scholarly journals On the Relationship Between 18O/16O Ratios of Precipitation and Climate

1988 ◽  
Vol 10 ◽  
pp. 217 ◽  
Author(s):  
U. Siegenthaler
Keyword(s):  
Water Vapour ◽  
Accumulation Rate ◽  
Ice Cores ◽  
Ice Age ◽  
Mean Annual Temperature ◽  
Mixing Ratio ◽  
Physical Processes ◽  
Monthly Data ◽  
Quantitative Understanding ◽  
The Relationship

A quantitative interpretation of oxygen-isotope data in ice cores in terms of climate has so far been hampered by the lack of a quantitative understanding of the processes which determine the isotopic composition of precipitation. Dansgaard (1964) has demonstrated that observed relations between 18O/16O and temperature can be explained reasonably well by the Rayleigh condensation model. This model is re-interpreted by noting that it predicts a dependence of the 18O/16O ratio on the water-vapour mixing ratio in the atmosphere. The relationship between the monthly data from different European stations and the water-vapour mixing ratio agrees remarkably well with the Rayleigh model. Data from Greenland snow show good correlation with the following parameters: mean annual temperature Ta, the water-vapour mixing ratio corresponding to Ta, and the accumulation rate. These correlations will be discussed in terms of the Rayleigh model and of the underlying physical processes. The correlation between 18O/16O ratios and the accumulation rate allows us to estimate the latter during the ice age. The change in the accumulation rate between the ice age and postglacial time can also be estimated from the chemical composition or the 10Be concentration. The different results will be compared.

scholarly journals On the Relationship Between 18O/16O Ratios of Precipitation and Climate

1988 ◽  
Vol 10 ◽  
pp. 217-217
Author(s):  
U. Siegenthaler
Keyword(s):  
Water Vapour ◽  
Accumulation Rate ◽  
Ice Cores ◽  
Ice Age ◽  
Mean Annual Temperature ◽  
Mixing Ratio ◽  
Physical Processes ◽  
Monthly Data ◽  
Quantitative Understanding ◽  
The Relationship

A quantitative interpretation of oxygen-isotope data in ice cores in terms of climate has so far been hampered by the lack of a quantitative understanding of the processes which determine the isotopic composition of precipitation. Dansgaard (1964) has demonstrated that observed relations between 18O/16O and temperature can be explained reasonably well by the Rayleigh condensation model. This model is re-interpreted by noting that it predicts a dependence of the 18O/16O ratio on the water-vapour mixing ratio in the atmosphere. The relationship between the monthly data from different European stations and the water-vapour mixing ratio agrees remarkably well with the Rayleigh model. Data from Greenland snow show good correlation with the following parameters: mean annual temperature Ta, the water-vapour mixing ratio corresponding to Ta, and the accumulation rate. These correlations will be discussed in terms of the Rayleigh model and of the underlying physical processes. The correlation between 18O/16O ratios and the accumulation rate allows us to estimate the latter during the ice age. The change in the accumulation rate between the ice age and postglacial time can also be estimated from the chemical composition or the 10Be concentration. The different results will be compared.

scholarly journals Enhanced Moisture Delivery into Victoria Land, East Antarctica During the Early Last Interglacial: Implications for West Antarctic Ice Sheet Stability

2021 ◽  
Author(s):  
Yuzhen Yan ◽  
Nicole E. Spaulding ◽  
Michael L. Bender ◽  
Edward J. Brook ◽  
John A. Higgins ◽  
...  
Keyword(s):  
Accumulation Rate ◽  
Ice Cores ◽  
Snow Accumulation ◽  
East Antarctica ◽  
Ice Age ◽  
Accumulation Rates ◽  
Last Interglacial ◽  
Ice Shelf ◽  
Ross Ice Shelf ◽  
Victoria Land

