Arctic Ocean water: A source of light absorbing particles to the atmosphere

Johan Ström (et al.).

Article

Ice-core data used for the construction of the Greenland Ice-Core Chronology 2005 and 2021 (GICC05 and GICC21)

2023. Sune Olander Rasmussen (et al.). Earth System Science Data 15 (8), 3351-3364

Article

We here describe, document, and make available a wide range of data sets used for annual-layer identification in ice cores from DYE-3, GRIP, NGRIP, NEEM, and EGRIP. The data stem from detailed measurements performed both on the main deep cores and shallow cores over more than 40 years using many different setups developed by research groups in several countries and comprise both discrete measurements from cut ice samples and continuous-flow analysis data.

The data series were used for counting annual layers 60 000 years back in time during the construction of the Greenland Ice-Core Chronology 2005 (GICC05) and/or the revised GICC21, which currently only reaches 3800 years back. Now that the underlying data are made available (listed in Table 1) we also release the individual annual-layer positions of the GICC05 timescale which are based on these data sets.

We hope that the release of the data sets will stimulate further studies of the past climate taking advantage of these highly resolved data series covering a large part of the interior of the Greenland ice sheet.

High-resolution aerosol concentration data from the Greenland NorthGRIP and NEEM deep ice cores

2022. Tobias Erhardt (et al.). Earth System Science Data 14 (3), 1215-1231

Article

Records of chemical impurities from ice cores enable us to reconstruct the past deposition of aerosols onto polar ice sheets and alpine glaciers. Through this they allow us to gain insight into changes of the source, transport and deposition processes that ultimately determine the deposition flux at the coring location. However, the low concentrations of the aerosol species in the ice and the resulting high risk of contamination pose a formidable analytical challenge, especially if long, continuous and highly resolved records are needed. Continuous flow analysis, CFA, the continuous melting, decontamination and analysis of ice-core samples has mostly overcome this issue and has quickly become the de facto standard to obtain high-resolution aerosol records from ice cores after its inception at the University of Bern in the mid-1990s.

Here, we present continuous records of calcium (Ca²⁺), sodium (Na⁺), ammonium (NH^+₄), nitrate (NO^-₃) and electrolytic conductivity at 1 mm depth resolution from the NGRIP (North Greenland Ice Core Project) and NEEM (North Greenland Eemian Ice Drilling) ice cores produced by the Bern Continuous Flow Analysis group in the years 2000 to 2011 (Erhardt et al., 2021). Both of the records were previously used in a number of studies but were never published in full 1 mm resolution. Alongside the 1 mm datasets we provide decadal averages, a detailed description of the methods, relevant references, an assessment of the quality of the data and its usable resolution. Along the way we will also give some historical context on the development of the Bern CFA system.

Compositions of Dust and Sea Salts in the Dome C and Dome Fuji Ice Cores From Last Glacial Maximum to Early Holocene Based on Ice-Sublimation and Single-Particle Measurements

2020. Ikumi Oyabu (et al.). Journal of Geophysical Research - Atmospheres 125 (4)

Article

We analyzed the chemical compositions of dust and sea-salt particles in the EPICA Dome C (EDC) ice core during 26-7 kyr BP using an ice-sublimation technique and compared the results with existing data of the Dome Fuji (DF) ice core. Combined with ion concentration data, our data suggested similar sea-salt fluxes in both cores and significantly lower dust flux in the EDC core. The differences in modal size and aspect ratio of dust particles between the two cores support the dominance of Patagonian source suggested by earlier works. The compositions of calcic dust showed major change at similar to 17 kyr BP, possibly reflecting a relative increase in dust transported via the upper troposphere. The calcium sulfate fraction was higher in the DF core than in the EDC core after similar to 17 kyr BP, suggesting that higher Patagonian dust contribution to the DF region. Abundant NaCl particles were found in the DF core in comparison with the EDC core from the LGM to early Holocene, possibly because of the high concentration of terrestrial dust in the DF core that reduced acid availability for sea-salt modification. During the Holocene, the lower NaCl fraction and Cl-/Na+ ratio in the EDC core suggested that most Cl- was lost to the atmosphere from snow at Dome C, while it was preserved at Dome Fuji as NaCl and solid solution.

