scholarly journals Duration of Greenland Stadial 22 and ice-gas Δage from counting of annual layers in Greenland NGRIP ice core

2012 ◽  
Vol 8 (6) ◽  
pp. 1839-1847 ◽  
Author(s):  
P. Vallelonga ◽  
G. Bertagna ◽  
T. Blunier ◽  
H. A. Kjær ◽  
T. J. Popp ◽  
...  
Keyword(s):  
High Resolution ◽  
Ice Core ◽  
Ice Age ◽  
Age Difference ◽  
Glacial Period ◽  
Annual Layer ◽  
Chemical Impurities ◽  
Dronning Maud Land ◽  
Ice Core Records

Abstract. High-resolution measurements of chemical impurities and methane concentrations in Greenland ice core samples from the early glacial period allow the extension of annual-layer counted chronologies and the improvement of gas age-ice age difference (Δage) essential to the synchronization of ice core records. We report high-resolution measurements of a 50 m section of the NorthGRIP ice core and corresponding annual layer thicknesses in order to constrain the duration of the Greenland Stadial 22 (GS-22) between Greenland Interstadials (GIs) 21 and 22, for which inconsistent durations and ages have been reported from Greenland and Antarctic ice core records as well as European speleothems. Depending on the chronology used, GS-22 occurred between approximately 89 (end of GI-22) and 83 kyr b2k (onset of GI-21). From annual layer counting, we find that GS-22 lasted between 2696 and 3092 years and was followed by a GI-21 pre-cursor event lasting between 331 and 369 yr. Our layer-based counting agrees with the duration of stadial 22 as determined from the NALPS speleothem record (3250 ± 526 yr) but not with that of the GICC05modelext chronology (2620 yr) or an alternative chronology based on gas-marker synchronization to EPICA Dronning Maud Land ice core. These results show that GICC05modelext overestimates accumulation and/or underestimates thinning in this early part of the last glacial period. We also revise the possible ranges of NorthGRIP Δdepth (5.49 to 5.85 m) and Δage (498 to 601 yr) at the warming onset of GI-21 as well as the Δage range at the onset of the GI-21 precursor warming (523 to 654 yr), observing that temperature (represented by the δ15N proxy) increases before CH4 concentration by no more than a few decades.

scholarly journals New constraints on the gas age-ice age difference along the EPICA ice cores, 0–50 kyr

2007 ◽  
Vol 3 (3) ◽  
pp. 527-540 ◽  
Author(s):  
L. Loulergue ◽  
F. Parrenin ◽  
T. Blunier ◽  
J.-M. Barnola ◽  
R. Spahni ◽  
...  
Keyword(s):  
Ice Core ◽  
Phase Relationship ◽  
Ice Cores ◽  
Climatic Conditions ◽  
Ice Age ◽  
Age Difference ◽  
Last Deglaciation ◽  
Last Glacial Period ◽  
Polar Ice Sheets ◽  
Dronning Maud Land

Abstract. Gas is trapped in polar ice sheets at ~50–120 m below the surface and is therefore younger than the surrounding ice. Firn densification models are used to evaluate this ice age-gas age difference (Δage) in the past. However, such models need to be validated by data, in particular for periods colder than present day on the East Antarctic plateau. Here we bring new constraints to test a firn densification model applied to the EPICA Dome C (EDC) site for the last 50 kyr, by linking the EDC ice core to the EPICA Dronning Maud Land (EDML) ice core, both in the ice phase (using volcanic horizons) and in the gas phase (using rapid methane variations). We also use the structured 10Be peak, occurring 41 kyr before present (BP) and due to the low geomagnetic field associated with the Laschamp event, to experimentally estimate the Δage during this event. Our results seem to reveal an overestimate of the Δage by the firn densification model during the last glacial period at EDC. Tests with different accumulation rates and temperature scenarios do not entirely resolve this discrepancy. Although the exact reasons for the Δage overestimate at the two EPICA sites remain unknown at this stage, we conclude that current densification model simulations have deficits under glacial climatic conditions. Whatever the cause of the Δage overestimate, our finding suggests that the phase relationship between CO2 and EDC temperature previously inferred for the start of the last deglaciation (lag of CO2 by 800±600 yr) seems to be overestimated.

