Secular Trends Of Accumulation Rate On Ice Cores From Dunde Ice Cap, China Over The Last 1000 Years

Cooperative research programs were conducted on the Dunde Ice Cap (38°06′N, 96°26′E), China, in 1984, 1986, 1987, by the Lanzhou Institute of Glaciology and Geocryology (LIGG), China and the Byrd Polar Research Center (BPRC), U.S.A. This paper gives the preliminary results of the analysis on accumulation rate of the ice cap over the last 1000 years. Three ice cores were recovered to bedrock from the ice-cap summit (5324 m a.s.l.). Core D-1 (139.8 m long) was divided in the field along the entire length and was shared equally between LIGG and BPRC. Core D-2 (136.6 m long) was returned frozen complete to the LIGG for ice-core measurements. In Core D-3 (138.4 m long) the upper sectors were melted and bottled in the field and the lower sectors were returned frozen to the BPRC, U.S.A. Core D-1 was analyzed in China along the entire length for oxygen isotope, liquid conductivity and pH. A year-by-year dating of the ice cores has been made with Dansgaard-Johnsen’s flow pattern by using the data of surface strain-rate (August 1986 to August 1987) and tritium measurements. The resulting time-scales of the ice cores in Dunde Ice Cap yield an age of 4600 yr B.P. The annual layer thicknesses of core D-1 were measured mainly by δ18O analysis and liquid conductivity. The lower δ18O is generally associated with higher electrical conductivity. Annual layer thickness was converted to accumulation rates and compared with meteorological records from Delingxa Meteorological Station. The mean accumulation rate is 518 mm in ice-equivalent. Particular attention is given to the possible impact of the Little Ice Age. Based on spectral analysis of time series for the accumulation variation with depth, short-term (30, 33 year at 0.01 level) and intermediate-term variation (120 year) were discussed. The ice-core research program has been supported by the Chinese National Foundation of Natural Science under Grant DO125-4860011.

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Secular Trends Of Accumulation Rate On Ice Cores From Dunde Ice Cap, China Over The Last 1000 Years

Annals of Glaciology ◽

10.3189/s0260305500009423 ◽

1990 ◽

Vol 14 ◽

pp. 363-363

Author(s):

Wu Xiaoling ◽

Li Zhongqin ◽

Xie Zichu

Keyword(s):

Accumulation Rate ◽

Ice Core ◽

Ice Cores ◽

Surface Strain ◽

Entire Length ◽

Ice Age ◽

Cooperative Research ◽

Ice Cap ◽

Annual Layer ◽

Lanzhou Institute

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Temperature and mineral dust variability recorded in two low-accumulation Alpine ice cores over the last millennium

Climate of the Past ◽

10.5194/cp-14-21-2018 ◽

2018 ◽

Vol 14 (1) ◽

pp. 21-37 ◽

Cited By ~ 13

Author(s):

Pascal Bohleber ◽

Tobias Erhardt ◽

Nicole Spaulding ◽

Helene Hoffmann ◽

Hubertus Fischer ◽

...

Keyword(s):

