Testing the ideal ice-core record for past temperature reconstructions using combined isotope and impurity analyses

2020 ◽  
Author(s):  
Thomas Münch ◽  
Maria Hörhold ◽  
Johannes Freitag ◽  
Melanie Behrens ◽  
Thomas Laepple
Keyword(s):  
Isotopic Composition ◽  
Spatial Scales ◽  
Ice Core ◽  
Ice Cores ◽  
Dimensional Structure ◽  
True Temperature ◽  
Impurity Species ◽  
Temperature Reconstructions ◽  
Isotope Record ◽  
Ice Core Record

<p>Ice cores represent one of the most important palaeoclimate archives, which record, among many other parameters, changes in stable oxygen and hydrogen isotopic composition and soluble ionic impurities. While impurities serve, for example, as proxies for sea ice, marine biological activity and volcanism, records of isotopic composition are the major proxy for the reconstruction of natural polar temperature variability. The latter is based on the temperature-dependent distillation and fractionation of the isotopic composition of water vapour along its atmospheric pathway and empirically determined relationships thereof.</p><p>However, temperature is by far not the only driver of isotopic composition changes. A single isotopic ice-core record will comprise variations caused by a multitude of processes, from variable atmospheric circulation and moisture pathways to the intermittency of precipitation and finally to the mixing and re-location of surface snow by wind drift (stratigraphic noise). Taken together, these additional processes constitute a large amount of noise in the single isotope record, which masks the true temperature-related variability. Averaging a sufficient number of records to reduce overall noise is one means to allow for quantitative reconstructions, but its effectiveness depends on the spatial scales of the involved processes. Here, we discuss an alternative approach. Assuming that major impurity species exhibit a seasonal cycle and are mainly also, along with the isotopic composition, deposited by precipitation and redistributed by wind, a large portion of their interannual variability should be linked, which would offer the possibility of using the impurities to correct the variability of the isotopic records.</p><p>In this contribution, we present the "ideal" dataset for testing this idea. We sampled and analysed isotopic composition and major impurity species on a four metre deep and 50 metre long trench at Kohnen Station, East Antarctica. This enables us to study the two-dimensional structure and relationship of both proxies to learn about their deposition mechanisms, their seasonality, and to test the ability of a combined isotope–impurity approach to reconstruct local temperatures by comparing so obtained temperature reconstructions with the local weather station data.</p><p> </p>

On the relationship between stable isotopes and major impurity species as inferred from a two-dimensional firn sampling approach at EDML, East Antarctica

2021 ◽  
Author(s):  
Thomas Münch ◽  
Maria Hörhold ◽  
Johannes Freitag ◽  
Melanie Behrens ◽  
Thomas Laepple
Keyword(s):  
Isotopic Composition ◽  
Interannual Variability ◽  
Ice Core ◽  
Ice Cores ◽  
Temperature Changes ◽  
Impurity Species ◽  
Intermittent Precipitation ◽  
Ice Core Record ◽  
Stable Oxygen ◽  
Atmospheric Variations

<p>Ice cores constitute a major palaeoclimate archive by recording, among many others, the atmospheric variations of stable oxygen and hydrogen isotopic composition of water and of soluble ionic impurities. While impurities are used as proxies for, e.g., variations in sea ice, marine biological activity and volcanism, stable isotope records are the main source of information for the reconstruction of polar temperature changes.</p><p>However, such reconstruction efforts are complicated by the fact that temperature is by far not the only driver of isotopic composition changes. A single isotopic ice-core record will comprise variations caused by a multitude of processes, from variable atmospheric circulation and moisture pathways to the intermittency of precipitation and finally to the mixing and re-location of surface snow by wind drift (stratigraphic noise). Under the assumption that specific trace components are originally deposited with the precipitated snow and its isotopic composition, the retrieved impurity records should display a similar spatial and seasonal to interannual variability as the isotope records, caused by local stratigraphic noise as well as the time-variable and intermittent precipitation patterns, respectively.</p><p>In this contribution, we investigate the possible relationship between isotope and impurity data at the East Antarctic low-accumulation site EDML. We sampled and analysed isotopic composition and major impurity species on a four metre deep and 50 metre long trench. This enables us (1) to study the spatial (horizontal times vertical) relationship in the data, and (2) to analyse and compare the seasonal and interannual variability after removing the strong contribution of local stratigraphic noise. By this, the study improves our understanding of the depositional mechanisms that play an important role for the formation of ice-core records, and it offers to investigate the potential of using impurities to correct isotopic variability in order to improve temperature reconstructions.</p>

scholarly journals Simulating the temperature and precipitation signal in an Alpine ice core