scholarly journals An 83 000-year-old ice core from Roosevelt Island, Ross Sea, Antarctica

2020 ◽  
Vol 16 (5) ◽  
pp. 1691-1713 ◽  
Author(s):  
James E. Lee ◽  
Edward J. Brook ◽  
Nancy A. N. Bertler ◽  
Christo Buizert ◽  
Troy Baisden ◽  
...  
Keyword(s):  
Ross Sea ◽  
Ice Core ◽  
Ice Cores ◽  
Ice Age ◽  
Age Difference ◽  
Last Deglaciation ◽  
Ice Streams ◽  
West Antarctic Ice Sheet ◽  
Annual Layer ◽  
West Antarctic

Abstract. In 2013 an ice core was recovered from Roosevelt Island, an ice dome between two submarine troughs carved by paleo-ice-streams in the Ross Sea, Antarctica. The ice core is part of the Roosevelt Island Climate Evolution (RICE) project and provides new information about the past configuration of the West Antarctic Ice Sheet (WAIS) and its retreat during the last deglaciation. In this work we present the RICE17 chronology, which establishes the depth–age relationship for the top 754 m of the 763 m core. RICE17 is a composite chronology combining annual layer interpretations for 0–343 m (Winstrup et al., 2019) with new estimates for gas and ice ages based on synchronization of CH4 and δ18Oatm records to corresponding records from the WAIS Divide ice core and by modeling of the gas age–ice age difference. Novel aspects of this work include the following: (1) an automated algorithm for multiproxy stratigraphic synchronization of high-resolution gas records; (2) synchronization using centennial-scale variations in methane for pre-anthropogenic time periods (60–720 m, 1971 CE to 30 ka), a strategy applicable for future ice cores; and (3) the observation of a continuous climate record back to ∼65 ka providing evidence that the Roosevelt Island Ice Dome was a constant feature throughout the last glacial period.

scholarly journals Synchronization of ice core records via atmospheric gases

2007 ◽  
Vol 3 (2) ◽  
pp. 325-330 ◽  
Author(s):  
T. Blunier ◽  
R. Spahni ◽  
J.-M. Barnola ◽  
J. Chappellaz ◽  
L. Loulergue ◽  
...  
Keyword(s):  
Time Series ◽  
High Resolution ◽  
Ice Core ◽  
Ice Cores ◽  
Atmospheric Gases ◽  
Different Types ◽  
Climate Records ◽  
Dronning Maud Land ◽  
Climate Events ◽  
Ice Core Records

Abstract. To interpret new high resolution climate records it becomes more and more important to know about the succession of climate events. Such knowledge is hard to get especially when dealing with different types of climate archives. Even for ice cores a direct synchronization between ice cores from Greenland and Antarctica has not been possible so far due to the lack of time markers occurring in both hemispheres. Fortunately, variations in the time series of global gas records can be used as indirect time markers. Here we discuss in detail the steps that are necessary to synchronize ice cores via global gas records exemplified on the synchronization of the EPICA ice core from Dronning Maud Land to a Greenland record from North GRIP.

scholarly journals New constraints on the gas age-ice age difference along the EPICA ice cores, 0–50 kyr

2007 ◽  
Vol 3 (2) ◽  
pp. 435-467 ◽  
Author(s):  
L. Loulergue ◽  
F. Parrenin ◽  
T. Blunier ◽  
J.-M. Barnola ◽  
R. Spahni ◽  
...  
Keyword(s):  
Ice Core ◽  
Phase Relationship ◽  
Ice Cores ◽  
Climatic Conditions ◽  
Ice Age ◽  
Age Difference ◽  
Last Deglaciation ◽  
Last Glacial Period ◽  
Polar Ice Sheets ◽  
Dronning Maud Land

