Additional co-authors: TJ Heaton, AG Hogg, KA Hughen, KF Kaiser, B Kromer, SW Manning, RW Reimer, DA Richards, JR Southon, S Talamo, CSM Turney, J van der Plicht, CE Weyhenmeyer

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IntCal13 and Marine13 radiocarbon age calibration curves 0-50,000 years cal BP

Since 65 million years ago (Ma), Earth's climate has undergone a significant and complex evolution, the finer details of which are now coming to light through investigations of deep-sea sediment cores. This evolution includes gradual trends of warming and cooling driven by tectonic processes on time scales of 10(5) to 10(7) years, rhythmic or periodic cycles driven by orbital processes with 10(4)- to 10(6)-year cyclicity, and rare rapid aberrant shifts and extreme climate transients with durations of 10(3) to 10(5) years. Here, recent progress in defining the evolution of global climate over the Cenozoic Era is reviewed. We focus primarily on the periodic and anomalous components of variability over the early portion of this era, as constrained by the latest generation of deep-sea isotope records. We also consider how this improved perspective has led to the recognition of previously unforeseen mechanisms for altering climate.

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Trends, Rhythms, and Aberrations in Global Climate 65 Ma to Present

The age calibration program, CALIB (Stuiver & Reimer 1986), first made available in 1986 and subsequently modified in 1987 (revision 2.0 and 2.1), has been amended anew. The 1993 program (revision 3.0) incorporates further refinements and a new calibration data set covering nearly 22,000 cal yr (≈18,400 14C yr). The new data, and corrections to the previously used data set, derive from a 6-yr (1986–1992) time-scale calibration effort of several laboratories.

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Extended 14C Data Base and Revised Calib 3.0 14C Age Calibration Program

[1] We present a 53-Myr stack (the “LR04” stack) of benthic δ18O records from 57 globally distributed sites aligned by an automated graphic correlation algorithm This is the first benthic δ18O stack composed of more than three records to extend beyond 850 ka, and we use its improved signal quality to identify 24 new marine isotope stages in the early Pliocene We also present a new LR04 age model for the Pliocene-Pleistocene derived from tuning the δ18O stack to a simple ice model based on 21 June insolation at 65°N Stacked sedimentation rates provide additional age model constraints to prevent overtuning Despite a conservative tuning strategy, the LR04 benthic stack exhibits significant coherency with insolation in the obliquity band throughout the entire 53 Myr and in the precession band for more than half of the record The LR04 stack contains significantly more variance in benthic δ18O than previously published stacks of the late Pleistocene as the result of higher-resolution records, a better alignment technique, and a greater percentage of records from the Atlantic Finally, the relative phases of the stack's 41- and 23-kyr components suggest that the precession component of δ18O from 27–16 Ma is primarily a deep-water temperature signal and that the phase of δ18O precession response changed suddenly at 16 Ma

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A Pliocene-Pleistocene stack of 57 globally distributed benthic δ18O records

Coral reefs drilled offshore of Barbados provide the first continuous and detailed record of sea level change during the last deglaciation. The sea level was 121 ± 5 metres below present level during the last glacial maximum. The deglacial sea level rise was not monotonic; rather, it was marked by two intervals of rapid rise. Varying rates of melt-water discharge to the North Atlantic surface ocean dramatically affected North Atlantic deep-water production and oceanic oxygen isotope chemistry. A global oxygen isotope record for ocean water has been calculated from the Barbados sea level curve, allowing separation of the ice volume component common to all oxygen isotope records measured in deep-sea cores.

A 17,000-year glacio-eustatic sea level record: influence of glacial melting rates on the Younger Dryas event and deep-ocean circulation

Oligocene to Miocene Carbon Isotope Cycles and Abyssal Circulation Changes

Oxygen-isotope tracer data combined with results from two linear barotropic coastal models are used to argue that the observed equatorward mean alongshelf flow in the Middle Atlantic Bight is a downstream extension of the mean alongshelf flow over the Scotian Shelf. Qualitative agreement between model results and observations supports the concept that the alongshelf pressure gradient associated with the mean alongshelf flow in the Middle Atlantic Bight has an upstream or downstream and not an offshelf origin. The role of the local large-scale general circulation is apparently to help keep the shelf water on the shelf rather than to drive the shelf mean flow.

On the continuity of mean flow between the Scotian Shelf and the Middle Atlantic Bight

Helium isotope data (3He/4He ratios and 4He concentrations) and H218O/H216O ratios obtained from stations occupied during the drift of Ice Station Weddell (February to June 1992) are used, together with hydrographic data, to study formation of deep and bottom water in the western Weddell Sea. The data indicate deep and bottom water formation along the entire track of the ice station (71.4 to 65.8°S, ≈53°W). Ice Shelf Water (ISW) seems to contribute significantly to the formation of Weddell Sea Deep Water (WSDW) and Weddell Sea Bottom Water (WSBW) in the southern part of the drift track. Toward the north, the fraction of ISW contained in WSDW/WSBW decreases. This trend is overlaid by high ISW fractions in the deep and bottom waters found in the vicinity of the Larsen Ice Shelf. The fraction of Western Shelf Water (WSW) in WSBW shows the opposite trend, increasing from south to north. The combined fraction of ISW and WSW in waters with potential temperatures below 0°C is about 20%, corresponding to a roughly 200 m thick layer. Overall, WSW seems to contribute approximately 2 to 3 times more water than ISW to the water column below the 0°C isotherm. Using the estimated flow of ISW over the sill north of the Filchner Depression of 1 Sv [Foldvik et al., 1985a] together with the ratio of WSW plus Winter Water (WW) to ISW, we calculate a value of about 5 Sv for the formation rate of WSBW with a potential temperature of −0.7°C. About one third of this flux represents near-surface waters (WSW/WW) which have recently been equilibrated with the atmosphere, whereas pure ISW contributes about 10%.

Richard G. Fairbanks

Papers

Oligocene to Miocene Carbon Isotope Cycles and Abyssal Circulation Changes

On the continuity of mean flow between the Scotian Shelf and the Middle Atlantic Bight

Isotope data from Ice Station Weddell: Implications for deep water formation in the Weddell Sea

Oscillating glacial northern and southern deep water formation from combined neodymium and carbon isotopes

Light and temperature effects on Sr/Ca and Mg/Ca ratios in the scleractinian coral Acropora sp.