2012 ◽  
Vol 8 (6) ◽  
pp. 6111-6134 ◽  
Author(s):  
S. Brönnimann ◽  
I. Mariani ◽  
M. Schwikowski ◽  
R. Auchmann ◽  
A. Eichler
Keyword(s):  
Meteorological Data ◽  
Ice Core ◽  
Ice Cores ◽  
Irregular Sampling ◽  
Temperature And Precipitation ◽  
Mean Temperature ◽  
Temperature Reconstructions ◽  
Ice Core Record ◽  
Precipitation Events

Abstract. Accumulation and δ18O data from Alpine ice cores provide information on past temperature and precipitation. However, their correlation with seasonal or annual mean temperature and precipitation at nearby sites is often low. Based on an example we argue that, to some extent, this is due to the irregular sampling of the atmosphere by the ice core (i.e. ice cores only record precipitation events and not dry periods) and the possible incongruity between annual layers and calendar year due to dating uncertainty. Using daily meteorological data from nearby stations and reanalyses we replicate the ice core from the Grenzgletscher (Switzerland, 4200 m a.s.l.) on a sample-by-sample basis. Over the last 15 yr of the ice core record, accumulation and δ18O variations can be well reproduced on a sub-seasonal scale. This allows a wiggle-matching approach for defining quasi-annual layers. For this period, correlations between measured and replicated quasi-annual δ18O values approach 0.8. Further back in time, the quality of the agreement deteriorates rapidly. Nevertheless, we find significant correlations for accumulation and precipitation over the entire length of the record (1938–1993), which is not the case when comparing ice core δ18O with annual mean temperature. A Monte Carlo resampling approach of long meteorological time series is used to further explore the relation, in a replicated ice core, between δ18O and annual mean temperature. Results show that meteorologically very different years can lead to quasi-identical values for δ18O. This poses limitations to the use of δ18O from Alpine ice cores for temperature reconstructions in regions with a variable seasonality in precipitation.

Theoretical limits and new approaches to reconstruct temperature from the isotopic composition of ice cores in low-accumulation regions

2020 ◽  
Author(s):  
Thomas Laepple ◽  
Thomas Münch ◽  
Mathieu Casado ◽  
Maria Hörhold ◽  
Johannes Freitag ◽  
...  
Keyword(s):  
Isotopic Composition ◽  
Ice Core ◽  
Ice Cores ◽  
Climate Signal ◽  
Multiple Cores ◽  
Temperature Reconstructions ◽  
Process Studies ◽  
Theoretical Considerations ◽  
Accumulation Region ◽  
Made In

<p>For several decades, ice-core water-isotope research was focused on retrieving and interpreting single cores, measured on increasingly finer resolution and higher analytic precision. However, not only the sampling resolution or analytical precision limits the ability to recover the climate signal, but also the way the climatic signal is imprinted in the isotopic composition profile obtained from ice cores. Therefore, despite three decades of Antarctic ice-coring and dozens of firn cores, especially the temperature evolution in the low accumulation region of East Antarctica during the last millennium is still barely known.  In the recent years, strong progress has been made in the understanding of the isotopic signal formation based on process studies, snow pits, snow trenches and replicate cores. Using this knowledge, we will review the limits of temperature reconstructions based on theoretical considerations, empirical signal-to-noise ratio estimates and forward models of the signal formation. We will further discuss new avenues for sharpening the ability to recover high-resolution temperature signals from firn and ice cores by optimally combining multiple cores and by combining isotope with impurity records.</p>

scholarly journals Past temperature reconstructions from deep ice cores: relevance for future climate change

2006 ◽  
Vol 2 (2) ◽  
pp. 145-165 ◽  
Author(s):  
V. Masson-Delmotte ◽  
G. Dreyfus ◽  
P. Braconnot ◽  
S. Johnsen ◽  
J. Jouzel ◽  
...  
Keyword(s):  
Climate Change ◽  
Temperature Change ◽  
Climate Models ◽  
Ice Core ◽  
Ice Cores ◽  
Future Climate ◽  
Future Climate Change ◽  
Interglacial Period ◽  
Temperature Reconstructions