Holocene dust in East Antarctica: Provenance and variability in time and space

2020. Barbara Delmonte (et al.). The Holocene 30 (4), 546-558

Article

In this paper, we provide a comprehensive overview of the state-of-knowledge of dust flux and variability in time and space in different sectors of East Antarctica during the Holocene. By integrating the literature data with new evidences, we discuss the dust flux and grain-size variability during the current interglacial and its provenance in the innermost part of the East Antarctic plateau as well as in peripheral regions located close to the Transantarctic Mountains. The local importance of aeolian mineral dust aerosol deflated from low-elevation areas of peripheral East Antarctica is also discussed in the light of new data from several coastal, low-elevation sites.

Interactions between the atmosphere, cryosphere, and ecosystems at northern high latitudes

2019. Michael Boy (et al.). Atmospheric Chemistry And Physics 19 (3), 2015-2061

Article

The Nordic Centre of Excellence CRAICC (Cryosphere-Atmosphere Interactions in a Changing Arctic Climate), funded by NordForsk in the years 2011-2016, is the largest joint Nordic research and innovation initiative to date, aiming to strengthen research and innovation regarding climate change issues in the Nordic region. CRAICC gathered more than 100 scientists from all Nordic countries in a virtual centre with the objectives of identifying and quantifying the major processes controlling Arctic warming and related feedback mechanisms, outlining strategies to mitigate Arctic warming, and developing Nordic Earth system modelling with a focus on short-lived climate forcers (SLCFs), including natural and anthropogenic aerosols. The outcome of CRAICC is reflected in more than 150 peer-reviewed scientific publications, most of which are in the CRAICC special issue of the journal Atmospheric Chemistry and Physics. This paper presents an overview of the main scientific topics investigated in the centre and provides the reader with a state-of-the-art comprehensive summary of what has been achieved in CRAICC with links to the particular publications for further detail. Faced with a vast amount of scientific discovery, we do not claim to completely summarize the results from CRAICC within this paper, but rather concentrate here on the main results which are related to feedback loops in climate change-cryosphere interactions that affect Arctic amplification.

Greenland records of aerosol source and atmospheric lifetime changes from the Eemian to the Holocene

2018. S. Schupbach (et al.). Nature Communications 9

Article

The Northern Hemisphere experienced dramatic changes during the last glacial, featuring vast ice sheets and abrupt climate events, while high northern latitudes during the last interglacial (Eemian) were warmer than today. Here we use high-resolution aerosol records from the Greenland NEEM ice core to reconstruct the environmental alterations in aerosol source regions accompanying these changes. Separating source and transport effects, we find strongly reduced terrestrial biogenic emissions during glacial times reflecting net loss of vegetated area in North America. Rapid climate changes during the glacial have little effect on terrestrial biogenic aerosol emissions. A strong increase in terrestrial dust emissions during the coldest intervals indicates higher aridity and dust storm activity in East Asian deserts. Glacial sea salt aerosol emissions in the North Atlantic region increase only moderately (50%), likely due to sea ice expansion. Lower aerosol concentrations in Eemian ice compared to the Holocene are mainly due to shortened atmospheric residence time, while emissions changed little.

Holocene winter climate variability in Central and Eastern Europe

2017. Aurel Persoiu (et al.). Scientific Reports 7

Article

Among abundant reconstructions of Holocene climate in Europe, only a handful has addressed winter conditions, and most of these are restricted in length and/or resolution. Here we present a record of late autumn through early winter air temperature and moisture source changes in East-Central Europe for the Holocene, based on stable isotopic analysis of an ice core recovered from a cave in the Romanian Carpathian Mountains. During the past 10,000 years, reconstructed temperature changes followed insolation, with a minimum in the early Holocene, followed by gradual and continuous increase towards the mid-to-late-Holocene peak (between 4-2 kcal BP), and finally by a decrease after 0.8 kcal BP towards a minimum during the Little Ice Age (AD 1300-1850). Reconstructed early Holocene atmospheric circulation patterns were similar to those characteristics of the negative phase of the North Atlantic Oscillation (NAO), while in the late Holocene they resembled those prevailing in the positive NAO phase. The transition between the two regimes occurred abruptly at around 4.7 kcal BP. Remarkably, the widespread cooling at 8.2 kcal BP is not seen very well as a temperature change, but as a shift in moisture source, suggesting weaker westerlies and increased Mediterranean cyclones penetrating northward at this time.

