James D. Hays

Bio: James D. Hays is an academic researcher from Columbia University. The author has contributed to research in topics: Glacial period & Sea ice. The author has an hindex of 35, co-authored 43 publications receiving 12325 citations. Previous affiliations of James D. Hays include Lamont–Doherty Earth Observatory.

Variations in the Earth's Orbit: Pacemaker of the Ice Ages

Abstract: 1) Three indices of global climate have been monitored in the record of the past 450,000 years in Southern Hemisphere ocean-floor sediments. 2) Over the frequency range 10(-4) to 10(-5) cycle per year, climatic variance of these records is concentrated in three discrete spectral peaks at periods of 23,000, 42,000, and approximately 100,000 years. These peaks correspond to the dominant periods of the earth's solar orbit, and contain respectively about 10, 25, and 50 percent of the climatic variance. 3) The 42,000-year climatic component has the same period as variations in the obliquity of the earth's axis and retains a constant phase relationship with it. 4) The 23,000-year portion of the variance displays the same periods (about 23,000 and 19,000 years) as the quasi-periodic precession index. 5) The dominant, 100,000-year climatic [See table in the PDF file] component has an average period close to, and is in phase with, orbital eccentricity. Unlike the correlations between climate and the higher-frequency orbital variations (which can be explained on the assumption that the climate system responds linearly to orbital forcing), an explanation of the correlation between climate and eccentricity probably requires an assumption of nonlinearity. 6) It is concluded that changes in the earth's orbital geometry are the fundamental cause of the succession of Quaternary ice ages. 7) A model of future climate based on the observed orbital-climate relationships, but ignoring anthropogenic effects, predicts that the long-term trend over the next sevem thousand years is toward extensive Northern Hemisphere glaciation.

Milankovitch and Climate

Abstract: 1 2 2 . 2 d J. Adem , A· Bergzr , Ph. Gaspar , P. Pest1aux an J.P. van Ypersele 1 Centro de Ciencias de la Atmosfera, UNAM, 04510 ~exico D.F. Universit~ Catholique de Louvain, Institut d 'Astronomie et de G~ophysique G. Lemattre, B-1348 Louvain-la-Neuve, Belgium The objective of the present work is to simulate 'the equilibrium climate at 5 different stages of the last deglaciation, in order to assess the respective role of different forcings: insolation, ice boundaries and sea surface temperature. We use as forcing the radiation data from Berger ( 1), the ice sheet boundaries from Denton (2) and the sea surface temperature from CLIMAP (3). In these experiments we use Adem's thermodynamic mode 1 which is a hemispheric grid model with a realistic distribution of continents and oceans and which includes these three forcings as input data. The procedure used is to simulate first the climate for present conditions and then for the 5 stages of the deglaciation for which Denton gives ice boundaries : 18, 13, 10, 8 and 7 kyr BP.

Pliocene-Pleistocene Sediments of the Equatorial Pacific: Their Paleomagnetic, Biostratigraphic, and Climatic Record

Abstract: Magnetic stratigraphy of 15 oriented cores from the equatorial Pacific was determined as far back as the Gilbert reversed-polarity epoch. Ranges of selected species of four major microfossil groups (diatoms, silicoflagellates, foraminifers and Radiolaria) are compared with the record of geomagnetic reversals during the last 4.5 m. y. in eastern equatorial Pacific deep-sea cores. Characteristics of the fossil assemblages are used as criteria for recognition of most of the paleomagnetic reversals that occurred during this interval. Two zones of major paleontological change occur characterized by extinctions of several species and coiling direction changes in some foraminifers. The first change comes in the middle of the Gauss normal magnetic series (about 3 m.y. B.P.) and the second near the Olduvai magnetic event (about 2.0 m.y. B.P.). Seven equatorial foraminiferal species, two radiolarian species, and two diatom species become extinct near reversals. The establishment of the true chronostratigraphic relationships of these selected microfossil species allows us to date zonations of previous authors and provides absolute dates that can be used in worldwide correlation of marine sediments. The percentage of calcium carbonate was determined throughout the lengths of four cores. Eight distinct carbonate cycles are present in the Brunhes series, having periodicities of about 75,000 years in the upper Brunhes to over 100,000 years in the lower Brunhes. It is possible to correlate these carbonate cycles among our cores and also to correlate them with the previous work of Arrhenius who equated the carbonate peaks with glacial stages and the troughs with interglacial stages. This interpretation is supported by paleomagnetic and C14 dating of the last carbonate high which is synchronous with the Wisconsin glaciation (80,000 to 11,500 years B.P.). It, therefore, is probable that there were eight major glacial fluctuations during the last 700,000 years. During the last 400,000 years there is good correlation between the carbonate cycles of the Pacific and evidence of climatic fluctuations in the Atlantic established by Ericson and Wollin (1968) and Emiliani (1966) based on fossil abundances and oxygen isotope ratios, respectively. The rates of sedimentation during the Brunhes series range between 3.5 mm/1000 years for siliceous ooze to 17.5 mm/1000 years for highly calcareous sediment.

