Abstract
Reconstructing past ocean-climate environments and heat transport requires proxies from which these conditions can be quantified. This is particularly important for the evaluation of numerical palaeoclimate models. Here we present new evidence for a reduced North Atlantic Current (NAC) at the termination of the third last glacial, for which palaeocurrent information was previously unavailable. This is based on an exquisitely preserved set of buried iceberg scours seen in three-dimensional seismic reflection images from the mid-Norwegian slope. The scours were formed ∼430 ka during the transition from glacial to interglacial conditions. The spiral geometry of the scours suggests that they were carved by grounded icebergs influenced by tidal and geostrophic ocean currents. Using the ratio between the estimated tidal and geostrophic current velocities and comparing them with velocities from the Last Glacial Maximum and the present, we show that the stage 12 NAC velocities may have been ∼50% slower than the present.
Highlights
Reconstructing past ocean-climate environments and heat transport requires proxies from which these conditions can be quantified
In the Norwegian Sea, the North Atlantic Current (NAC) splits into the Norwegian Atlantic Slope Current (NASC) and the Norwegian Atlantic Front Current (NAFC) (Fig. 1)
A surface with landforms interpreted as iceberg scour marks at the top of the Naust U package was dated to B430 ka based on a spike in ice-rafted detritus[4] at three ODP sites on the Vøring Plateau (Fig. 1)
Summary
Reconstructing past ocean-climate environments and heat transport requires proxies from which these conditions can be quantified. We present new evidence for a reduced North Atlantic Current (NAC) at the termination of the third last glacial, for which palaeocurrent information was previously unavailable. This is based on an exquisitely preserved set of buried iceberg scours seen in three-dimensional seismic reflection images from the mid-Norwegian slope. Understanding the environmental changes through different glacial–interglacial cycles allows for a better understanding of ice-age chronology and extent This is crucial for the validation of numerical palaeoclimate models[7] and our understanding of historic, present and future sea level variability, ocean dynamics, ice sheet stability and climate change[8,9,10,11,12,13,14]. The present-day mean velocity of the NASC current[21] is 20–40 cm s À 1 while tidal currents of 20–30 cm s À 1 are recorded here[22]
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