scholarly journals Weighting alternative for water stable isotopes: Statical comparison between station- and firn/ice-records

2017 ◽  
Vol 38 (2) ◽  
pp. 105-124
Author(s):  
István Gábor Hatvani ◽  
Zoltán Kern
Keyword(s):  
Stable Isotope ◽  
Air Temperature ◽  
Ice Core ◽  
Precipitation Amount ◽  
Ice Cores ◽  
Arithmetic Means ◽  
Depositional Processes ◽  
Water Stable Isotope ◽  
Annual Water ◽  
Water Isotope

Abstract It is generally accepted that ice cores archive amount-weighted water stable isotope signals. In order to achieve an improved understanding of the nature of water stable isotope signals stored in ice cores annual δ18O and δ2H averages (i.e. amount-weighted) were calculated for two Antarctic meteorological stations, Vernadsky and Hal­ley Bay, using monthly precipitation amount and monthly net accumulation as weights, respectively. These were then compared with the annual mean δ18O δ2H and records of the nearest available ice cores. In addition, at the stations, both arithmetic means (i.e. time-weighted) and amount-weighted (precipitation amount and net accumulation used as weights) annual air temperature averages were calculated and then compared to amount weighted annual mean δ18O and δ2H using correlation- and regression analyses. The main hypothesis was that amount weighted annual mean water isotope and temperature records from the stations would be able to replicate the annual water isotope signal stored in ice cores to a higher degree. Results showed that (i) amount weighting is incapable of ameliorating the signal replication between the stations and the ice cores, while arithmetic means gave the stronger linear relationships; (ii) post depositional processes may have a more determining effect on the isotopic composition of the firn than expected; and (iii) mean annual air temperature provided the closest match to ice core derived annual water isotope records. This latter conveys a similar message to that of recent findings, in as much as ambient temperature, via equilibrium isotope fractionation, is imprinted into the uppermost snow layer by vapor exchange even between precipitation events. Together, these observations imply that ice core stable water isotope records can be a more continuous archive of near-surface temperature changes than hitherto believed.

Post-depositional processes visible in the integration of EGRIP high-resolution water isotope record and visual stratigraphy

2021 ◽  
Author(s):  
Valerie Morris ◽  
Julien Westhoff ◽  
Bruce Vaughn ◽  
Ilka Weikusat ◽  
Tyler Jones ◽  
...  
Keyword(s):  
High Resolution ◽  
Ice Core ◽  
Ice Cores ◽  
Strong Relationship ◽  
Dark Field ◽  
Scanning System ◽  
Climate Signal ◽  
Depositional Processes ◽  
Isotope Record ◽  
Water Isotope

<p>With recent advances in analytical techniques, water stable isotope ratios can be measured in astounding detail in ice core records (~mm scale or equivalent to subannual resolution). While this has enabled the study of past climates across a vast range of timescales, the full set of processes driving the highest frequency variability in these water isotope records remains poorly understood. In the EastGRIP ice core, we observe a strong relationship between high-frequency water isotope anomalies (sharp transitions on the scale of cms) and variability in the visual stratigraphy of the ice. The water isotope timeseries reveals these anomalies that would otherwise be missed using traditional lower resolution discrete sampling methods (5-50 cm scale).  A comparison with the dark-field imaging of stratigraphic layers (high-resolution line-scanning system; 50µm/pix) from the EGRIP ice core indicates a correlation between bubble-free ice layers and the sharp transitions observed in the isotope record.  Prior to this comparison, such anomalies in high-resolution isotope records were often dismissed as analytical artifacts. The striking correspondence to the bubble-free ice layers, which is a parameter measured independently from the isotopes, suggests the isotope variability is real. We are investigating a range of depositional and post-depositional processes that may may be able to explain the origin of this variability and its relationship to the physical properties of the ice. This study has implications for frequency analysis of the isotope data, and the related analysis of isotope diffusion and its effects on the recorded climate signal. Understanding these anomalies opens new doors to the interpretation of climate signals in ice cores.</p>

scholarly journals The influence of the synoptic regime on stable water isotopes in precipitation at Dome C, East Antarctica

2017 ◽  
Author(s):  
Elisabeth Schlosser ◽  
Anna Dittmann ◽  
Barbara Stenni ◽  
Jordan G. Powers ◽  
Kevin W. Manning ◽  
...  
Keyword(s):  
Relative Humidity ◽  
Ice Core ◽  
Precipitation Amount ◽  
Ice Cores ◽  
Source Area ◽  
Back Trajectory ◽  
Data Set ◽  
Moisture Source ◽  
Significant Difference ◽  
Water Isotope

