Oxygen 18/16 variability in Greenland snow and ice with 10 -3- to 105-year time resolution
TL;DR: The Greenland Ice Sheet Project 2 (GISP2) ice core has been used to provide a 100,000 +-year detailed oxygen isotope profile covering almost a full glacial-interglacial cycle as discussed by the authors.
Abstract: The 3-km-long Greenland Ice Sheet Project 2 (GISP2) ice core presents a 100,000 +- year detailed oxygen isotope profile covering almost a full glacial-interglacial cycle. Measuranents of isotopic fluctuations in snow, frost, and atmospheric water vapor samples collected during summer field seasons (up to 20%0) are compatible with the large and abrupt 80/160 changes observed in accumulated tim. Snow pit 1580 profiles from the GISP2 summit area, however, show rapid smoothing of the 180/160 signal near the surface. Beyond about 2-m depth the smoothedi5180 signal is fairly well preserved and can be interpreted in terms of average local weather conditions and climate. The longer climate fluctuations also have regional and often global significance. In the older part of the record, corresponding to marine isotope stages (MIS) 5a to 5d, the effect of orbital climate forcing via the 19- and 23-kyr precession cycles and the 41-kyr obliquity cycle is obvious. From the end ofMIS 5a, at about 75,000 years B.P., till the end of the glacial at the Younger Dryas-Preboreal transition, at 11,650 years B.P., the O180/160 record shows frequent, rapid switches between intermediate interstadial and low stadial values. Fourier spectra of the oscillations that are superimposed on the orbitally induced changes contain a strong periodicity at 1.5 kyr, a broad peak at 4.0 kyr, and additional shorter periods. Detailed comparison of the GISP2 180/160 record with the Vostok, Antarctica, 15D record; Pacific Ocean foraminiferal 180/160; Grande Pile, France, tree pollen; and insolation indicates that a counterpart to many of the rapid 180/160 fluctuations of GISP2 can be found in the other records, and that the GISP2 isotopic changes clearly are the local expression of climate changes of worldwide extent. Correlation of events on the independent GISP2 and SPECMAP time scales for the interval 10,000-50,000 years B.P. shows excellent chronometric agreement, except possibly for the event labeled 3.1. The glacial to interglacial transition evidently started simultaneously in the Arctic and the Antarctic, but its development and its expression in Greenland isotopes was later suppressed by the influence of meltwater, especially from the Barents Sea ice sheet, on deep water formation and ocean circulation. Meltwaters from different ice sheets bordering the North Atlantic also influenced ocean circulation during the Bolling-Allerod interstadial complex and the Younger Dryas and led to a distinct development of European climate and Greenland 180/160 values. The Holocene interval with long-term stable mean isotopic values contains several fluauations with periods from years to millennia. Dominant is a 6.3-year oscillation with amplitude up to 3 to 4%0. Periodicities of 11 and 210 years, also found in the solar-modulated records of the cosmogenic isotopes 1oBe and 14C, suggest solar processes as the cause of these cycles. Depression of180/160 values (cooling) by volcanic eruptions is observed in stacked GISP21580 records, but the effect is small and not likely to trigger major climate changes.
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TL;DR: In this paper, a new common stratigraphic timescale for the North Greenland Ice Core Project (NGRIP) and GRIP ice cores is presented, which covers the period 7.9-14.8 kyr before present and includes the Bolling, Allerod, Younger Dryas, and early Holocene periods.
Abstract: [1] We present a new common stratigraphic timescale for the North Greenland Ice Core Project (NGRIP) and GRIP ice cores. The timescale covers the period 7.9–14.8 kyr before present and includes the Bolling, Allerod, Younger Dryas, and early Holocene periods. We use a combination of new and previously published data, the most prominent being new high-resolution Continuous Flow Analysis (CFA) impurity records from the NGRIP ice core. Several investigators have identified and counted annual layers using a multiparameter approach, and the maximum counting error is estimated to be up to 2% in the Holocene part and about 3% for the older parts. These counting error estimates reflect the number of annual layers that were hard to interpret, but not a possible bias in the set of rules used for annual layer identification. As the GRIP and NGRIP ice cores are not optimal for annual layer counting in the middle and late Holocene, the timescale is tied to a prominent volcanic event inside the 8.2 kyr cold event, recently dated in the DYE-3 ice core to 8236 years before A. D. 2000 (b2k) with a maximum counting error of 47 years. The new timescale dates the Younger Dryas-Preboreal transition to 11,703 b2k, which is 100–150 years older than according to the present GRIP and NGRIP timescales. The age of the transition matches the GISP2 timescale within a few years, but viewed over the entire 7.9–14.8 kyr section, there are significant differences between the new timescale and the GISP2 timescale. The transition from the glacial into the Bolling interstadial is dated to 14,692 b2k. The presented timescale is a part of a new Greenland ice core chronology common to the DYE-3, GRIP, and NGRIP ice cores, named the Greenland Ice Core Chronology 2005 (GICC05). The annual layer thicknesses are observed to be log-normally distributed with good approximation, and compared to the early Holocene, the mean accumulation rates in the Younger Dryas and Bolling periods are found to be 47 ± 2% and 88 ± 2%, respectively.
