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

/pdf/intcal13-and-marine13-radiocarbon-age-calibration-curves-0-4f3vsbzfqx.pdf

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.

/pdf/trends-rhythms-and-aberrations-in-global-climate-65-ma-to-cflhxkixnq.pdf

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.

/pdf/extended-14c-data-base-and-revised-calib-3-0-14c-age-4x1nxe8awy.pdf

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

/pdf/a-pliocene-pleistocene-stack-of-57-globally-distributed-n5iphe7mt2.pdf

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

Variations in the stable isotopic composition of benthic foraminifera from Deep-Sea Drilling Project (DSDP) site 502B in the Caribbean Sea are used to reconstruct Atlantic intermediate water circulation variability over the last 1.2 m.y. Comparison of this record with other North Atlantic benthic isotope records indicates that Atlantic intermediate water circulation was relatively enhanced during glacial maxima when North Atlantic deep water (NADW) production was reduced. However, a simple, compensatory relationship between intermediate and deepwater circulation is not apparent. Geochemical models have shown that such changes in ocean circulation can affect atmospheric CO2 levels by changing vertical nutrient and alkalinity profiles. The Δδ13C difference between Caribbean site 502B and deep equatorial Pacific site 677 is highly coherent and in phase with ice volume. Like the δ18O record, there is an increase in amplitude (40%) and a large increase in 100 kyr power after 0.7 Ma. The 1.2‰ Δδ13C amplitude scales to 70 ppm V in atmospheric CO2 using Boyle's (1986) box model result. The implied increase in CO2 amplitude after 0.7 Ma may suggest a positive feedback role in effecting the higher-amplitude climatic fluctuations which characterize the last 0.7 m.y.

Pleistocene δ13C variability of North Atlantic intermediate water

Oxygen isotope (H218O/H216O)/salinity data identify freshwater sources along the northeastern North American continental margin The oxygen isotope (δ18O)-salinity (S) properties of various water types are distinguished Sea ice formation on the Labrador Shelf is shown to influence δ18O-S values It is estimated that 2–3 m of freshwater is extracted from the water column to form sea ice It is hypothesized that waters on the Scotian Shelf, Gulf of Maine, and the Middle Atlantic Bight are composed of slope water diluted by an upstream low-salinity source This upstream source is a mixture of brine-enriched Labrador Shelf Water and St Lawrence River water The δ18O value of the apparent freshwater component (δ18OS=0) of waters on the Scotian Shelf and farther south is ≈−20‰, which has been used to suggest a sole high-latitude freshwater source We show instead that the St Lawrence River contributes ≈35% of the freshwater on the Scotian Shelf, in agreement with the physical oceanographic evidence The remaining freshwater is supplied by high-latitude rivers dominated by Arctic runoff Finally, the isotope evidence identifies Baffin Bay as an important pathway by which freshwater from the Arctic Ocean can reach the Labrador Sea

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/1999JC900155

Freshwater sources to the coastal ocean off northeastern North America: Evidence from H2 18O/H2 16O

Carbon isotopic fractionation in multiple species of planktonic foraminifera from core-tops in the tropical Atlantic

Seasonal variations in the oxygen-18/oxygen-16 ratio of calcite shells of living planktonic foraminifera in the Sargasso Sea off Bermuda are a direct function of surface water temperature. Seasonal occurrence as well as depth habitat are determining factors in the oxygen isotopic composition of planktonic foraminifera. These relationships may be used to determine the seasonal temperature contrast of oceans in the past.

https://science.sciencemag.org/content/sci/206/4417/447.full.pdf

Richard G. Fairbanks

Papers

Pleistocene δ13C variability of North Atlantic intermediate water

Freshwater sources to the coastal ocean off northeastern North America: Evidence from H2 18O/H2 16O

Carbon isotopic fractionation in multiple species of planktonic foraminifera from core-tops in the tropical Atlantic

Seasonal Oxygen Isotopic Variations in Living Planktonic Foraminifera off Bermuda.

Tropical Atlantic coral oxygen isotopes: glacial–interglacial sea surface temperatures and climate change