Low-volatility vapors and new particle formation over the Southern Ocean during the Antarctic Circumnavigation Expedition

Abstract

Aerosols have a major impact on our climate (Stocker et al., 2014). They scatter and absorb solar radiation and are part of cloud formation processes as cloud condensation nuclei (CCN) or ice nucleating particles (INP). The combination of aerosol-radiation and aerosol-cloud interactions contributes the largest fraction of uncertainty to the overall radiative forcing budget (Stocker et al., 2014). The present day (PD) aerosol forcing is calculated against a preindustrial (PI) baseline, which is poorly constrained because direct measurements of PI aerosols are impossible. Additionally, the radiative forcing due to aerosol-cloud interactions (RF aci ) is non-linearly dependent on the total aerosol number concentration and is much more sensitive to changes in low concentration regimes, which are more representative of the the PI time (Carslaw et al., 2013(Carslaw et al., , 2017. Therefore, the highly uncertain concentration and distribution of PI aerosols has a disproportionately large effect on the PD RF aci uncertainty. One way to constrain this uncertainty is to better characterize natural sources of aerosols, which were predominant during the PI time. However, there are very few places on Earth that may still resemble PI-like conditions with minimum anthropogenic influence. Among these locations, the Southern Ocean is probably the region with the highest number of PI-like days during summer (Hamilton et al., 2014). Recently, Regayre et al. (2020) demonstrated that a small set of measurements over the Southern Ocean can be as effective as a two orders of magnitude larger and more heterogeneous set of data from the Northern Hemisphere in reducing the RF aci in a global climate model. This highlights the value of measurements in pristine and remote locations.

A central arctic extreme aerosol event triggered by a warm air-mass intrusion

“…To go further into the effect of aerosol acidity on the aerosol organic fraction, we select an organic molecule relevant for marine and Polar locations, MSA, which is produced from aqueous and gas phase oxidation of DMS, derived from dimethylsulfoniopropionate, a gas produced by phytoplankton 58 that participates in marine secondary aerosol formation 47,48,59,60 . MSA partitioning is mediated by gas-phase concentration, temperature, relative humidity and aerosol composition and properties 60 . To understand the effect of the warm air-mass intrusion together with changes in aerosol composition and acidity on MSA partitioning, we examine gas and particulate phase concentrations and variability.…”

“…The model was further used to calculate the partitioning of MSA between gas and particle phase 96 . The MSA properties are based on the values reported in Baccarini et al 60 . While there is a difference in the absolute value between measured and predicted partitioning, the relative difference between the background, first and second peaks remains visible.…”

Exploring the coupled ocean and atmosphere system with a data science approach applied to observations from the Antarctic Circumnavigation Expedition

“…A2). This increase was caused by the strongest new particle formation event measured during the entire expedition (Baccarini et al, 2021). In fact, this event constitutes the most pronounced difference in the time series of LV1 (climatic zones and large-scale horizontal gradients) and LV14 (hotspot-driven climatic zones).…”

Arctic observations of Hydroperoxymethyl Thioformate (HPMTF) – seasonal behavior and relationship to other oxidation products from Dimethyl Sulfide at the Zeppelin Observatory, Svalbard

“…This hypothesis is supported by the higher importance of OHinitiated DMS oxidation at lower latitudes in the study by Fung et al (2022), and the DMS conversion yields of MSA and HPMTF in the different model runs by Wollesen de Jonge et al ( 2021), where the HPMTF/MSA ratio was considerably lower in the AtmMain case compared to cases with higher temperature and lower RH. This could be both due to differing sources and sinks, such as dry/wet deposition of MSA (Bergin et al, 1995) and HPMTF (Khan et al, 2021), heterogeneous oxidation of MSA (g) (Mungall et al, 2018) and evaporation of MSA from the particle-to the gas phase (Baccarini et al, 2021).…”