Terrestrial runoff is an important source of biological INPs in Arctic marine systems

Wieber, Corina; Jensen, Lasse Z.; Vergeynst, Leendert; Maire, Lorenz; Juul-Pedersen, Thomas; Finster, Kai; Šantl-Temkiv, Tina

doi:https://doi.org/10.5194/egusphere-2024-1633

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https://doi.org/10.5194/egusphere-2024-1633

Preprints

04 Jul 2024

| 04 Jul 2024

Terrestrial runoff is an important source of biological INPs in Arctic marine systems

Corina Wieber, Lasse Z. Jensen, Leendert Vergeynst, Lorenz Maire, Thomas Juul-Pedersen, Kai Finster, and Tina Šantl-Temkiv

Abstract. The accelerated warming of the Arctic manifests in sea ice loss and melting glaciers, significantly altering the dynamics of marine biota. This disruption in marine ecosystems can lead to the emission of biological ice nucleating particles (INPs) from the ocean into the atmosphere. Once airborne, these INPs induce cloud droplet freezing, thereby affecting cloud lifetime and radiative properties. Despite the potential atmospheric impacts of marine INPs, their properties and sources remain poorly understood. Analysing sea bulk water and the sea surface microlayer in two southwest Greenlandic fjords, collected between June and September 2018, and investigating the INPs along with the microbial communities, we could demonstrate a clear seasonal variation in the number of INPs and a notable input from terrestrial runoff. We found the highest INP concentration in June during the late stage of the phytoplankton bloom and active melting processes causing enhanced terrestrial runoff. These highly active INPs were smaller in size and less heat-sensitive than those found later in the summer and those previously identified in Arctic marine systems. A negative correlation between salinity and INP abundance suggests freshwater input as sources of INPs. Stable oxygen isotope analysis, along with the strong correlation between INPs and the presence of the bacterium Aquaspirillum arcticum, highlighted meteoric water as the primary origin of the freshwater influx, suggesting that the notably active INPs originate from terrestrial sources such as glacial and soil runoff.

Received: 31 May 2024 – Discussion started: 04 Jul 2024

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Journal article(s) based on this preprint

19 Mar 2025

Terrestrial runoff is an important source of biological ice-nucleating particles in Arctic marine systems

Corina Wieber, Lasse Z. Jensen, Leendert Vergeynst, Lorenz Meire, Thomas Juul-Pedersen, Kai Finster, and Tina Šantl-Temkiv

Atmos. Chem. Phys., 25, 3327–3346, https://doi.org/10.5194/acp-25-3327-2025,https://doi.org/10.5194/acp-25-3327-2025, 2025

Short summary

Corina Wieber, Lasse Z. Jensen, Leendert Vergeynst, Lorenz Maire, Thomas Juul-Pedersen, Kai Finster, and Tina Šantl-Temkiv

Interactive discussion

Status: closed

RC1:
'Comment on egusphere-2024-1633', Anonymous Referee #1, 23 Jul 2024

This manuscript is based on a wealth of data obtained with a range of scientifically sound methods. It shows how meltwater from terrestrial surfaces increases the abundance and modifies the composition of INPs in a Greenlandic fjord at a particular time of the year. The evidence leading to this insight convincingly unfolds throughout the manuscript. There is little I can suggest to further improve this well written manuscript.
Figure 1: Perhaps add photographs of the sites, so the reader gets an impression of the surroundings in which the samples were collected.
Section 3.2 discusses differences between SML and SBW in terms of INPs. Lines 276-279 state: "In addition, our study revealed enhanced INP-10 concentrations in the SML compared to the corresponding SBW samples (Fig. 3b). This finding aligns with observations by Wilson et al. (2015) and Hartmann et al. (2021), whereas Irish et al. (2017) observed no significant upconcentration of INPs in the SML." Yet, a closer look at Figure 3b reveals that one third of the samples does not show an upconcentration. So, better qualify the cited statement.
Can you extrapolate the trendlines in Figure 7b to get a rough estimate of what INP concentration might be in pure meteoric water (fMW = 1.0)? This number would allow for a more quantitative comparisons with INP concentration in other freshwaters discussed in lines 480-487.