Snow particle sizes and their distributions in Dronning Maud Land, Antarctica, at sample, local and regional scales

2016. Susanne Ingvander (et al.). Antarctic Science 28 (3), 219-231

Article

In this study, snow particle size variability was investigated along a transect in Dronning Maud Land from the coast to the polar plateau. The aim of the study was to better understand the spatial and temporal variations in surface snow properties. Samples were collected twice daily during a traverse in 2007-08 to capture regional variability. Local variability was assessed by sampling in 10 x 10m grids (5m spacing) at selected locations. The particle size and shape distributions for each site were analysed through digital image analysis. Snow particle size variability is complex at different scales, and shows an internal variability of 0.18-3.31 mm depending on the sample type (surface, grid or pit). Relationships were verified between particle size and both elevation and distance to the coast (moisture source). Regional seasonal changes were also identified, particularly on the lower elevations of the polar plateau. This dataset may be used to quantitatively analyse the optical properties of surface snow for remote sensing. The details of the spatial and temporal variations observed in our data provide a basis for further studies of the complex and coupled processes affecting snow particle size and the interpretation of remote sensing of snow covered areas.

Chemical compositions of solid particles present in the Greenland NEEM ice core over the last 110,000 years

2015. Ikumi Oyabu (et al.). Journal of Geophysical Research - Atmospheres 120 (18), 9789-9813

Article

This study reports the chemical composition of particles present along Greenland's North Greenland Eemian Ice Drilling (NEEM) ice core, back to 110,000years before present. Insoluble and soluble particles larger than 0.45 mu m were extracted from the ice core by ice sublimation, and their chemical composition was analyzed using scanning electron microscope and energy dispersive X-ray spectroscopy and micro-Raman spectroscopy. We show that the dominant insoluble components are silicates, whereas NaCl, Na2SO4, CaSO4, and CaCO3 represent major soluble salts. For the first time, particles of CaMg(CO3)(2) and Ca(NO3)(2)center dot 4H(2)O are identified in a Greenland ice core. The chemical speciation of salts varies with past climatic conditions. Whereas the fraction of Na salts (NaCl+Na2SO4) exceeds that of Ca salts (CaSO4+CaCO3) during the Holocene (0.6-11.7kyr B.P.), the two fractions are similar during the BOlling-AllerOd period (12.9-14.6kyr B.P.). During cold climate such as over the Younger Dryas (12.0-12.6kyr B.P.) and the Last Glacial Maximum (15.0-26.9kyr B.P.), the fraction of Ca salts exceeds that of Na salts, showing that the most abundant ion generally controls the salt budget in each period. High-resolution analyses reveal changing particle compositions: those in Holocene ice show seasonal changes, and those in LGM ice show a difference between cloudy bands and clear layers, which again can be largely explained by the availability of ionic components in the atmospheric aerosol body of air masses reaching Greenland.

Retrieving the paleoclimatic signal from the deeper part of the EPICA Dome C ice core

