Search

Mineral dust is a natural tracer of atmospheric composition and climate variability. Yet, there is still much to be known about the Southern Hemisphere dust cycle during the last Pleistocene. Major efforts have attempted to solve the ‘puzzle’ of the origin of the potential source areas that contribute dust to the Southern Ocean and East Antarctica (EA). Here we present a comprehensive geochemical characterization of an important potential source area, which role as a dust supplier to different environments of the SH has significantly been underestimated, that is, the Southern Africa (SAF) region. On the basis of Sr-Nd-Pb isotope ratios and rare earth element concentrations analyzed in sediments collected along the major dust-producing areas in the Namibian coast (Kuiseb, Omaruru and Huab riverbeds and the Namibian sand sea region), this study demonstrates for the first time that SAF emerges as the second most important dust source to EA during interglacial times.

Melting of the Greenland Ice Sheet is a leading cause of land-ice mass loss and cryosphere-attributed sea level rise. Blooms of pigmented glacier ice algae lower ice albedo and accelerate surface melting in the ice sheet’s southwest sector. Although glacier ice algae cause up to 13% of the surface melting in this region, the controls on bloom development remain poorly understood. Here we show a direct link between mineral phosphorus in surface ice and glacier ice algae biomass through the quantification of solid and fluid phase phosphorus reservoirs in surface habitats across the southwest ablation zone of the ice sheet. We demonstrate that nutrients from mineral dust likely drive glacier ice algal growth, and thereby identify mineral dust as a secondary control on ice sheet melting., SCOPUS: ar.j, info:eu-repo/semantics/published

Identifying the provenance of mineral dust depositions in Antarctica is crucial to reconstruct Southern Hemisphere (SH) atmospheric circulation, validate numerical models, evaluate their contribution as micronutrients in the Southern Ocean and assess their control on the climate changes. For the last few decades, it has been demonstrated Southern South America (SSA) is the main precursor of dust reaching Antarctica during both ice ages and interglacial periods (e.g. Gili et al., 2017, 2016). However, the origin of modern dust depositions on the Antarctic continent is still poorly constrained. Back in the nineties, together with SSA, Australia, New Zealand, and Southern Africa were firstly identified as dust contributors to East Antarctica (EA) (e.g. Delmonte et al., 2004a). Since then, only SSA and Australian dust sources benefited from detailed studies. While some works identified the Makgadikgadi and Etosha Pans as southern Africa's major mineral dust sources in the SH, it was not until recently the Namib Desert coastal areas were described as another important regional dust sources. Within the Namib Desert and along the coast, the Kuiseb (K), Omaruru (O) and Huab (H) dry riverbeds are the three main areas identified as the dustiest ones with the higher frequency of dust emission events (Von Holdt et al., 2017). Here we use Sr, Nd and Pb isotopes (measured on HR-MC-ICP-MS) to characterize and evaluate the influence of this region in Southern Africa as a dust source to EA. Samples collected in K, O and H desertic areas were analyzed together with snow samples collected along a ~250 km N-S transect (defined from the coast to inland) at seven different sampling sites in the surroundings of Dronning Maud Land, EA. In addition, using the bulk of the Huab region, dust aerosols were generated into an atmospheric simulation chamber (CESAM) to reproduce, mechanically the saltation and sandblasting processes responsible for the release of mineral dust in natural conditions. Our isotopic results show Namibia’s coast emerged as another possible source end-member, together with some regions in SSA, that supply dust to EA during warmer periods.References:Delmonte, B., Basile-Doelsch, I., Petit, J.R., Maggi, V., Revel-Rolland, M., Michard, A., Jagoutz, E., Grousset, F., 2004. Comparing the EPICA and Vostok dust records during the last 220,000 years: stratigraphical correlation and provenance in glacial periods. Earth-Sci. Rev. 66, 63–87.Gili, S., Gaiero, D.M., Goldstein, S.L., Chemale, F. Jr., Koester, E., Jweda, J., Vallelonga, P., Kaplan, M.R., 2016. Provenance of dust to Antarctica: a lead isotopic perspective. Geophys. Res. Lett. 43. http://dx.doi.org/10.1002/2016GL068244.Gili, S., D.M. Gaiero, S.L. Goldstein, F. Chemale, J. Jweda, M.R. Kaplan, R.A. Becchio, and E. Koester (2017). Glacial/interglacial changes of Southern Hemisphere wind circulation from the geochemistry of South American dust. Earth Planet. Sci. Lett., 469, 98-109, doi: 10.1016/j.epsl.2017.04.007.Von Holdt, JR., Eckardt FD., and Wiggs GFS., 2017. Landsat identifies aeolian dust emission dynamics at the landform scale. Remote Sensing of Environment 198., 229–243.

International audience

Atmospheric mineral dust is intrinsically linked with climate. Although dust flux variability on glacial–interglacial timescales is well documented, Holocene dust records remain scarce. To fill this gap, we conducted elemental, isotopic and sedimentological analyses on a peat core from the Karukinka Natural Park in Tierra del Fuego. An 8000-year-old mineral dust record was extracted indicating three periods of elevated dust deposition: (i) 8.1–7.4 cal ka BP, (ii) 4.2 cal ka BP and (iii) 2.4–1.4 cal ka BP. The two oldest peaks are related to volcanic eruptions of the Hudson and Monte Burney volcanoes, respectively. The most recent dust peak, however, has a rare earth element and neodymium isotopic composition that resembles the geochemical signature of outwash plain sediments from the Darwin Cordillera. Since the timing of this dust peak corresponds to a period of glacier retreat between Neoglacial advances III and IV, we infer that Holocene aeolian dust fluxes in southern Patagonia are mostly driven by glacial sediment availability. Our results underline the important role of glaciers in producing aeolian dust in high-latitude regions, and they imply that the current retreat of glaciers worldwide may result in elevated atmospheric dust loads.