinity etc.) therefore are widely used to study Quaternary oceanographic and climatic evolution (Leventer et al., 2010; Crosta, 2011). In the Arctic area diatoms tend to be less silicified and, therefore, more easily dissolved in the sediments (Leventer et al., 2010; Crosta, 2011). In this work, we present the results of the combined study of diatom and foraminifera assemblages together with sedimentological characteristics of the long Calypso core GS191-01PC collected on the Bellsund Drift (South-western margin of Spitzbergen) during the expedition of the RV G.O.Sars (5-15 June 2014), in the framework of the Project Eurofleets-2 PREPARED. The study focuses on the last 10 ka with the final aim to understand the variations of the sea surface temperature a. The preliminary results of the micropaleontological and sedimentological analyses allow to recognize three different units that correspond to three different climatic periods: the Cold event 8.2, the Holocene Climate Optimun (6-4 ka) and Neoglacial period (4-2 ka). Chemical-geochemical (organic and total carbon, major and trace elements) analyses and radiocarbon data support the results based on microfossils assemblages and sedimentological data

Micropaleontological study of a sediment core collected on the Bellsund Drift (Svalbard): the last 2ka.

The last 2000 years BP are important to understand the recent climate change. Moreover, the studies of environmental changes recorded in this period offer the possibility to understand how our climate can change in the near future. With these premises, we present the results of the combined study of diatom and foraminifera assemblages together with the sedimentological characteristics of the long Calypso core GS191-01PC. This core was collected on the Bellsund Drift (south-western margin of Spitzbergen) during the expedition of the RV G.O. Sars (5–15 June 2014), in the framework of the Project Eurofleets-2 PREPARED. The study focuses on the 2000 year BP with the final aim to understand paleoclimatic variations. Diatom assemblage shows that warm periods are characterised by Coscinodiscus group and in same levels there are high percentages of the fresh-water diatom Aulocoseia spp. One the other hand, cold periods are characterised by the presence of the cold species Thalassiosira antarctica and higher percentage of the polar planktonic foraminifera Neogloboquadrina pachyderma. The preliminary results of the micropaleontological and sedimentological analyses allow to recognize an alternation four different climatic periods. On the base of the age model, constructed with 14C AMS and paleomagnetic data, we interpret these periods as the Little Ice Age and the Dark Age Period interbedded with the Roman Warm Period and the Medieval Warm Period

Living and dead foraminiferal assemblages of the last decades from Kveithola Trough: Taphonomic processes and ecological highlights

We examine the living and dead benthic foraminiferal assemblages from the topmost 10 cm (using 150 μm sieve fraction) of three sedimentological short records collected in the Kveithola Trough (northwest Barents Sea). Our aim is to reconstruct the environmental variations of the last decades, connected to the interaction among the North Atlantic and the Arctic water masses. Our samples are collected at water depths between 150 and 380 m during the Eurofleets2-BURSTER oceanographic cruise, on board of the R/V Polarstern (June 2016). In the Cell Tracker Green (CTG) labelled living foraminiferal fauna, the main species are Pullenia bulloides, Globobulimina auriculata, and Nonionellina labradorica, while in the dead assemblages the main species are Cassidulina neoteretis, Cibicidoides lobatulus, and Cassidulina reniforme (outer, inner, and shelf stations, respectively). The dead foraminiferal assemblages show no significant traceable environmental changes in the Kveithola Trough area occurred during the last ca. 100 years. Conversely, the living foraminiferal fauna shows that this area is subject to variations related to circulation changes and organic matter burial in sediments, to which the biota adapts quickly. Moreover, the species that are only observed in the dead foraminiferal assemblages and not in the living CTG-labelled foraminiferal assemblages (e.g. C. reniforme) are typical of colder water and highlight the ongoing warming of the Arctic area. We find that the preservation of foraminiferal tests may bias the paleontological results. The agglutinated tests are often disintegrated, and the delicate calcareous ones are broken. The environmental conditions (style of sedimentation, bottom currents, interaction with other communities) can weaken the foraminiferal tests and make them prone to breakage or dissolution

Water masses oscillations west off Svalbard during the past 150 years: micropaleontological evidences.