Abstract. The correct derivation of paleotemperatures from ice cores requires exact knowledge of all processes involved before and after the deposition of snow and consecutive formation of ice. At the Antarctic deep ice core drilling site Dome C, a unique data set of daily precipitation amount, type and stable water isotope ratios is available that enables us to study atmospheric processes that influence the stable water isotope ratio of precipitation in detail. Meteorological data from both automatic weather station and a mesoscale atmospheric model were used to investigate how different atmospheric flow patterns determine the precipitation parameters. A classification of synoptic situations that cause precipitation at Dome C was established and, together with back-trajectory calculations, was utilized to estimate moisture source areas. With the resulting source area conditions (wind speed, sea surface temperature (SST) and relative humidity) as input, the precipitation stable isotopic composition was modelled using the so-called Mixed Cloud Isotope Model (MCIM). The model generally underestimates the depletion of 18O in precipitation. It was shown that, contrary to the assumption widely used in ice core studies, a more northern moisture source does not necessarily mean stronger isotopic fractionation. This is due to the fact that snowfall events at Dome C are often associated with warm air advection due to amplification of planetary waves, which considerably increases the site temperature and thus reduces the temperature difference between source area and deposition site. Also, no correlation was found between relative humidity at the moisture source and the deuterium excess in precipitation. The significant difference in the isotopic signal of hoar frost and diamond dust was shown to disappear after removal of seasonality.

scholarly journals Surface mass balance and water stable isotopes derived from firn cores on three ice rises, Fimbul Ice Shelf, Antarctica

2016 ◽  
Vol 10 (6) ◽  
pp. 2763-2777 ◽  
Author(s):  
Carmen P. Vega ◽  
Elisabeth Schlosser ◽  
Dmitry V. Divine ◽  
Jack Kohler ◽  
Tõnu Martma ◽  
...  
Keyword(s):  
High Resolution ◽  
Stable Isotope ◽  
Mass Balance ◽  
Temporal Variability ◽  
Ice Cores ◽  
Surface Mass Balance ◽  
Ice Shelf ◽  
Climate Signal ◽  
Surface Mass ◽  
Water Stable Isotope

Abstract. Three shallow firn cores were retrieved in the austral summers of 2011/12 and 2013/14 on the ice rises Kupol Ciolkovskogo (KC), Kupol Moskovskij (KM), and Blåskimen Island (BI), all part of Fimbul Ice Shelf (FIS) in western Dronning Maud Land (DML), Antarctica. The cores were dated back to 1958 (KC), 1995 (KM), and 1996 (BI) by annual layer counting using high-resolution oxygen isotope (δ18O) data, and by identifying volcanic horizons using non-sea-salt sulfate (nssSO42−) data. The water stable isotope records show that the atmospheric signature of the annual snow accumulation cycle is well preserved in the firn column, especially at KM and BI. We are able to determine the annual surface mass balance (SMB), as well as the mean SMB values between identified volcanic horizons. Average SMB at the KM and BI sites (0.68 and 0.70 mw. e. yr−1) was higher than at the KC site (0.24 mw. e. yr−1), and there was greater temporal variability as well. Trends in the SMB and δ18O records from the KC core over the period of 1958–2012 agree well with other previously investigated cores in the area, thus the KC site could be considered the most representative of the climate of the region. Cores from KM and BI appear to be more affected by local meteorological conditions and surface topography. Our results suggest that the ice rises are suitable sites for the retrieval of longer firn and ice cores, but that BI has the best preserved seasonal cycles of the three records and is thus the most optimal site for high-resolution studies of temporal variability of the climate signal. Deuterium excess data suggest a possible effect of seasonal moisture transport changes on the annual isotopic signal. In agreement with previous studies, large-scale atmospheric circulation patterns most likely provide the dominant influence on water stable isotope ratios preserved at the core sites.

scholarly journals Ranges of moisture-source temperature estimated from Antarctic ice cores stable isotope records over glacial–interglacial cycles