Lithospheric Plate Motion, Sea Level Changes and Climatic and Ecological Consequences

Abstract: We demonstrate quantitatively that the world-wide Mid to Upper Cretaceous transgression and subsequent regression may have been caused by a contemporaneous pulse of rapid spreading at most of the mid-oceanic ridges between −110 to −85 m.y. The rapid spreading caused the ridges to expand and hence reduced the volumetric capacity of the basins. The subsequent regression was caused by a reduction in spreading rates beginning at −85 m.y.

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

Abstract: 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.

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

Abstract: [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

Geochemistry of eocene calc-alkaline volcanic rocks from the Kastamonu area, Northern Turkey

Abstract: Analytical data for Sr, Rb, Cs, Ba, Pb, rare earth elements, Y, Th, U, Zr, Hf, Sn, Nb, Mo, Ni, Co, V, Cr, Sc, Cu and major elements are reported for eocene volcanic rocks cropping out in the Kastamonu area, Pontic chain of Northern Turkey. SiO2% versus K2O% relationship shows that the analyzed samples belong to two major groups: the basaltic andesitic and the andesitic ones. High-K basaltic andesites and low-K andesites occur too. Although emplaced on continental type basement (the North Anatolian Crystalline Swell), the Pontic eocene volcanics show elemental abundances closely comparable with typical island arc calc-alkaline suites, e.g. low SiO2% range, low to moderate K2O% and large cations (Cs, Rb, Sr, Ba, Pb) contents and REE patterns with fractionated light and almost flat heavy REE patterns. ΣREE and highly charged cations (Th, U, Hf, Sn, Zr) are slightly higher than typical calc-alkaline values. Ferromagnesian elements show variable values. Within the basaltic andesite group the increase of K%, large cations, ΣREE, La/Yb ratio and high valency cations and the decrease of ferromagnesian element abundances with increasing SiO2% content indicate that the rock types making up this group developed by crystalliquid fractionation of olivine and clinopyroxene from a basic parent magma. Trace element concentration suggest that the andesite group was not derived by crystal-liquid fractionation processes from the basaltic andesites, but could represent a distinct group of rocks derived from a different parent magma.

Global Sea Floor Topography from Satellite Altimetry and Ship Depth Soundings

Abstract: A digital bathymetric map of the oceans with a horizontal resolution of 1 to 12 kilometers was derived by combining available depth soundings with high-resolution marine gravity information from the Geosat and ERS-1 spacecraft. Previous global bathymetric maps lacked features such as the 1600-kilometer-long Foundation Seamounts chain in the South Pacific. This map shows relations among the distributions of depth, sea floor area, and sea floor age that do not fit the predictions of deterministic models of subsidence due to lithosphere cooling but may be explained by a stochastic model in which randomly distributed reheating events warm the lithosphere and raise the ocean floor.

Evidence for general instability of past climate from a 250-kyr ice-core record

Abstract: RECENT results1,2 from two ice cores drilled in central Greenland have revealed large, abrupt climate changes of at least regional extent during the late stages of the last glaciation, suggesting that climate in the North Atlantic region is able to reorganize itself rapidly, perhaps even within a few decades. Here we present a detailed stable-isotope record for the full length of the Greenland Ice-core Project Summit ice core, extending over the past 250 kyr according to a calculated timescale. We find that climate instability was not confined to the last glaciation, but appears also to have been marked during the last interglacial (as explored more fully in a companion paper3) and during the previous Saale–Holstein glacial cycle. This is in contrast with the extreme stability of the Holocene, suggesting that recent climate stability may be the exception rather than the rule. The last interglacial seems to have lasted longer than is implied by the deep-sea SPECMAP record4, in agreement with other land-based observations5,6. We suggest that climate instability in the early part of the last interglacial may have delayed the melting of the Saalean ice sheets in America and Eurasia, perhaps accounting for this discrepancy.