Abstract. Gas is trapped in polar ice sheets at ~50–120 m below the surface and is therefore younger than the surrounding ice. Firn densification models are used to evaluate this ice age-gas age difference (Δage) in the past. However, such models are not well tested on low accumulation and cold sites of the East Antarctic plateau, especially for periods with different climatic conditions. Here we bring new constraints to test a firn densification model applied to the EPICA Dome C (EDC) site for the last 50 kyr, by linking the EDC ice core to the EPICA Dronning Maud Land (EDML) ice core, both in the ice phase (using volcanic horizons) and in the gas phase (using rapid methane variations). We use the structured 10Be peak, occurring 41 kyr before present (BP) and due to the low geomagnetic field associated with the Laschamp event, to experimentally estimate the Δage and Δdepth during this event. It allows us to evaluate the model and to link together climatic archives from EDC and EDML to NorthGRIP (Greenland). Our results reveal an overestimate of the Δage by the firn densification model during the last glacial period at EDC. Tests with different accumulation rates and temperature scenarios do not entirely resolve this discrepancy. Our finding suggests that the phase relationship between CO2 and EDC temperature inferred at the start of the last deglaciation (lag of CO2 by 800±600 yr) is overestimated and that the CO2 increase could well have been in phase or slightly leading the temperature increase at EDC.

scholarly journals The WAIS-Divide deep ice core WD2014 chronology – Part 2: Methane synchronization (68–31 ka BP) and the gas age-ice age difference

2014 ◽  
Vol 10 (4) ◽  
pp. 3537-3584 ◽  
Author(s):  
C. Buizert ◽  
K. M. Cuffey ◽  
J. P. Severinghaus ◽  
D. Baggenstos ◽  
T. J. Fudge ◽  
...  
Keyword(s):  
Ice Core ◽  
Impurity Content ◽  
Ice Cores ◽  
Ice Age ◽  
Age Difference ◽  
Atmospheric Methane ◽  
High Accumulation ◽  
West Antarctic Ice Sheet ◽  
Annual Layer ◽  
West Antarctic

Abstract. The West Antarctic Ice Sheet (WAIS)-Divide ice core (WAIS-D) is a newly drilled, high-accumulation deep ice core that provides Antarctic climate records of the past ∼68 ka at unprecedented temporal resolution. The upper 2850 m (back to 31.2 ka BP) have been dated using annual-layer counting. Here we present a chronology for the deep part of the core (67.8–31.2 ka BP), which is based on stratigraphic matching to annual-layer-counted Greenland ice cores using globally well-mixed atmospheric methane. We calculate the WAIS-D gas age-ice age difference (Δage) using a combination of firn densification modeling, ice flow modeling, and a dataset of δ15N-N2, a proxy for past firn column thickness. The largest Δage at WAIS-D occurs during the last glacial maximum, and is 525 ± 100 years. Internally consistent solutions can only be found when assuming little-to-no influence of impurity content on densification rates, contrary to a recently proposed hypothesis. We synchronize the WAIS-D chronology to a linearly scaled version of the layer-counted Greenland Ice Core Chronology (GICC05), which brings the age of Dansgaard-Oeschger (DO) events into agreement with the U/Th absolutely dated Hulu speleothem record. The small Δage at WAIS-D provides valuable opportunities to investigate the timing of atmospheric greenhouse gas variations relative to Antarctic climate, as well as the interhemispheric phasing of the bipolar "seesaw".

scholarly journals The WAIS Divide deep ice core WD2014 chronology – Part 1: Methane synchronization (68–31 ka BP) and the gas age–ice age difference

2015 ◽  
Vol 11 (2) ◽  
pp. 153-173 ◽  
Author(s):  
C. Buizert ◽  
K. M. Cuffey ◽  
J. P. Severinghaus ◽  
D. Baggenstos ◽  
T. J. Fudge ◽  
...  
Keyword(s):  
Ice Core ◽  
Impurity Content ◽  
Ice Cores ◽  
Ice Age ◽  
Age Difference ◽  
Atmospheric Methane ◽  
High Accumulation ◽  
Data Set ◽  
Annual Layer ◽  
West Antarctic