Citation: https://doi.org/10.5194/egusphere-2024-1633-RC1
- AC1: 'Reply on RC1', Corina Wieber, 07 Nov 2024
  
  The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2024/egusphere-2024-1633/egusphere-2024-1633-AC1-supplement.pdf
  
  Citation: https://doi.org/10.5194/egusphere-2024-1633-AC1
RC2:
'Comment on egusphere-2024-1633', Anonymous Referee #2, 13 Aug 2024

General Comments:
Wieber et al. highlight a possible importance of terrestrial runoff as a source of biological ice nucleating particles (INPs) based on the measurements in two southwest Greenlandic fjords for the period between June and September 2018. Although the INP data are limited to a narrow temperature regime above about -14 degree C, it seems that the samples in June contained highly active INPs compared with those in July and September, and this result is potentially unique. For example, the results of freezing experiments before and after filtration (Fig. 4) and heat treatments (Fig. 5) indicate that the INP properties for the samples in June 2018 were somewhat different from those in July and September 2018. However, I would have to say that explanations related to the main conclusions of this work have several fatal flaws (see the following specific comments). Thus, I cannot recommend the publication in Atmospheric Chemistry and Physics.
Specific Comments:
1) The authors propose two alternate explanations for the seasonal variations in INP properties proposed by the authors (Lines 382-393). The first explanation is that INPs in June may have been released by pollen, fungal spores, or lichen in terrestrial environments and transported into the seawater by streams. On the other hand, based on the analysis of the eukaryotic community derived from 18S rRNA data (Figs. S4, S5, and S8-S11, and Table S1), the authors suggest that fewer organisms exhibit correlations with INPs active at -10 degree C, and these correlations are weak (Lines 407-408). I think that there is a discrepancy between the first explanation and the 18S rRNA data. Why did the authors lead to the above first explanation?
2) The authors propose two alternate explanations for the seasonal variations in INP properties proposed by the authors (Lines 382-393). On the other hand, according to explanations related to the analysis of the bacterial community derived from 16S rRNA data (Figs. S6, S7, S12, and S13, and Table S2), it seems that certain mechanisms related to the bacterial community are more important than those related to the eukaryotic community for the seasonal variations in INP properties. Why did the authors exclude the possible contribution of the mechanisms related to the bacterial community from the two explanations?
3) I strongly suggest that the authors perform additional analyses and discuss the possible relationship between the variation of the bacterial communities derived from 16S rRNA data and terrestrial runoff. In particular, the authors should compare the bacterial communities found in the sea water samples with those in terrestrial and marine sources, and then evaluate whether the bacterial communities found in the June sea water samples were indeed characterized by terrestrial runoff. In addition, the authors should give more detailed explanations for the reason why the authors focused on the relation between only three taxa (Aquaspirillum arcticum, Colwellia sp., and SUP05) and a high concentration of INPs active at -10 degree C (Lines 431-446) and ignored other taxa.
4) Although the authors explain that “we found a strong negative correlation between salinity and the concentration of INPs active at -10 degree C with significantly lower salinity but higher concentration of INPs observed in June (Fig. 7a) and these correlations suggest a strong impact of salinity within the observed fjords, pointing towards terrestrial runoff or melting sea ice as input of freshwater and potentially INPs (Lines 427-430)”, I doubt if there is a possibility that this is a result from the depression of the freezing point caused by salinity. If the authors believe that a negative correlation between salinity and INP abundance suggests freshwater input as sources of INPs (Line 25-26), they should provide evidence that this negative correlation was not caused by the depression of the freezing point.