2015. J.-L. Tison (et al.). The Cryosphere 9 (4), 1633-1648

Article

An important share of paleoclimatic information is buried within the lowermost layers of deep ice cores. Because improving our records further back in time is one of the main challenges in the near future, it is essential to judge how deep these records remain unaltered, since the proximity of the bedrock is likely to interfere both with the recorded temporal sequence and the ice properties. In this paper, we present a multiparametric study (delta D-delta O-18(ice), delta O-18(atm), total air content, CO2, CH4, N2O, dust, high-resolution chemistry, ice texture) of the bottom 60 m of the EPICA (European Project for Ice Coring in Antarctica) Dome C ice core from central Antarctica. These bottom layers were subdivided into two distinct facies: the lower 12 m showing visible solid inclusions (basal dispersed ice facies) and the upper 48 m, which we will refer to as the basal clean ice facies. Some of the data are consistent with a pristine paleoclimatic signal, others show clear anomalies It is demonstrated that neither large-scale bottom refreezing of subglacial water, nor mixing (be it internal or with a local basal end term from a previous/initial ice sheet configuration) can explain the observed bottom-ice properties. We focus on the high-resolution chemical profiles and on the available remote sensing data on the subglacial topography of the site to propose a mechanism by which relative stretching of the bottom-ice sheet layers is made possible, due to the progressively confining effect of subglacial valley sides. This stress field change, combined with bottom-ice temperature close to the pressure melting point, induces accelerated migration recrystallization, which results in spatial chemical sorting of the impurities, depending on their state (dissolved vs. solid) and if they are involved or not in salt formation. This chemical sorting effect is responsible for the progressive build-up of the visible solid aggregates that therefore mainly originate from within, and not from incorporation processes of debris from the ice sheet's substrate. We further discuss how the proposed mechanism is compatible with the other ice properties described. We conclude that the paleoclimatic signal is only marginally affected in terms of global ice properties at the bottom of EPICA Dome C, but that the timescale was considerably distorted by mechanical stretching of MIS20 due to the increasing influence of the subglacial topography, a process that might have started well above the bottom ice. A clear paleoclimatic signal can therefore not be inferred from the deeper part of the EPICA Dome C ice core. Our work suggests that the existence of a flat monotonic ice bedrock interface, extending for several times the ice thickness, would be a crucial factor in choosing a future oldest ice drilling location in Antarctica.

Eemian interglacial reconstructed from a Greenland folded ice core

2013. D. Dahl-Jensen (et al.). Nature 493 (7433), 489-494

Article

Efforts to extract a Greenland ice core with a complete record of the Eemian interglacial (130,000 to 115,000 years ago) have until now been unsuccessful. The response of the Greenland ice sheet to the warmer-than-present climate of the Eemian has thus remained unclear. Here we present the new North Greenland Eemian Ice Drilling ('NEEM') ice core and show only a modest ice-sheet response to the strong warming in the early Eemian. We reconstructed the Eemian record from folded ice using globally homogeneous parameters known from dated Greenland and Antarctic ice-core records. On the basis of water stable isotopes, NEEM surface temperatures after the onset of the Eemian (126,000 years ago) peaked at 8 +/- 4 degrees Celsius above the mean of the past millennium, followed by a gradual cooling that was probably driven by the decreasing summer insolation. Between 128,000 and 122,000 years ago, the thickness of the northwest Greenland ice sheet decreased by 400 +/- 250 metres, reaching surface elevations 122,000 years ago of 130 +/- 300 metres lower than the present. Extensive surface melt occurred at the NEEM site during the Eemian, a phenomenon witnessed when melt layers formed again at NEEM during the exceptional heat of July 2012. With additional warming, surface melt might become more common in the future.

Observed metre scale horizontal variability of elemental carbon in surface snow

2013. J. Svensson (et al.). Environmental Research Letters 8 (3), 034012

Article

Surface snow investigated for its elemental carbon (EC) concentration, based on a thermal-optical method, at two different sites during winter and spring of 2010 demonstrates metre scale horizontal variability in concentration. Based on the two sites sampled, a clean and a polluted site, the clean site (Arctic Finland) presents the greatest variability. In side-by-side ratios between neighbouring samples, 5 m apart, a ratio of around two was observed for the clean site. The median for the polluted site had a ratio of 1.2 between neighbouring samples. The results suggest that regions exposed to snowdrift may be more sensitive to horizontal variability in EC concentration. Furthermore, these results highlight the importance of carefully choosing sampling sites and timing, as each parameter will have some effect on EC variability. They also emphasize the importance of gathering multiple samples from a site to obtain a representative value for the area.

