Publications

The remote central Arctic during summertime has a pristine atmosphere with very low aerosol particle concentrations. As the region becomes increasingly ice-free during summer, enhanced ocean-atmosphere fluxes of aerosol particles and precursor gases may therefore have impacts on the climate. However, large knowledge gaps remain regarding the sources and physicochemical properties of aerosols in this region. Here, we present insights into the molecular composition of semi-volatile aerosol components collected in September 2018 during the MOCCHA (Microbiology-Ocean-Cloud-Coupling in the High Arctic) campaign as part of the Arctic Ocean 2018 expedition with the Swedish Icebreaker Oden. Analysis was performed offline in the laboratory using an iodide High Resolution Time-of-Flight Chemical Ionization Mass Spectrometer with a Filter Inlet for Gases and AEROsols (FIGAERO-HRToF-CIMS). Our analysis revealed significant signal from organic and sulfur-containing compounds, indicative of marine aerosol sources, with a wide range of carbon numbers and O : C ratios. Several of the sulfur-containing compounds are oxidation products of dimethyl sulfide (DMS), a gas released by phytoplankton and ice algae. Comparison of the time series of particulate and gas-phase DMS oxidation products did not reveal a significant correlation, indicative of the different lifetimes of precursor and oxidation products in the different phases. This is the first time the FIGAERO-HRToF-CIMS was used to investigate the composition of aerosols in the central Arctic. The detailed information on the molecular composition of Arctic aerosols presented here can be used for the assessment of aerosol solubility and volatility, which is relevant for understanding aerosol–cloud interactions.

The flow field, vortex behaviour and pressure losses in a small-scale cyclone have been studied at a wide range of flow rate 0.23–39.7 NLPM (measured at 1 atm and 20 ◦C ) using the LES simulations that have been validated based on experimental measurements of the
cyclone pressure drop. The following flow characteristics such as (1) the radial distribution of the tangential velocity; (2) the maximum tangential velocity and axial downward flow rate; (3) natural vortex length and rotation frequency of the vortex end; and (4) pressure
losses in the cyclone have been analysed as a function of Reynolds number. The radial distribution of the tangential velocity inside the cyclone has been described by a proposed equation for adapted Burger’s vortex. The position of the lower end of the vortex (natural
vortex length) as well as its rotational frequency have been investigated with the pressure sensing method. A unique vortex behaviour such as “vortex end jump” was revealed at some Reynolds numbers. Additionally, a deep analysis of the pressure losses in the cyclone
has been performed which showed that the main pressure losses (up to 48%) occur in the vortex finder. Four flow regimes were revealed and a one-term power series model has been proposed to describe the effects of the Reynolds number on the Euler number (dimensionless pressure losses).

Mechanisms of Arctic amplification and Arctic climate change are difficult to pinpoint, and current climate models do not represent the complex local processes and feedbacks at play, in particular for aerosol–climate interactions. This Perspective highlights the role of aerosols in contemporary Arctic climate change and stresses that the Arctic natural aerosol baseline is changing fast and its regional characteristics are very diverse. We argue that to improve understanding of present day and future Arctic, more detailed knowledge is needed on natural Arctic aerosol emissions, their evolution and transport, and the effects on cloud microphysics. In particular, observation and modelling work should focus on the sensitivity of aerosol–climate interactions to the rapidly evolving base state of the Arctic.

In the Nordic countries (Denmark, Finland, Iceland, Norway and Sweden), the Urban
Green Infrastructure (UGI) has been traditionally targeted at reducing flood risk. However, other
Ecosystem Services (ES) became increasingly relevant in response to the challenges of urbanization
and climate change. In total, 90 scientific articles addressing ES considered crucial contributions to the
quality of life in cities are reviewed. These are classified as (1) regulating ES that minimize hazards
such as heat, floods, air pollution and noise, and (2) cultural ES that promote well-being and health.
We conclude that the planning and design of UGI should balance both the provision of ES and their
side effects and disservices, aspects that seem to have been only marginally investigated. Climatesensitive planning practices are critical to guarantee that seasonal climate variability is accounted for
at high-latitude regions. Nevertheless, diverging and seemingly inconsistent findings, together with
gaps in the understanding of long-term effects, create obstacles for practitioners. Additionally, the
limited involvement of end users points to a need of better engagement and communication, which
in overall call for more collaborative research. Close relationships and interactions among different
ES provided by urban greenery were found, yet few studies attempted an integrated evaluation.
We argue that promoting interdisciplinary studies is fundamental to attain a holistic understanding
of how plant traits affect the resulting ES; of the synergies between biophysical, physiological and
psychological processes; and of the potential disservices of UGI, specifically in Nordic cities.