Abstract. The West Antarctic Ice Sheet Divide (WAIS Divide, WD) ice core is a newly drilled, high-accumulation deep ice core that provides Antarctic climate records of the past ∼68 ka at unprecedented temporal resolution. The upper 2850 m (back to 31.2 ka BP) have been dated using annual-layer counting. Here we present a chronology for the deep part of the core (67.8–31.2 ka BP), which is based on stratigraphic matching to annual-layer-counted Greenland ice cores using globally well-mixed atmospheric methane. We calculate the WD gas age–ice age difference (Δage) using a combination of firn densification modeling, ice-flow modeling, and a data set of δ15N-N2, a proxy for past firn column thickness. The largest Δage at WD occurs during the Last Glacial Maximum, and is 525 ± 120 years. Internally consistent solutions can be found only when assuming little to no influence of impurity content on densification rates, contrary to a recently proposed hypothesis. We synchronize the WD chronology to a linearly scaled version of the layer-counted Greenland Ice Core Chronology (GICC05), which brings the age of Dansgaard–Oeschger (DO) events into agreement with the U/Th absolutely dated Hulu Cave speleothem record. The small Δage at WD provides valuable opportunities to investigate the timing of atmospheric greenhouse gas variations relative to Antarctic climate, as well as the interhemispheric phasing of the "bipolar seesaw".

scholarly journals Synchronization of ice core records via atmospheric gases

2007 ◽  
Vol 3 (1) ◽  
pp. 365-381 ◽  
Author(s):  
T. Blunier ◽  
R. Spahni ◽  
J.-M. Barnola ◽  
J. Chappellaz ◽  
L. Loulergue ◽  
...  
Keyword(s):  
Time Series ◽  
High Resolution ◽  
Ice Core ◽  
Ice Cores ◽  
Atmospheric Gases ◽  
Different Types ◽  
Climate Records ◽  
Dronning Maud Land ◽  
Climate Events ◽  
Ice Core Records

Abstract. To interpret new high resolution climate records it becomes more and more important to know about the succession of climate events. Such knowledge is hard to get especially when dealing with different types of climate archives. Even for ice cores a direct synchronization between ice cores from Greenland and Antarctica has not been possible so far due to the lack of time markers occurring in both hemispheres. Fortunately, variations in the time series of global gas records can be used as indirect time markers. Here we discuss in detail the steps that are necessary to synchronize ice cores via global gas records exemplified on the synchronization of the EPICA ice core from Dronning Maud Land to a Greenland record from North GRIP.

scholarly journals Duration of Greenland Stadial 22 and ice-gas Δage from counting of annual layers in Greenland NGRIP ice core

2012 ◽  
Vol 8 (4) ◽  
pp. 2583-2605 ◽  
Author(s):  
P. Vallelonga ◽  
G. Bertagna ◽  
T. Blunier ◽  
H. A. Kjær ◽  
T. J. Popp ◽  
...  
Keyword(s):  
Ice Core ◽  
Ice Age ◽  
Dust Particles ◽  
Last Glacial Period ◽  
Annual Layer ◽  
Multiple Analytes ◽  
Ch4 Concentration ◽  
The Last Glacial

Abstract. The NorthGRIP ice core chronology GICC05modelext is composed of the annual-layer counted GICC05 chronology to 60 kyr before 2000 AD (b2k), and an ice flow model dating the deepest part of the ice core to 123 kyr b2k. Determination of annual strata in ice beyond 60 kyr b2k has been challenged by the thinning of annual layers to <1 cm and the appearance of microfolds in some early glacial strata. We report high-resolution measurements of a 50 m section of the NorthGRIP ice core and corresponding annual layer thicknesses, constraining the duration of the Greenland Stadial (GS-22) between Greenland Interstadials (GIs) 21 and 22 which occurred between approximately 89 (end of GI-22) and 83 kyr b2k (onset of GI-21) depending on the chronology used. Multiple analytes (insoluble dust particles, electrolytic conductivity, ammonium and sodium) were determined in annual layers of ice often thinner than 1 cm. From annual layer counting, we find that GS-22 lasted 2894 ± 198 yr and was followed by a GI-21 pre-cursor event lasting 350 ± 19 yr. Our layer-based counting agrees with the duration of GS-22 determined from the NALPS speleothem record (3250 ± 526 yr) but not with that of the GICC05modelext chronology (2620 yr). These results show that GICC05modelext overestimates accumulation and/or underestimates thinning in this early part of the last glacial period. We also revise the NorthGRIP ice depth-gas depth (5.67 ± 0.18 m) and ice age-gas age (550 ± 52 yr) differences at the warming onset of GI-21, observing that δ15N increases before CH4 concentration by no more than a few decades.