Sulphate and chloride aerosols during Holocene and last glacial periods preserved in the Talos Dome Ice Core, a peripheral region of Antarctica

2013. Yoshinori Iizuka, Torbjorn Karlin, Margareta Hansson. Tellus. Series B, Chemical and physical meteorology 65, 20197

Article

Antarctic ice cores preserve the record of past aerosols, an important proxy of past atmospheric chemistry. Here we present the aerosol compositions of sulphate and chloride particles in the Talos Dome (TD) ice core from the Holocene and Last Glacial Period. We find that the main salt types of both periods are NaCl, Na2SO4 and CaSO4, indicating that TD ice contains relatively abundant sea salt (NaCl) from marine primary particles. By evaluating the molar ratio of NaCl to Na2SO4, we show that about half of the sea salt does not undergo sulphatisation during late Holocene. Compared to in inland Antarctica, the lower sulphatisation rate at TD is probably due to relatively little contact between sea salt and sulphuric acid. This low contact rate can be related to a reduced time of reaction for marine-sourced aerosol before reaching TD and/or to a reduced post-depositional effect from the higher accumulation rate at TD. Many sulphate and chloride salts are adhered to silicate minerals. The ratio of sulphate-adhered mineral to particle mass and the corresponding ratio of chloride-adhered mineral both increase with increasing dust concentration. Also, the TD ice appears to contain Ca(NO3)(2) or CaCO3 particles, thus differing from aerosol compositions in inland Antarctica, and indicating the proximity of peripheral regions to marine aerosols.

Variability of Be-10 and delta O-18 in snow pits from Greenland and a surface traverse from Antarctica

2013. A. -M Berggren (et al.). Nuclear Instruments and Methods in Physics Research Section B 294, 568-572

Article

To examine temporal variability of Be-10 in glacial ice, we sampled snow to a depth of 160 cm at the NEEM (North Greenland Eemian Ice Drilling) drilling site in Greenland. The samples span three years between the summers of 2006 and 2009. At the same time, spatial variability of Be-10 in glacial ice was explored through collection of the upper similar to 5 cm of surface snow in Antarctica during part of the Swedish-Japanese traverse from Svea to Syowa station during the austral summer in 2007-2008. The results of the Greenlandic 1 Be snow suggested variable concentrations that apparently do not clearly reflect the seasonal change as indicated by the delta O-18 data. The Be-10 concentration variability most likely reflects also effects of aerosol loading and deposition pathways, possibly in combination with post-depositional processes. The Antarctic traverse data expose a negative correlation between Be-10 and delta O-18, while there are weaker but still significant correlations to altitude and distance to the coast (approximated by the distance to the 70th latitude). These relationships indicate that geographical factors, mainly the proximity to the coast, may strongly affect 1 Be concentrations in snow in Queen Maud Land, Antarctica.

The rates of sea salt sulfatization in the atmosphere and surface snow of inland Antarctica

2012. Yoshinori Iizuka (et al.). Journal of Geophysical Research 117, D04308

Article

Most of the aerosol particles present in the surface snow and ice of inland Antarctica come from primary sea salt (sodium chloride) and marine biological activity (methansulfonic and sulfuric acids). Melted water from surface snow, firn, and Holocene ice contains mainly sodium, chloride, and sulfate ions. Although it is well known that sea salt aerosols react rapidly with sulfuric acid, a process known as sulfatization, it is not known when this process takes place. In this research we undertake to measure the proportion of sea salt aerosols that undergo sulfatization in the atmosphere and surface snow, as opposed to deeper ice, in order to understand the suitability of sea salt aerosols as a proxy for past climates in deep ice cores. We directly measure the sulfatization rates in recently fallen snow (0-4 m in depth) collected at the Dome Fuji station, using X-ray dispersion spectroscopy to determine the constituent elements of soluble particles and computing the molar ratios of sodium chloride and sodium sulfate. We estimate that about 90% of the initial sea salt aerosols sulfatize as they are taken up by precipitation over Dome Fuji or in the snowpack within one year after being deposited on the ice sheet.

