| Summary: | This palaeoclimatological study of the Arctic examines two sediment cores from the Arctic Ocean for planktonic foraminifera from the interglacial Marine Isotope Stage 5 (MIS 5). MIS 5 is of particular importance as it was the most recent interglacial period prior to the Holocene and provides a baseline context for understanding modern sea-ice loss and warming sea-surface temperatures. This study developed a foraminifer assemblage-based estimate of sea surface conditions by examining two Western Arctic cores, P1-93-AR-P21 (P21) from Northwind Ridge and P1-94-AR-PC9 (PC9) from Mendeleev Ridge. Twelve samples taken from each core at intervals of 5 cm correspond to MIS 5 based on preliminary age models (from 69-121 cm in P21 and 105-169 cm in PC9). Samples were washed through >63 micron sieves and the coarse fraction was split until a subset of approximately 300 foraminifers remained. Planktonic foraminifera were picked from each final subset of a sample. Six distinct morpho-species were identified, and the presence of other organisms and overall abundance of foraminifers were also noted. Four species emerged as abundant in both cores, two relatively warm water species (Turborotalita quinqueloba and T. egelida) and two cold water species that dominate today’s Arctic Ocean (Neogloboquadrina pachyderma and N. incompta). N. pachyderma and T. quinqueloba were the two most prominent species during MIS 5 in both cores. N. pachyderma ranged from 23-75% in P21 and from 9-76% in PC9, while T. quinqueloba ranged from 7-65% in P21 and 16-84% in PC9. Changes in the proportional abundance of each pair of species combined were plotted against core depth to more accurately develop an age model for these cores and understand climatological trends in the Arctic Ocean during MIS 5.
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