In this manuscript, the ambient ice-nucleation particle (INP) concentration and ice nucleation efficiency of aerosol particles collected from the southern tip of South America are presented along with some complementary field observations from three different locations in the studied region. Key findings out of this study are (including but not limited to):

*A majority of assessed INPs show the indication of proteinaceous component (evidenced by the freezing assay with heat treatment), and

*the field observations imply that the mixing of large aerosol particles from the continental source with other sources occur in the planetary boundary layer over the study region, and the authors link the observations to their INP data implications (which are detailed in the manuscript).

These findings are relevant to the ACP journal scope as ACP supports many INP-related papers. The INP data from the studied region, especially relatively long-term data as presented in this manuscript, is rare and invaluable. While the field data and offline lab measurements are reasonably well-blended, the manuscript is a bit lengthy, and this reviewer identified some speculative parts (discussed below). For that matter, this manuscript may fit more as the ‘measurement reports’ manuscript type under ACP, in this reviewer’s opinion. While this reviewer does not have a strong opinion to turn this research article into a different manuscript type, the authors may consider it if the editor and other reviewers address a similar point. Nevertheless, the manuscript is overall well-written, and this reviewer can support the publication of this manuscript (in any manuscript type) in ACP after minor and technical revisions.

[Minor comments]

P1L22-23: Pore condensation freezing can occur below -38 dC as long as the ice saturation condition is met. For that matter, the authors’ statement, which sounds limiting the heterogeneous ice nucleation (and/or cloud droplet freezing) to the temperatures above -38 dC seems misleading. The reviewer suggests to the authors to rephrase this sentence to focus on discussing only immersion or clarify it differently.

P2L51: The reviewer agrees with the authors about the importance of long-term INP measurements/monitoring. The authors might want to discuss the importance of highly time-resolved INP data somewhere in this manuscript as well. In the reviewer’s opinion, both long time coverage and fine time resolution of INP data are currently missing in the atmospheric science community. The reviewer thinks the time resolution employed for aerosol sampling in this study (P3L77) is valid and the associated offline INP data generated out of a week or two aerosol samples are still invaluable. Some extra discussion regarding the time resolution would add more value to the current manuscript, and the readers will appreciate seeing the discussion of limitations and future outlook.

Sect. 2.1 & P14L330-334: The authors use the meteorological data measured at the airport and connect these to their aerosol measurements and sampling activities carried out at the mountain station, which seems several kilometers apart at least. The authors might want to clarify that the meteorological data were not available at the station in the text. Also, please include a justification and discussion of why they think it is reasonable to refer to the met data at the airport for their studied aerosol properties from the mountain station in the manuscript.

P3L74-76: Please address if any dryers were installed upstream of MPSS and APS. If the authors conducted the ‘wet’ particle size distribution measurements without a dryer, please address why dry particle diameter measurements, which are typically used for the n_s estimation, were not carried out and associated limitations (if any).

P3L76: The reviewer wonders why the 800 nm pore size filter was chosen to be used for this study (instead of the one with a smaller pore size). By looking at the particle size distribution figures in Sect. 3, it appears that a substantial fraction of <800 nm particles were measured during the DACAPO-PESO campaign. Later, the authors discuss the key feature of large particles (>500 nm). Therefore, there seemingly is a logical size leap between 500-800 nm. Please elaborate on the discussion/limitation.

P3L85-88: The authors might consider explaining the purpose of keeping samples frozen. What was the typical time span between sampling and offline INP measurements? All INP measurements were completed within a certain amount of time after the sample was taken? The aerosol sampling was done for 1-2 weeks (P3L77), and the filter was exposed to the ambient air and temperature during sampling while the filter is kept unfrozen. Do the authors think such a long sampling interval impacts the degradation of collected aerosol particles over the employed sampling time? Please include the discussion in the manuscript.

P4L91: How did the authors determine the suspending water amount to be 3-4 mL? Based on the set lower detection limit of detectable INPs in the authors’ offline assay? Please include the clarification in the manuscript.

P15L346-361: The authors might consider including the specs of the back trajectory analysis method somewhere in the manuscript (even in the method section). It seems that the back trajectory analysis is one of the crucial analytical tools in this study. The reviewer wonders if the authors can incorporate the air mass height information in Figs. 8 and 11. Do the back trajectory data support that air masses travel through the free tropospheric conditions?

P15L369-370: “A general enhancement of aerosol concentrations …” This sounds ambitious and speculative. So do the authors are suggesting that the aerosol intrusion from BL bumps up the aerosol concentration? Please detail what’s meant by this sentence in the manuscript.

