Meltwater discharge anomalies in marine isotope stage 3 from a sediment core in the south of Antarctic Polar Front, Drake Passage

Abstract

Marine isotope stages (MISs) I to 5 were identified in the planktonic delta(18)O record in sediment core DP00-02 just south of the Antarctic Polar Front within the Drake Passage, Antarctica. The oxygen isotope record based on Neogloboquadrina pachyderma sinistral is well correlated with the contemporaneous global delta(18)O stratigraphy. Marked differences from the global climate curve suggest a local/regional overprint, particularly during the MIS 3, which is considered as a colder time period in the ocean record than the MIS 1 and MIS 5 interglacial periods. The comparison shows that negative 5180 shifts in the core DP00-02 during the MIS 3 are larger than mean global changes that show a shift equal to or smaller than 0.5parts per thousand. The isotope shift, exceeding the glacial-interglacial ice volume effect, probably resulted from changes in the isotope composition of sea water which is linearly related to decreases in salinity rather than increases in sea-surface temperature. Increased ice-rafted debris (IRD) content during this period interval indicates strong influx of IRD from melting ice shelves and iceberg, which may be related to upwelling of warmer Circumpolar Deep Water.