Time Series ◽

Mineral Dust ◽

Ice Core ◽

Ice Cores ◽

Temperature Reconstruction ◽

Relative Increase ◽

Ice Age ◽

European Alps ◽

Stable Water Isotopes ◽

Annual Layer

Abstract. Among ice core drilling sites in the European Alps, Colle Gnifetti (CG) is the only non-temperate glacier to offer climate records dating back at least 1000 years. This unique long-term archive is the result of an exceptionally low net accumulation driven by wind erosion and rapid annual layer thinning. However, the full exploitation of the CG time series has been hampered by considerable dating uncertainties and the seasonal summer bias in snow preservation. Using a new core drilled in 2013 we extend annual layer counting, for the first time at CG, over the last 1000 years and add additional constraints to the resulting age scale from radiocarbon dating. Based on this improved age scale, and using a multi-core approach with a neighbouring ice core, we explore the time series of stable water isotopes and the mineral dust proxies Ca2+ and insoluble particles. Also in our latest ice core we face the already known limitation to the quantitative use of the stable isotope variability based on a high and potentially non-stationary isotope/temperature sensitivity at CG. Decadal trends in Ca2+ reveal substantial agreement with instrumental temperature and are explored here as a potential site-specific supplement to the isotope-based temperature reconstruction. The observed coupling between temperature and Ca2+ trends likely results from snow preservation effects and the advection of dust-rich air masses coinciding with warm temperatures. We find that if calibrated against instrumental data, the Ca2+-based temperature reconstruction is in robust agreement with the latest proxy-based summer temperature reconstruction, including a “Little Ice Age” cold period as well as a medieval climate anomaly. Part of the medieval climate period around AD 1100–1200 clearly stands out through an increased occurrence of dust events, potentially resulting from a relative increase in meridional flow and/or dry conditions over the Mediterranean.

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A first chronology for the NEEM ice core

Climate of the Past Discussions ◽

10.5194/cpd-9-2967-2013 ◽

2013 ◽

Vol 9 (3) ◽

pp. 2967-3013 ◽

Cited By ~ 9

Author(s):

S. O. Rasmussen ◽

P. Abbott ◽

T. Blunier ◽

A. Bourne ◽

E. Brook ◽

...

Keyword(s):

Accumulation Rate ◽

Ice Core ◽

Conductivity Measurement ◽

Ice Cores ◽

Monte Carlo Analysis ◽

Heat Diffusion ◽

Ice Age ◽

Age Difference ◽

Electrical Conductivity Measurement ◽

Volcanic Origin

Abstract. A stratigraphy-based chronology for the North Greenland Eemian Ice Drilling (NEEM) ice core has been derived by transferring the annual layer counted Greenland Ice Core Chronology 2005 (GICC05) from the NGRIP core to the NEEM core using 787 match points of mainly volcanic origin identified in the Electrical Conductivity Measurement (ECM) and Dielectrical Profiling (DEP) records. Tephra horizons found in both the NEEM and NGRIP ice cores are used to test the matching based on ECM and DEP and provide additional horizons used for the time scale transfer. A thinning function reflecting the accumulated strain along the core has been determined using a Dansgaard–Johnsen flow model and an isotope-dependent accumulation rate parameterization. Flow parameters are determined from Monte Carlo analysis constrained by the observed depth-age horizons. In order to construct a chronology for the gas phase, the ice age–gas age difference (Δage) has been reconstructed using a coupled firn densification–heat diffusion model. Temperature and accumulation inputs to the Δage model, initially derived from the water isotope proxies, have been adjusted to optimize the fit to timing constraints from δ15N of nitrogen and high-resolution methane data during the abrupt onsets of interstadials. The ice and gas chronologies and the corresponding thinning function represent the first chronology for the NEEM core, and based on both the flow and firn modelling results, the accumulation history for the NEEM site has been reconstructed, providing the necessary basis for further analysis of the records from NEEM.

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Temperature and mineral dust variability recorded in two low accumulation Alpine ice cores over the last millennium

10.5194/cp-2017-80 ◽

2017 ◽

Cited By ~ 2

Author(s):

Pascal Bohleber ◽

Tobias Erhardt ◽

Nicole Spaulding ◽

Helene Hoffmann ◽

Hubertus Fischer ◽

...

Keyword(s):