Abstract. Ice cores provide unique archives of past climate and environmental changes based only on physical processes. Quantitative temperature reconstructions are essential for the comparison between ice core records and climate models. We give an overview of the methods that have been developed to reconstruct past local temperatures from deep ice cores and highlight several points that are relevant for future climate change. We first analyse the long term fluctuations of temperature as depicted in the long Antarctic record from EPICA Dome C. The long term imprint of obliquity changes in the EPICA Dome C record is highlighted and compared to simulations conducted with the ECBILT-CLIO intermediate complexity climate model. We discuss the comparison between the current interglacial period and the long interglacial corresponding to marine isotopic stage 11, ~400 kyr BP. Previous studies had focused on the role of precession and the thresholds required to induce glacial inceptions. We suggest that, due to the low eccentricity configuration of MIS 11 and the Holocene, the effect of precession on the incoming solar radiation is damped and that changes in obliquity must be taken into account. The EPICA Dome C alignment of terminations I and VI published in 2004 corresponds to a phasing of the obliquity signals. A conjunction of low obliquity and minimum northern hemisphere summer insolation is not found in the next tens of thousand years, supporting the idea of an unusually long interglacial ahead. As a second point relevant for future climate change, we discuss the magnitude and rate of change of past temperatures reconstructed from Greenland (NorthGRIP) and Antarctic (Dome C) ice cores. Past episodes of temperatures above the present-day values by up to 5°C are recorded at both locations during the penultimate interglacial period. The rate of polar warming simulated by coupled climate models forced by a CO2 increase of 1% per year is compared to ice-core-based temperature reconstructions. In Antarctica, the CO2-induced warming lies clearly beyond the natural rhythm of temperature fluctuations. In Greenland, the CO2-induced warming is as fast or faster than the most rapid temperature shifts of the last ice age. The magnitude of polar temperature change in response to a quadrupling of atmospheric CO2 is comparable to the magnitude of the polar temperature change from the Last Glacial Maximum to present-day. When forced by prescribed changes in ice sheet reconstructions and CO2 changes, climate models systematically underestimate the glacial-interglacial polar temperature change.

scholarly journals The magnitude and impact of the 431 CE Tierra Blanca Joven eruption of Ilopango, El Salvador

2020 ◽  
Vol 117 (42) ◽  
pp. 26061-26068 ◽  
Author(s):  
Victoria C. Smith ◽  
Antonio Costa ◽  
Gerardo Aguirre-Díaz ◽  
Dario Pedrazzi ◽  
Andrea Scifo ◽  
...  
Keyword(s):  
High Resolution ◽  
El Salvador ◽  
Central America ◽  
State Of The Art ◽  
Ice Core ◽  
Ice Cores ◽  
Ash Layer ◽  
Ice Core Record ◽  
Climatic Impacts ◽  
Eruption Magnitude

The Tierra Blanca Joven (TBJ) eruption from Ilopango volcano deposited thick ash over much of El Salvador when it was inhabited by the Maya, and rendered all areas within at least 80 km of the volcano uninhabitable for years to decades after the eruption. Nonetheless, the more widespread environmental and climatic impacts of this large eruption are not well known because the eruption magnitude and date are not well constrained. In this multifaceted study we have resolved the date of the eruption to 431 ± 2 CE by identifying the ash layer in a well-dated, high-resolution Greenland ice-core record that is >7,000 km from Ilopango; and calculated that between 37 and 82 km3of magma was dispersed from an eruption coignimbrite column that rose to ∼45 km by modeling the deposit thickness using state-of-the-art tephra dispersal methods. Sulfate records from an array of ice cores suggest stratospheric injection of 14 ± 2 Tg S associated with the TBJ eruption, exceeding those of the historic eruption of Pinatubo in 1991. Based on these estimates it is likely that the TBJ eruption produced a cooling of around 0.5 °C for a few years after the eruption. The modeled dispersal and higher sulfate concentrations recorded in Antarctic ice cores imply that the cooling would have been more pronounced in the Southern Hemisphere. The new date confirms the eruption occurred within the Early Classic phase when Maya expanded across Central America.

scholarly journals Black carbon variability since preindustrial times in Eastern part of Europe reconstructed from Mt Elbrus, Caucasus ice cores

2016 ◽  
Author(s):  
Saehee Lim ◽  
Xavier Faïn ◽  
Patrick Ginot ◽  
Vladimir Mikhalenko ◽  
Stanislav Kutuzov ◽  
...  
Keyword(s):  
Black Carbon ◽  
20Th Century ◽  
Biomass Burning ◽  
Mass Concentration ◽  
Ice Core ◽  
Ice Cores ◽  
Anthropogenic Emissions ◽  
Ice Core Record ◽  
Summer Time ◽  
Mass Concentrations

