Angelo Viola

Nitrate dry deposition in Svalbard

ABSTRACT Arctic regions are generally nutrient limited, receiving an extensive part of their bio-available nitrogen from the deposition of atmospheric reactive nitrogen. Reactive nitrogen oxides, as nitric acid (HNO3) and nitrate aerosols (p-NO3), can either be washed out from the atmosphere by precipitation or dry deposited, dissolving to nitrate ( ). During winter, is accumulated in the snowpack and released as a pulse during spring melt. Quantification of deposition is essential to assess impacts on Arctic terrestrial ecology and for ice core interpretations. However, the individual importance of wet and dry deposition is poorly quantified in the high Arctic regions where in-situ measurements are demanding. In this study, three different methods are employed to quantify dry deposition around the atmospheric and ecosystem monitoring site, Ny-Ålesund, Svalbard, for the winter season (September 2009 to May 2010): (1) A snow tray sampling approach indicates a dry deposition of –10.27±3.84 mg m−2 (± S.E.); (2) A glacial sampling approach yielded somewhat higher values –30.68±12.00 mg m−2; and (3) Dry deposition was also modelled for HNO3 and p-NO3 using atmospheric concentrations and stability observations, resulting in a total combined nitrate dry deposition of –10.76±1.26 mg m−2. The model indicates that deposition primarily occurs via HNO3 with only a minor contribution by p-NO3. Modelled median deposition velocities largely explain this difference: 0.63 cm s−1 for HNO3 while p-NO3 was 0.0025 and 0.16 cm s−1 for particle sizes 0.7 and 7 µm, respectively. Overall, the three methods are within two standard errors agreement, attributing an average 14% (total range of 2–44%) of the total nitrate deposition to dry deposition. Dry deposition events were identified in association with elevated atmospheric concentrations, corroborating recent studies that identified episodes of rapid pollution transport and deposition to the Arctic.

Atmospheric observations at the Amundsen-Nobile Climate Change Tower in Ny-Ålesund, Svalbard

The Amundsen-Nobile Climate Change Tower (CCT) is one of the important scientific platforms operating in Ny-Ålesund, Svalbard. The CCT is equipped with a consistent set of meteorological sensors installed at different heights to provide continuous measurements of the atmospheric parameters that affect the climate and its variability. In this paper, some features of the main meteorological parameters observed during the 6 years of measurements since November 2009 are presented in order to describe the thermodynamic characteristic of the lower layers of the atmosphere and the peculiarities of CCT. Monthly and seasonal behavior of temperature, humidity and wind as well as radiation budget and albedo variability are also shown. Such preliminary statistical description aims to provide an overview of the phenomenology occurring in the Kongsfjord area, useful to proceed with further analysis of the arctic climatic system. Even if the time series are not long enough to consider the parameters variability on a climatological time scale, useful assumptions can be made for detailed analysis concerning turbulence studies, data intercomparison at different time and space scales, validation of theory and numerical model results. CCT dataset is stored in a dedicated built-in digital infrastructure that allows other users, in the frame of international cooperations, to visualize, access and download the data and contribute to strengthen the collaboration within the scientific community operating in Svalbard.

Vertical Profiles and Chemical Properties of Aerosol Particles upon Ny-Ålesund (Svalbard Islands)

Size-segregated particle samples were collected in the Arctic (Ny-Alesund, Svalbard) in April 2011 both at ground level and in the free atmosphere exploiting a tethered balloon equipped also with an optical particle counter (OPC) and meteorological sensors. Individual particle properties were investigated by scanning electron microscopy coupled with energy dispersive microanalysis (SEM-EDS). Results of the SEM-EDS were integrated with particle size and optical measurements of the aerosols properties at ground level and along the vertical profiles. Detailed analysis of two case studies reveals significant differences in composition despite the similar structure (layering) and the comparable texture (grain size distribution) of particles in the air column. Differences in the mineral chemistry of samples point at both local (plutonic/metamorphic complexes in Svalbard) and remote (basic/ultrabasic magmatic complexes in Greenland and/or Iceland) geological source regions for dust. Differences in the particle size and shape are put into relationship with the mechanism of particle formation, that is, primary (well sorted, small) or secondary (idiomorphic, fine to coarse grained) origin for chloride and sulfate crystals and transport/settling for soil (silicate, carbonate and metal oxide) particles. The influence of size, shape, and mixing state of particles on ice nucleation and radiative properties is also discussed.

Observations of near surface wind speed, temperature and radiative budget at Dome C, Antarctic Plateau during 2005

Abstract The annual and diurnal behaviours of near surface wind speed, temperature, and the radiative budget at Concordia Station (Dome C) in different seasons are shown. The wind speed was lowest in summer when a daily cycle was also observed. The largest mean values were concurrent with boundary layer growth in the afternoon. In winter and spring the wind speed reached the highest mean values. Perturbations in the wind flow were due to warming events which occurred periodically at Dome C. The lowest temperatures were in April and at the end of August. The coreless winter behaviour was perturbed by warming events which in many cases produced an increase in temperature of c. 20°C. The average temperature profiles show permanent thermal inversion, with the exception of a few hours in the afternoons during the summer. The strongest ground-based thermal inversions were observed in the polar winter. The largest potential temperature gradients were limited to a 30–40 m deep layer close to the surface. The net radiation was negative almost all the time with the exception of the period from mid-December to mid-January.

Wavelike Structures in the Turbulent Layer During the Morning Development of Convection at Dome C, Antarctica

In the period January–February 2014, observations were made at the Concordia station, Dome C, Antarctica to study atmospheric turbulence in the boundary layer using a high-resolution sodar. The turbulence structure was observed beginning from the lowest height of about 2 m, with a vertical resolution of less than 2 m. Typical patterns of the diurnal evolution of the spatio-temporal structure of turbulence detected by the sodar are analyzed. Here, we focus on the wavelike processes observed within the transition period from stable to unstable stratification occurring in the morning hours. Thanks to the high-resolution sodar measurements during the development of the convection near the surface, clear undulations were detected in the overlying turbulent layer for a significant part of the time. The wavelike pattern exhibits a regular braid structure, with undulations associated with internal gravity waves attributed to Kelvin–Helmholtz shear instability. The main spatial and temporal scales of the wavelike structures were determined, with predominant periodicity of the observed wavy patterns estimated to be 40–50 s. The horizontal scales roughly estimated using Taylor’s frozen turbulence hypothesis are about 250–350 m.

Environmental changes in the Arctic: an Italian perspective

Global warming affects the Arctic two/four times faster than any other region of the planet. The components of the climate system strongly react to changes with an immediate impact on the environment and on the whole living system. As a consequence of the increasing concern, in the last two decades the research in the Arctic has rapidly grown, with the aim to better understand processes and amplification mechanisms as well as to assess consequences at mid-latitudes and on the rest of the planet. Italian scientists have provided a relevant contribution to the Arctic science with a wide range of research activities conducted so far, not only at Ny-Ålesund (Svalbard Islands), where the Italian National Research Council (CNR) manages the “Dirigibile Italia Arctic Station”, but also at Thule (Greenland) and on the surrounding seas, and in the Arctic Ocean. The strategic objectives of the wide range of activities developed since 2008 aim to reinforce the flagship sites (super-sites) as key components of an integrated pan-Arctic observing network, where it is possible to study the complex dimensions of the Arctic regional climate system and to fully develop multidisciplinary research activities in a framework of international cooperation. This special issue presents a collection of reports on recent scientific achievements and provides the state-of-the-art and future perspectives of Italian research in the Arctic.

Towards a calibration laboratory in Ny-Ålesund

Multitudes of measurements are needed to understand the environment and its evolution. The Arctic region is a fundamental observation area for climate change evaluation: climate change comes first and comes faster in the arctic. The higher accuracy required to quickly capture trends; the extreme range and conditions of sensors exposure; a robust comparability asked by the different measurement networks; the need of dedicated calibration procedures, together with the logistical problems associated with such remote location, motivate the proposal for a joint effort to address metrology experience and activities for Arctic research applications. The Ny-Ålesund international research base and community offers a unique infrastructure to directly link metrological traceability to on site polar measurements. The contribution reports a study on the implementation of specific calibration procedures, metrological validation of measurements and instrument tests, uncertainties evaluations including quantities of influence, and the feasibility of a metrology laboratory in Ny-Ålesund.

