Alberto J. Aristarain

Bio: Alberto J. Aristarain is an academic researcher from Instituto Antártico Argentino. The author has contributed to research in topics: Ice core & Snow. The author has an hindex of 16, co-authored 22 publications receiving 1156 citations.

A Review of Antarctic Surface Snow Isotopic Composition : Observations, Atmospheric Circulation, and Isotopic Modeling

Abstract: 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.

20th-Century doubling in dust archived in an Antarctic Peninsula ice core parallels climate change and desertification in South America.

Abstract: 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 ≈1°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.

Ice core evidence for a 20th century decline of sea ice in the Bellingshausen Sea, Antarctica

Abstract: [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.

Past antarctic peninsula climate (1850-1980) deduced from an ice core isotope record

Abstract: A detailed climatic study of the Antarctic Peninsula from 1850 to 1980 has been carried out through the analysis of deuterium content in the snow layers of Dalinger Dome (James Ross Island, Antarctic Peninsula). It is based on the high correlation found between mean deuterium contents at this site and temperature data from stations within this region going back as far as April 1903 for the Argentine Orcadas station. The strong correlation between isotopes and temperatures first reveals a 1956 isotope reference for the region considered. Secondly, the isotope-temperature gradient is estimated at 4.5%. °C−1 for deuterium. After checking that the major temperature anomalies on the Antarctic Peninsula recorded since 1904 (according to available data) correspond to annual mean stable isotope peaks at Dalinger Dome, the amplitude of four prior anomalies are estimated in °C. Finally, a cooling of about 2 °C since 1850 is suggested for the region.

Volcanic deposits in Antarctic snow and ice

Abstract: Major volcanic eruptions are able to spread large amounts of sulfuric acid all over the world. Acid layers of volcanic origin were detected for the first time a few years ago by Hammer in Greenland ice. The present paper deals with volcanic deposits in the Antarctic. The different methods that can be used to find volcanic acid deposits in snow and ice cores are compared: electrical conductivity, sulfate, and acidity measurements. Numerous snow and ice samples collected at several Antarctic locations were analyzed. The results reveal that the two major volcanic events recorded by H2SO4, fallout in Antarctic ice over the last century are the eruptions of Krakatoa (1883) and Agung (1963), both located at equatorial latitudes in the southern hemisphere. The volcanic signals are found to be particularly well defined at central Antarctic locations apparently in relation to the low snow accumulation rates in these areas. It is demonstrated that volcanic sulfuric acid in snow is not even partially neutralized by ammonia. The possible influence of Antarctic volcanic activity on snow chemistry is also discussed, using the three recent eruptions of the Deception Island volcano as examples. Only one of them seems to have had a significant effect on the chemistry of snow at a location 200 km from this volcano. It is concluded that Antarctic volcanic ice records are less complicated than Greenland records because of the limited number of volcanos in the southern hemisphere and the apparently higher signal to background ratio for acidity in Antarctica than in Greenland.

Isotopic Patterns in Modern Global Precipitation

Abstract: The International Atomic Energy Agency (IAEA), in cooperation with the World Meteorological Organization (WMO), has been conducting a world-wide survey of hydrogen (H/'H) and oxygen (O/O) isotope composition of monthly precipitation since 1961 At present, 72 IAEA/WMO network stations are in operation Another 82 stations belonging to national organizations continue to send their results to the IAEA for publication The paper focuses on basic features of spatial and temporal distribution of deuterium and O in global precipitation, as derived from the IAEA/WMO isotope database The internal structure and basic characteristics of this database are discussed in some detail The existing phenomenological relationships between observed stable isotope composition of precipitation and various climate-related parameters such as local surface air temperature and amount of precipitation are reviewed and critically assessed Attempts are presented towards revealing interannual fluctuations in the accumulated isotope records and relating them to changes of precipitation amount and the surface air temperature over the past 30 years

