A database of surface Antarctic snow isotopic composition is constructed using available measurements, with an estimate of data quality and local variability. Although more than 1000 locations are documented, the spatial coverage remains uneven with a majority of sites located in specific areas of East Antarctica. The database is used to analyze the spatial variations in snow isotopic composition with respect to geographical characteristics (elevation, distance to the coast) and climatic features (temperature, accumulation) and with a focus on deuterium excess. The capacity of theoretical isotopic, regional, and general circulation atmospheric models (including "isotopic" models) to reproduce the observed features and assess the role of moisture advection in spatial deuterium excess fluctuations is analyzed.

Crustal dust in the atmosphere impacts Earth's radiative forcing directly by modifying the radiation budget and affecting cloud nucleation and optical properties, and indirectly through ocean fertilization, which alters carbon sequestration. Increased dust in the atmosphere has been linked to decreased global air temperature in past ice core studies of glacial to interglacial transitions. We present a continuous ice core record of aluminum deposition during recent centuries in the northern Antarctic Peninsula, the most rapidly warming region of the Southern Hemisphere; such a record has not been reported previously. This record shows that aluminosilicate dust deposition more than doubled during the 20th century, coincident with the Ϸ1°C Southern Hemisphere warming: a pattern in parallel with increasing air temperatures, decreasing relative humidity, and widespread desertification in Patagonia and northern Argentina. These results have far-reaching implications for understanding the forces driving dust generation and impacts of changing dust levels on climate both in the recent past and future.aluminosilicate dust ͉ global warming ͉ human impacts ͉ Patagonia ͉ radiative transfer C rustal dust in the atmosphere has a direct impact on climate forcing in two significant ways: modifying the radiation balance and affecting cloud nucleation and optical properties (1, 2). Atmospheric crustal dust also supplies iron, an essential nutrient for phytoplankton, to ocean surface waters and may indirectly affect climate by modulating the biological export of carbon to the deep ocean (3). Impacts of atmospheric dust on regional radiation budgets are similar in magnitude to those from sulfate and biomass burning aerosols (4) but can be either negative or positive (1). Estimates of the optical properties of dust have been revised recently as a result of improved in situ and remote sensing measurements (5, 6), but warming has been predicted across areas of high albedo (7, 8) such as snow-and ice-covered regions of the Antarctic Peninsula where recent warming has been pronounced (9). Although atmospheric dustiness has been linked to large-amplitude, large-scale temperature changes in past ice core studies of glacial to interglacial transitions (10, 11), it is unclear whether projected climate warming in coming decades to centuries will result in more or less atmospheric dust (12). Decadal changes in dust flux have been reported for ice cores from the Antarctic Peninsula (13, 14), but reliable, high-time-resolution records of changes in dust levels during recent decades and centuries are sparse (15).Ice core records offer the possibility of reconstructing past changes in dust concentration (10,11,(13)(14)(15)(16)(17)(18)(19)(20). Most previous high-resolution ice core studies used as proxies of atmospheric dust the non-sea-salt component of soluble calcium (nssCa) or magnesium (nssMg) that are computed by using estimated elemental ratios in sea salt aerosols (11,19). At many ice core sites, particularly coastal locations, the nssCa ...

[1] This study uses ice core methanesulphonic acid (MSA) records from the Antarctic Peninsula, where temperatures have been warming faster than anywhere else in the Southern Hemisphere, to reconstruct the 20th century history of sea ice change in the adjacent Bellingshausen Sea. Using satellite-derived sea ice and meteorological data, we show that ice core MSA records from this region are a reliable proxy for regional sea ice change, with years of increased winter sea ice extent recorded by increased ice core MSA concentrations. Our reconstruction suggests that the satellite-observed sea ice decline in the Bellingshausen Sea during recent decades is part of a long-term regional trend that has occurred throughout the 20th century. The long-term perspective on sea ice in the Bellingshausen Sea is consistent with evidence of 20th century warming on the Antarctic Peninsula and may reflect a progressive deepening of the Amundsen Sea Low due to increasing greenhouse gas concentrations and, more recently, stratospheric ozone depletion. As a first-order estimate, our MSA-based reconstruction suggests that sea ice in the Bellingshausen Sea has retreated southward by ∼0.7°during the 20th century. Comparison with other 20th century sea ice observations, reconstructions, and model simulations provides a coherent picture of Antarctic sea ice decline during the 20th century, although with regional-scale differences evident in the timing and magnitude of this sea ice decline. This longer-term perspective contrasts with the small overall increase in Antarctic sea ice that is observed in post-1979 satellite data.

