(Table 1) Stable-isotopes for foraminifers at DSDP Holes 3-16 and 73-519

A stable-isotope stratigraphy was established for planktonic and benthic foraminifers from upper Miocene-lower Pliocene pelagic sediments from the Mid-Atlantic Ridge. A correlation of stable-isotope and biostratigraphic data with magnetostratigraphic age revealed the following: (1) the late Miocene carbon-isotope shift in the South Atlantic bottom waters was minute compared with the shift reported for other deep-sea locations (Haq et al., 1980), (2) a significant cooling or continental ice-volume increase occurred between 5.7 and 5.2 Ma, and (3) a period of warming or ice-volume decrease followed, with the rate of warming increasing beginning at 4.5 Ma and reaching a climax at 4.3 Ma. The timing of these paleoceanographic events is correlated with the onset and termination of the Messinian salinity crisis in the Mediterranean Sea.

Stable carbon and oxygen isotope ratios of benthic foraminifera from the East Atlantic Ocean

The glacial to interglacial delta13C records of the benthic foraminifera Cibicidoides wuellerstorfi and the Uvigerina peregrina group from deep-sea cores cannot be adjusted by a generally valid constant. The delta13C values of the U. peregrina group largely correlate with the accumulation rates of organic carbon, suggesting a local "habitat effect"; those of C. wuellerstorfi vary independently with respect to the carbon flux and record fluctuations in the delta13C of the ambient bottom water isotopic composition.

Stable isotope and Mg/Ca record of IODP Site 339-U1385

Although millennial-scale climate variability (<10 ka) has been well studied during the last glacial cycles, little is known about this important aspect of climate in the early Pleistocene, prior to the Middle Pleistocene Transition. Here we present an early Pleistocene climate record at centennial resolution for two representative glacials (marine isotope stages (MIS) 37-41 from approximately 1235 to 1320 ka) during the "41 ka world" at Integrated Ocean Drilling Program Site U1385 (the "Shackleton Site") on the southwest Iberian margin. Millennial-scale climate variability was suppressed during interglacial periods (MIS 37, MIS 39, and MIS 41) and activated during glacial inceptions when benthic d18O exceeded 3.2 per mil. Millennial variability during glacials MIS 38 and MIS 40 closely resembled Dansgaard-Oeschger events from the last glacial (MIS 3) in amplitude, shape, and pacing. The phasing of oxygen and carbon isotope variability is consistent with an active oceanic thermal bipolar see-saw between the Northern and Southern Hemispheres during most of the prominent stadials. Surface cooling was associated with systematic decreases in benthic carbon isotopes, indicating concomitant changes in the meridional overturning circulation. A comparison to other North Atlantic records of ice rafting during the early Pleistocene suggests that freshwater forcing, as proposed for the late Pleistocene, was involved in triggering or amplifying perturbations of the North Atlantic circulation that elicited a bipolar see-saw response. Our findings support similarities in the operation of the climate system occurring on millennial time scales before and after the Middle Pleistocene Transition despite the increases in global ice volume and duration of the glacial cycles.