Micropalaeontological proxies are highly sensitive to environmental changes and are useful tools to investigate the paleo-features (i.e., temperature, sea ice coverage, nutrient supply, etc.) of Arctic environments. The box core GS191-02BC was collected at 1650 m of water depth on the Bellsund Drift crest, on the western slope of Svalbard (Lucchi et al., 2014). It consists of 25 cm of bioturbated sediments, which were analysed for calcareous nannofossils, benthic and planktic foraminifera and diatoms associations. The record covers the last 150 years, from 1866 CE to 2014 CE (210Pb ages). The H/P ratio (Emiliania huxleyi/Coccolithus pelagicus) of calcareous nannofossil was used to investigate the fluctuations between the warm, salty Atlantic Waters (AWs) and the cool, fresher Arctic Waters (ArWs; Carbonara et al., 2016). A ratio >1 was related to predominant AWs influence, while the <1 ratio was referred to the ArWs influence (Andruleit and Baumann, 1998). This proxy was coupled with distributional variations of total nannofossil and diatom abundances using “Sea Ice Margin” (Actinocyclus curvatulus and Fragilariopsis oceanica) and “Cold Water Group” (Thalassiosira antarctica, Rhizosolenia hebetata and Bacterosira bathyomphala) diatom species and variations in planktic and benthic foraminifera associations. The ratio of the benthic foraminifera Epistomenella exigua/Oridorsalis tener was used as a food availability index. Three principal water masses fluctuations were identified: i) from 1905 CE to 1980 CE there is a shift from Arctic to Atlantic waters affinity, ii) from1980 CE to 2005 CE, the AWs dominated conditions shift to a cooler environment (ArWs dominated), in which diatoms bloom while calcareous nannofossil abundance decreases, iii) from 2005 to 2014, there is a return to warmer waters conditions. These micropalaeontological evidences highlight that over the last 150 years, the investigated area went through intense and fast changes. In this framework, sedimentological and geochemical considerations will be furtherly made to have a complete overview of the reported events

The climatic significance of laminated sediments from turbid meltwaters on the NW Barents Sea continental margin (Arctic)

The recent depositional architecture of the north-western Barents Sea continental margin derives from past climate changes with alternating deposition of highly consolidated glacigenic diamicton (continental shelf) and debris flows (continental slope). These are associated to shelf-edge glaciations, and low-density, normally consolidated biogenic-rich sediments deposited during interglacial conditions. In addition, sub-bottom records outline the presence of acoustically laminated deposits locally having thickness exceeding 10 m, which lithofacies characteristics indicating deposition from turbid meltwaters (plumites) during short-living, phases of glacial retreat (meltwater pulses, MWP). One of the youngest stratigraphic intervals recognized along the NW Barents Sea margin was related to the MWP-1a that was responsible for the deposition of about 1.1 x 1011 tonnes of sediments on the upper slope of the Storfjorden-Kveithola TMFs (south of Svalbard) (Lucchi et al., 2015). New compositional analyses of such plumites revealed a distinct signature that allow us to distinguish deposition from glacial melting from that related to the ice-sheet sub-glacial erosion and transport to the edge of margins. Sediment facies and compositional analyses lead to a new climate-related interpretation of the laminated deposits recognized during Marine Isotopic Stages 3 and 2 on the NW margin of the Barents Sea, including Heinrich Event H2

