A major glacial-interglacial change in aeolian dust composition inferred from Rare Earth Elements in Antarctic ice
Introduction
Ice cores provide compelling evidence that airborne dust from the austral continents reached Antarctica during the past climatic cycles (e.g. Wolff et al., 2006, Fischer et al., 2007, Delmonte et al., 2008). However, dust concentrations in Antarctic ice are extremely low, ranging from ∼15 ng g−1 during interglacials up to ∼800 ng g−1 during glacial stages. As snow accumulation rates were reduced during cold periods, a glacial/interglacial flux ratio of ∼25 was deduced by Lambert et al. (2008). The dust trapped in Antarctic ice is composed of detrital minerals such as clays, quartz and feldspars (Gaudichet et al., 1988). In particular, illite, chlorite, smectite and kaolinite are present at any time but a significantly smaller amount of kaolinite was observed in Last Glacial Maximum (LGM) samples (Gaudichet et al., 1992).
One important question of Antarctic glaciology concerns the provenance of dust trapped in the ice. The answer would provide important information on the past atmospheric circulation, serving to validate global circulation models and offering clues on the ancient environmental conditions of the surrounding continents. Sr and Nd isotope studies in East Antarctic ice cores (Delmonte et al., 2008), along with atmospheric circulation modelling (Lunt and Valdes, 2001) have identified South America as a major dust contributor during glacial stages.
During cold periods, weathering and glacial erosion likely played an important role in the dust production in southern South America (Gaiero et al., 2007, Sugden et al., 2009) and a persistent westerly circulation might have allowed the transfer of dust towards the interior of Antarctica (Krinner and Genthon, 2003). However, there is a lack of knowledge concerning the characteristics and the source of the dust transported to Antarctica during interglacial stages. Some preliminary studies suggested that glacial/interglacial changes in dust composition may have occurred (Gabrielli et al., 2005a, Winckler and Fischer, 2006, Siggaard-Andersen et al., 2007, Delmonte et al., 2007, Lanci et al., 2008, Marino et al., 2008). It was also suggested that Australia could be an important contributor of dust for Antarctica during the Holocene (Revel-Rolland et al., 2006) and at present (Li et al., 2008).
Rare earth elements (REE) can provide a robust, specific and versatile tool for the geochemical characterization of the aeolian dust in Antarctic ice. The 14 REE (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu) range in atomic number from 57 (La) to 71 (Lu). From here on, we differentiate between light REE (LREE; La, Ce, Pr, Nd), medium REE (MREE; Sm, Eu, Gd, Tb, Dy, Ho) and heavy REE (HREE; Er, Tm, Yb, Lu). As their atomic mass increases, their radius decreases but they keep the same external electronic configuration. Therefore, their chemical properties remain essentially identical, allowing REE to behave like isotopes. REE are lithophilic refractory elements that, due to their low solubility, are mostly transported in the environment in the particulate phase. All these characteristics prevent REE from being strongly fractionated by weathering and diagenetic processes (except Ce and Eu that might be fractionated by redox processes) and thus they are ideal as geochemical tracers (Henderson, 1984).
The main advantage of using REE is that, as they are 14 elements, they are potentially more suitable for delineating changes in the aeolian dust composition. In addition, REE in polar ice are rarely influenced by sources (e.g. volcanic ash fallout as found by Wei et al., 2008) other than continental rocks and soil dust (Gabrielli et al., 2009).
Here, we show the first record of REE concentrations determined in the EPICA ice core from Dome C in Antarctica (hereafter EDC) from 2.9 to 33.7 kyr BP, which includes the Holocene, the last transition, the LGM and part of the last glacial epoch. Based on these novel dust tracers we provide strong evidence of a large glacial/interglacial change in dust composition that started at ∼15 kyr BP and continued through the Holocene, except for an oscillation that occurred ∼8 kyr BP which indicates a short return towards more glacial-like dust. In addition, we present a preliminary evaluation of the dust provenance and the linkage between the dust composition and the atmospheric transport.
Section snippets
Samples
The samples originate from a deep ice core drilled in Dome C on the East Antarctic Plateau (75°06' S; 123°21' E; altitude 3233 m; mean annual temperature −54 °C) within the framework of the European Project for Ice Coring in Antarctica (EPICA) (EPICA community members 2004). A total of 294 samples were extracted from between 112 and 656 m depth which, according to the EDC3 timescale (Parrenin et al., 2007) spans a period between 2.9 and 33.7 kyr BP. Temporal spacing of the samples is ∼60 and ∼140
REE concentrations and enrichment factors
REE concentrations show large variations during the last climatic cycle with lower values during the Holocene (e.g. average La = 0.39 pg g−1; Lu = 0.003 pg g−1) and higher values (20–30 times) during the LGS (e.g. La = 7.6 pg g−1; Lu = 0.078 pg g−1) (Table 2). REE are highly correlated with the dust concentrations determined in the same samples (R ∼ 0.90–0.95) and their plotted time series are very similar (Fig. 2a, b).