Citation: https://doi.org/10.5194/egusphere-2024-1633-RC2
- AC2: 'Reply on RC2', Corina Wieber, 07 Nov 2024
  
  The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2024/egusphere-2024-1633/egusphere-2024-1633-AC2-supplement.pdf
  
  Citation: https://doi.org/10.5194/egusphere-2024-1633-AC2

Interactive discussion

Status: closed

RC1:
'Comment on egusphere-2024-1633', Anonymous Referee #1, 23 Jul 2024

This manuscript is based on a wealth of data obtained with a range of scientifically sound methods. It shows how meltwater from terrestrial surfaces increases the abundance and modifies the composition of INPs in a Greenlandic fjord at a particular time of the year. The evidence leading to this insight convincingly unfolds throughout the manuscript. There is little I can suggest to further improve this well written manuscript.
Figure 1: Perhaps add photographs of the sites, so the reader gets an impression of the surroundings in which the samples were collected.
Section 3.2 discusses differences between SML and SBW in terms of INPs. Lines 276-279 state: "In addition, our study revealed enhanced INP-10 concentrations in the SML compared to the corresponding SBW samples (Fig. 3b). This finding aligns with observations by Wilson et al. (2015) and Hartmann et al. (2021), whereas Irish et al. (2017) observed no significant upconcentration of INPs in the SML." Yet, a closer look at Figure 3b reveals that one third of the samples does not show an upconcentration. So, better qualify the cited statement.
Can you extrapolate the trendlines in Figure 7b to get a rough estimate of what INP concentration might be in pure meteoric water (fMW = 1.0)? This number would allow for a more quantitative comparisons with INP concentration in other freshwaters discussed in lines 480-487.

Citation: https://doi.org/10.5194/egusphere-2024-1633-RC1
- AC1: 'Reply on RC1', Corina Wieber, 07 Nov 2024
  
  The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2024/egusphere-2024-1633/egusphere-2024-1633-AC1-supplement.pdf
  
  Citation: https://doi.org/10.5194/egusphere-2024-1633-AC1
RC2:
'Comment on egusphere-2024-1633', Anonymous Referee #2, 13 Aug 2024

General Comments:
Wieber et al. highlight a possible importance of terrestrial runoff as a source of biological ice nucleating particles (INPs) based on the measurements in two southwest Greenlandic fjords for the period between June and September 2018. Although the INP data are limited to a narrow temperature regime above about -14 degree C, it seems that the samples in June contained highly active INPs compared with those in July and September, and this result is potentially unique. For example, the results of freezing experiments before and after filtration (Fig. 4) and heat treatments (Fig. 5) indicate that the INP properties for the samples in June 2018 were somewhat different from those in July and September 2018. However, I would have to say that explanations related to the main conclusions of this work have several fatal flaws (see the following specific comments). Thus, I cannot recommend the publication in Atmospheric Chemistry and Physics.
Specific Comments:
1) The authors propose two alternate explanations for the seasonal variations in INP properties proposed by the authors (Lines 382-393). The first explanation is that INPs in June may have been released by pollen, fungal spores, or lichen in terrestrial environments and transported into the seawater by streams. On the other hand, based on the analysis of the eukaryotic community derived from 18S rRNA data (Figs. S4, S5, and S8-S11, and Table S1), the authors suggest that fewer organisms exhibit correlations with INPs active at -10 degree C, and these correlations are weak (Lines 407-408). I think that there is a discrepancy between the first explanation and the 18S rRNA data. Why did the authors lead to the above first explanation?
2) The authors propose two alternate explanations for the seasonal variations in INP properties proposed by the authors (Lines 382-393). On the other hand, according to explanations related to the analysis of the bacterial community derived from 16S rRNA data (Figs. S6, S7, S12, and S13, and Table S2), it seems that certain mechanisms related to the bacterial community are more important than those related to the eukaryotic community for the seasonal variations in INP properties. Why did the authors exclude the possible contribution of the mechanisms related to the bacterial community from the two explanations?
3) I strongly suggest that the authors perform additional analyses and discuss the possible relationship between the variation of the bacterial communities derived from 16S rRNA data and terrestrial runoff. In particular, the authors should compare the bacterial communities found in the sea water samples with those in terrestrial and marine sources, and then evaluate whether the bacterial communities found in the June sea water samples were indeed characterized by terrestrial runoff. In addition, the authors should give more detailed explanations for the reason why the authors focused on the relation between only three taxa (Aquaspirillum arcticum, Colwellia sp., and SUP05) and a high concentration of INPs active at -10 degree C (Lines 431-446) and ignored other taxa.
4) Although the authors explain that “we found a strong negative correlation between salinity and the concentration of INPs active at -10 degree C with significantly lower salinity but higher concentration of INPs observed in June (Fig. 7a) and these correlations suggest a strong impact of salinity within the observed fjords, pointing towards terrestrial runoff or melting sea ice as input of freshwater and potentially INPs (Lines 427-430)”, I doubt if there is a possibility that this is a result from the depression of the freezing point caused by salinity. If the authors believe that a negative correlation between salinity and INP abundance suggests freshwater input as sources of INPs (Line 25-26), they should provide evidence that this negative correlation was not caused by the depression of the freezing point.