P21L433-435 & P19L403-405: These sentences are provoking but sound very ambitious. While this reviewer agrees that the ground-level INP & aerosol measurements are important, verifying what’s stated in these parts (especially on P21) seemingly requires more measurements and evidence to constrain vilifications (e.g., cloud height INP data, vertical distribution of INPs over the studied site, online biological particle concentration measurements, INP measurement in precipitation samples etc.). Perhaps, the authors soften the tone of this sentence and also include the list of limitations and things to do as a future outlook? This reviewer thinks the limitations/outlooks are as important as good scientific results.

P22L472-475: A chemical analysis of the aerosol particles would definitely add some complementary information (at least for the aerosol source identification), but the aerosol composition is not necesarrily the same as the INP composition. How about biological particle composition & rainwater INP & vertical distribution & ice crystal residuals measurement?

[Technical comments]

P2L36: INPs – already abbreviated previously.

Figs. 8 & 11 captions: 600 m AGL or AMSL?

P19L402-403: “of all discussed…” The reviewer does not understand this sentence. Please rephrase it.

[Misc. feedback]

Sects. 3.2 & 3.4: The reviewer finds the method used to estimate the biogenic INPs contribution (i.e., F_bio-INP) interesting and useful yet speculative. In future fieldwork in a similar location, the deployment of an online biological particle sensor and linking such online data to F_bio-INP can even add/solidify more value to this F_bio-INP idea, in the reviewer’s opinion.

General Comment

In the current manuscript, aerosol particle samples were collected close to Punta Arenas, Chile, on Cerro Mirador at the southernmost tip of South America between May 2019 and March 2020. The objective was to evaluate the capability of these particles to act as ice nucleating particles (INP) and to identify their possible sources. Also, the INP data were complemented with meteorological data, air mass backward trajectories, and lidar observations. I consider that this study is relevant for the ice nucleation community and it is especially important for the Southern Hemisphere due to the lack of studies in this region. Also, I think that the database generated in this study is valuable because of the long-term sampling time. The present manuscript is within the ACP scope and it can be accepted for its publication once the following minor comments are considered.  

Minor comments:

Line 6 Why do the authors state that 90% and 80% of the INP are proteinaceous material. I mean, how did you calculate these percentages? I could not find any chemical analysis to determine the quantity of proteinaceous material within the samples.

Line 58  In this part the authors mention that it is important to perform INP measurements in the Southern Ocean; however, the samples were collected in a mountain close to the coast and not in the open ocean. Therefore, it is very likely that the present results were influenced by continental aerosol sources. 

How far away is Punta Arenas from Cerro Mirador? Can anthropogenic particles emitted in Punta Arenas influence the measurements performed in Cerro Mirador? Also, are there fertile soils close to your sampling site? Or why did you compare your results with O’Sullivan et al. (2014)? The description of the sampling site needs to be improved.

Line 76 I suggest changing the word “aerosols” to aerosol particles. Also, it is mentioned that the used filters contain a pore size of 800 nm; however, afterward it is mentioned that the analysis was performed for particles >500 nm. Please explain this discrepancy.  

Line 78 What was the used aerosol sampler?.

Line 85 Can the authors please elaborate more on the sample storage protocol? Is there any chance that the samples could have experienced a memory effect when stored at -20C? For how long were the samples stored prior to the ice nucleation analysis? Did the authors evaluate the impact of long-term storage?

Line 94-95 I am wondering if the PCR-tray with the sample was heated or if the heat was only applied to the sample?

Line 121 I believe that “V” corresponds to the volume of the liquid deposited on each well instead of the air volume. Please clarify this.

Line 149 - 150 Describe in more detail how ns was calculated.

Line 175-178 This classification should be in the methods section.

Line 203 I do not understand why the authors compare their results with those from Tobo et al. (2013) and the former study was performed on aerosol particles from a forest while the present study focuses on coastal particles. 

Line 228-229 Why did you choose these temperatures or do they refer to a range of temperatures? 

Figure 3b I did not completely get the purpose and meaning of panel b. 

Line 269 According to Figure 4, the black dots correspond to the heated samples and the red dots to the unheated samples; however, in line 269 the authors state the opposite. Also, this is not consistent between the text in the figure caption and the figure legend.

Line 324 and 375 Why Samples 11 and 12 were selected for the case study? It is unclear to me what was the motivation to have the Case study and also the cluster analysis performed in Section 3.5. Is it not better to remove the Case study and to add those 2 samples to the cluster analysis shown in Section 3.5?

Line 328 Please add the used software to get the air mass the backward trajectories in the Methods.

Line 330 I am wondering how valid it is to correlate the meteorological data from the airport with the INP data from the Cerro Mirador.

Line 401 Based on the heat treatment analysis the authors state that some INPs were of biogenic origin; however, it is unclear what is the source of bulk INPs, i.e., those that are not of biogenic origin?