(Fig. 4) Multiproxy data set of box core MSM5/5-712-1

A multiproxy data set of an AMS radiocarbon dated 46 cm long sediment core from the continental margin off western Svalbard reveals multidecadal climatic variability during the past two millennia. Investigation of planktic and benthic stable isotopes, planktic foraminiferal fauna, and lithogenic parameters aims to unveil the Atlantic Water advection to the eastern Fram Strait by intensity, temperatures, and salinities. Atlantic Water has been continuously present at the site over the last 2,000 years. Superimposed on the increase in sea ice/icebergs, a strengthened intensity of Atlantic Water inflow and seasonal ice-free conditions were detected at ~ 1000 to 1200 AD, during the well-known Medieval Climate Anomaly (MCA). However, temperatures of the MCA never exceeded those of the 20th century. Since ~ 1400 AD significantly higher portions of ice rafted debris and high planktic foraminifer fluxes suggest that the site was located in the region of a seasonal highly fluctuating sea ice margin. A sharp reduction in planktic foraminifer fluxes around 800 AD and after 1730 AD indicates cool summer conditions with major influence of sea ice/icebergs. High amounts of the subpolar planktic foraminifer species Turborotalia quinqueloba in size fraction 150-250 µm indicate strengthened Atlantic Water inflow to the eastern Fram Strait already after ~ 1860 AD. Nevertheless surface conditions stayed cold well into the 20th century indicated by low planktic foraminiferal fluxes. Most likely at the beginning of the 20th century, cold conditions of the terminating Little Ice Age period persisted at the surface whereas warm and saline Atlantic Water already strengthened, hereby subsiding below the cold upper mixed layer. Surface sediments with high abundances of subpolar planktic foraminifers indicate a strong inflow of Atlantic Water providing seasonal ice-free conditions in the eastern Fram Strait during the last few decades.

Benthic foraminifera asemblages and isotopic composition of surface sediment samples off Morocco

The influence of different primary productivity regimes on live (Rose Bengal stained) and dead benthic foraminiferal distribution, as well as on the stable carbon isotopic composition of foraminiferal tests, was investigated in sediment surface samples (0-1 cm) from the upwelling region off Morocco between Cape Ghir (31°N) and Cape Yubi (27°N). A combination of factor analysis, detrended correspondence analysis (DCA) and canonical correspondence analysis (CCA) was applied to the benthic foraminiferal data sets. Five major assemblages for both the live and dead fauna were revealed by factor analysis. In the cape regions organic matter fluxes are enhanced by high chlorophyll-a concentrations in the overlying surface waters. Here, benthic foraminiferal faunas are characterized by identical live and dead assemblages, high standing stocks, and low species delta13C values, indicating constant year-round high productivity. Bulimina marginata dominates the unique fauna at the shallowest station off Cape Ghir indicating highest chlorophyll-a concentrations. Off both capes, the succession of the Bulimina aculeata/Uvigerina mediterranea assemblage, the Sphaeroidina bulloides/Gavelinopsis translucens assemblage, and the Hoeglundina elegans assemblage from the shelf to the deep sea reflects the decrease in chlorophyll-a concentrations, hence the export flux. In contrast, the area between the capes is characterized by differently composed live and dead assemblages, low standing stocks, and less depleted delta13C values, thus reflecting low primary productivity. High foraminiferal numbers of Epistominella exigua, Eponides pusillus, and Globocassidulina subglobosa in the dead fauna indicate a seasonally varying primary productivity signal. Significantly lower mean delta13C values were recorded in Bulimina mexicana, Cibicidoides kullenbergi, H. elegans, U. mediterranea and Uvigerina peregrina. Cibicidoides wuellerstorfi is a faithful recorder of bottom water delta13C in the Canary Islands regions. The mean delta13C signal of this species is not significantly influenced by constant high organic matter fluxes. The species-specific offset between live and dead specimens is the same.

Palynological counts (dinoflagellate cysts) and foraminiferal geochemistry (d18O, d18C, Mg/Ca) of the Pliocene-Pleistocene transition in the North Atlantic

The position of the North Atlantic Current (NAC) during the intensification of Northern Hemisphere glaciation (iNHG) has been evaluated using dinoflagellate cyst assemblages and foraminiferal geochemistry from a ~260 kyr interval straddling the base of the Quaternary System from two sites: eastern North Atlantic Deep Sea Drilling Project Site 610 in the path of the present NAC and central North Atlantic Integrated Ocean Drilling Program Site U1313 in the subtropical gyre. Stable isotope and foraminiferal Mg/Ca analyses confirm cooling near the marine isotope stage (MIS) G7-G6 transition (2.74 Ma). However, a continued dominance of the dinoflagellate cyst Operculodinium centrocarpum sensu Wall and Dale (1966) indicates an active NAC in the eastern North Atlantic for a further 140 kyr. At MIS 104 (~2.60 Ma), a profound dinoflagellate cyst assemblage turnover indicates NAC shutdown in the eastern North Atlantic, implying elevated atmospheric pressure over the Arctic and a resulting shift in the westerlies that would have driven the NAC. These findings challenge recent suggestions that there was no significant southward shift of the NAC or the Arctic Front during iNHG, and reveal a fundamental climatic reorganization near the base of the Quaternary.