Aeolian dust in the Talos Dome ice core (East Antarctica, Pacific/Ross Sea sector): Victoria Land versus remote sources over the last two climate cycles

2010. Barbara Delmonte (et al.). Journal of Quaternary Science 25 (8), 1327-1337

Article

A new ice core (TALDICE) drilled at Tabs Dome (East Antarctica, Ross Sea sector) preserves a ca. 250 ka long record of palaeoclimate and atmospheric history. We investigate dust variability and provenance at the site during glacial periods and the Holocene through the Sr-Nd isotopic composition of ice core dust and potential source areas (PSA). We provide new isotopic data on dust sources from Victoria Land such as regoliths, glacial drifts, aeolian sands and beach deposits. Some of these sources are located at high altitude and are known to have been ice free throughout the Pleistocene. The major features of the TALDICE dust record are very similar to those from central East Antarctica. During glacial times, South America was the dominant dust supplier for Tabs Dome as well as for the entire East Antarctic plateau. Conversely, during the Holocene the principal input of mineral dust at Tabs Dome probably derives from proximal sources which are the ice-free areas of northern Victoria Land, located at similar altitude with respect to the drilling site. Atmospheric mobilisation of dust from these neighbouring areas and transport inland to Tabs Dome can be ultimately associated with advection of maritime air masses from the Pacific/Ross Sea region. Copyright (C) 2010 John Wiley & Sons, Ltd.

Changes in environment over the last 800,000 years from chemical analysis of the EPICA Dome C ice core

2010. E. W. Wolff (et al.). Quaternary Science Reviews 29 (1-2), 285-295

Article

The EPICA ice core from Dome C extends 3259 m in depth, and encompasses 800 ka of datable and sequential ice. Numerous chemical species have been measured along the length of the cores. Here we concentrate on interpreting the main low-resolution patterns of major ions. We extend the published record for non-sea-salt calcium, sea-salt sodium and non-sea-salt sulfate flux to 800 ka. The non-sea-salt calcium record confirms that terrestrial dust originating from South America closely mirrored Antarctic climate, both at orbital and millennial timescales. A major cause of the main trends is most likely climate in southern South America, which could be sensitive to subtle changes in atmospheric circulation. Sea-salt sodium also follows temperature, but With a threshold at low temperature. We re-examine the use of sodium as a sea ice proxy, concluding that it is probably reflecting extent, with high salt concentrations reflecting larger ice extents. With this interpretation, the sodium flux record indicates low ice extent operating as an amplifier in warm interglacials. Non-sea-salt sulfate flux is almost constant along the core, confirming the lack of change in marine productivity (for sulfur-producing organisms) in the areas of the Southern Ocean contributing to the flux at Dome C. For the first time we also present long records of reversible species such as nitrate and chloride, and show that the pattern of post-depositional losses described for shallower ice is maintained in older ice. It appears possible to use these concentrations to constrain snow accumulation rates in interglacial ice at this site, and the results suggest a possible correction to accumulation rates in one early interglacial. Taken together the chemistry records offer a number of constraints on the way the Earth system combined to give the major climate fluctuations of the late Quaternary period.

Aeolian dust in East Antarctica (EPICA-Dome C and Vostok): provenance during glacial ages over the last 800 kyr.

2008. Barbara Delmonte (et al.). GEOPHYSICAL RESEARCH LETTERS 35 (7)

Article

Aeolian mineral dust archived in Antarctic ice cores represents a key proxy for Quaternary climate evolution. The longest and most detailed dust and climate sequences from polar ice are provided today by the Vostok and by the EPICA-Dome C (EDC) ice cores. Here we investigate the geographic provenance of dust windborne to East Antarctica during Early and Middle Pleistocene glacial ages using strontium and neodymium isotopes as tracers. The isotopic signature of Antarctic dust points towards a dominant South American origin during Marine Isotopic Stage (MIS) 8, 10, 12, and back to MIS 16 and 20 as deduced from EDC core. Data provide evidence for a persistent overall westerly circulation pattern allowing efficient transfer of dust from South America to the interior of Antarctica over the last 800 kyr. Some small but significant dissimilarity between old and recent glacial ages suggests a slightly reduced Patagonian contribution during ancient glaciations.