Time Series ◽

Mineral Dust ◽

Ice Core ◽

Ice Cores ◽

Temperature Reconstruction ◽

Ice Age ◽

European Alps ◽

Annual Layer ◽

Instrumental Temperature

Abstract. Among ice core drilling sites in the European Alps, the Colle Gnifetti (CG) glacier saddle is the only one to offer climate records back to at least 1000 years. This unique long-term archive is the result of an exceptionally low net accumulation driven by wind erosion and rapid annual layer thinning. To-date, however, the full exploitation of the CG time series has been hampered by considerable dating uncertainties and the seasonal summer bias in snow preservation. Using a new core drilled in 2013 we extend annual layer counting, for the first time at CG, over the last 1000 years and add additional constraints to the resulting age scale from radiocarbon dating. Based on this improved age scale, and using a multi-core approach with a neighboring ice core, we explore the potential for reconstructing long-term temperature variability from the stable water isotope and mineral dust proxy time series. A high and potentially non-stationary isotope/temperature sensitivity limits the quantitative use of the stable isotope variability thus far. However, we find substantial agreement comparing the mineral dust proxy Ca2+ with instrumental temperature. The temperature-related variability in the Ca2+ record is explained based on the temperature-dependent snow preservation bias combined with the advection of dust-rich air masses coinciding with warm temperatures. We show that using the Ca2+ trends for a quantitative temperature reconstruction results in good agreement with instrumental temperature and the latest summer temperature reconstruction derived from other archives covering the last 1000 years. This includes a Little Ice Age cold period as well as a medieval climate anomaly. In particular, part of the medieval climate period around 1100–1200 AD stands out through an increased occurrence of dust events, potentially resulting from a relative increase in meridional flow and dry conditions over the Mediterranean.

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Air Content Of The Byrd Core And Past Changes In The West Antarctic Ice Sheet

Annals of Glaciology ◽

10.1017/s0260305500002901 ◽

1982 ◽

Vol 3 ◽

pp. 269-273 ◽

Cited By ~ 42

Author(s):

D. Raynaud ◽

I. M. Whillans

Keyword(s):

Stable Isotope ◽

Accumulation Rate ◽

Ice Core ◽

Ice Sheet ◽

Ice Cores ◽

Isotope Ratios ◽

Ice Age ◽

Gas Content ◽

Stable Isotope Ratios ◽

Antarctic Ice Sheet

Analyses of ice cores taken from the Antarctic ice sheet can provide information on the environmental conditions under which the ice was formed. New results from measurements of gas content and stable isotope ratios in the Byrd station ice core are discussed and interpreted in terms of past iceflow changes.165 selected ice samples from 32 different depth levels along the core were processed for total gas content V and stable isotope ratios. This large dataset is used to discuss the variability and significance of the values of V at different depths. The short term variations of V are mainly explained by heterogeneities of the pore volume when the firn pores close off.The general trends in the values of V with depth are then used to investigate the possibility of past changes in the ice sheet. They suggest near-steady flow during the past few tens of thousands of years and that a thickening of about 200 to 250 m occurred in this area of the ice sheet at the end of the last ice age. This thickening could be due to a change in the accumulation rate.

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A 1000 year climate ice-core record from the Guliya ice cap, China: its relationship to global climate variability

Annals of Glaciology ◽

10.1017/s0260305500015780 ◽

1995 ◽

Vol 21 ◽

pp. 175-181 ◽

Cited By ~ 70

Author(s):

L. G. Thompson ◽

E. Mosley-Thompson ◽

M.E. Davis ◽

P.N. Lin ◽

J. Dai ◽

...

Keyword(s):

Global Climate ◽

Monsoon Season ◽

Eastern China ◽

Ice Core ◽

Ice Cores ◽

Ice Age ◽

Ice Cap ◽

Western Kunlun ◽

Ice Core Record ◽

Western Side

In 1992, an American-Chinese expedition successfully recovered three ice cores (308.6, 93.2 and 34.5m) from the Guliya ice cap (summit 6710 m a.s.l) in the far western Kunlun on the Qinghai–Tibetan Plateau, China. Guliya resembles a “polar” icecap with 10 m, 200 m and basal temperatures of –15.6°, –5.9° and –2.1°C, respectively. The 308.6 m core to bedrock is the longest ice core retrieved from an elevation greater than 4000 m a.s.l. and provides the first ice-core history from the western side of the Qinghai Plateau. The Plateau experiences a pronounced annual precipitation cycle during which 70–80% of annual total precipitation falls in the summer monsoon season. This leads to a marked visible stratigraphy in the glaciers which allows accurate dating of the ice cores and reconstruction of the net mass accumulation. This paper presents (1) the results of the geophysical program to determine ice thickness, ice flow and surface topography, (2) an assessment of net accumulation from stake measurements, snow pits and shallow core samples, and (3) the analyses of the upper 100 m of the 308.6 m core which provide a 1000 year history, including the ‘“Little Ice Age”, which is compared with Chinese historical records. Extended periods of positive accumulation on Guliya are closely contemporaneous with dry periods in eastern China. A trans-Pacific teleconnection is suggested by the strong temporal coherence between extended wet and dry phases on Guliya and on the Quelccaya ice cap, Peru.