Cape Lookout cold-water coral area, coral ages and environmental parameters for the last glacial cycle

Climatic and oceanographic changes, as occurring at a glacial-interglacial scale, may alter the environmental conditions needed for the development of prolific cold-water coral reefs and mounds. Studies constraining the temporal distribution of cold-water corals in the NE Atlantic suggested the cyclic changes of the Atlantic Meridional Overturning Circulation as the main driver for the development and dispersal of cold-water coral ecosystems. However, conclusions were hindered by lack of data from the NW Atlantic. Aiming to overcome this lack of data, the temporal occurrence of cold-water corals in the Cape Lookout area along the southeastern US margin was explored by U-series dating. Furthermore, the local influence of the regional water masses, namely the Gulf Stream, on cold-water coral proliferation and occurrence since the Last Glacial Maximum was examined. Results suggest that the occurrence of cold-water corals in the Cape Lookout area is restricted to interglacial periods, with corals being present during the last ~7 kyr and also during the Eemian (~125 ka). The reconstructed local environmental conditions suggest an offshore displacement of the Gulf Stream and increased influence from the Mid-Atlantic Bight shelf waters during the last glacial period. During the deglacial sea level rise, the Gulf Stream moved coastward providing present-day-like conditions to the surface waters. Nevertheless, present-day conditions at the ocean sea floor were not established before 7.5 cal ka BP once the ultimate demise of the Laurentide ice-sheet caused the final sea level rise and the displacement of the Gulf Stream to its present location. Occasional presence of the Gulf Stream over the site during the Mid- to Late Holocene coincides with enhanced bottom current strength and a slightly higher bottom water temperature, which are environmental conditions that are favorable for cold-water coral growth.

Middle Miocene evolution and stable isotope ratios of Globorotalia (Fohsella) in the western equatorial Pacific

Evolution of the planktic foraminiferal lineage Globorotalia (Fohsella) occurred during the Miocene between 23.7 and 11.8 Ma and forms the basis for stratigraphic subdivision of the early middle Miocene (Zones N 10 through N 12). Important morphologic changes within the G. (Fohsella) lineage included a marked increase in test size, a transition from a rounded to an acute periphery, and the development of a keel in later forms. We found that the most rapid changes in morphology of G. (Fohsella) occurred between 13 and 12.7 Ma and coincided with an abrupt increase in the delta18O ratios of shell calcite. Comparison of isotopic results of G. (Fohsella) with other planktic foraminifers indicate that delta18O values of the lineage diverge from surface-dwelling species and approach deep-dwelling species after 13.0 Ma, indicating a change in depth habitat from the surface mixed layer to intermediate depth near the thermocline. Isotopic and faunal evidence suggests that this change in depth stratification was associated with an expansion of the thermocline in the western equatorial Pacific. After adapting to a deeper water habitat at 13.0 Ma, the G. (Fohsella) lineage became extinct abruptly at 11.8 Ma during a period when isotopic and faunal evidence suggest a shoaling of the thermocline. Following the extinction of G. (Fohsella), the ecologic niche of the lineage was filled by the Globorotalia (Menardella) group, which began as a deep-water form and later evolved to an intermediate-water habitat. We suggest that the evolution of G. (Fohsella) and G. (Menardella) were tightly linked to changes in the structure of the thermocline in the western equatorial Pacific.