Recent Rapid Regional Climate Warming on the Antarctic Peninsula

Abstract: The Intergovernmental Panel on Climate Change (IPCC) confirmed that mean global warming was 0.6 ± 0.2 °C during the 20th century and cited anthropogenic increases in greenhouse gases as the likely cause of temperature rise in the last 50 years. But this mean value conceals the substantial complexity of observed climate change, which is seasonally- and diurnally-biased, decadally-variable and geographically patchy. In particular, over the last 50 years three high-latitude areas have undergone recent rapid regional (RRR) warming, which was substantially more rapid than the global mean. However, each RRR warming occupies a different climatic regime and may have an entirely different underlying cause. We discuss the significance of RRR warming in one area, the Antarctic Peninsula. Here warming was much more rapid than in the rest of Antarctica where it was not significantly different to the global mean. We highlight climate proxies that appear to show that RRR warming on the Antarctic Peninsula is unprecedented over the last two millennia, and so unlikely to be a natural mode of variability. So while the station records do not indicate a ubiquitous polar amplification of global warming, the RRR warming on the Antarctic Peninsula might be a regional amplification of such warming. This, however, remains unproven since we cannot yet be sure what mechanism leads to such an amplification. We discuss several possible candidate mechanisms: changing oceanographic or changing atmospheric circulation, or a regional air-sea-ice feedback amplifying greenhouse warming. We can show that atmospheric warming and reduction in sea-ice duration coincide in a small area on the west of the Antarctic Peninsula, but here we cannot yet distinguish cause and effect. Thus for the present we cannot determine which process is the probable cause of RRR warming on the Antarctic Peninsula and until the mechanism initiating and sustaining the RRR warming is understood, and is convincingly reproduced in climate models, we lack a sound basis for predicting climate change in this region over the coming century.

Global Scale Attribution of Anthropogenic and Natural Dust Sources and their Emission Rates Based on MODIS Deep Blue Aerosol Products

Abstract: [1] Our understanding of the global dust cycle is limited by a dearth of information about dust sources, especially small-scale features which could account for a large fraction of global emissions. Here we present a global-scale high-resolution (0.1°) mapping of sources based on Moderate Resolution Imaging Spectroradiometer (MODIS) Deep Blue estimates of dust optical depth in conjunction with other data sets including land use. We ascribe dust sources to natural and anthropogenic (primarily agricultural) origins, calculate their respective contributions to emissions, and extensively compare these products against literature. Natural dust sources globally account for 75% of emissions; anthropogenic sources account for 25%. North Africa accounts for 55% of global dust emissions with only 8% being anthropogenic, mostly from the Sahel. Elsewhere, anthropogenic dust emissions can be much higher (75% in Australia). Hydrologic dust sources (e.g., ephemeral water bodies) account for 31% worldwide; 15% of them are natural while 85% are anthropogenic. Globally, 20% of emissions are from vegetated surfaces, primarily desert shrublands and agricultural lands. Since anthropogenic dust sources are associated with land use and ephemeral water bodies, both in turn linked to the hydrological cycle, their emissions are affected by climate variability. Such changes in dust emissions can impact climate, air quality, and human health. Improved dust emission estimates will require a better mapping of threshold wind velocities, vegetation dynamics, and surface conditions (soil moisture and land use) especially in the sensitive regions identified here, as well as improved ability to address small-scale convective processes producing dust via cold pool (haboob) events frequent in monsoon regimes.

Nitrogen oxides in the troposphere: Global and regional budgets

Abstract: The cycle of nitrogen oxides in the troposphere is discussed from both global and regional perspectives. Global sources for NO(x) are estimated to be of magnitude 50 (+ or - 25) x 10 to the 12th gm N/yr. Nitrogen oxides are derived from combustion of fossil fuels (40 percent) and biomass burning (25 percent) with the balance from lightning and microbial activity in soils. Estimates for the rate of removal of NOx based on recent atmospheric and precipitation chemistry data are consistent with global source strengths derived here. Industrial and agricultural activities provide approximately two thirds of the global source for NOx. In North America, sources from combustion of fossil fuels exceed natural sources by a factor of 3-13. Wet deposition removes about one third of the combustion source of NOx over North America, while dry deposition removes a similar amount. The balance is exported from the continent. Deposition of nitrate in precipitation over eastern Canada and the western Atlantic is clearly influenced by sources of NOx in the eastern United States.

Relation between long-term trends of oxygen-18 isotope composition of precipitation and climate.

Abstract: Stable isotope ratios of oxygen ((18)O/(16)O) and hydrogen (D/H) in water have long been considered powerful indicators of paleoclimate. However, quantitative interpretation of isotope variations in terms of climate changes is hampered by a limited understanding of physical processes controlling the global isotope behavior. Analysis was conducted of time series of (18)O content (delta (18)O) of monthly precipitation and surface air temperature available through the International Atomic Energy Agency-World Meteorological Organization global network, "Isotopes in Precipitation." This study indicates that long-term changes of isotopic composition of precipitation over mid-and high-latitude regions during the past three decades closely followed long-term changes of surface air temperature with the average 8180-temperature coefficient around 0.6 per mil per degree Celsius.