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

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

Multi-proxy analysis of Late Quaternary ODYSSEA Contourite Depositional System (Ross Sea, Antarctica) and the depositional record of contour current and cold, dense waters

The Ross Ice Shelf is the Antarctic region that over the last deglaciation experienced the greatest change in areal ice cover. Today, cold, dense and saline water masses (brines) produced in the Ross Sea polynya, flow from the shelf to the deep ocean providing a significant contribution to the propelling of the global ocean circulation regulating the climate. In particular, the Hillary Canyon in the Eastern Ross Sea is the main conduit through which brines descend the slope to reach the deeper ocean and is thus one of the greatest regions of cold, dense water export in the world. A Contourite Depositional System (the ODYSSEA CDS) on the western flank of the Hillary Canyon is inferred to have been generated through several hundred-thousand years by along-slope, contour currents that transported and accumulated the sediments brought down the Hillary Canyon by means of brines. A multi-proxy investigation was conducted on the shallowest part of the ODYSSEA CDS depositional sequences, which we expect to contain i) the record of the brine formation, ii) the indication on contour current strength through time, and iii) their interplay and modulation associated to climate change. Six gravity cores, collected in both the proximal and distal area of the ODYSSEA CDS, were studied through multi-proxy analyses including sediment physical properties (texture, structures, water content, wet bulk density), compositional characteristics (XRF, geochemistry and detrital apatite, zircon, and rutile U-Pb on ice-rafted debris) (Lucchi et al., 2019; Neofitu et al., 2020) and microfossil content (planktonic and benthic foraminifera, calcareous nannofossils and diatoms). An age model has been reconstructed combining palaeomagnetic record, biostratigraphic content, tephrochronology and AMS radiocarbon dating on planktonic foraminifera tests. Inferred variations in dense water formation, contour current strength and ice sheet dynamics are discussed in the light of our data interpretation