1,789 citations
Cites methods from "Oxygen 18/16 variability in Greenla..."
...The 20 year resolution GISP2 isotope profile of Grootes and Stuiver [1997] and Stuiver and Grootes [2000] is presented on the timescale of Meese et al. [1997]....
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TL;DR: Specific as well as more general approaches to constrained randomisation, providing a full range of examples, and some implementational aspects of the realisation of these methods in the TISEAN software package are discussed.
1,556 citations
Cites methods from "Oxygen 18/16 variability in Greenla..."
...As an application, let us construct randomised versions of part of an ice core data set, taken from the Greenland Ice Sheet Project Two (GISP2) [44]....
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TL;DR: In this paper, the authors present a continuous record of the Asian monsoon over the last 16 ka from δ18O measurements of stalagmite calcite, which is combined with a chronology from 45 precise 230Th dates.
1,527 citations
University of Copenhagen1, University of Bern2, Royal Holloway, University of London3, Carnegie Institution for Science4, Centre national de la recherche scientifique5, Utrecht University6, Joint Institute for the Study of the Atmosphere and Ocean7, Aberystwyth University8, University of Wales, Lampeter9, University of Sheffield10, University of Washington11
TL;DR: In this paper, a more detailed and extended version of the Greenland Stadials (GS) and Greenland Interstadials (GI) template for the whole of the last glacial period is presented, based on a synchronization of the NGRIP, GRIP, and GISP2 ice-core records.
1,417 citations
TL;DR: In this paper, a Fortran 90 program (REDFIT) is presented that overcomes this problem by fitting a first-order autoregressive (AR1) process, being characteristic for many climatic processes, directly to unevenly spaced time series.
1,048 citations
Cites background or methods from "Oxygen 18/16 variability in Greenla..."
...In the second example, we investigate the glacial part of the oxygen-isotope record from the GISP2 ice core from Greenland ( Grootes and Stuiver, 1997; Fig. 2A), which reflects, to a large extent, air temperature above Greenland....
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...This spectral peak is associated with the so-called Dansgaard–Oeschger oscillations, the dominant mode of millennial-scale climate fluctuations during the last glacial period (e.g. Grootes and Stuiver, 1997 )....
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...In the second example, we investigate the glacial part of the oxygen-isotope record from the GISP2 ice core from Greenland (Grootes and Stuiver, 1997; Fig....
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...This spectral peak is associated with the so-called Dansgaard–Oeschger oscillations, the dominant mode of millennial-scale climate fluctuations during the last glacial period (e.g. Grootes and Stuiver, 1997)....
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...Fig. 2. (A) Oxygen-isotope time series from Greenland GISP2 ice core ( Grootes and Stuiver, 1997 ) between 15–60 thousand years before present (kyr BP)....
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TL;DR: In this paper, 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 isotope records measured in deep-sea cores.
Abstract: 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.
4,483 citations
TL;DR: In this paper, the authors 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, and find that climate instability was not confined to the last glaciation, but appears also have been marked during the last interglacial (as explored more fully in a companion paper), and during the previous Saale-Holstein glacial cycle.
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.
4,367 citations
TL;DR: It is concluded that changes in the earth's orbital geometry are the fundamental cause of the succession of Quaternary ice ages and 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.
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.
3,408 citations
TL;DR: Using the concept of "orbital tuning", a continuous, high-resolution deep-sea chronostratigraphy has been developed spanning the last 300,000 yr as mentioned in this paper.
3,256 citations
TL;DR: In this article, the authors present records of sea surface temperature from North Atlantic sediments spanning the past 90 kyr which contain a series of rapid temperature oscillations closely matching those in the ice-core record, confirming predictions that the ocean must bear the imprint of the Dansgaard-Oeschger events.
Abstract: OXYGEN isotope measurements in Greenland ice demonstrate that a series of rapid warm-cold oscillations—called Dansgaard–Oeschger events—punctuated the last glaciation1. Here we present records of sea surface temperature from North Atlantic sediments spanning the past 90 kyr which contain a series of rapid temperature oscillations closely matching those in the ice-core record, confirming predictions that the ocean must bear the imprint of the Dansgaard–Oeschger events2,3. Moreover, we show that between 20 and 80 kyr ago, the shifts in ocean-atmosphere temperature are bundled into cooling cycles, lasting on average 10 to 15 kyr, with asymmetrical saw-tooth shapes. Each cycle culminated in an enormous discharge of icebergs into the North Atlantic (a 'Hein-rich event'4,5), followed by an abrupt shift to a warmer climate. These cycles document a previously unrecognized link between ice sheet behaviour and ocean–atmosphere temperature changes. An important question that remains to be resolved is whether the cycles are driven by external factors, such as orbital forcing, or by inter-nal ice-sheet dynamics.
2,179 citations