ABSTRACT. An updated compilation of published and new data of major-ion (Ca, Cl, K, Mg, Na, NO 3 , SO 4 ) and methylsulfonate (MS) concentrations in snow from 520 Antarctic sites is provided by the national ITASE (International Trans-Antarctic Scientific Expedition) programmes of Australia, Brazil, China, Germany, Italy, Japan, Korea, New Zealand, Norway, the United Kingdom, the United States and the national Antarctic programme of Finland. The comparison shows that snow chemistry concentrations vary by up to four orders of magnitude across Antarctica and exhibit distinct geographical patterns. The Antarctic-wide comparison of glaciochemical records provides a unique opportunity to improve our understanding of the fundamental factors that ultimately control the chemistry of snow or ice samples. This paper aims to initiate data compilation and administration in order to provide a framework for facilitation of Antarctic-wide snow chemistry discussions across all ITASE nations and other contributing groups. The data are made available through the ITASE web page (http:// www2.umaine.edu/itase/content/syngroups/snowchem.html) and will be updated with new data as they are provided. In addition, recommendations for future research efforts are summarized.

A detailed climatic study of

Major volcanic eruptions are able to Chichon have given a strong impetus to investigaspread large amounts of sulfuric acid all over the tions concerning the atmospheric impact of large world. Acid layers of volcanic origin were volcanic eruptions. An empirical approach has detected for the first time a few years ago by often been used in determining the climatic Hammer in Greenland ice. The present paper deals implications of eruptions, based on the comparison with volcanic deposits in the Antarctic. The of historical volcanic records with available different methods that can be used to find climate data compilations. Such data may have volcanic acid deposits in snow and ice cores are various origins: ancient temperature measurements, compared: electrical conductivity, sulfate, and glacial isotope records, tree ring records, acidity measurements. Numerous snow and ice glacier variations, etc [0liver, 1976; Rampino et samples collected at several Antarctic locations al., 1979; Hammer et al., 1981; Sch•nwiese, 1981; were analyzed. The results reveal that the two Porter, 1981; La Marche and Hirschboeck, 1984]. 1981; Hammer et al., 1981; Toon and Pollack, discussed the different possible processes 1982]. involved at the air-snow interface. However there The recent eruptions of Mount St. Helens and E1 is now increasing evidence that the concentrations of the elements in the ice follow the concentrations in the air, so it appears reasonable to

More than 400 firn samples were collected at an altitude of 1660 m on the small ice sheet covering James Ross Island (northeastern coast of the Antarctic Peninsula). Chemical analysis of these samples provides information about the marine background aerosol composition in the area. The samples cover the years 1975–1979 (pit samples) and the last 15 years (firn core samples). Major impurities (Na, K, Ca, Al, H, SO4, and NO3) were determined by using flameless atomic absorption, neutron activation, acid titration, or ion chromatography. Aerosols are contributed mainly by the surrounding ocean; however, secondary aerosol deposition (H2SO4 and HNO3) is also important. All samples were found to be slightly acidic (pH generally in the range 5–6). Strong seasonal variations (maximum values in summer) are found in the H2SO4 deposition. A photochemical mechanism is proposed to explain the local production of H2SO4 from gaseous marine sulfur compounds. From these results, a yearly deposition of ∼0.13 Tg of H2SO4 is calculated for the entire Antarctic continent.

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