Climate changes modulated the history of Arctic iodine during the Last Glacial Cycle

Iodine has a significant impact on promoting the formation of new ultrafine aerosol particles and accelerating tropospheric ozone loss, thereby affecting radiative forcing and climate. Therefore, understanding the long-term natural evolution of iodine, and its coupling with climate variability, is key to adequately assess its effect on climate on centennial to millennial timescales. Here, using two Greenland ice cores (NEEM and RECAP), we report the Arctic iodine variability during the last 127,000 years. We find the highest and lowest iodine levels recorded during interglacial and glacial periods, respectively, modulated by ocean bioproductivity and sea ice dynamics. Our sub-decadal resolution measurements reveal that high frequency iodine emission variability occurred in pace with Dansgaard/Oeschger events, highlighting the rapid Arctic ocean-ice-atmosphere iodine exchange response to abrupt climate changes. Finally, we discuss if iodine levels during past warmer-than-present climate phases can serve as analogues of future scenarios under an expected ice-free Arctic Ocean. We argue that the combination of natural biogenic ocean iodine release (boosted by ongoing Arctic warming and sea ice retreat) and anthropogenic ozone-induced iodine emissions may lead to a near future scenario with the highest iodine levels of the last 127,000 years.

Determination of the Concentration of Ultrafine Aerosol Using an Ionization Sensor

As public awareness of the threats related to ultrafine aerosols increases, there is a growing need for inexpensive, real-time exposure assessment devices. In this work, the well-established technology used in the smoke detector with a radioactive source was tested in laboratory conditions to check its suitability for determining the number concentration of the ultrafine aerosol. It has been shown that the sensor output changes linearly with the change of diesel soot concentration in the range up to 8.3 × 105 particles cm−3. The sensor has also been shown to be able to detect rapid changes in aerosol concentration. Empirical equations describing the influence of air velocity, temperature, relative humidity, and pressure on the sensor output were determined. The collected results confirm that the ionization sensor can be used to assess ultrafine aerosol exposure, although additional engineering work is required to increase the resolution of the output signal measurement and to compensate for the effects of weather conditions. The presented method can be used for concentration monitoring and risk assessment in environmental engineering, materials engineering, cosmetics industry, textiles, sports, chemical, mining, energy, etc.

Evaluating the Response of Global Column Resistance to a Large Volcanic Eruption by an Aerosol-Coupled Chemistry Climate Model

Global electric circuits could be the key link between space weather and lower atmosphere climate. It has been suggested that the ultrafine erosol layer in the middle to upper stratosphere could greatly contribute to local column resistance and return current density. In previous work by Tinsley, Zhou, and Plemmons (Atmos. Res., 2006, 79 (3–4), 266–295), the artificial ultrafine layer was addressed and caused a significant symmetric effect on column resistance at high latitudes. In this work, we use an updated erosol coupled chemistry-climate model to establish a new global electric circuit model. The results show that the ultrafine aerosol layer exits the middle stratosphere, but due to the Brewer-Dobson circulation, there are significant seasonal variations in the ion loss due to variations in the ultrafine aerosol layer. In the winter hemisphere in the high latitude region, the column resistance will consequently be higher than that in the summer hemisphere. With an ultrafine aerosol layer in the decreasing phase of solar activity, the column resistance would be more sensitive to fluctuations in the low-energy electron precipitation (LEE) and middle-energy electron precipitation (MEE) particle fluxes.

Ultrafine Aerosol Particle Sizer Based on Piezoresistive Microcantilever Resonators with Integrated Air-Flow Channel

To monitor airborne nano-sized particles (NPs), a single-chip differential mobility particle sizer (DMPS) based on resonant micro cantilevers in defined micro-fluidic channels (µFCs) is introduced. A size bin of the positive-charged fraction of particles herein is separated from the air stream by aligning their trajectories onto the cantilever under the action of a perpendicular electrostatic field of variable strength. We use previously described µFCs and piezoresistive micro cantilevers (PMCs) of 16 ng mass fabricated using micro electro mechanical system (MEMS) technology, which offer a limit of detection of captured particle mass of 0.26 pg and a minimum detectable particulate mass concentration in air of 0.75 µg/m3. Mobility sizing in 4 bins of a nebulized carbon aerosol NPs is demonstrated based on finite element modelling (FEM) combined with a-priori knowledge of particle charge state. Good agreement of better than 14% of mass concentration is observed in a chamber test for the novel MEMS-DMPS vs. a simultaneously operated standard fast mobility particle sizer (FMPS) as reference instrument. Refreshing of polluted cantilevers is feasible without de-mounting the sensor chip from its package by multiply purging them alternately in acetone steam and clean air.

Large hemispheric difference in ultrafine aerosol concentrations in the lowermost stratosphere

<p>On the NASA Atmospheric Tomography Mission (ATom), we observed a sharp hemispheric contrast in the concentration of ultrafine aerosols (3-12 nm diameter) in the lowermost stratosphere that persisted through all four seasons. Exploring possible causes, we show that this is likely caused by aircraft, which emit both ultrafine aerosol and precursor gases for new particle formation (NPF) in quantities that agree well with our observations. While aircraft may emit a range of NPF precursors, we focus here on sulphur dioxide (a major source of atmospheric sulphuric acid), of which we have observations from the same mission.  We observe the same hemispheric contrast in sulphur dioxide as ultrafine aerosol, and find that the observed concentrations are in alignment with inventoried aircraft emissions. We present box modeling and thermodynamic calculations that support the plausibility of NPF under the conditions and sulphur dioxide concentrations observed on ATom.</p><p>While the direct climate impact of ultrafine aerosol in the lowermost stratosphere (LMS) may currently be small, our observations show a definitive size distribution shift of the background aerosol distribution in the northern hemisphere. This is important for assessing aviation impacts, and the expected impacts of increased air-traffic. Furthermore, climate intervention via injection of sulphate or aerosols into the stratosphere is a current subject of research. Our study shows that NPF is possible and likely already happening in the LMS, which must be accounted for in models for stratospheric modification, and points out that we must consider that any intentional stratospheric modification will be applied to two very different hemispheres: a largely pristine southern hemisphere; and an already anthropogenically modified northern hemisphere.</p>

Large hemispheric difference in ultrafine aerosol concentrations in the lowermost stratosphere at mid and high latitudes

The details of aerosol processes and size distributions in the stratosphere are important for both heterogeneous chemistry and aerosol-radiation interactions. Using in-situ, global-scale measurements of the size distribution of particles with diameters > 3 nm from the NASA Atmospheric Tomography Mission (ATom), we identify a mode of ultrafine aerosol in the lowermost stratosphere (LMS) at mid and high latitudes. This mode is substantial only in the northern hemisphere (NH), and was observed in all four seasons. We also observe elevated SO2, an important precursor for new particle formation (NPF) and growth, in the NH LMS. We use box modelling and thermodynamic calculations to show that NPF can occur in the LMS conditions observed on ATom. Aircraft emissions are shown as likely sources of this SO2, as well as a potential source of ultrafine particles directly emitted by, or formed in the plume of the engines. These ultra-fine particles have the potential to grow to larger sizes, and to coagulate with larger aerosol, affecting heterogeneous chemistry and aerosol-radiation interactions. Understanding all sources and characteristics of stratospheric aerosol is important in the context of anthropogenic climate change as well as proposals for climate intervention via stratospheric sulphur injection. This analysis not only adds to the, currently sparse, observations of the global impact of aviation, but also introduces another aspect of climate influence, namely a size distribution shift of the background aerosol distribution in the LMS.