Abstract. The S27 ice core, drilled in the Allan Hills Blue Ice Area of East Antarctica, is located in Southern Victoria Land ~80 km away from the present-day northern edge of the Ross Ice Shelf. Here, we utilize the reconstructed accumulation rate of S27 covering the Last Interglacial (LIG) period between 129 and 116 thousand years before present (ka) to infer moisture transport into the region. The accumulation rate is based on the ice age-gas age differences calculated from the ice chronology, which is constrained by the stable water isotopes of the ice, and an improved gas chronology based on measurements of oxygen isotopes of O2 in the trapped gases. The peak accumulation rate in S27 occurred at 128.2 ka, near the peak LIG warming in Antarctica. Even the most conservative estimate yields a six-fold increase in the accumulation rate in the LIG, whereas other Antarctic ice cores are typically characterized by a glacial-interglacial difference of a factor of two to three. While part of the increase in S27 accumulation rates must originate from changes in the large-scale atmospheric circulation, additional mechanisms are needed to explain the large changes. We hypothesize that the exceptionally high snow accumulation recorded in S27 reflects open-ocean conditions in the Ross Sea, created by reduced sea ice extent and increased polynya size, and perhaps by a southward retreat of the Ross Ice Shelf relative to its present-day position near the onset of LIG. The proposed ice shelf retreat would also be compatible with a sea-level high stand around 129 ka significantly sourced from West Antarctica. The peak in S27 accumulation rates is transient, suggesting that if the Ross Ice Shelf had indeed retreated during the early LIG, it would have re-advanced by 125 ka.

scholarly journals Borehole temperatures reveal details of 20th century warming at Bruce Plateau, Antarctic Peninsula

2012 ◽  
Vol 6 (3) ◽  
pp. 675-686 ◽  
Author(s):  
V. Zagorodnov ◽  
O. Nagornov ◽  
T. A. Scambos ◽  
A. Muto ◽  
E. Mosley-Thompson ◽  
...  
Keyword(s):  
Surface Temperature ◽  
Antarctic Peninsula ◽  
Accumulation Rate ◽  
Ice Cores ◽  
Temperature History ◽  
Mean Annual Temperature ◽  
Measured Temperature ◽  
Climate Trends ◽  
Cold Temperatures ◽  
Reconstructed Surface

Abstract. Two ice core boreholes of 143.18 m and 447.73 m (bedrock) were drilled during the 2009–2010 austral summer on the Bruce Plateau at a location named LARISSA Site Beta (66°02' S, 64°04' W, 1975.5 m a.s.l.). Both boreholes were logged with thermistors shortly after drilling. The shallow borehole was instrumented for 4 months with a series of resistance thermometers with satellite uplink. Surface temperature proxy data derived from an inversion of the borehole temperature profiles are compared to available multi-decadal records from weather stations and ice cores located along a latitudinal transect of the Antarctic Peninsula to West Antarctica. The LARISSA Site Beta profiles show temperatures decreasing from the surface downward through the upper third of the ice, and warming thereafter to the bed. The average temperature for the most recent year is −14.78°C (measured at 15 m depth, abbreviated T15). A minimum temperature of −15.8°C is measured at 173 m depth, and basal temperature is estimated to be −10.2°C. Current mean annual temperature and the gradient in the lower part of the measured temperature profile have a best fit with an accumulation rate of 1.9×103 kg m−2 a−1 and basal heat flux (q) of 88 mW m−2, if steady-state conditions are assumed. However, the mid-level temperature variations show that recent temperature has varied significantly. Reconstructed surface temperatures (Ts=T15) over the last 200 yr are derived by an inversion technique (Tikhonov and Samarskii, 1990). From this, we find that cold temperatures (minimum Ts=−16.2°C) prevailed from ~1920 to ~1940, followed by a gradual rise of temperature to −14.2°C around 1995, then cooling over the following decade and warming in the last few years. The coldest period was preceded by a relatively warm 19th century at T15≥−15°C. To facilitate regional comparisons of the surface temperature history, we use our T15 data and nearby weather station records to refine estimates of lapse rates (altitudinal, adjusted for latitude: Γa(l)). Good temporal and spatial consistency of Γa(l) over the last 35 yr are observed, implying that the climate trends observed here are regional and consistent over a broad altitude range.

scholarly journals Isotope Climatic Record Over The Last 2.5 KA from Dome C, Antarctica, Ice cores

1982 ◽  
Vol 3 ◽  
pp. 17-22 ◽  
Author(s):  
J. P. Benoist ◽  
J. Jouzel ◽  
C. Lorius ◽  
L. Merlivat ◽  
M. Pourchet
Keyword(s):  
Isotope Composition ◽  
Accumulation Rate ◽  
Maximum Amplitude ◽  
Ice Cores ◽  
Ice Age ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Temperature Changes ◽  
Low Pass ◽  
Climatic Record

