Interplay of bottom currents and glacial input on western margin of the Svalbard: evidence from giant piston cores spanning the last 90 ka.

The present and future climate development is subject to considerable changes due to the increasing human influence on the climate system. The polar regions are particularly affected by this change. However, the extent and speed of this change are controversial. A better assessment requires accurate knowledge of the natural climate variability, i.e. in the periods when human influence did not play a role. This PhD project focuses on the reconstruction of past-climate variability caused by natural forcing and the response of the paleo Svalbard-Barents Sea Ice Sheet using climate signatures preserved in Arctic marine sediments. The geological dataset used for this study derives from two oceanographic cruises under the framework of the Eurofleets2 PREPARED, where core GS191-02PC was recovered from the Isfjorden drift in 1322 m water depth, and from the CAGE19-3KH Calypso piston coring expedition, where core CAGE19-3KH-05GPC was collected from the western termination of Vestnesa Ridge at a water depth of 1321 m bsf and core CAGE19-3KH-15GPC was collected from the Isfjorden Drift at a water depth of 1579 m bsf. The three studied cores were collected employing Calypso Giant Piston corer. The laboratory analyses included: X-Ray radiography and computed tomography (CAT-scan), Core visual description, Multi Sensor Core Logging (MSCL), X-ray fluorescence (XRF) core scan, X-ray diffraction (XRD), Total Organic carbon (TOC) and Total Nitrogen (TN), and grain size analysis. The three cores (spanning from Marine Isotopic Stage-5b to the Marine Isotopic Stage-1) were correlated on the basis of the magnetic susceptibility and identification of marker beds having a regional distribution since the early Weichselian. It was possible to identify and characterize several major climatic events during the last 90 ky such the Meltwater Pulse MWP 1-A (14.6-14.3 ky), (MWP)1-A0 , or MWP-19ky (20.5-20.0 ky), the Heinrich event H2 (23-24 ky), the Heinrich event H4 (38-40 ky), and the Heinrich event H6 (60 ky). These events are characterized by a particular sediment structure that clearly indicates ice melting under warm conditions, and a characteristic mineralogical composition that allows their reliable recognition. The sedimentological record reveals a highly dynamic ice sheet under variable climatic conditions. The sedimentation in the studied sites is clearly affected by the interplay of down-slope processes mainly occurring during ice sheet waxing and waning and along-slope processes dominated by contour currents during warm conditions when the ice sheet is fairly retreated inland. The interplay between these two main processes causes the depocenters to shift on glacial-interglacial time scales.