Abstract
Abstract. A marine sediment core (JM09-KA11-GC) from the Kveithola Trough at the western Barents Sea margin has been investigated in order to reconstruct sub-surface temperatures and sea ice distribution at a sub-centennial resolution throughout the Holocene. The relationship between past variability of Atlantic water inflow and sea ice distribution has been established by measurement of planktic foraminifera, stable isotopes and biomarkers from sea ice diatoms and phytoplankton. Throughout the early Holocene (11 900–7300 cal yr BP), the foraminiferal fauna is dominated by the polar species Neogloboquadrina pachyderma (sinistral) and the biomarkers show an influence of seasonal sea ice. Between 10 900 and 10 700 cal yr BP, a clear cooling is shown both by fauna and stable isotope data corresponding to the so-called Preboreal Oscillation. After 7300 cal yr BP, the sub-polar Turborotalita quinqueloba becomes the most frequent species, reflecting a stable Atlantic water inflow. Sub-surface temperatures reach 6 °C and biomarker data indicate mainly ice-free conditions. During the last 1100 cal yr BP, biomarker abundances and distributions show the reappearance of low-frequency seasonal sea ice and the planktic fauna show a reduced salinity in the sub-surface water. No apparent temperature decrease is observed during this interval, but the rapidly fluctuating fauna and biomarker distributions indicate more unstable conditions.
Highlights
Sea ice is a pivotal element of the climate system (e.g. Kvingedal, 2005; Stroeve et al, 2012) and plays a major role in determining ocean circulation in the North Atlantic
The planktic foraminiferal fauna consists of six species and is dominated by two: Neogloboquadrina pachyderma and Turborotalita quinqueloba
This paper presents a multi-proxy study of sub-surface and sea ice conditions in the western Barents Sea throughout the Holocene
Summary
Sea ice is a pivotal element of the climate system (e.g. Kvingedal, 2005; Stroeve et al, 2012) and plays a major role in determining ocean circulation in the North Atlantic. Some recent studies have suggested that enhanced advection of Atlantic water into the Arctic might be one of the main causes of the recent sea ice decline (Kinnard et al, 2011; Spielhagen et al, 2011), so ice conditions in the Barents Sea are especially influenced by changing oceanic fronts. Husum and Hald (2012) developed an Arctic training set based on the > 100 μm size fraction and found that the most robust reconstructions of sea surface temperatures using transfer functions were obtained when using summer temperatures from sub-surface water masses at 100 m water depth. Since the absence of IP25 from Arctic marine sediments is believed to either represent open water or perennial ice cover, the additional determination of brassicasterol and other phytoplankton lipids has been used to distinguish between these two oceanographic extremes (e.g. Müller et al, 2009, 2011; Belt and Müller, 2013). Navarro-Rodriguez et al (2013) showed that the occurrence of IP25 in surface sediments from the Barents Sea was extremely sensitive to sea ice cover in recent decades
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