Data on climatic changes over thousands of years is needed for a better understanding of the shorter term variations which are of interest to man. For this purpose we measured the isotope composition (δD‰) of two adjacent ice cores drilled in the Dome C area. The time scale was established using the remarkably constant mean annual accumulation rate (37 kg m−2) determined by various techniques. The detailed isotope records were smoothed to filter out the δ value fluctuations not directly related to local temperature changes. With respect to conditions over the last 2.5 ka, the combined smoothed δ curve indicates a cooler climate from about 1800 to 1200 AD and a slightly warmer period from about 1200 to 700 AD. These periods may well correspond to the suggested world-wide Little Ice Age and medieval warm phase. Using the present δD‰/T°C measured at the surface, the maximum amplitude for these two periods, after smoothing with a low pass filter of 512 a, is approximately -0.35 and +0.3°C, respectively.

scholarly journals A first chronology for the NEEM ice core

2013 ◽  
Vol 9 (3) ◽  
pp. 2967-3013 ◽  
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.

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

1982 ◽  
Vol 3 ◽  
pp. 269-273 ◽  
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.

Ice cores and climatic change

1977 ◽  
Vol 280 (972) ◽  
pp. 143-168 ◽  
Keyword(s):  
Ice Sheets ◽  
Ice Cores ◽  
Ice Age ◽  
Isotopic Ratios ◽  
Temperature Profiles ◽  
Physical Processes ◽  
Similar Relation ◽  
Stable Isotopic ◽  
Last Ice Age ◽  
Glacial Periods

The paper deals primarily with the use of stable isotopic ratios to determine the former climate of ice sheets. Studies of temperature profiles throughout ice sheets have shown that for at least several thousand years, changes of isotopic δ ratios have been proportional to changes of surface temperatures; this relationship is discussed in terms of the physical processes involved. It is considered reasonable to use a similar relation for earlier periods in Antarctica, but in Greenland the relation may have varied with time. When determining past climates from the isotopic record, allowances have to be made for changes in the flow and thickness of ice sheets during major glacial periods. These factors are considered in relation to major ice cores from Vostok and Byrd stations in Antarctica and from Camp Century in Greenland. Vostok is the simplest case glaciologically, Camp Century the most complex. On purely glaciological grounds it appears that the ice age gave way to present-day climates some 10 000 ± 1000 a B.P., the coldest period being 20 000 + 3000 a B.P., when the climate in Antarctica was 6-8 °C colder than at present. Glaciological data suggest a duration of 50 000 to 100 000 years for the last ice age. Before this period, climates in Greenland and Antarctica appear to have been around 2-3 °C warmer than at present.

scholarly journals A 1200 year record of accumulation from northern Greenland

1995 ◽  
Vol 21 ◽  
pp. 19-25 ◽  
Author(s):  
Arne Friedmann ◽  
John C. Moore ◽  
Thorsteinn Thorsteinsson ◽  
Josef Kipfstuhl ◽  
Hubertus Fischer
Keyword(s):  
Air Temperature ◽  
Little Ice Age ◽  
Accumulation Rate ◽  
Ice Cores ◽  
Ice Age ◽  
Greenhouse Warming ◽  
Accumulation Rates ◽  
Density Profiles ◽  
Secular Changes ◽  
Over Time

We present the first detailed study of regional and secular changes in accumulation rate from northern Greenland. Four 100–150 m ice cores from this previously little investigated region have been dielectrically profiled and a good chronology for all four ice cores established by modelling the density profiles and identifying volcanic peaks in the records. This made it possible to calculate the accumulation rates of each core. The current accumulation rates show that there is a large region of low accumulation rate to the northeast of central Greenland with drops in accumulation rate of 25% 150 km, and 50% 300 km from Summit.Relatively large variations in accumulation rate over time are seen in all the cores. We have compared the resulting accumulation-rate record, which should be related to changes in local air temperature over northern Greenland, with Scandinavian tree-ring records and have interpreted the data as showing an early Medieval Warm Epoch, but no pronounced “Little Ice Age” and no unequivocal greenhouse warming effect as yet in northern Greenland.

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

2013 ◽  
Vol 9 (6) ◽  
pp. 2713-2730 ◽  
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.

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

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

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.

Sign in / Sign up

Export Citation Format

Share Document