the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
The role of tides and sea ice on the carbonate chemistry in a coastal polynya in the south-eastern Weddell Sea
- 1School of Environmental Sciences, University of East Anglia, Norwich Research Park, NR4 7TJ Norwich, United Kingdom
- 2Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Postfach 120161, 27515 Bremerhaven, Germany
- 3Instituto de Oceanografía y Cambio Global, IOCAG, Universidad de Las Palmas de Gran Canaria, ULPGC, 35017 Las Palmas de Gran Canaria, Spain
- 4Department of Marine Sciences, University of Gothenburg, Carl Skottsbergs Gata 22B, SE-413 19 Gothenburg, Sweden
- 5Plymouth Marine Laboratory, Prospect Place, PL1 3DH Plymouth, United Kingdom
- 6British Antarctic Survey, High Cross, Madingley Road, CB3 0ET Cambridge, United Kingdom
- 7NIOZ Royal Netherlands Institute for Sea Research, department of Ocean Systems, P.O. Box 59, 1790 AB, Den Burg, Texel, The Netherlands
- 8Scripps Institution of Oceanography, UC San Diego, 8622 Kennel Way, La Jolla, CA 92037, United States
- 9School of Ocean and Earth Science, National Oceanography Centre, University of Southampton, Southampton, SO14 3ZH, United Kingdom
- 1School of Environmental Sciences, University of East Anglia, Norwich Research Park, NR4 7TJ Norwich, United Kingdom
- 2Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Postfach 120161, 27515 Bremerhaven, Germany
- 3Instituto de Oceanografía y Cambio Global, IOCAG, Universidad de Las Palmas de Gran Canaria, ULPGC, 35017 Las Palmas de Gran Canaria, Spain
- 4Department of Marine Sciences, University of Gothenburg, Carl Skottsbergs Gata 22B, SE-413 19 Gothenburg, Sweden
- 5Plymouth Marine Laboratory, Prospect Place, PL1 3DH Plymouth, United Kingdom
- 6British Antarctic Survey, High Cross, Madingley Road, CB3 0ET Cambridge, United Kingdom
- 7NIOZ Royal Netherlands Institute for Sea Research, department of Ocean Systems, P.O. Box 59, 1790 AB, Den Burg, Texel, The Netherlands
- 8Scripps Institution of Oceanography, UC San Diego, 8622 Kennel Way, La Jolla, CA 92037, United States
- 9School of Ocean and Earth Science, National Oceanography Centre, University of Southampton, Southampton, SO14 3ZH, United Kingdom
Abstract. Tides significantly affect polar coastlines by modulating ice shelf melt and modifying shelf water properties through transport and mixing. However, the effect of tides on the marine carbonate chemistry in such regions, especially around Antarctica, remains largely unexplored. We address this topic with two case studies in a coastal polynya in the south-eastern Weddell Sea, neighbouring the Ekström Ice Shelf. The case studies were conducted in January 2015 (PS89) and January 2019 (PS117), capturing semi-diurnal oscillations in the water column. These are pronounced in both physical and biogeochemical variables for PS89. During rising tide, advection of sea ice melt water from the north-east created a fresher, warmer, more deeply mixed water column with lower dissolved inorganic carbon (DIC) and total alkalinity (TA) content. During ebbing tide, water from underneath the ice shelf decreased the polynya's temperature, increased the DIC and TA content, and created a more stratified water column. The variability during the PS117 case study was much smaller, as it had less sea ice melt water input during rising tide and was better mixed with sub-ice shelf water. The contrasts in the variability between the two case studies could be wind and sea ice driven, and underline the complexity and highly dynamic nature of the system.
The variability in the polynya induced by the tides results in an air-sea CO2 flux that can range between a strong sink (-20 mmol m-2 day-1) and a small source (7 mmol m-2 day-1) on a semi-diurnal time scale. If the variability induced by tides is not taken into account, there is a potential risk of overestimating the polynya's CO2 uptake by 98 % or underestimating it by 108 % (mistaking it for a source instead of a variable sink), compared to the average flux determined over several days. Given the disproportionate influence of polynyas on heat and carbon exchange in polar oceans, we recommend that future studies around the Antarctic and Arctic coastlines consider the timing of tidal currents in their sampling strategies and analyses. This will help constrain variability in oceanographic measurements and avoid potential biases in our understanding of these highly complex systems.
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Notice on discussion status
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
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Preprint
(19104 KB)
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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
Journal article(s) based on this preprint
Elise Sayana Droste et al.
