Stable isotopes, CaCO3, opal and terrigeneous of ODP Site 108-663 (Table A1)

High- and low-latitude forcing of terrestrial African paleoclimate variability is demonstrated using 900 ka eolian and biogenic component records from Ocean Drilling Program site 663 in the eastern equatorial Atlantic. Terrigenous (eolian dust) and phytolith (savannah grass cuticle) accumulation rate records vary predominantly at 100 and 41 kyr periodicities and spectral phase estimates implicate high-latitude forcing. The abundance of freshwater diatoms (Melosira) transported from dry African lake beds varies coherently at 23-19 kyr orbital periodicities and at a phasing which implicates low-latitude precessional monsoon forcing. Modeling studies demonstrate that African climate is sensitive to both high- and low-latitude boundary conditions. African monsoon intensity is modulated by direct insolation variations due to orbital precession, whereas remote high-latitude forcing can be related to cool North Atlantic sea surface temperatures (SSTs) which promote African aridity and enhance dust-transporting wind speeds. The site 663 terrigenous and phytolith records covary with North Atlantic SST variability at 41 °N (site 607). We suggest that Pleistocene African climate has responded to both high-latitude North Atlantic SST variability as well as low-latitude precessional monsoon forcing; the high-latitude influence dominates the sedimentary record. Prior to circa 2.4 Ma, terrigenous variations occurred primarily at precessional periodicities (23-19 kyr), indicating that African climate was largely controlled by low-latitude insolation variations prior to the onset of high-amplitude glacial-interglacial climate change.

Stable isotopes, core logging data, relative paleointensity, dry bulk density, biogenic opal, CN-data (TC, TOC, CaCO3, TN), element concentrations, and coarse fraction of three sediment cores from the western Bering Sea

We used piston cores recovered in the western Bering Sea to reconstruct millennial-scale changes in marine productivity and terrigenous matter supply over the past ~180 kyr. Based on a geochemical multi-proxy approach, our results indicate closely interacting processes controlling marine productivity and terrigenous matter supply comparable to the situation in the Okhotsk Sea. Overall, terrigenous inputs were high, whereas export production was low. Minor increases in marine productivity occurred during intervals of Marine Isotope Stage 5 and interstadials, but pronounced maxima were recorded during interglacials and Termination I. The terrigenous material is suggested to be derived from continental sources on the eastern Bering Sea shelf and to be subsequently transported via sea ice, which is likely to drive changes in surface productivity, terrigenous inputs, and upper-ocean stratification. From our results we propose glacial, deglacial, and interglacial scenarios for environmental change in the Bering Sea. These changes seem to be primarily controlled by insolation and sea-level forcing which affect the strength of atmospheric pressure systems and sea-ice growth. The opening history of the Bering Strait is considered to have had an additional impact. High-resolution core logging data (color b*, XRF scans) strongly correspond to the Dansgaard-Oeschger climate variability registered in the NGRIP ice core and support an atmospheric coupling mechanism of Northern Hemisphere climates.

Mid-Pleistocene Mg/Ca, temperature and stable isotopes from Globigerinoides ruber white and Globorotalia inflata of sediment core GeoB3801-6 from the subtropical South Atlantic

The glacial marine isotope stage 14 (MIS 14) appears in many climate records as an unusually warm glacial. During this period an almost monospecific, up to 1.5 m thick, laminated layer of the giant diatom Ethmodiscus rex has been deposited below the South Atlantic Subtropical Gyre. This oligotrophic region is today less favorable for diatom growth with sediments typically consisting of calcareous nannofossil oozes. We have reconstructed temperatures and the stable oxygen isotopic compositions of sea surface and thermocline water (d18Ow) from planktonic foraminiferal (Globigerinoides ruber and Globorotalia inflata) Mg/Ca and stable oxygen isotopes to test whether perturbations in surface ocean conditions contributed to the deposition of the diatom layer at ~530 kyr B.P. Temperatures and d18Ow values reconstructed from this diatom ooze interval are highly variable, with maxima similar to interglacial values. Since the area of the Ethmodiscus oozes resembles the region where Agulhas rings are present, we interpret these hydrographic changes to reflect the varying influence of warm and saline water of Indian Ocean origin that entered the Subtropical Gyre trapped in Agulhas rings. The formation of the Ethmodiscus oozes is associated with a period of maximum Agulhas leakage and a maximum frequency of Agulhas ring formation caused by a termination-type position of the Subtropical Front during the unusual warm MIS 14. The input of silica through the Agulhas rings enabled the shift in primary production from calcareous nannoplankton to diatoms, leading to the deposition of the massive diatom oozes.