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

Climate-related variabilities in the Styx-M ice core record from northern Victoria Land, East Antarctica, during 1979-2014

The historical climate variability in East Antarctica inferred from ice cores remains under debate owing to the vastness and complexity of the region. This study evaluates the potential climate variabilities in the Styx-M ice core records (δ18O, d-excess, and snow accumulation) from northern Victoria Land adjacent to the Ross Sea sector of East Antarctica during 1979-2014. Results show that the primary moisture source in this area is the Pacific Ocean sector. Although the annual mean δ18O values was limited to directly indicate the temperature changes, a weak relevance between the average δ18O values and the temperature signal during the austral summer season is detectable. δ18O, d-excess, and snow accumulation correlate with sea surface temperature and sea ice extent in the Ross Sea sector. A coupled influence of the SAM, ASL, and ENSO climate indices is expected, because the oceanic environment in this region is influenced by them. The pronounced intrusion of oceanic moisture coupled with atmospheric circulation patterns over the Ross Sea region makes the Styx-M ice core a promising record of the local oceanic conditions, with the snow accumulation rate being a direct proxy. Additionally, the analysis of trace elements from 1979 to 1999 revealed the presence of crustal dust sourced from the Transantarctic Mountains, as well as non-crustal sources, both intricately linked with atmospheric transport. These results demonstrate that the contributions of-and variations in-oceanic conditions associated with atmospheric circulation changes are detectable and dominant in the Styx-M ice core. This study serves as a basis for interpreting longer parts of the Styx-M ice core.

Fast Liquid Chromatography Coupled with Tandem Mass Spectrometry for the Analysis of Vanillic and Syringic Acids in Ice Cores

The development of new analytical systems and the improvement of the existing ones to obtain high-resolution measurements of chemical markers in samples from ice cores, is one of the main challenges the paleoclimatic scientific community is facing. Different chemical species can be used as markers for tracking emission sources or specific environmental processes. Although some markers, such as methane sulfonic acid (a proxy of marine productivity), are commonly used, there is a lack of data on other organic tracers in ice cores, making their continuous analysis analytically challenging. Here, we present an innovative combination of fast liquid chromatography coupled with tandem mass spectrometry (FLC-MS/MS) to continuously determine organic markers in ice cores. After specific optimization, this approach was applied to the quantification of vanillic and syringic acids, two specific markers for biomass burning. Using the validated method, detection limits of 3.6 and 4.6 pg mL^–1 for vanillic and syringic acids, respectively, were achieved. Thanks to the coupling of FLC-MS/MS with the continuous flow analytical system, we obtained one measurement every 30 s, which corresponds to a sampling resolution of a sample every 1.5 cm with a melting rate of 3.0 cm min^–1. To check the robustness of the method, we analyzed two parallel sticks of an alpine ice core over more than 5 h. Vanillic acid was found with concentrations in the range of picograms per milliliter, suggesting the combustion of coniferous trees, which are found throughout the Italian Alps.

Seasonal Evolution of the Chemical Composition of Atmospheric Aerosol in Terra Nova Bay (Antarctica)

Atmospheric aerosol samples were collected at Faraglione Camp, 3 km away from the Italian Mario Zucchelli Station (Terra Nova Bay, Ross Sea), from 1 December 2013 to 2 February 2014. A two-step extraction procedure was applied to characterize the soluble and insoluble components of PM10-bound metals. Samples were analyzed for Al, Fe, Cd, Cu, and Pb by square wave anodic stripping voltammetry (SWASV) and by graphite furnace atomic absorption spectrophotometer (GF-AAS). The mean atmospheric concentrations were (reported as means ± SD) Al 24 ± 3 ng m−3; Fe 23 ± 4 ng m−3; Cd 0.92 ± 0.53 pg m−3; Cu 43 ± 9 pg m−3, and Pb 16 ± 5 pg m−3. The fractionation pattern was metal-specific, with Al, Fe, and Pb mainly present in the insoluble fractions, Cd in the soluble one, and Cu equally distributed between the two fractions. The summer evolution showed overall constant behavior of both fractions for Al and Fe, while a bell-shaped trend was observed for the three trace metals. Cd and Cu showed a bell-shaped evolution involving both fractions. A seasonal increase in Pb occurred only for the insoluble fraction, while the soluble fraction remained almost constant. Sequential extraction and enrichment factors indicated a crustal origin for Al, Fe, and Pb, and additional (marine or anthropogenic) contributions for Cd and Cu. Back trajectory analysis showed a strong contribution of air masses derived from the Antarctic plateau. A potential low contribution from anthropized areas cannot be excluded. Further studies are necessary to better characterize the chemical composition of the aerosol, to discriminate between natural and anthropogenic sources, and to evaluate a quantitative source apportionment.

Seasonal Evolution of Size-Segregated Particulate Mercury in the Atmospheric Aerosol Over Terra Nova Bay, Antarctica

Size-fractionated particulate mercury (PHg) measurements were performed from November 2017 to January 2018 at Terra Nova Bay (Antarctica) for the first time. Samples were collected every 10 days by a six-stage high-volume cascade impactor with size classes between 10 μm and 0.49 μm. Total PHg concentrations were maxima (87 ± 8 pg m⁻³) in November, then decreased to values ~40% lower and remained almost constant until the end of the sampling period (~30 pg m⁻³). The trimodal aerosol mass distribution reveals that from 30% to 90% of the total PHg came in the size > 1.0 μm. Hg in the two coarse fractions was probably produced by the adsorption of oxidized Hg species transported by air masses from the Antarctic plateau or produced locally by sea ice edges. PHg in accumulation mode seemed to be related to gas–particle partitioning with sea salt aerosol. Finally, average dry deposition fluxes of PHg were calculated to be 0.36 ± 0.21 ng m⁻² d⁻¹ in the accumulation mode, 47 ± 44 ng m⁻² d⁻¹ in the first coarse mode, and 37 ± 31 ng m⁻² d⁻¹ in the second coarse mode. The present work contributed to the comprehension of the Hg biogeochemical cycle, but further research studies are needed.

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.