Glacial meltwater and primary production are drivers of strong CO<sub>2</sub> uptake in fjord and coastal waters adjacent to the Greenland Ice Sheet

Meire, L.; Søgaard, D. H.; Mortensen, J.; Meysman, F. J. R.; Soetaert, K.; Arendt, K. E.; Juul-Pedersen, T.; Blicher, M. E.; Rysgaard, S.

doi:https://doi.org/10.5194/bg-12-2347-2015

Articles | Volume 12, issue 8

https://doi.org/10.5194/bg-12-2347-2015

© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.

https://doi.org/10.5194/bg-12-2347-2015

© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.

Articles | Volume 12, issue 8

Research article

|

21 Apr 2015

Research article |

| 21 Apr 2015

Glacial meltwater and primary production are drivers of strong CO₂ uptake in fjord and coastal waters adjacent to the Greenland Ice Sheet

L. Meire, D. H. Søgaard, J. Mortensen, F. J. R. Meysman, K. Soetaert, K. E. Arendt, T. Juul-Pedersen, M. E. Blicher, and S. Rysgaard

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Final revised paper (published on 21 Apr 2015)
Preprint (discussion started on 19 Dec 2014)

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Status: closed

AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment

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RC C8147: 'Review of: Glacial meltwater and primary production as drivers for strong CO2 uptake in fjord and coastal waters adjacent to the Greenland Ice Sheet', Anonymous Referee #1, 19 Jan 2015
RC C8345: 'review', Anonymous Referee #2, 27 Jan 2015
AC C9012: 'Authors response on reviews, 07/03/2015', L. Meire, 07 Mar 2015

Peer-review completion

AR: Author's response | RR: Referee report | ED: Editor decision

AR by Lorenz Meire on behalf of the Authors (09 Mar 2015) Author's response Manuscript

ED: Referee Nomination & Report Request started (10 Mar 2015) by Christoph Heinze

RR by Anonymous Referee #2 (10 Mar 2015)

Suggestions for revision or reasons for rejection

Please make a sensitivity analysis of the computations using more recent (and possinbly more adequate) constants such as Millero et al. (2006).

I still have the impression at such low temperatures and salinities the computations of the thermodynamics of CO2 remain guess work, and a sensitivity analysis might reinforce the confidence on the computations presented in this paper.

It might be useful to check if in the frame of large-scale projects such as EPOCA some sort of recommendations have been made regarding the choice constants.

Page 11 : "no to vary" => not to vary

Page 18 : We can compute from AT = 161 µM, DIC = 61 µM, temp = 5°C, S = 0, a pCO2 of 0 µatm. How realistic is this ?

Page 18 : "These relations are similar to those obtained by Rysgaard et al. (2012) (TA = 161 + 61*S and DIC = 169 + 55*S)" is an overstatement. DIC of 169 µM is not similar to 61 µM.

Page 18 : "Both these sets of relations show that the freshwater endmember is undersaturated." They do not. You need to compute the pCO2 which is not done in text.

Page 19 : You might want to refer to some of the papers of the Delille group that have looked into salinity effects on the dynamics of brines and sea-ice underlying seawater such as Delille et al. 2009 although there might be more recent papers.

Page 19 : "The undersaturation in CO2 that has been previously observed in other high latitude systems affected by glacier meltwater (Evans et al., 2014; Sejr et al., 2011; Torres et al., 2011) could possibly be explained by this same mechanism." Please discuss wether the salinity distributions in these studies show the effect of meltwater inputs. This would make this statement slightly less speclative.

In Figure 2 it might be useful to indicate approximately the total depth profile.

References

Delille B., B. Jourdain, A.V. Borges, J.-L. Tison & D. Delille (2007) Biogas (CO2, O2 , dimethylsulfide) dynamics in Spring Antarctic fast ice, Limnology and Oceanography, 52(4), 1367-1379.

Millero, F. J., T. B. Graham, F. Huang, H. Bustos-Serrano, and D. Pierrot (2006), Dissociation constants of carbonic acid in seawater as a function of salinity and temperature, Mar. Chem., 100(1–2), 80–94, doi:10.1016/j.marchem.2005.12.001

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ED: Publish subject to minor revisions (Editor review) (12 Mar 2015) by Christoph Heinze

AR by Lorenz Meire on behalf of the Authors (23 Mar 2015) Author's response Manuscript

ED: Publish subject to technical corrections (25 Mar 2015) by Christoph Heinze

AR by Lorenz Meire on behalf of the Authors (27 Mar 2015) Manuscript

Short summary

The Greenland Ice Sheet releases large amounts of freshwater, which strongly influences the biogeochemistry of the adjacent fjord systems and continental shelves. Here we present seasonal observations of the carbonate system in the surface waters of a west Greenland tidewater outlet glacier fjord. Our data reveal a permanent undersaturation of CO2 in the surface layer of the entire fjord and adjacent shelf, creating a high annual uptake of 65gCm-2yr-1.

Glacial meltwater and primary production are drivers of strong CO2 uptake in fjord and coastal waters adjacent to the Greenland Ice Sheet

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Glacial meltwater and primary production are drivers of strong CO₂ uptake in fjord and coastal waters adjacent to the Greenland Ice Sheet