Holocene climate in the subarctic fjord Malangen, northern Norway: a multi-proxy study |
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| Authors: | MORTEN HALD KATRINE HUSUM TORE O VORREN KARI GRØSFJELD HENNING B JENSEN ALLA SHARAPOVA |
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| Institution: | Department of Geology, University of Tromsø, NO-9037 Tromsø, Norway;Kari Grøsfield, Geological Survey of Norway, NO-7491 Trondheim Norway;Geological Survey of Norway, Polar Environmental Centre, NO-9296 Tromsø, Norway;St. Petersburg University, Division of Historical Geology, St. Petersburg 199034, Russia |
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| Abstract: | A Holocene sedimentary record from the deep-silled Malangen fjord in northern Norway reveals regional changes in sedimentary environment and climate. Down-core analysis of two sediment cores includes multi-core sensor logging, grain size, x-radiography, foraminifera, oxygen isotopes, dinoflagellates, pollen, trace elements and radiocarbon datings. The cores are located just proximal to the submarine Younger Dryas moraine complex, and reveal the deglaciation after Younger Dryas and the postglacial evolution. Five sedimentary units have been identified. The oldest units, V and IV, bracket the Younger Dryas glacial readvance in the fjord between 12 700?cal. years BP and 11 800?cal. years BP. This is followed by deposition of glaciomarine sediments (units IV and III) starting around 12 100?cal. years BP. Glaciomarine sedimentation ceased in the fjord c. 10 300?cal. years BP and was replaced by open marine sedimentation (units II and I). A rapid stepwise warming occurred during the Preboreal. Onset of surface water warming lagged bottom water warming by several hundred years. The δFormula: See Text]O record indicates a significant, gradual bottom water cooling (c. 4°C) between 8000 and 2000?cal. years BP, a trend also supported by the other proxy data. Other records in the region, as well as GCM simulations, also support this long-term climatic evolution. Superimposed on this cooling were brief warmings around 6000?cal. years BP and 2000?cal. years BP. The long-term change may be driven by orbitally forced reduction in insolation, whereas the short-term changes may be linked to for example solar forcing, meltwater and NAO changes all causing regional changes in the North Atlantic heat transport. |
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