2012 ◽  
Vol 8 (3) ◽  
pp. 1109-1125 ◽  
Author(s):  
R. Uemura ◽  
V. Masson-Delmotte ◽  
J. Jouzel ◽  
A. Landais ◽  
H. Motoyama ◽  
...  
Keyword(s):  
Air Temperature ◽  
Ice Core ◽  
Ice Cores ◽  
Regression Equations ◽  
Temperature Changes ◽  
Source Temperature ◽  
Moisture Source ◽  
Isotopic Model ◽  
Temperature Proxy ◽  
Coefficient Of Regression

Abstract. A single isotope ratio (δD or δ18O) of water is widely used as an air-temperature proxy in Antarctic ice core records. These isotope ratios, however, do not solely depend on air-temperature but also on the extent of distillation of heavy isotopes out of atmospheric water vapor from an oceanic moisture source to a precipitation site. The temperature changes at the oceanic moisture source (Δ Tsource) and at the precipitation site (Δ Tsite) can be retrieved by using deuterium-excess (d) data. A new d record from Dome Fuji, Antarctica spanning the past 360 000 yr is presented and compared with records from Vostok and EPICA Dome C ice cores. In previous studies, to retrieve Δ Tsource and Δ Tsite information, different linear regression equations were proposed using theoretical isotope distillation models. A major source of uncertainty lies in the coefficient of regression, βsite which is related to the sensitivity of d to Δ Tsite. We show that different ranges of temperature and selections of isotopic model outputs may increase the value of βsite by more than a factor of two. To explore the impacts of this coefficient on reconstructed temperatures, we apply for the first time the exact same methodology to the isotope records from the three Antarctica ice cores. We show that uncertainties in the βsite coefficient strongly affect (i) the glacial–interglacial magnitude of Δ Tsource; (ii) the imprint of obliquity in Δ Tsource and in the site-source temperature gradient. By contrast, we highlight the robustness of Δ Tsite reconstruction using water isotopes records.

scholarly journals Investigating late Holocene variations in hydroclimate and the stable isotope composition of precipitation using southern South American peatlands: an hypothesis

2012 ◽  
Vol 8 (5) ◽  
pp. 1457-1471 ◽  
Author(s):  
T. J. Daley ◽  
D. Mauquoy ◽  
F. M. Chambers ◽  
F. A. Street-Perrott ◽  
P. D. M. Hughes ◽  
...  
Keyword(s):  
Stable Isotope ◽  
Air Temperature ◽  
Regional Differences ◽  
Late Holocene ◽  
Isotope Composition ◽  
Precipitation Amount ◽  
Surface Air Temperature ◽  
Global Network ◽  
Stable Isotope Composition ◽  
Δd And Δ18o

Abstract. Ombrotrophic raised peatlands provide an ideal archive for integrating late Holocene records of variations in hydroclimate and the estimated stable isotope composition of precipitation with recent instrumental measurements. Modern measurements of mean monthly surface air temperature, precipitation, and δD and δ18O-values in precipitation from the late twentieth and early twenty-first centuries provide a short but invaluable record with which to investigate modern relationships between these variables, thereby enabling improved interpretation of the peatland palaeodata. Stable isotope data from two stations in the Global Network for Isotopes in Precipitation (GNIP) from southern South America (Punta Arenas, Chile and Ushuaia, Argentina) were analysed for the period 1982 to 2008 and compared with longer-term meteorological data from the same locations (1890 to present and 1931 to present, respectively). δD and δ18O-values in precipitation have exhibited quite different trends in response to local surface air temperature and precipitation amount. At Punta Arenas, there has been a marked increase in the seasonal difference between summer and winter δ18O-values. A decline in the deuterium excess of summer precipitation at this station was associated with a general increase in relative humidity at 1000 mb over the surface of the Southeast Pacific Ocean, believed to be the major vapour source for the local precipitation. At Ushuaia, a fall in δ18O-values was associated with an increase in the mean annual amount of precipitation. Both records are consistent with a southward retraction and increase in zonal wind speed of the austral westerly wind belt. These regional differences, observed in response to a known driver, should be detectable in peatland sites close to the GNIP stations. Currently, insufficient data with suitable temporal resolution are available to test for these regional differences over the last 3000 yr. Existing peatland palaeoclimate data from two sites near Ushuaia, however, provide evidence for changes in the late Holocene that are consistent with the pattern observed in modern observations.

scholarly journals Climate dependent contrast in surface mass balance in East Antarctica over the past 216 ka