The Southern Hemisphere at glacial terminations: insights from the Dome C ice core

2008. R. Roethlisberger (et al.). Climate of the past 4 (4), 345-356

Article

The many different proxy records from the European Project for Ice Coring in Antarctica (EPICA) Dome C ice core allow for the first time a comparison of nine glacial terminations in great detail. Despite the fact that all terminations cover the transition from a glacial maximum into an interglacial, there are large differences between single terminations. For some terminations, Antarctic temperature increased only moderately, while for others, the amplitude of change at the termination was much larger. For the different terminations, the rate of change in temperature is more similar than the magnitude or duration of change. These temperature changes were accompanied by vast changes in dust and sea salt deposition all over Antarctica. Here we investigate the phasing between a South American dust proxy (non-sea-salt calcium flux, nssCa(2+)), a sea ice proxy (sea salt sodium flux, ssNa(+)) and a proxy for Antarctic temperature (deuterium, delta D). In particular, we look into whether a similar sequence of events applies to all terminations, despite their different characteristics. All proxies are derived from the EPICA Dome C ice core, resulting in a relative dating uncertainty between the proxies of less than 20 years. At the start of the terminations, the temperature (delta D) increase and dust (nssCa(2+) flux) decrease start synchronously. The sea ice proxy (ssNa(+) flux), however, only changes once the temperature has reached a particular threshold, approximately 5 degrees C below present day temperatures (corresponding to a delta D value of -420 parts per thousand). This reflects to a large extent the limited sensitivity of the sea ice proxy during very cold periods with large sea ice extent. At terminations where this threshold is not reached (TVI, TVIII), ssNa(+) flux shows no changes. Above this threshold, the sea ice proxy is closely coupled to the Antarctic temperature, and interglacial levels are reached at the same time for both ssNa(+) and delta D. On the other hand, once another threshold at approximately 2 degrees C below present day temperature is passed (corresponding to a delta D value of -402 parts per thousand), nssCa(2+) flux has reached interglacial levels and does not change any more, despite further warming. This threshold behaviour most likely results from a combination of changes to the threshold friction velocity for dust entrainment and to the distribution of surface wind speeds in the dust source region.

Comparison of northern and central Greenland ice core records of methanesulfonate covering the last glacial period

2007. Ulf Jonsell (et al.). Journal of Geophysical Research 112 (D14)

Article

Methanesulfonate (MS⁻) is measured in ice cores with the objective to obtain a proxy record of marine phytoplankton production of dimethylsulfide (DMS). We present a continuous MS⁻ record covering the last glacial period from the North Greenland Ice Core Project (NGRIP) ice core and compare this record with the corresponding records previously presented from Greenland and, in particular, with the GISP2 ice core located 320 km south of NGRIP. Despite that the records have similar mean concentrations, their responses to climatic changes during the last glacial period are slightly different. NGRIP MS⁻ concentrations were higher during the cold marine isotopic stages (MIS) 2 and 4 and lower during the warm MIS 5. This long-term trend in MS⁻, which is similar to the inverse of the corresponding trend in δ ¹⁸O, is not detected in the GISP2 MS⁻ record. A systematic response in MS⁻ concentrations to changes between Greenland stadials and interstadials is only detected in the GISP2 record. The different responses of the MS⁻ signals to climate change during the last glacial period are possibly related to the partitioning of air masses reaching the two sites. In contrast to observations from Antarctic records, dust concentrations do not affect the MS⁻ concentrations in the ice, whereas the deposition of sulfate probably is enhanced by high dust concentrations in the atmosphere. The MS⁻ signal has a higher potential of being a proxy record of DMS production changes in Greenlandic compared to Antarctic ice cores.

Correlation between concentrations of acids and oxygen isotope ratios in polar surface snow caused by local redeposition

2007. Ulf Jonsell, Margareta Hansson, Carl-Magnus Mörth. Tellus: B 59 (2), 326-335

Article

Investigation of centimeter-scale snow surface chemistry has been carried out at two polar sites with different site characteristics–in Dronning Maud Land, Antarctica and on the Greenland ice sheet, respectively. Large variations in both impurity content and stable oxygen isotope ratios (δ18O) were found on the submeter scale. δ18O and the concentration of nitrate correlated at both sites (r = 0.81 and 0.82, respectively). At the Antarctic site, δ18O is also correlated to concentrations of methanesulphonate (r = 0.84) and sulphate (r = 0.83) while no such correlation exists at the Greenland site. Instead, a strong anticorrelation (r = –0.85) between sulphate and methanesulphonate is found among the samples from the Greenland site. The ions correlating with δ18O at the two sites were probably deposited as acids. Our tentative explanation is that local redeposition of water vapour enriching the snow surface with the lighter isotopes is associated with simultaneous enhanced scavenging of the acids. The responsible process thereby significantly alters the chemical signals of the snow surface.

