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This paper presents an age–depth model based on an ultra-high-resolution, 80-m-thick sedimentary succession from a marine continental shelf basin, the Kattegat. This is an area of dynamic deglaciation of the Fennoscandian Ice Sheet during the Late Pleistocene. The Kattegat is also a transitional area between the saline North Sea and the brackish Baltic Sea. As such, it records general development of currents and exchange between these two systems. Data for the succession were provided through the Integrated Ocean Drilling Program Site M0060. The site indicates onset of deglaciation at c. 18 ka BP and relatively continuous sedimentation until 13 ka BP. At this point, sediments record a hiatus until c. 9–7 ka BP. The uppermost sedimentary unit contains redeposited material, but it is estimated to represent only the last c. 9–7 ka BP. The age–depth model is based on 17 select, radiocarbon-dated samples and is integrated with a set of physical and chemical proxies. The integrated records provide novel constraints on the timing of major palaeoenvironmental changes, such as the transition from glaciomarine proximal to glaciomarine distal and marine conditions, and their connections to known major events and processes in the region and the North Atlantic. Depositional evidence specifically documents connections between the Fennoscandian Ice Sheet behaviour and atmospheric and oceanic warming. Glacial retreat may have also depended on topographic factors such as changes in basin width and depth, linked to relative sea level changes and land uplift. The results indicate an early response of the Fennoscandian Ice Sheet to changing climate, and the ice sheet's possible influence on oceanic circulation during the Late Pleistocene deglaciation.

Numerous hydro-acoustic studies of the seabed of the Baltic Sea have revealed the unusual occurrence of sediment contourite drifts and re-suspension at greater water depths. In addition, radiocarbon dating of bulk sediments indicates significant age reversals. We present new geophysical, sediment proxy data (including extensive radiocarbon dating) and hydrographic measurements, which are combined with results of numerous marine geological studies performed during the last decades. These data indicate that a deep-water formation process significantly affected the seabed dynamics during regional climatically cold phases during the last c. 7,000 years. We propose that, during the colder periods (e.g. the Little Ice Age), newly formed bottom waters likely caused widespread re-suspension of organic carbon-rich laminated sediments that were deposited during the preceding warm periods in shallower areas, and this material was transported to and re-deposited in the deeper parts of the Baltic Sea sub-basins. In our scenario, a topographic feature, known as the Baltic Sea Klint, acted as a hydrographic barrier for deep-water formed in the northern Baltic. Thus, during the cold periods increased lateral matter influx from the northern Baltic led to the accumulation of much thicker macroscopically homogenous clayey sediments in sub-basins north of the Klint. Moreover, deep-water formation produced bottom currents that led to the formation of sediment contourite drifts at water depths of >200 m in the Bothnian Sea, the Åland Deep and northern central Baltic Sea sub-basins. Bottom water ventilation in the Baltic Sea is generally assumed to be determined solely by the inflow of oxygen-rich, saline water from the North Sea, but we challenge this assumption and postulate that deep-water formation is a key process that ventilates the bottom waters of the Baltic Sea during climatically cold periods with substantial implications for its sedimentary archive.

Anisotropy of magnetic susceptibility data obtained from discrete sub-samples recovered from two Integrated Ocean Drilling Program sites (Expedition 347 sites M0061 and M0062 in the Baltic Sea) by an Advanced Piston Corer are compared to results obtained on sub-samples recovered by replicate 6 m long Kullenberg piston cores. Characteristic natural remanence directions were obtained from the total of 1097 sub-samples using principal component analyses. The three principal anisotropy axes of sub-samples taken from Advanced Piston Core liners align to the sub-sample axes, with the maximum axis (K1) parallel to the split core surfaces, possibly caused by outwards relaxation of the core-liners after splitting. A second anomalous anisotropy fabric is characterized by steep values of the angular difference between the inclination of the minimum anisotropy axes (K3) and that expected for horizontal bedding (90°). This fabric is confined to the upper 1–2 m of the Kullenberg cores and specific sections of the advanced piston cores, and we attribute it to conical deformation caused by either excessive penetration speeds and downwards dragging of sediment along the edge of the liner or stretching caused by undersampling. By using our data in an example, we present a protocol to accept palaeomagnetic secular variation data that uses (i) a threshold 90-K3 value of 15°, combined with a modelled, locally applicable minimum inclination of 65° and (ii) an A95 cone of confidence based on Fisher statistics applied to virtual geomagnetic pole distributions.