Interactive discussion
Status: closed
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RC1: 'Comment on os-2022-19', Anonymous Referee #1, 29 Apr 2022
The authors have written an interesting case study that nicely demonstrates how sampling bias can influence marine observations in highly dynamic environments in Antarctic coastal waters. They illustrate this with carbonate chemistry observations from a single location over 1-2 days during two separate years. The authors attribute the observed physical and chemical oceanographic changes to tidally induced currents and mixing.
Figure 2 shows the expected tidal influence (from a model) alongside the measured currents using an ADCP. Based on this figure alone, it is a little difficult to determine to what extent the tide dominates the observed current movement during the observational period. This is mostly due to the compressed y-axis on panels A, B, G and H. I think the authors have tried to address this with Figure F1, but maybe a plot of the residual u and v component might be more helpful here, or perhaps a progressive vector diagram that shows the trajectory of a water parcel during each period? If tides really are dominant then the water parcel, of course, would pretty much end up back where it started. Although as the authors mentioned in Line 286, the net transport during the experimental period appears to be to the south/southeast. Which would imply a transport path against the prevailing coastal/Weddell Gyre current?
Admittedly, this is a minor point. Even if the tidal influence was not as significant, the sampling bias problems that the paper is highlighting would remain unchanged. Finally, the caption in Figure D1 incorrectly labels panels C and D.
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AC1: 'Response to reviewer's comments', Elise Droste, 21 Jul 2022
Dear reviewer,
On behalf of all co-authors and myself, I'd like to thank you for your comments on our manuscript. Please find our responses in the attached document. We've included our responses to all other reviewers, to which we might have made references in our responses to your comments.
Best regards,
Elise Droste
Mario Hoppema, Melchor González-Dávila, Juana Magdalena Santana-Casiano, Bastien Y. Queste, Giorgio Dall’Olmo, Hugh J. Venables, Gerd Rohardt, Sharyn Ossebaar, Daniel Schuller, Sunke Trace-Kleeberg, and Dorothee C. E. Bakker
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AC1: 'Response to reviewer's comments', Elise Droste, 21 Jul 2022
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RC2: 'Comment on os-2022-19', Anonymous Referee #2, 21 May 2022
This study presents physical and biogeochemical measurements in a polynya and discusses variability and controlling factors during a complete tidal cycle in 2 different years in the eastern Weddell Sea. The data and discussions include using numerical output from a tidal model and considerations of snapshot sampling that may lead to biases and are an important contribution to marine carbonate chemistry, biogeochemical cycling and air-sea CO2 uptake in dynamic environments. The biogeochemical focus is DIC and TA and CO2 fluxes in the context of sea ice and tides. Calcium carbonate saturation for both aragonite and calcite are mentioned in the appendix figures but not really in the text. Some additional text in the Introduction and Methods is required to show how these variables were calculated, what they mean for these coastal polynya system and would put the results into greater context with regards the organisms found here. It would also be helpful to include more discussion of and reference to the theoretical lines drawn in Figure 5, whereby a short description of key processes that drive variability in the carbonate system in the Introduction would improve the understanding. Figure 3 green markers in panel A are difficult to see. Figure D1 panels C and D descriptions are reversed in the caption. Figure E1 interpretation would be assisted by marking depths of discrete samples in panels C and D to better compare to higher vertical resolution in panels A and B. There is assumption that the interpretation of biogeochemical data from the discrete samples is reliable as the physical variables from the high resolution CTD data, however additional processes such as primary production/respiration, location of a deep Chl maximum… would imprint additional variability particularly in the surface layer that is not captured by changing salinity and temperature (water mass) interactions. A comment in the text to consider this and consider adding references to support the statement that would complement the discussion. Figure G1 determining the difference between red dashed and dotted lines was difficult, perhaps a more striking difference would assist here (e.g. different colours). Aragonite saturation is mentioned here and would benefit from an introduction in the main text in terms of the definition and how it is determined, and relevance of the value depicted by the red line here, low value towards 1 relevant for calcifying organisms? Figure G2 calcite saturation is shown here, check consistency with Figure G1 and include definitions and how they are determined in the text.
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AC2: 'Response to reviewer's comments', Elise Droste, 21 Jul 2022
Dear reviewer,
On behalf of all co-authors and myself, I'd like to thank you for your comments on our manuscript. Please find our responses in the attached document. We've included our responses to all other reviewers, to which we might have made references in our responses to your comments.
Best regards,
Elise Droste
Mario Hoppema, Melchor González-Dávila, Juana Magdalena Santana-Casiano, