Ice-nucleating particle concentration measurements from Ny-Ålesund during the Arctic spring–summer in 2018

• Published in: Atmospheric Chemistry and Physics
• Main Authors: Rinaldi, Matteo, Hiranuma, Naruki, Santachiara, Gianni, Mazzola, Mauro, Mansour, Karam, Paglione, Marco, Rodriguez, Cheyanne A., Traversi, Rita, Becagli, Silvia, Cappelletti, David, Belosi, Franco
• Format: Text
• Language: English
• Published: 2021
• Subjects: Arctic; Greenland; Ny-Ålesund; Svalbard; Svalbard Archipelago; Iceland; Ny Ålesund
• Online Access: https://doi.org/10.5194/acp-21-14725-2021; https://acp.copernicus.org/articles/21/14725/2021/

In this study, we present atmospheric ice-nucleating particle (INP) concentrations from the Gruvebadet (GVB) observatory in Ny-Ålesund (Svalbard). All aerosol particle sampling activities were conducted in April–August 2018. Ambient INP concentrations ( n INP) were measured for aerosol particles collected on filter samples by means of two offline instruments: the Dynamic Filter Processing Chamber (DFPC) and the West Texas Cryogenic Refrigerator Applied to Freezing Test system (WT-CRAFT) to assess condensation and immersion freezing, respectively. DFPC measured n INPs for a set of filters collected through two size-segregated inlets: one for transmitting particulate matter of less than 1 µm (PM 1 ), the other for particles with an aerodynamic diameter of less than 10 µm aerodynamic diameter (PM 10 ). Overall, n INP <math xmlns="http://www.w3.org/1998/Math/MathML" id="M8" display="inline" overflow="scroll" dspmath="mathml"><msub><mi/><mrow><msub><mi mathvariant="normal">PM</mi><mn mathvariant="normal">10</mn></msub></mrow></msub></math> <svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="21pt" height="10pt" class="svg-formula" dspmath="mathimg" md5hash="1bed5e190fcfd3954e7ac4cd885e2f62"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-21-14725-2021-ie00001.svg" width="21pt" height="10pt" src="acp-21-14725-2021-ie00001.png"/></svg:svg> measured by DFPC at a water saturation ratio of 1.02 ranged from 3 to 185 m −3 at temperatures ( T s) of −15 to −22 ∘ C. On average, the super-micrometer INP ( n INP <math xmlns="http://www.w3.org/1998/Math/MathML" id="M15" display="inline" overflow="scroll" dspmath="mathml"><mrow><msub><mi/><mrow><msub><mi mathvariant="normal">PM</mi><mn mathvariant="normal">10</mn></msub></mrow></msub><mo>-</mo><mi>n</mi></mrow></math> <svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="40pt" height="13pt" class="svg-formula" dspmath="mathimg" md5hash="fa845fc327db7849282a297ec6b51aa0"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-21-14725-2021-ie00002.svg" width="40pt" height="13pt" src="acp-21-14725-2021-ie00002.png"/></svg:svg> INP <math xmlns="http://www.w3.org/1998/Math/MathML" id="M16" display="inline" overflow="scroll" dspmath="mathml"><msub><mi/><mrow><msub><mi mathvariant="normal">PM</mi><mn mathvariant="normal">1</mn></msub></mrow></msub></math> <svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="18pt" height="10pt" class="svg-formula" dspmath="mathimg" md5hash="33d1ec1655f620effad74db4efd95dc1"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-21-14725-2021-ie00003.svg" width="18pt" height="10pt" src="acp-21-14725-2021-ie00003.png"/></svg:svg> ) accounted for approximately 20 %–30 % of n INP <math xmlns="http://www.w3.org/1998/Math/MathML" id="M18" display="inline" overflow="scroll" dspmath="mathml"><msub><mi/><mrow><msub><mi mathvariant="normal">PM</mi><mn mathvariant="normal">10</mn></msub></mrow></msub></math> <svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="21pt" height="10pt" class="svg-formula" dspmath="mathimg" md5hash="e4f8f7b0ecf0ba64ec19150bd2e660c8"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-21-14725-2021-ie00004.svg" width="21pt" height="10pt" src="acp-21-14725-2021-ie00004.png"/></svg:svg> in spring, increasing in summer to 45 % at −22 ∘ C and 65 % at −15 ∘ C. This increase in super-micrometer INP fraction towards summer suggests that super-micrometer aerosol particles play an important role as the source of INPs in the Arctic. For the same T range, WT-CRAFT measured 1 to 199 m −3 . Although the two n INP datasets were in general agreement, a notable n INP offset was observed, particularly at −15 ∘ C. Interestingly, the results of both DFPC and WT-CRAFT measurements did not show a sharp increase in n INP from spring to summer. While an increase was observed in a subset of our data (WT-CRAFT, between −18 and −21 ∘ C), the spring-to-summer n INP enhancement ratios never exceeded a factor of 3. More evident seasonal variability was found, however, in our activated fraction (AF) data, calculated by scaling the measured n INP to the total aerosol particle concentration. In 2018, AF increased from spring to summer. This seasonal AF trend corresponds to the overall decrease in aerosol concentration towards summer and a concomitant increase in the contribution of super-micrometer particles. Indeed, the AF of coarse particles resulted markedly higher than that of sub-micrometer ones (2 orders of magnitude). Analysis of low-traveling back-trajectories and meteorological conditions at GVB matched to our INP data suggests that the summertime INP population is influenced by both terrestrial (snow-free land) and marine sources. Our spatiotemporal analyses of satellite-retrieved chlorophyll a , as well as spatial source attribution, indicate that the maritime INPs at GVB may come from the seawaters surrounding the Svalbard archipelago and/or in proximity to Greenland and Iceland during the observation period. Nevertheless, further analyses, performed on larger datasets, would be necessary to reach firmer and more general conclusions.