Citation: https://doi.org/10.5194/egusphere-2024-1633-RC2
- AC2: 'Reply on RC2', Corina Wieber, 07 Nov 2024
  
  The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2024/egusphere-2024-1633/egusphere-2024-1633-AC2-supplement.pdf
  
  Citation: https://doi.org/10.5194/egusphere-2024-1633-AC2

Peer review completion

AR: Author's response | RR: Referee report | ED: Editor decision | EF: Editorial file upload

AR by Corina Wieber on behalf of the Authors (07 Nov 2024) Author's response Author's tracked changes Manuscript

ED: Referee Nomination & Report Request started (08 Nov 2024) by Luis A. Ladino

RR by Anonymous Referee #1 (19 Nov 2024)

RR by Anonymous Referee #3 (17 Dec 2024)

Suggestions for revision or reasons for rejection

Wieber et al. present an intriguing study examining INPs, microbial community composition, and oxygen isotope analysis in bulk seawater and SML samples collected from Greenlandic fjords. The results contribute valuable insights into the interplay between these components, and the manuscript is both well-organized and clearly written. The authors have addressed previous feedback effectively. I have only a few remaining minor suggestions to address prior to acceptance.

Figure 1: It would enhance clarity to include the location of Nuuk on the inset map.

Lines 159–161: Providing additional detail on why these specific heat treatment temperatures were chosen and which classes of INPs they are expected to target would be helpful.

Line 204: Could the authors clarify whether the Turner fluorometer used in this study uses fluorescence modules as in newer Turner models? If so, it would be helpful to specify the chl-a module used, as certain modules (e.g., non-acidification) require preparatory steps, such as acetone extraction in the dark.

Lines 311–315: Given the limited number of data points, it is important to confirm whether the observed correlations are statistically significant. Reporting p-values, consistent with the approach used elsewhere in the manuscript would ensure rigor in these interpretations.

Lines 322–323: The moderate correlation between INPs and chl-a is particularly interesting, as prior studies (e.g., Irish et al. and Creamean et al.) did not observe such correlations. However, the robustness of this relationship hinges on its statistical significance, as noted in the previous comment.

Line 522: Could the authors clarify whether the observed precipitation originates from melted glacial snow or from freshly fallen rain/snow?

Hide

ED: Publish subject to minor revisions (review by editor) (23 Dec 2024) by Luis A. Ladino

I congratulate the authors for significantly improving the manuscript; however, the following minor and technical comments need to be properly addressed before the manuscript can be accepted for publication.

Referee #3:

Wieber et al. present an intriguing study examining INPs, microbial community composition, and oxygen isotope analysis in bulk seawater and SML samples collected from Greenlandic fjords. The results contribute valuable insights into the interplay between these components, and the manuscript is both well-organized and clearly written. The authors have addressed previous feedback effectively. I have only a few remaining minor suggestions to address prior to acceptance.

Figure 1: It would enhance clarity to include the location of Nuuk on the inset map.