scholarly journals A comparison of annual layer thickness model estimates with observational measurements using the Berkner Island ice core, Antarctica

2017 ◽  
Vol 29 (4) ◽  
pp. 382-393
Author(s):  
A. Massam ◽  
S.B. Sneed ◽  
G.P. Lee ◽  
R.R. Tuckwell ◽  
R. Mulvaney ◽  
...  
Keyword(s):  
High Resolution ◽  
Layer Thickness ◽  
Inductively Coupled Plasma ◽  
Ice Core ◽  
Ultra Violet ◽  
Analytical Techniques ◽  
Inductively Coupled ◽  
Annual Layer ◽  
Icp Ms ◽  
Chemical Profiles

AbstractA model to estimate the annual layer thickness of deposited snowfall at a deep ice core site, compacted by vertical strain with respect to depth, is assessed using ultra-high-resolution laboratory analytical techniques. A recently established technique of high-resolution direct chemical analysis of ice using ultra-violet laser ablation inductively-coupled plasma mass spectrometry (LA ICP-MS) has been applied to ice from the Berkner Island ice core, and compared with results from lower resolution techniques conducted on parallel sections of ice. The results from both techniques have been analysed in order to assess the capability of each technique to recover seasonal cycles from deep Antarctic ice. Results do not agree with the annual layer thickness estimates from the age–depth model for individual samples <1 m long as the model cannot reconstruct the natural variability present in annual accumulation. However, when compared with sections >4 m long, the deviation between the modelled and observational layer thicknesses is minimized to within two standard deviations. This confirms that the model is capable of successfully estimating mean annual layer thicknesses around analysed sections. Furthermore, our results confirm that the LA ICP-MS technique can reliably recover seasonal chemical profiles beyond standard analytical resolution.

Reconstructing an Interdecadal Pacific Oscillation Index from a Pacific Basin–Wide Collection of Ice Core Records

2021 ◽  
Vol 34 (10) ◽  
pp. 3839-3852
Author(s):  
Stacy E. Porter ◽  
Ellen Mosley-Thompson ◽  
Lonnie G. Thompson ◽  
Aaron B. Wilson
Keyword(s):  
Ice Core ◽  
Ice Cores ◽  
Tropical Pacific ◽  
Ice Age ◽  
Pacific Basin ◽  
Interdecadal Pacific Oscillation ◽  
The Pacific ◽  
Instrumental Period ◽  
The Tropical Pacific ◽  
Ice Core Records

AbstractUsing an assemblage of four ice cores collected around the Pacific basin, one of the first basinwide histories of Pacific climate variability has been created. This ice core–derived index of the interdecadal Pacific oscillation (IPO) incorporates ice core records from South America, the Himalayas, the Antarctic Peninsula, and northwestern North America. The reconstructed IPO is annually resolved and dates to 1450 CE. The IPO index compares well with observations during the instrumental period and with paleo-proxy assimilated datasets throughout the entire record, which indicates a robust and temporally stationary IPO signal for the last ~550 years. Paleoclimate reconstructions from the tropical Pacific region vary greatly during the Little Ice Age (LIA), although the reconstructed IPO index in this study suggests that the LIA was primarily defined by a weak, negative IPO phase and hence more La Niña–like conditions. Although the mean state of the tropical Pacific Ocean during the LIA remains uncertain, the reconstructed IPO reveals some interesting dynamical relationships with the intertropical convergence zone (ITCZ). In the current warm period, a positive (negative) IPO coincides with an expansion (contraction) of the seasonal latitudinal range of the ITCZ. This relationship is not stationary, however, and is virtually absent throughout the LIA, suggesting that external forcing, such as that from volcanoes and/or reduced solar irradiance, could be driving either the ITCZ shifts or the climate dominating the ice core sites used in the IPO reconstruction.

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