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<p>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 (<span class="inline-formula"><i>n</i></span>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 <span class="inline-formula"><i>n</i></span>INPs for a set of filters collected through two size-segregated inlets: one for transmitting particulate matter of less than 1 <span class="inline-formula">µm</span> (PM<span class="inline-formula">₁</span>), the other for particles with an aerodynamic diameter of less than 10 <span class="inline-formula">µm</span> aerodynamic diameter (PM<span class="inline-formula">₁₀</span>). Overall, <span class="inline-formula"><i>n</i></span>INP<span class="inline-formula"><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><span><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></span></span> measured by DFPC at a water saturation ratio of 1.02 ranged from 3 to 185 m<span class="inline-formula">⁻³</span> at temperatures (<span class="inline-formula"><i>T</i></span>s) of <span class="inline-formula">−15</span> to <span class="inline-formula">−22</span> <span class="inline-formula">^∘</span>C. On average, the super-micrometer INP (<span class="inline-formula"><i>n</i></span>INP<span class="inline-formula"><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><span><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></span></span>INP<span class="inline-formula"><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><span><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></span></span>) accounted for approximately 20 %–30 % of <span class="inline-formula"><i>n</i></span>INP<span class="inline-formula"><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><span><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></span></span> in spring, increasing in summer to 45 % at <span class="inline-formula">−22</span> <span class="inline-formula">^∘</span>C and 65 % at <span class="inline-formula">−15</span> <span class="inline-formula">^∘</span>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 <span class="inline-formula"><i>T</i></span> range, WT-CRAFT measured 1 to 199 m<span class="inline-formula">⁻³</span>. Although the two <span class="inline-formula"><i>n</i></span>INP datasets were in general agreement, a notable <span class="inline-formula"><i>n</i></span>INP offset was observed, particularly at <span class="inline-formula">−15</span> <span class="inline-formula">^∘</span>C. Interestingly, the results of both DFPC and WT-CRAFT measurements did not show a sharp increase in <span class="inline-formula"><i>n</i></span>INP from spring to summer. While an increase was observed in a subset of our data (WT-CRAFT, between <span class="inline-formula">−18</span> and <span class="inline-formula">−21</span> <span class="inline-formula">^∘</span>C), the spring-to-summer <span class="inline-formula"><i>n</i></span>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 <span class="inline-formula"><i>n</i></span>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 <span class="inline-formula"><i>a</i></span>, 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.</p>