The Yermak Plateau is located north of Svalbard at the entrance to the Arctic Ocean, i.e. in an area highly sensitive to climate change. A multi proxy approach was carried out on Core PS92/039-2 to study glacial-interglacial environmental changes at the northern Barents Sea margin during the last 160 ka. The main emphasis was on the reconstruction of sea ice cover, based on the sea ice proxy IP25 and the related phytoplankton - sea ice index PIP25. Sea ice was present most of the time but showed significant temporal variability decisively affected by movements of the Svalbard Barents Sea Ice Sheet. For the first time, we prove the occurrence of seasonal sea ice at the eastern Yermak Plateau during glacial intervals, probably steered by a major northward advance of the ice sheet and the formation of a coastal polynya in front of it. Maximum accumulation of terrigenous organic carbon, IP25 and the phytoplankton biomarkers (brassicasterol, dinosterol, HBI III) can be correlated to distinct deglaciation events. More severe, but variable sea ice cover prevailed at the Yermak Plateau during interglacials. The general proximity to the sea ice margin is further indicated by biomarker (GDGT) - based sea surface temperatures below 2.5 °C.

Laminated, organic-rich silts and clays with high dissolved gas content characterize sediments at IODP Site M0063 in the Landsort Deep, which at 459 m is the deepest basin in the Baltic Sea. Cores recovered from Hole M0063A experienced significant expansion as gas was released during the recovery process, resulting in high sediment loss. Therefore, during operations at subsequent holes, penetration was reduced to 2 m per 3.3 m core, permitting expansion into 1.3 m of initially empty liner. Fully filled liners were recovered from Holes B through E, indicating that the length of recovered intervals exceeded the penetrated distance by a factor of >1.5. A typical down-core logarithmic trend in gamma density profiles, with anomalously low-density values within the upper ∼1 m of each core, suggests that expansion primarily occurred in this upper interval. Thus, we suggest that a simple linear correction is inappropriate. This interpretation is supported by anisotropy of magnetic susceptibility data that indicate vertical stretching in the upper ∼1.5 m of expanded cores. Based on the mean gamma density profiles of cores from Holes M0063C and D, we obtain an expansion function that is used to adjust the depth of each core to conform to its known penetration. The variance in these profiles allows for quantification of uncertainty in the adjusted depth scale. Using a number of bulk 14C dates, we explore how the presence of multiple carbon source pathways leads to poorly constrained radiocarbon reservoir age variability that significantly affects age and sedimentation rate calculations.

Variations in the Holocene circulation of the West Greenland Current (WGC) in the Disko Bugt region have been reconstructed from a suite of sediment cores. Palaeoceanographic proxies include magnetic susceptibility (MS) and X-ray fluorescence titanium counts, which document a major shift in circulation at c. 6000 cal a BP. Before this date, sediments in southern Disko Bugt were characterized by high terrigeneous and basaltic input, suggesting widespread influence of meltwater plumes. Our data show that the WGC re-circulated in the southern Disko Bugt area because a potential northern pathway, the narrow Vaigat Strait, was blocked by icebergs that calved from marine outlet glaciers in eastern Disko Bugt. Sediments in southern Disko Bugt deposited after c. 6000 cal a BP have significantly lower terrestrial and basaltic sediment input, which coincides with minimum Holocene ice sheet extent. The reduced meltwater and iceberg discharge to the embayment caused the Vaigat Strait to become free of blocking icebergs and terrigenous input was partly diverted to the outer shelf. Thus, the modern circulation pattern of the WGC was established in the Disko Bugt region through the opening of the Vaigat Strait c. 6000 cal a BP. Copyright (C) 2013 John Wiley & Sons, Ltd.

Hollerup

Bjornoya, a small (178 km(2)) island situated between the mainland of Norway and southern Spitsbergen, provides the opportunity for the reconstruction of early Holocene terrestrial and limnic palaeoenvironments in the southwestern Barents Sea. The AMS C-14 dating technique, geochemical, mineral magnetic, micro- and macrofossil analyses were applied to sediments recovered from lake Stevatnet and the results are interpreted in terms of palaeoenvironmental conditions between 9800 and 8300 C-14 BP. After the disappearance of local glaciers before ca 9800 C-14 BP, the lake productivity increased rapidly at the same time as pioneer plant communities developed on soils which gradually became more stable. Insect data indicates that strong seasonal contrasts with mean July temperatures around 9 degrees C and mean January temperatures around -12 degrees C prevailed between 9500 and 8300 C-14 BP. These high summer temperatures, possibly as much as 4-5 degrees C higher than the present, favoured the development of a flora including Dryas and Angelica cf. archangelica. The enhanced freeze/thaw processes led to an increased erosion of minerogenic and organic material. After 8000 C-14 BP the temperatures may have gradually declined. The environmental reconstruction derived from our data set supports the conceptual insolation model which proposes maximum Holocene seasonality for the Northern Hemisphere at ca 9000 C-14 BP.