The REE enrichment factors [Ef(REE)Ce] calculated as (REEice/Ceice)/(REEcrust/Cecrust),
REE as a tracer of aeolian dust provenance
REE physical characteristics prevent them from being strongly chemically fractionated by environmental processes. However, the literature highlights how REE can be mobilized under certain conditions. A classic experimental work (Balashov and Girin, 1969) shows that 20–95% of the REE in clays are readily leachable and therefore may be available for migration, with the MREE being most susceptible and the LREE least. In particular, REE can be mobilized during both humid and temperate weathering (
Conclusions
REE prove to be sensitive indicators of changes in aeolian dust composition trapped in Antarctic ice during the last climatic cycle. The dust shows a persistent crustal-like REE composition during the LGS that was possibly produced either by the atmospheric mixing of the abundant emissions derived from multiple source areas or by the averaging of individual heterogeneous sources within one single region (e.g. South America). If confirmed by further developments in the REE analysis, the LREE
Acknowledgments
This work was supported in Italy by the Consorzio per l'Attuazione del Programma Nazionale delle Ricerche in Antartide, under projects on Environmental Contamination and Glaciology. In France it was supported by the Institut Universitaire de France, the Agence de l'Environnement et de la Maîtrise de l'Energie, the Institut National des Sciences de l'Univers and the Université Joseph Fourier of Grenoble. This work is a contribution to the European Project for Ice Coring in Antarctica (EPICA), a
References (50)
- et al.
The 8 k event: cause and consequences of a major Holocene abrupt climate change
Quat. Sci. Rev
(2005) - et al.
Patagonian origin of glacial dust deposited in East Antarctica (Vostok and Dome C) during glacial stages 2, 4 and 6
Earth Planet. Sci. Lett.
(1997) - et al.
An improved method for decontaminating polar snow and ice cores for heavy metals analysis
Anal. Chim. Acta
(1994) - et al.
Comparing the Epica and Vostok dust records during the last 220,000 years: stratigraphical correlation and provenance in glacial periods
Earth-Sci. Rev.
(2004) - et al.
Trace elements in Vostok Antarctic ice during the last four climatic cycles
Earth Planet. Sci. Lett.
(2005) - et al.
Variations in atmospheric trace elements in Dome C (East Antarctica) ice over the last two climatic cycles
Atmos. Environ.
(2005) - et al.
A climatic control on the accretion of meteoric and super-chondritic iridium-platinum to the Antarctic ice cap
Earth Planet. Sci. Lett.
(2006) - et al.
The signature of river- and wind-borne materials exported from Patagonia to the southern latitudes: a view from REEs and implications for paleoclimatic interpretations
Earth Planet. Sci. Lett.
(2004) - et al.
A uniform isotopic and chemical signature of dust exported from Patagonia: rock sources and occurence in the southern environments
Chemical Geology
(2007) - et al.
Late Pleistocene and Holocene climate of SE Australia reconstructed from dust and river loads deposited offshore the River Murray Mouth
Earth Planet. Sci. Lett.
(2007)
Eastern Australia: a possible source of dust in East Antarctica interglacial ice
Earth Planet. Sci. Lett.
Soluble and insoluble lithium dust in the EPICA Dome C ice core — implications for changes of the East Antarctic dust provenance during the recent glacial–interglacial transition
Earth Planet. Sci. Lett.
The 8.2 ka event from Greenland ice cores
Quat. Sci. Rev.
Lead isotopic compositions in the EPICA Dome C ice core and Southern Hemisphere Potential Source Areas
Quat. Sci. Rev.
The effect of climate and facies environment on the fractionation of the rare earths during sedimentation
Geochem. Int.
On the reserve of mobile rare earth elements in sedimentary rocks
Geochem. Int.
A clean laboratory for ultralow concentration heavy metal analysis
Fresen. J. Anal. Chem.
Glacial to Holocene implications of the new 27000-year dust record from the EPICA Dome C (East Antarctica) ice core
Clim. Dyn.
Late quaternary interglacials in East Antarctica from ice core dust records
Aeolian dust in East Antarctica (EPICA-Dome C and Vostok): provenance during glacial ages over the last 800 kyr
Geophys. Res. Lett.
Evidence of early Holocene glacial advances in southern South America from cosmogenic surface-exposure dating
Geology
Eight glacial cycles from an Antarctic ice core
Nature
Glacial/interglacial changes in mineral dust and sea-salt records in polar ice cores: sources, transport, and deposition
Rev. Geophys.
Direct determination of Rare Earth Elements at the sub picogram per gram level in Antarctic ice by ICP-SFMS using a desolvation system
Anal. Chem.
Cited by (81)
Climate-driven redox changes in the southern Scotia Sea over the last 35 kyr: Insights from sedimentary sulfur isotope
2024, Palaeogeography, Palaeoclimatology, PalaeoecologyHemispheric-scale heavy metal pollution from South American and Australian mining and metallurgy during the Common Era
2024, Science of the Total EnvironmentGeochemistry of aeolian material from the McMurdo Dry Valleys, Antarctica: Insights into Southern Hemisphere dust sources
2020, Earth and Planetary Science LettersAirborne dust traffic from Australia in modern and Late Quaternary times
2020, Global and Planetary ChangeCitation Excerpt :In fact, based on Sr and Nd isotopes, Revel-Rolland et al. (2006) had foreshadowed this possibility. Further, Gabrielli et al. (2010) examined the REE composition of dust analysed from the Dome C ice core covering the 33.7 to 2.9 ka period. These authors noted a significant change of dust composition that commenced at 15 kyr BP that persisted in composition throughout the Holocene; this was attributed to a change in atmospheric trajectories.
- 1
Climate Analysis and Consulting, Germany.