A deglacial–middle Holocene record of biogenic sedimentation and paleoproductivity changes from the northern Norwegian continental shelf

Abstract

The relative proportions of marine organic carbon and biogenic carbonate in a high‐resolution record from a glacial trough on the northern Norwegian continental shelf were used to decipher changes in biogenic sedimentation and paleoproductivity from the last deglaciation to the middle Holocene. Decadal‐scale to century‐scale oscillations in biogenic sedimentation and surface ocean productivity recorded in the Andfjorden sediments are synchronous with abrupt climate changes in open oceanic and atmospheric regimes of the high northern latitudes. Following several fluctuations during the Bølling‐Allerød interstadial, the most dramatic drop in marine organic carbon and biogenic carbonate proportions occurred during the Younger Dryas. However, many short‐term and low‐amplitude events during the Preboreal and the Holocene have also affected biogenic sedimentation in the outer Andfjorden. Apparently, these abrupt changes in biogenic sedimentation were caused by the suppression of a potential upwelling center in the outer Andfjorden by variable Atlantic Water inflow over the past 14,000 years. The adjustment of decadal high‐productivity coastal systems to freshwater‐forced multiple cooling events during the late glacial to middle Holocene highlights the impact of global climate changes on the climate‐sensitive local ecosystems off coastal Norway.

Climate-induced changes in sedimentary regimes for organic matter supply on the continental shelf off northern Norway

“…With the highly fluctuating sedimentation rates and an inadequate number of AMS 14 C dates, documentation of proxy records as accumulation rates is not recommended. As Knies et al (2003) pointed out, bulk and compound-specific accumulation rates in the Andfjord simply follow the jumps in linear sedimentation rates, owing to the low resolution of the age model, and would therefore distort interpretation of biogeochemical processes and their changes from bulk and molecular geochemical data. Because linear sedimentation rates are often higher and more variable in coastal and shelf settings than the concentration of a given compound (e.g., sterols, alkenones), calculation of accumulation rates only makes sense if a well constrained and high-resolution age model is available.…”

“…The samples were freeze-dried, carefully ground, and stored for another four weeks at Ϫ30°C prior to organo-geochemical analyses. The age of the cored sediment was published by Knies et al (2003) and later revised by Ebbesen and Hald (2004). A suite of nine calibrated accelerator mass spectrometry (AMS) 14 C dates and the detection of the Vedde Ash at 436.5 cm (10.31 14 C ka; Birks et al, 1996) were used to establish the age model by linear interpolation (Table 1).…”

“…A baseline study on carbonate and organic carbon records from the Andfjord (Fig. 1) (Knies et al, 2003) indicates that the marine productivity on the shelf adjusted quickly to sudden changes in the oceanic regime.…”

Late Pleistocene–Holocene radiolarian paleotemperatures in the Norwegian Sea based on artificial neural networks

“…years B.P., and correlated this peak to the Greenland GRIP ice core 8200 years event. Knies et al (2003) reported two prominent lows in marine organic carbon in Andfjorden that may correlate with the Preboreal Oscillation (PBO; 11.17-11.05 ka) and the Greenland 8.2 ka event, as discussed by Bjö rck et al (1996) and Alley et al (1997), respectively. The PBO is probably also present in our data (Fig.…”

Geochemical characterisation of northern Norwegian fjord surface sediments: A baseline for further paleo-environmental investigations

“…Al, Fe, Ti and Si) indicates marine carbonate productivity to be the main calcite and Ca source in all three fjords. However, we note that to confirm this assumption it is necessary to investigate the organic components (such as C org and 13 C org ) of the sediments samples to distinguish the marine and terrigenous origin of Ca (Faust, 2014;Knies et al, 2003). Nevertheless, the increase in Ca/Al from the inside towards the entrance of the Ofot-and Tysfjord fjords (Fig.…”