BURSTER: BOTTOM CURRENTS IN A STAGNANT ENVIRONMENT

The glacigenic Kveithola Trough is an abrupt and narrow (100 km-long and 13 kmwide) sedimentary system located in the NW Barents Sea (Rebesco et al., 2011; Ruther et al., 2012; Bjarnadóttir et al., 2013). Along with the larger Storfjorden glacial system, it hosted, during the last glaciation, ice streams draining ice from the southern Svalbard in the north and Bear Island in the south (Andreassen et al., 2008; Pedrosa et al., 2011). During the CORIBAR Cruise on board RV Maria S. Merian (16.07. - 15.08.2013; Tromsø - Tromsø) a wealth of geophysical data including PARASOUND sub-bottom profiles and multibeam, and sediment samples retrieved by gravity-, multi-, boxcorer, and the seafloor drill rig MeBo (Hanebuth et al., 2013) were collected on the Kveithola Drift, a complex morphological and depositional feature confined in the innermost part of the glacially-erode Kveithola Trough. The internal seismic reflections of the drift show a drastic thinning and termination towards the north. Here a distinct moat can be identified, which implies the strong influence of dense bottom currents, inferred to flow (or at least to have flown in the past) towards the outer shelf. The highly dynamic environment depicted from the morphological and structural characteristics of the sediment drift is in contrast with the sediment facies and preserved biota observed in surface sediments. The retrieved sediments have a strong smell of H2S and are mostly black, organic matter-rich, with abundant black worm tubes (Pogonophora worms), and occasionally with living reddish polychaetes (possibly ampharetid polychaetes). The recent and living benthic foraminiferal assemblage observed in the sediments is characterized by the presence of typically oxygen-depleted environmental taxa. Any bottom current-related sedimentary structure was observed on surface sediments. The Kveithola Drift that formed under persistent dense bottom currents appears today as a “stagnant environment” strongly affected by low-oxygen conditions with likely ongoing seep activity. The presence of an apparently stagnant, possibly chemosynthetic, environment in the sediment drift area of the inner Kveithola Through was an unexpected discovery. We therefore think it is of primary importance to better define the bio-geochemical and oceanographic characteristics of the inner area of the Kveithola Trough in order to better define this “anomalous” sedimentary system and to understand the local and global impact of this type of environment in terms of carbon cycle and the transfer of chemosynthetic-derived products to the deeper environments as consequence of regional oceanographic patterns. The BURSTER project aims to investigate the geodynamic and hydrographic conditions, and the active gas seepage present in the pockmark-field piercing the sediment drift located in the inner part of the Kveithola Trough. The type of investigation is strongly multidisciplinary including physical and biological oceanography, water, sediment and gas geochemistry, micropaleontology, microbiology geophysics, and sedimentology. The investigations will be carried out within three working days with the aim of outlining the principal oceanographic, biological and geological aspects of the area on which building up further investigations

BURSTER - Bottom Currents in a Stagnant Environment. EUROFLEETS-2 Cruise Summary Report

Eurofleets 2- BURSTER cruise was conducted onboard the German icebreaker RV Polarstern (Expedition PS99-1a) during June 13–23, 2016 (Bremerhaven-Longyearbyen) having the principal objective of investigating the hydrographic and bio-geochemical conditions of the Kveithola glacial trough (south of Svalbard), and to uncover the possible existence of gas seepage activity in the area. Although the BURSTER research was intended as a preparatory study for the writing of a major research project, the amount of planned activities onboard was really ambitious. Thanks to a tireless, enthusiastic group formed by 11 students out of 23 scientists, a Teacher at Sea (GIFT, EU programme), and a technician from a small-medium enterprise operating with a transportable electron microscope (Nanovision Srl,), 89 multi-cores (22.50 m of sediments and 830 sub-samples), 265 water samples, 28 CTD casts along 7 transects and 2.57 km of benthic camera survey (OFOS), were collected during only 48 hours. In addition, according to the project work program, 24 hours were dedicated to the maintenance/recovery of two moorings that were deployed west of Svalbard during the Eurofleets 2- PREPARED project (RV G.O. Sars, June 2014). BURSTER group was actively supported by 4 scientists of the Italian PNRA project DEFROST, 4 AWI scientists of expedition PS99-1 and the Chief scientist, T. Soltwedel. The cruise successfully recovered evidences of chemosynthetic activity in the Kveithola Trough with the presence of benthic fauna and large tabular and/or irregular-shaped rocks that share the same characteristics of methanogenic environments observed in gas seepage areas. The promising preliminary results obtained from this initial survey of the area will represent the base for the writing of a major project for a detailed investigation of the microbial, biologic and oceanographic system of the Kveithola Trough