Spatial and temporal variability of snow chemical composition and accumulation rate at Talos Dome site (East Antarctica)

Volcanic Fluxes Over the Last Millennium as Recorded in the Gv7 Ice Core (Northern Victoria Land, Antarctica)

Major explosive volcanic eruptions may significantly alter the global atmosphere for about 2–3 years. During that period, volcanic products (mainly H2SO4) with high residence time, stored in the stratosphere or, for shorter times, in the troposphere are gradually deposited onto polar ice caps. Antarctic snow may thus record acidic signals providing a history of past volcanic events. The high resolution sulphate concentration profile along a 197 m long ice core drilled at GV7 (Northern Victoria land) was obtained by Ion Chromatography on around 3500 discrete samples. The relatively high accumulation rate (241 ± 13 mm we yr −1) and the 5-cm sampling resolution allowed a preliminary counted age scale. The obtained stratigraphy covers roughly the last millennium and 24 major volcanic eruptions were identified, dated, and tentatively ascribed to a source volcano. The deposition flux of volcanic sulphate was calculated for each signature and the results were compared with data from other Antarctic ice cores at regional and continental scale. Our results show that the regional variability is of the same order of magnitude as the continental one.

Sub-1 mL sample requirement for simultaneous determination of 17 organic and inorganic anions and cations in Antarctic ice core samples by dual capillary ion chromatography

The significant advance of delivering high value multi-species data from sub-1 mL ice core sample volumes allows higher temporal resolution in deposition records of inorganic and low molecular weight organic anions and cations. The determination of these species is a fundamental strategic requirement in modern paleoclimate studies. Herein, for the first time, a dual capillary ion chromatography (Cap-IC) based method for the simultaneous separation of 17 organic and inorganic anions and cations in low volume Antarctic ice core samples is presented. The total amount of sample required for direct injection has been reduced to 190 μL, which is 35 times lower than the amount of sample required by standard ion chromatography methods. A dual Cap-IC system configured for the simultaneous determination of cations and anions was used throughout. A range of chromatographic parameters was optimised for both anion and cation systems to obtain baseline separations of all target analytes in a suitable run time and to minimise the amount of sample required. Baseline separation of matrix and trace 'marker' ions were achieved in less than 35 min, after injecting only 40 μL of sample in each IC system. Limits of detection (LODs) for all analytes determined were within a range similar to that achieved by previously published standard bore IC-based methods. Intra- and inter-day repeatability were evaluated, with both parameters being typically below 3% for peak area. In further validation of the method, a comparative analysis of a set of 420 ice core samples from Aurora Basin North site, Antarctica, previously analysed by standard IC, established that the proposed low sample volume technique was applicable as a routine measurement approach in ice core analysis projects.

Prominent features in isotopic, chemical and dust stratigraphies from coastal East Antarctic ice sheet (Eastern Wilkes Land)

In this work we present the isotopic, chemical and dust stratigraphies of two snow pits sampled in 2013/14 at GV7 (coastal East Antarctica: 70°41' S - 158°51' E, 1950 m a.s.l.). A large number of chemical species are measured aiming to study their potentiality as environmental changes markers. Seasonal cluster backward trajectories analysis was performed and compared with chemical marker stratigraphies. Sea spray aerosol is delivered to the sampling site together with snow precipitation especially in autumn-winter by air masses arising from Western Pacific Ocean sector. Dust show maximum concentration in spring when the air masses arising from Ross Sea sector mobilize mineral dust from ice-free areas of the Transantarctic mountains. The clear seasonal pattern of sulfur oxidized compounds allows the dating of the snow-pit and the calculation of the mean accumulation rate, which is 242 ± 71 mm w.e. for the period 2008-2013. Methanesulfonic acid and NO₃^- do not show any concentration decreasing trend as depth increases, also considering a 12 m firn core record. Therefore these two compounds are not affected by post-depositional processes at this site and can be considered reliable markers for past environmental changes reconstruction. The rBC snow-pit record shows the highest values in summer 2012 likely related to large biomass burning even occurred in Australia in this summer. The undisturbed accumulation rate for this site is demonstrated by the agreement between the chemical stratigraphies and the annual accumulation rate of the two snow-pits analysed in Italian and Korean laboratories.

Sea salt sodium record from Talos Dome (East Antarctica) as a potential proxy of the Antarctic past sea ice extent

Antarctic sea ice has shown an increasing trend in recent decades, but with strong regional differences from one sector to another of the Southern Ocean. The Ross Sea and the Indian sectors have seen an increase in sea ice during the satellite era (1979 onwards). Here we present a record of ssNa⁺ flux in the Talos Dome region during a 25-year period spanning from 1979 to 2003, showing that this marker could be used as a potential proxy for reconstructing the sea ice extent in the Ross Sea and Western Pacific Ocean at least for recent decades. After finding a positive relationship between the maxima in sea ice extent for a 25-year period, we used this relationship in the TALDICE record in order to reconstruct the sea ice conditions over the 20th century. Our tentative reconstruction highlighted a decline in the sea ice extent (SIE) starting in the 1950s and pointed out a higher variability of SIE starting from the 1960s and that the largest sea ice extents of the last century occurred during the 1990s.

Paleo-environmental record of polycyclic aromatic hydrocarbons and polychlorobiphenyls at the peripheral site GV7 in Victoria Land (East Antarctica)

In this paper we investigated the presence of Polycyclic Aromatic Hydrocarbons and Polychlorobiphenyls in a 50-m deep snow/firn core collected at the peripheral site GV7 in East Antarctica during the 2013-2014 XXIX Italian expedition. The concentration depth profile was obtained on the basis of the total concentration of fourteen PAHs and seven PCBs individually determined by gas chromatography triple quadrupole mass spectrometry. Both classes of pollutants showed synchronized concentration vs time profile throughout the whole period of time covered by the snow/firn core (1892-2012). A correlation between major explosive volcanic eruptions and the concentration maxima of the pollutants was found. PAH maximum (9 ng/L) was about twice the background level (5 ng/L). PCBs showed a similar but more limited trend with barely visible volcanic maxima. This concurrence highlights the contribution of the major explosive volcanic events to the global contamination level for PAHs, as expected, but also for PCBs whose industrial production and use began in 1930. Excluding the maximum values, PAHs and PCBs showed an increase in the period 1956-1986: PCBs from about 0.05 to 0.21 ng/l (400% increase), and PAHs from about 3.5 to 7.8 ng/l (100% increase). Finally, in the last decade (2000-2010) the trend of these pollutants was different: (i) PCBs constantly decrease (from 0.15 ng/L to 0.10 ng/L), thanks to the implemented restriction on their production and on their use only in closed systems in many countries; (ii) PAHs remains practically constant around 6.5 ng/L.