Stable isotope stratigraphy of the Arctic Ocean: Fram strait to central Arctic

Abstract

A comparison of stable isotope and textural records of sediment cores from the Fram Strait and central Arctic Ocean to isotopic records from low latitude oceans indicates that the Arctic Mediterranean responded dynamically to climatic change during the Pleistocene. Core MG-123, from the Fram Strait, shows at least four significant low δ 18O intervals, 5 high δ 13C intervals, and five intervals with a low amount of coarse sediment. The association of high δ 18O values with coarse sediment intervals indicates increased glacial ice in the Fram Strait during glacial phases of the climate cycle. Peaks within the low δ 18O intervals increase in magnitude from oldest to youngest, suggesting that glacial/interglacial transitions are “pulsed”. The magnitude of the different low δ 18O intervals increases from oldest to youngest. This is interpreted to indicate that there has been a progressive intensification of the oceanographic response to glacial/interglacial transitions in the Fram Strait during the past 524 ky. Time series spectral analysis suggests an age of approximately 524 ky for the oldest sediment in core MG-123, yielding an average sedimentation rate of approximately 1.66 cm/1000 yr. Stable isotope records from the central Arctic Ocean indicate that sedimentation rates are on the order of 1–3 mm/1000 yr. The isotope records support the established central Arctic Ocean lithostratigraphy. Coarse sediment deposition in the central Arctic is not as clearly related to glacial conditions as it is in the Fram Strait. The oxygen isotope range of central Arctic Ocean records is accentuated relative to the global ice volume signal recorded from lower latitude cores. This may be caused by variations in salinity, temperature, and thickness of the Arctic Ocean's low salinity surface layer. Oceanographic responses to climatic change recorded in the Fram Strait are also recorded in the central Arctic Ocean but with decreased resolution due to the magnitude of difference in the sedimentation rates between the two areas.