Lines 159–161: Providing additional detail on why these specific heat treatment temperatures were chosen and which classes of INPs they are expected to target would be helpful.

Line 204: Could the authors clarify whether the Turner fluorometer used in this study uses fluorescence modules as in newer Turner models? If so, it would be helpful to specify the chl-a module used, as certain modules (e.g., non-acidification) require preparatory steps, such as acetone extraction in the dark.

Lines 311–315: Given the limited number of data points, it is important to confirm whether the observed correlations are statistically significant. Reporting p-values, consistent with the approach used elsewhere in the manuscript would ensure rigor in these interpretations.

Lines 322–323: The moderate correlation between INPs and chl-a is particularly interesting, as prior studies (e.g., Irish et al. and Creamean et al.) did not observe such correlations. However, the robustness of this relationship hinges on its statistical significance, as noted in the previous comment.

Line 522: Could the authors clarify whether the observed precipitation originates from melted glacial snow or from freshly fallen rain/snow?

Editor:

Minor comments:
I am surprised the authors did not include the following study in their discussion: “Surface warming in Svalbard may have led to increases in highly active ice-nucleating particles” By Tobo et al. I strongly suggest adding it to the revised manuscript.

Technical comments:
Line 39: Add a reference after “atmosphere.”
Lines 97 and 100: Replace “microlayer” by “SML”
Line 110: Replace “Sea surface microlayer” by “SML”
Line 110: Replace “sea bulk water” by “SBW”
Lines 114-115: Please indicate the depth at which the SBW samples were collected.
Line 117: Replace “g l −1” by “g L −1”
Lines 119, 169 and along the text: Replacle “ml” by “mL”
Lines 135, 225, 304 and along the text: Replace “µl” by “µL”
Line 149: Please add “where” before “c is”
Lines 203, 313, 453 and along the text: Replace “Kobbefjord” by “KF”
Line 281: Should “upconcentration”be “concentration”?
Line 281: Why “INPs in the SML”? This section also shows SBW results.
Line 312: Should “sampling dates in Kobbefjord” be “sampling dates in KF and GF”?
Line 398: Replace “ice nuclei” by “INPs”
Line 489: Replace “Pseudomonas” by “Pseudomonas”
Figura S5: Each box contains the T50 values of the SML and BSW samples?
Figure 4: Replace “freezing temperature” by “T50 temperature”

Hide

AR by Corina Wieber on behalf of the Authors (10 Jan 2025) Author's response Author's tracked changes Manuscript

ED: Publish as is (10 Jan 2025) by Luis A. Ladino

AR by Corina Wieber on behalf of the Authors (16 Jan 2025)

Journal article(s) based on this preprint

19 Mar 2025

Terrestrial runoff is an important source of biological ice-nucleating particles in Arctic marine systems

Corina Wieber, Lasse Z. Jensen, Leendert Vergeynst, Lorenz Meire, Thomas Juul-Pedersen, Kai Finster, and Tina Šantl-Temkiv

Atmos. Chem. Phys., 25, 3327–3346, https://doi.org/10.5194/acp-25-3327-2025,https://doi.org/10.5194/acp-25-3327-2025, 2025

Short summary

Corina Wieber, Lasse Z. Jensen, Leendert Vergeynst, Lorenz Maire, Thomas Juul-Pedersen, Kai Finster, and Tina Šantl-Temkiv

Supplement

https://doi.org/10.5194/egusphere-2024-1633-supplement

Corina Wieber, Lasse Z. Jensen, Leendert Vergeynst, Lorenz Maire, Thomas Juul-Pedersen, Kai Finster, and Tina Šantl-Temkiv

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The Arctic region is subjected to profound changes due to the warming climate. Ice nucleating particles (INPs) in the seawater can get transported to the atmosphere and impact cloud formation. However, the sources of characteristics of INPs in the marine areas are poorly understood. We investigated the INPs in seawater from Greenlandic fjords and identified a seasonal variability and highly active INPs originating from terrestrial sources.


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