Abstract. Black carbon (BC), emitted by fossil fuel combustion and biomass burning, is the second largest man-made contributor to global warming after carbon dioxide (Bond et al., 2013). However, limited information exists on its past emissions and atmospheric variability. In this study, we present the first high-resolution record of refractory BC (rBC, including mass concentration and size) reconstructed from ice cores drilled at a high-altitude Eastern European site in Mt. Elbrus (ELB), Caucasus (5115 m a.s.l.). The ELB ice core record, covering the period 1825–2013, reflects the atmospheric load of rBC particles at the ELB site transported from the European continent with a larger rBC input from sources located in the Eastern part of Europe. In the first half of the 20th century, European anthropogenic emissions resulted in a 1.5-fold increase in the ice core rBC mass concentrations as respect to its level in the preindustrial era (before 1850). The rBC mass concentrations increased by a 5-fold in 1960–1980, followed by a decrease until ~ 2000. Over the last decade, the rBC signal for summer time slightly increased. We have compared the signal with the atmospheric BC load simulated using past BC emissions (ACCMIP and MACCity inventories) and taken into account the contribution of different geographical region to rBC distribution and deposition at the ELB site. Interestingly, the observed rBC variability in the ELB ice core record since the 1960s is not in perfect agreement with the simulated atmospheric BC load. Similar features between the ice core rBC record and the best scenarios for the atmospheric BC load support that anthropogenic BC increase in the 20th century is reflected in the ELB ice core record. However, the peak in BC mass concentration observed in ~ 1970 in the ice core is estimated to occur a decade later from past inventories. BC emission inventories for the period 1960s–1970s may be underestimating European anthropogenic emissions. Furthermore, for summer time snow layers of the last 2000s, the slightly increasing trend of rBC deposition likely reflects recent changes in anthropogenic and biomass burning BC emissions in the Eastern part of Europe. Our study highlights that the past changes in BC emissions of Eastern Europe need to be considered in assessing on-going air quality regulation.

scholarly journals The Elbrus (Caucasus, Russia) ice core record – Part 1: reconstruction of past anthropogenic sulfur emissions in south-eastern Europe

2019 ◽  
Vol 19 (22) ◽  
pp. 14119-14132 ◽  
Author(s):  
Susanne Preunkert ◽  
Michel Legrand ◽  
Stanislav Kutuzov ◽  
Patrick Ginot ◽  
Vladimir Mikhalenko ◽  
...  
Keyword(s):  
Eastern Europe ◽  
Western Europe ◽  
Ice Core ◽  
Ice Cores ◽  
Fold Increase ◽  
South Eastern ◽  
Basal Ice ◽  
Ice Core Record ◽  
South Eastern Europe ◽  
The 19Th Century

Abstract. This study reports on the glaciochemistry of a deep ice core (182 m long) drilled in 2009 at Mount Elbrus in the Caucasus, Russia. Radiocarbon dating of the particulate organic carbon fraction in the ice suggests that the basal ice dates to 280±400 CE (Common Era). Based on chemical stratigraphy, the upper 168.6 m of the core was dated by counting annual layers. The seasonally resolved chemical records cover the years 1774–2009 CE, thus being useful to reconstruct many aspects of atmospheric pollution in south-eastern Europe from pre-industrial times to the present day. After having examined the extent to which the arrival of large dust plumes originating from the Sahara and Middle East modifies the chemical composition of the Elbrus (ELB) snow and ice layers, we focus on the dust-free sulfur pollution. The ELB dust-free sulfate levels indicate a 6- and 7-fold increase from 1774–1900 to 1980–1995 in winter and summer, respectively. Remaining close to 55±10 ppb during the 19th century, the annual dust-free sulfate levels started to rise at a mean rate of ∼3 ppb per year from 1920 to 1950. The annual increase accelerated between 1950 and 1975 (8 ppb per year), with levels reaching a maximum between 1980 and 1990 (376±10 ppb) and subsequently decreasing to 270±18 ppb at the beginning of the 21st century. Long-term dust-free sulfate trends observed in the ELB ice cores are compared with those previously obtained in Alpine and Altai (Siberia) ice, with the most important differences consisting in a much earlier onset and a more pronounced decrease in the sulfur pollution over the last 3 decades in western Europe than south-eastern Europe and Siberia.