Correlations between concentrations of acids andoxygen isotope ratios in polar surface snow

2007. Ulf Jonsell, Margareta E. Hansson, Carl-Magnus Mörth. Tellus. Series B, Chemical and physical meteorology 59b, 326-335

Article

Investigation of centimeter-scale snow surface chemistry has been carried out at two polar sites with different site

characteristics–in Dronning Maud Land, Antarctica and on the Greenland ice sheet, respectively. Large variations

in both impurity content and stable oxygen isotope ratios (

δ18O) were found on the submeter scale. δ18

O and the

concentration of nitrate correlated at both sites (r

= 0.81 and 0.82, respectively). At the Antarctic site, δ18

O is also

correlated to concentrations of methanesulphonate (r

= 0.84) and sulphate (r =

0.83) while no such correlation exists

at the Greenland site. Instead, a strong anticorrelation (r

=

–0.85) between sulphate and methanesulphonate is found

among the samples from the Greenland site. The ions correlating with

δ18

O at the two sites were probably deposited as

acids. Our tentative explanation is that local redeposition of water vapour enriching the snow surface with the lighter

isotopes is associated with simultaneous enhanced scavenging of the acids. The responsible process thereby significantly

alters the chemical signals of the snow surface.

Margareta HanssonProfessor

About me

Publications

Arctic Ocean water: A source of light absorbing particles to the atmosphere

Ice-core data used for the construction of the Greenland Ice-Core Chronology 2005 and 2021 (GICC05 and GICC21)

High-resolution aerosol concentration data from the Greenland NorthGRIP and NEEM deep ice cores

Compositions of Dust and Sea Salts in the Dome C and Dome Fuji Ice Cores From Last Glacial Maximum to Early Holocene Based on Ice-Sublimation and Single-Particle Measurements

Holocene dust in East Antarctica: Provenance and variability in time and space

Interactions between the atmosphere, cryosphere, and ecosystems at northern high latitudes

Greenland records of aerosol source and atmospheric lifetime changes from the Eemian to the Holocene

Holocene winter climate variability in Central and Eastern Europe

Snow particle sizes and their distributions in Dronning Maud Land, Antarctica, at sample, local and regional scales

Chemical compositions of solid particles present in the Greenland NEEM ice core over the last 110,000 years

Retrieving the paleoclimatic signal from the deeper part of the EPICA Dome C ice core

Eemian interglacial reconstructed from a Greenland folded ice core

Observed metre scale horizontal variability of elemental carbon in surface snow

Sulphate and chloride aerosols during Holocene and last glacial periods preserved in the Talos Dome Ice Core, a peripheral region of Antarctica

Variability of Be-10 and delta O-18 in snow pits from Greenland and a surface traverse from Antarctica

The rates of sea salt sulfatization in the atmosphere and surface snow of inland Antarctica

Aeolian dust in the Talos Dome ice core (East Antarctica, Pacific/Ross Sea sector): Victoria Land versus remote sources over the last two climate cycles

Changes in environment over the last 800,000 years from chemical analysis of the EPICA Dome C ice core

Aeolian dust in East Antarctica (EPICA-Dome C and Vostok): provenance during glacial ages over the last 800 kyr.

The Southern Hemisphere at glacial terminations: insights from the Dome C ice core

Comparison of northern and central Greenland ice core records of methanesulfonate covering the last glacial period

Correlation between concentrations of acids and oxygen isotope ratios in polar surface snow caused by local redeposition

Correlations between concentrations of acids andoxygen isotope ratios in polar surface snow