Papers by Viorela Ciobanu
High-resolution, well-dated climate archives provide an opportunity to investigate the dynamic in... more High-resolution, well-dated climate archives provide an opportunity to investigate the dynamic interactions of climate patterns relevant for future projections. Here, we present data from a new, annually-dated ice core record from the eastern Ross Sea. Comparison of the Roosevelt Island Climate Evolution (RICE) ice core records with climate reanalysis data for the 1979-2012 calibration period shows that RICE records reliably capture temperature and snow precipitation variability of the region. RICE is compared with data from West Antarctica (West Antarctic Ice Sheet Divide Ice Core) and the western (Talos Dome) and eastern (Siple Dome) Ross Sea. For most of the past 2,700 years, the eastern Ross Sea was warming with perhaps increased snow accumulation and decreased sea ice extent. However, West Antarctica cooled whereas the western Ross Sea showed no significant temperature trend. From the 17th Century onwards, this relationship changes. All three regions now show signs of warming, with snow accumulation declining in West Antarctica and the eastern Ross Sea, but increasing in the western Ross Sea. Analysis of decadal to centennial-scale climate variability superimposed on the longer term trend reveal that periods characterised by opposing temperature trends between the Eastern and Western Ross Sea have occurred since the 3rd Century but are masked by longer-term trends. This pattern here is referred to as the Ross Sea Dipole, caused by a sensitive response of the region to dynamic interactions of the Southern Annual Mode and tropical forcings.
Climate of the Past Discussions, 2017
High-resolution, well-dated climate archives provide an opportunity to investigate the dynamic in... more High-resolution, well-dated climate archives provide an opportunity to investigate the dynamic interactions of climate patterns relevant for future projections. Here, we present data from a new, annually-dated ice core record from the eastern Ross Sea. Comparison of the Roosevelt Island Climate Evolution (RICE) ice core records with climate reanalysis data for the 1979–2012 calibration period shows that RICE records reliably capture temperature and snow precipitation variability of the region. RICE is compared with data from West Antarctica (West Antarctic Ice Sheet Divide Ice Core) and the western (Talos Dome) and eastern (Siple Dome) Ross Sea. For most of the past 2,700 years, the eastern Ross Sea was warming with perhaps increased snow accumulation and decreased sea ice extent. However, West Antarctica cooled whereas the western Ross Sea showed no significant temperature trend. From the 17th Century onwards, this relationship changes. All three regions now show signs of war...
Atmospheric Measurement Techniques Discussions, 2016
Paleo–atmospheric records of carbon dioxide and its stable carbon isotope composition (δ<... more Paleo–atmospheric records of carbon dioxide and its stable carbon isotope composition (δ<sup>13</sup>C) obtained from polar ice cores provide important constraints on the natural variability of the carbon cycle. However, the measurements are both analytically challenging and time-consuming thus data exist only from a limited number of sampling sites and time periods. Additional analytical resources with high analytical precision and throughput are thus desirable to extend and confirm the existing datasets. Also, consistent measurements derived by independent laboratories and a variety of analytical systems helps to further increase confidence in the global CO<sub>2</sub> paleo reconstructions. Here, we describe our new setup for simultaneous measurements of atmospheric CO<sub>2</sub> mixing ratios, atmospheric δ<sup>13</sup>C and δ<sup>18</sup>O-CO<sub>2</sub> in air extracted from ice core sam...
Carbonaceous particles (total carbon, TC) are a major fraction of the fine aerosol and affect cli... more Carbonaceous particles (total carbon, TC) are a major fraction of the fine aerosol and affect climate and human health. TC is classified into the sub-fractions elemental carbon (EC) and organic carbon (OC). EC originates only from fossil fuel combustion and biomass burning. OC can be emitted directly as primary organic aerosol from biogenic emissions, wood burning and fossil fuel combustion or can be formed in-situ in the atmosphere (secondary organic aerosol) (Szidat et al. 2006). Radiocarbon (14C) analysis is a direct and quantitative tool for distinguishing fossil and non-fossil sources, since 14C in fossil fuels is completely depleted whereas other sources have a contemporary 14C level. This study presents source apportionment results from the winter season over a time period of 5 years (2007/2008-2011/2012) using 14C measurements on aerosol filters collected simultaneously at 16 air quality monitoring stations across Switzerland. For every year 5 winter smog episode days were s...
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2015
This paper reports on novel separation methods developed for the direct determination of 14 C in ... more This paper reports on novel separation methods developed for the direct determination of 14 C in organic carbon (OC) and elemental carbon (EC), two sub-fractions of total carbon (TC) of atmospheric air particulate matter. Until recently, separation of OC and EC has been performed off-line by manual and time-consuming techniques that relied on the collection of massive CO2 fractions. We present here two on-line hyphenated techniques between a Sunset OC/EC analyzer and a MICADAS (MIni radioCArbon DAting System) accelerator mass spectrometer (AMS) equipped with a gas ion source. The first implementation facilitates the direct measurement in the low sample size range (<10 μg C) with high throughput on a routine basis, while the second explores the potential for a continuous-flow real-time CO2 gas feed into the ion source. The performance achieved with reference materials and real atmospheric samples will be discussed to draw conclusions on the improvement offered in the field of 14 C aerosol source apportionment.
Atmospheric Chemistry and Physics, 2012
Radiocarbon (14 C) measurements of elemental carbon (EC) and organic carbon (OC) separately (as o... more Radiocarbon (14 C) measurements of elemental carbon (EC) and organic carbon (OC) separately (as opposed to only total carbon, TC) allow an unambiguous quantification of their non-fossil and fossil sources and represent an improvement in carbonaceous aerosol source apportionment. Isolation of OC and EC for accurate 14 C determination requires complete removal of interfering fractions with maximum recovery. The optimal strategy for 14 C-based source apportionment of carbonaceous aerosols should follow an approach to subdivide TC into different carbonaceous aerosol fractions for individual 14 C analyses, as these fractions may differ in their origins. To evaluate the extent of positive and negative artefacts during OC and EC separation, we performed sample preparation with a commercial Thermo-Optical OC/EC Analyser (TOA) by monitoring the optical properties of the sample during the thermal treatments. Extensive attention has been devoted to the setup of TOA conditions, in particular, heating program and choice of carrier gas. Based on different types of carbonaceous aerosols samples, an optimised TOA protocol (Swiss 4S) with four steps is developed to minimise the charring of OC, the premature combustion of EC and thus artefacts of 14 C-based source apportionment of EC. For the isolation of EC for 14 C analysis, the water-extraction treatment on the filter prior to any thermal treatment is an essential prerequisite for subsequent radiocarbon measurements; otherwise the non-fossil contribution may be overestimated due to the positive bias from Published by Copernicus Publications on behalf of the European Geosciences Union.
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Papers by Viorela Ciobanu