scholarly journals Characterization and formation of melt layers in polar snow: observations and experiments from West Antarctica

2005 ◽  
Vol 51 (173) ◽  
pp. 307-312 ◽  
Author(s):  
Sarah B. Das ◽  
Richard B. Alley
Keyword(s):  
Field Experiments ◽  
Preferential Flow ◽  
Ice Core ◽  
Ice Cores ◽  
West Antarctica ◽  
Near Surface ◽  
Fine Grained ◽  
Ice Core Record ◽  
Temperature Records ◽  
Polar Snow

AbstractSurface melting rarely occurs across most of the Antarctic ice sheet, away from the warmer coastal regions. Nonetheless, isolated melt features are preserved in the firn and ice in response to infrequent and short-lived melting events. An understanding of the formation and occurrence of these melt layers will help us to interpret records of past melt occurrences from polar ice cores such as the Siple Dome ice-core record from West Antarctica. A search in the near-surface firn in West Antarctica found that melt features are extremely rare, and consist of horizontal, laterally continuous, one to a few millimeter thick, ice layers with few air bubbles. The melt layers found date from the 1992/93 and 1991/92 summers. Field experiments to investigate changes in stratigraphy taking place during melt events reproduced melt features as seen in the natural stratigraphy. Melting conditions of varying intensity were created by passively heating the near-surface air for varying lengths of time inside a clear plastic hotbox. Melt layers formed due entirely to preferential flow and subsequent refreezing of meltwater from the surface into near-surface, fine-grained, crust layers. Continuous melt layers were formed experimentally when positive-degree-day values exceeded 1ºC-day, a value corresponding well with air-temperature records from automatic weather station sites where melt layers formed in the recent past.

Spatial variability of surface snow isotopic composition on the East Antarctic Plateau and implications for climate reconstructions

2020 ◽  
Author(s):  
Maria Hörhold ◽  
Alexander Weinhart ◽  
Sepp Kipfstuhl ◽  
Johannes Freitag ◽  
Georgia Micha ◽  
...  
Keyword(s):  
Isotopic Composition ◽  
Ice Core ◽  
Empirical Relationship ◽  
Ice Cores ◽  
Stable Water Isotopes ◽  
Antarctic Plateau ◽  
Mean Temperature ◽  
Spatial Coverage ◽  
Surface Snow ◽  
Relationship Of

<p>The reconstruction of past temperatures based on ice core records relies on the quantitative but empirical relationship of stable water isotopes and annual mean temperature. However, its relation varies through space and time. On the East Antarctic Plateau, temperature reconstructions from ice cores are poorly constrained or even fail on decadal and smaller time scales. The observed discrepancy between annual mean temperature and isotopic composition partly relies on surface processes altering the signal after deposition but also, to a great deal, on spatially coherent processes prior to or during deposition. However, spatial coverage over larger areas on the East Antarctic Plateau is challenging. We here present in-situ measurements of the isotopic composition of surface snow with unprecedented statistical quality and coverage. 1m surface snow profiles were collected during an overland traverse between Kohnen station and Plateau Station, covering a 1200km long transect. We explore regional differences of the temperature-isotope relationship and discuss possible mechanisms affecting the isotopic composition in areas with accumulation rates lower than 60mmWEa^-1.</p>

scholarly journals Bidirectional permeability measurements of polar firn

2002 ◽  
Vol 35 ◽  
pp. 63-66 ◽  
Author(s):  
Gina L. Luciano ◽  
Mary R. Albert
Keyword(s):  
Ice Core ◽  
Ice Cores ◽  
Free Path Length ◽  
Mean Free Path ◽  
Transport Processes ◽  
Climate History ◽  
Chemical Modeling ◽  
Vertical Permeability ◽  
Ice Core Record ◽  
Sphere Radius

AbstractIce cores provide a valuable archive of climate history. for a complete understanding of this archive, it is important to understand air–snow exchange processes through the snow and firn in order to fully decode the ice-core record. Transport processes through the snow and firn are dependent upon their physical properties. In this paper, bidirectional permeabilities from selected sections of a 13 mcore from Summit, Greenland, are presented. Differences between lateral and vertical permeabilities are evident throughout the core in permeameter data and in microstructure statistics. Both lateral and vertical permeabilities are consistent with overall patterns of previous polar permeability data with depth. the differences between lateral and vertical permeability measurements for some samples can be attributed to equivalent sphere radius. Further studies examining mean free-path length may be helpful in chemical modeling and in deriving an equation relating permeability to microstructure.

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