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Trends and features of climatic changes in the past 5000 years recorded by the Dunde ice core

Annals of Glaciology ◽

10.3189/1992aog16-1-21-24 ◽

1992 ◽

Vol 16 ◽

pp. 21-24 ◽

Cited By ~ 19

Author(s):

Yao Tandong ◽

L. G. Thompson

Keyword(s):

Accumulation Rate ◽

Ice Core ◽

Climatic Changes ◽

Ice Age ◽

The Tibetan Plateau ◽

Temperature Relation ◽

The Core ◽

The Past ◽

Ice Cap ◽

The Qilian Mountains

Α δ18O record from Dunde Ice Cap, located in the Qilian mountains on the northeastern margin of the Tibetan Plateau, has been analyzed and interpreted. With an ice temperature of –7.3°C at a depth of 10 m and –4.7°C at the bottom of the ice cap, and an accumulation rate of 400 mm a−1, the Dunde core has provided interesting results. The upper part of this core, core D-l, can be easily dated by a combination of δ18O, microparticle concentration and conductivity. It can also be dated as far back as 4550 BP by counting dust layers in ice. Based on the time scale established by the above methods and on the δ18O–temperature relation, the δ18O fluctuations in the upper 120 m of the core can be interpreted as mainly due to climatic changes during the past ~ 5000 years. The warmest periods in the past ~ 5000 years in the core were found to be centered on the present, 3000, and 4100 BP, and the colder periods center around 500, 1200, 4000, and 4500 BP. It is clear from the ice-core record that the Little Ice Age was only one of many cold periods in the past, although it was the coldest period in the past 500 years.

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A first chronology for the North Greenland Eemian Ice Drilling (NEEM) ice core

Climate of the Past ◽

10.5194/cp-9-2713-2013 ◽

2013 ◽

Vol 9 (6) ◽

pp. 2713-2730 ◽

Cited By ~ 85

Author(s):

S. O. Rasmussen ◽

P. M. Abbott ◽

T. Blunier ◽

A. J. Bourne ◽

E. Brook ◽

...

Keyword(s):

Accumulation Rate ◽

Ice Core ◽

Conductivity Measurement ◽

Ice Cores ◽

Heat Diffusion ◽

Ice Age ◽

Age Difference ◽

Volcanic Origin ◽

The North ◽

North Greenland

Abstract. A stratigraphy-based chronology for the North Greenland Eemian Ice Drilling (NEEM) ice core has been derived by transferring the annual layer counted Greenland Ice Core Chronology 2005 (GICC05) and its model extension (GICC05modelext) from the NGRIP core to the NEEM core using 787 match points of mainly volcanic origin identified in the electrical conductivity measurement (ECM) and dielectrical profiling (DEP) records. Tephra horizons found in both the NEEM and NGRIP ice cores are used to test the matching based on ECM and DEP and provide five additional horizons used for the timescale transfer. A thinning function reflecting the accumulated strain along the core has been determined using a Dansgaard–Johnsen flow model and an isotope-dependent accumulation rate parameterization. Flow parameters are determined from Monte Carlo analysis constrained by the observed depth-age horizons. In order to construct a chronology for the gas phase, the ice age–gas age difference (Δage) has been reconstructed using a coupled firn densification-heat diffusion model. Temperature and accumulation inputs to the Δage model, initially derived from the water isotope proxies, have been adjusted to optimize the fit to timing constraints from δ15N of nitrogen and high-resolution methane data during the abrupt onset of Greenland interstadials. The ice and gas chronologies and the corresponding thinning function represent the first chronology for the NEEM core, named GICC05modelext-NEEM-1. Based on both the flow and firn modelling results, the accumulation history for the NEEM site has been reconstructed. Together, the timescale and accumulation reconstruction provide the necessary basis for further analysis of the records from NEEM.