First Observations of Energy Budget and Bulk Fluxes at Ny Ålesund (Svalbard) during a 2010 Transition Period as Analyzed with the BEAR Station

A small-size meteorological mast, BEAR (Budget of Energy for Arctic regions) has been developed as a part of a new autonomous buoy for monitoring the sea ice mass balance. BEAR complements observations of the thickness and thermodynamic properties of the ice/snow pack determined by the so-called Ice-T (Ice-Thickness) buoy, giving access to bulk fluxes and energy budget at the surface, using meteorological measurements. The BEAR mast has been tested with success during ten days in April-May 2010 at Ny Alesund, in the Svalbard archipelago (Norway) showing that meteorological data were close to measurements at the same level of the Italian Climate Change Tower (CCT) from the ISAC-CNR. A discussion is undertaken on bulk fluxes determination and uncertainties. Particularly, the strategy to systematically use different relevant fluxes parameterizations is pointed out to explore flux range uncertainty before to analyze energy budget. Net radiation, bulk fluxes and energy budget are estimated using as average 10 minutes, 24 hours and the ten days of the experiment. The observation period was very short, but we observe a spring transition when the net radiation begins to warm the surface while the very small turbulent heat flux cools the surface.

Multi-year particle fluxes in Kongsfjorden, Svalbard

High latitude regions are warming faster than other areas due to reduction of snow cover, sea ice loss, changes in atmospheric and ocean circulation. The combination of these processes, collectively known as polar amplification, provides an extraordinary opportunity to document the ongoing thermal destabilisation of the terrestrial cryosphere and the release of land-derived material into the aquatic environment. This study presents a six-year time-series (2010-2016) of physical parameters and particles fluxes collected by an oceanographic mooring in Kongsfjorden (Spitsbergen, Svalbard). In recent 5 decades, Kongsfjorden has been experiencing rapid loss of sea ice coverage and retreat of local glaciers as a result of the progressive increase of ocean and air temperatures. The overarching goal of this study was to continuous monitoring the inner fjord particle sinking and to understand to what extent the temporal evolution of particulate fluxes were linked to the progressive changes in both Atlantic and freshwater input. Our data show high peaks of settling particles during warm seasons, in terms of both organic and inorganic matter. The different sources of suspended particles were described as a mixing of 10 glacier carbonate, glacier-silicoclastic and autochthonous marine input. The glacier releasing sediments into the fjord resulted to be the predominant source, while the sediment input by rivers was reduced at the mooring site. Our time-series showed that the seasonal sunlight exerted first-order control on the particulate fluxes in the inner fjord. The marine fraction peaked when the solar radiation was maxima in May-June while the land-derived fluxes exhibited a 1-2 months lag consistent with the maximum air temperature and glacier melting. The inter-annual time-weighted total mass fluxes varied two-order of magnitudes over time, 15 with relatively higher values in 2011, 2013 and 2015. Our results suggest that the land-derived input will remarkably increase over time in a warming scenario. Further studies are therefore needed to understand the future response of the Kongsfjorden ecosystem alterations in respect to the enhanced release of glacier-derived material.

Some aspects of the local atmospheric circulation in the Castelporziano Estate derived from sodar wind measurements

To characterize the local low-level circulation in the Tyrrhenian Sea coastal area near Rome, the wind velocity field observed by Doppler sodar operating in the Estate of Castelporziano, has been studied. The prevailing diurnal behavior of the wind speed and wind direction as a function of the season was highlighted for the winter and the summer 2007. Two different patterns of the local circulation can be alternately observed in the night to early morning and after the sunset to late evening. The data analysis has shown that the statistical distribution of wind direction during the night, in winter, presents great occurrence at low levels in the northeastern sector and around 100°. Moreover, it has been observed that the nocturnal components of the wind direction at low-level changes with the height, and these changes can be associated with the effects induced by the large-scale flow on the local circulation at higher levels.