2016 ◽  
Vol 62 (236) ◽  
pp. 1037-1048 ◽  
Author(s):  
F. PARRENIN ◽  
S. FUJITA ◽  
A. ABE-OUCHI ◽  
K. KAWAMURA ◽  
V. MASSON-DELMOTTE ◽  
...  
Keyword(s):  
Mass Balance ◽  
Ice Core ◽  
Ice Cores ◽  
East Antarctica ◽  
Surface Mass Balance ◽  
Last Interglacial ◽  
Surface Mass ◽  
The Past ◽  
Water Stable Isotope ◽  
Global Mean Sea Level

ABSTRACTDocumenting past changes in the East Antarctic surface mass balance is important to improve ice core chronologies and to constrain the ice-sheet contribution to global mean sea-level change. Here we reconstruct past changes in the ratio of surface mass balance (SMB ratio) between the EPICA Dome C (EDC) and Dome Fuji (DF) East Antarctica ice core sites, based on a precise volcanic synchronization of the two ice cores and on corrections for the vertical thinning of layers. During the past 216 000 a, this SMB ratio, denoted SMBEDC/SMBDF, varied between 0.7 and 1.1, being small during cold periods and large during warm periods. Our results therefore reveal larger amplitudes of changes in SMB at EDC compared with DF, consistent with previous results showing larger amplitudes of changes in water stable isotopes and estimated surface temperature at EDC compared with DF. Within the last glacial inception (Marine Isotope Stages, MIS-5c and MIS-5d), the SMB ratio deviates by up to 0.2 from what is expected based on differences in water stable isotope records. Moreover, the SMB ratio is constant throughout the late parts of the current and last interglacial periods, despite contrasting isotopic trends.

scholarly journals Influence of the Tungurahua eruption on the ice core records of Chimborazo, Ecuador

2010 ◽  
Vol 4 (3) ◽  
pp. 1343-1363 ◽  
Author(s):  
P. Ginot ◽  
U. Schotterer ◽  
W. Stichler ◽  
M. A. Godoi ◽  
B. Francou ◽  
...  
Keyword(s):  
Stable Isotope ◽  
Ice Core ◽  
Chemical Species ◽  
Ice Cores ◽  
Ionic Species ◽  
Ash Deposition ◽  
Snow Melting ◽  
Water Percolation ◽  
Core Column ◽  
Preliminary Study

Abstract. The comparison of two shallow ice cores recovered in 1999 and 2000 from the same place on Chimborazo summit glacier revealed the influence of the coincident Tungurahua volcanic eruption on their stable isotope and chemical records. The surface snow melting and water percolation induced from the ash deposition caused a preferential elution and re-localization of certain ionic species, while the stable isotope records were not very affected. Additionally, the comparison of the ionic amount and some selected ratios preserved along the ice core column reports under which processes the chemical species are introduced in the snow pack, as snow flake condensation nuclei, by atmospheric scavenging or by dry deposition. This preliminary study is essential for the interpretation of the deep Chimborazo ice core, or for other sites where surrounding volcanic activity may disturb the glaciochemical records.

scholarly journals Precipitation regime and stable oxygen isotopes at Dome C, East Antarctica – a comparison of two extreme years 2009 and 2010

2015 ◽  
Vol 15 (21) ◽  
pp. 30473-30509
Author(s):  
E. Schlosser ◽  
B. Stenni ◽  
M. Valt ◽  
A. Cagnati ◽  
J. G. Powers ◽  
...  
Keyword(s):  
Stable Isotope ◽  
Ice Core ◽  
Ice Cores ◽  
Isotope Ratios ◽  
Atmospheric Model ◽  
Stable Isotope Ratios ◽  
Stable Water Isotopes ◽  
Precipitation Regime ◽  
Meridional Transport ◽  
Measuring Period

Abstract. At the East Antarctic deep ice core drilling site Dome C, daily precipitation measurements have been initiated in 2006 and are being continued until today. The amounts and stable isotope ratios of the precipitation samples as well as crystal types are determined. Within the measuring period, the two years 2009 and 2010 showed striking contrasting temperature and precipitation anomalies, particularly in the winter seasons. The reasons for these anomalies and their relation to stable isotope ratios are analysed using data from the mesoscale atmospheric model WRF (Weather Research and Forecasting Model) run under the Antarctic Mesoscale Prediction System (AMPS). 2009 was relatively warm and moist due to frequent warm air intrusions connected to amplification of Rossby waves in the circumpolar westerlies, whereas the winter of 2010 was extremely dry and cold. It is shown that while in 2010 a strong zonal atmospheric flow was dominant, in 2009 an enhanced meridional flow prevailed, which increased the meridional transport of heat and moisture onto the East Antarctic plateau and led to a number of high-precipitation/warming events at Dome C. This was also evident in a positive (negative) SAM index and a negative (positive) ZW3 index during the winter months of 2010 (2009). Changes in the frequency or seasonality of such event-type precipitation can lead to a strong bias in the air temperature derived from stable water isotopes in ice cores.