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Interpolation methods for Antarctic ice-core timescales: application to Byrd, Siple Dome and Law Dome ice cores

Climate of the Past ◽

10.5194/cp-10-1195-2014 ◽

2014 ◽

Vol 10 (3) ◽

pp. 1195-1209 ◽

Cited By ~ 11

Author(s):

T. J. Fudge ◽

E. D. Waddington ◽

H. Conway ◽

J. M. D. Lundin ◽

K. Taylor

Keyword(s):

Accumulation Rate ◽

Ice Core ◽

Ice Cores ◽

Linear Interpolation ◽

Atmospheric Methane ◽

Interpolation Methods ◽

The Past ◽

Annual Layer ◽

Siple Dome ◽

Abrupt Changes

Abstract. Antarctic ice cores have often been dated by matching distinctive features of atmospheric methane to those detected in annually dated ice cores from Greenland. Establishing the timescale between these tie-point ages requires interpolation. While the uncertainty at tie points is relatively well described, uncertainty of the interpolation is not. Here we assess the accuracy of three interpolation schemes using data from the WAIS Divide ice core in West Antarctica; we compare the interpolation methods with the annually resolved timescale for the past 30 kyr. Linear interpolation yields large age errors (up to 380 years) between tie points, abrupt changes in duration of climate events at tie points, and an age bias. Interpolations based on the smoothest accumulation rate (ACCUM) or the smoothest annual-layer thickness (ALT) yield timescales that more closely agree with the annually resolved timescale and do not have abrupt changes in duration at tie points. We use ALT to assess the uncertainty in existing timescales for the past 30 kyr from Byrd, Siple Dome, and Law Dome. These ice-core timescales were developed with methods similar to linear interpolation. Maximum age differences exceed 1000 years for Byrd and Siple Dome, and 500 years for Law Dome. For the glacial–interglacial transition (21 to 12 kyr), the existing timescales are, on average, older than ALT by 40 years for Byrd, 240 years for Siple Dome, and 150 years for Law Dome. Because interpolation uncertainty is often not considered, age uncertainties for ice-core records are often underestimated.

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Glacial Stage Ice-Core Records from the Subtropical Dunde Ice Cap, China

Annals of Glaciology ◽

10.1017/s0260305500008776 ◽

1990 ◽

Vol 14 ◽

pp. 288-297 ◽

Cited By ~ 69

Author(s):

L.G. Thompson ◽

E. Mosley-Thompson ◽

M.E. Davis ◽

J.F. Bolzan ◽

J. Dai ◽

...

Keyword(s):

Accumulation Rate ◽

Ice Core ◽

Ice Cores ◽

Major Change ◽

Late Glacial ◽

Ice Cap ◽

The North ◽

Glacial Stage ◽

Isotope Record ◽

Temperature Proxy

The first ice-core record of both the Holocene and Wisconsin/Würm Late Glacial Stage (LGS) from the subtropics has been extracted from three ice cores to bedrock from the Dunde ice cap on the north-central Qinghai-Tibetan Plateau. Ice thicknesses at the ice-cap summit average 138 m, the bedrock surface is relatively flat, surface and basal temperatures are −7.3 and −4.7°C, respectively and the ice cap exhibits radial flow away from the summit dome. These records reveal a major change in the climate of the plateau ∼10 000 years ago and suggest that LGS conditions were colder, wetter and dustier than Holocene conditions. This is inferred from the more negative δ18O ratios, increased dust content, decreased soluble aerosol concentrations, and reduced ice-crystal sizes, which characterize the LGS part of the cores. Total β radioactivity from shallow ice cores indicates that over the last 24 years the average accumulation rate has been ∼400 mm a−1 at the summit. The ice cores have been dated using a combination of annual layers in the insoluble dust and δ18O in the upper sections of core, visible dust layers which are annual, and ice-flow modeling. The oxygen-isotope record which serves as a temperature proxy indicates that the last 60 years have been the warmest in the entire record.

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