The Effect of Surface Sublimation on the Snow Isotope Signal

2021 ◽  
Author(s):  
Sonja Wahl ◽  
Alexandra Zuhr ◽  
Maria Hörhold ◽  
Anne-Katrine Faber ◽  
Hans Christian Steen-Larsen
Keyword(s):  
Isotopic Composition ◽  
Climate Modeling ◽  
Ice Core ◽  
Greenland Ice Sheet ◽  
Layer By Layer ◽  
Climate Signal ◽  
North East ◽  
Depositional Processes ◽  
Surface Snow ◽  
Water Isotope

<p>Post-depositional processes affect the stable water isotope signal of surface snow between precipitation events. Combined vapor-snow exchange processes and isotope diffusion influence the top layer of snow as well as buried layers below. This implies, that ice core isotope climate proxy records can not be interpreted as a precipitation weighted temperature signal alone.</p><p>Here we present to what extend surface sublimation can explain in-situ observed changes of the stable water isotope signal in the snow.<br>We use direct observations of the isotopic composition of the sublimation flux together with surface snow samples taken in the North-East of the Greenland Ice Sheet accumulation zone throughout the summer months of 2019 to demonstrate sublimation impacts.<br>We show that, contrary to the understanding of effectless layer-by-layer removal of snow, sublimation involves fractionation and therefore influences the isotopic composition of the snow. Complementary measurements of humidity as well as isotope fluxes constrain the local vapor snow exchange and allow for the quantification of post-depositional influences while the snow is exposed to the atmosphere.<br>This improved process understanding of the formation of the climate signal found in snow is important for merging climate modeling and ice core proxies. </p>

scholarly journals Climatic and atmospheric circulation pattern variability from ice-core isotope/geochemistry records (Altai, Tien Shan and Tibet)

2006 ◽  
Vol 43 ◽  
pp. 49-60 ◽  
Author(s):  
Vladimir B. Aizen ◽  
Elena M. Aizen ◽  
Daniel R. Joswiak ◽  
Koji Fujita ◽  
Nozomu Takeuchi ◽  
...  
Keyword(s):  
Air Temperature ◽  
Isotope Geochemistry ◽  
Eastern Mediterranean ◽  
Meteorological Data ◽  
Ice Core ◽  
Ice Cores ◽  
Snow Accumulation ◽  
Tien Shan ◽  
Synoptic Climatology ◽  
The Tibetan Plateau

AbstractSeveral firn/ice cores were recovered from the Siberian Altai (Belukha plateau), central Tien Shan (Inilchek glacier) and the Tibetan Plateau (Zuoqiupu glacier, Bomi) from 1998 to 2003. The comparison analyses of stable-isotope/geochemistry records obtained from these firn/ice cores identified the physical links controlling the climate-related signals at the seasonal-scale variability. The core data related to physical stratigraphy, meteorology and synoptic atmospheric dynamics were the basis for calibration, validation and clustering of the relationships between the firn-/ice-core isotope/ geochemistry and snow accumulation, air temperature and precipitation origin. The mean annual accumulation (in water equivalent) was 106 gcm−2 a−1 at Inilchek glacier, 69 gcm−2 a−1 at Belukha and 196 g cm−2 a−1 at Zuoqiupu. The slopes in regression lines between the δ18O ice-core records and air temperature were found to be positive for the Tien Shan and Altai glaciers and negative for southeastern Tibet, where heavy amounts of isotopically depleted precipitation occur during summer monsoons. The technique of coupling synoptic climatology and meteorological data with δ18O and d-excess in firn-core records was developed to determine climate-related signals and to identify the origin of moisture. In Altai, two-thirds of accumulation from 1984 to 2001 was formed from oceanic precipitation, and the rest of the precipitation was recycled over Aral–Caspian sources. In the Tien Shan, 87% of snow accumulation forms by precipitation originating from the Aral–Caspian closed basin, the eastern Mediterranean and Black Seas, and 13% from the North Atlantic.

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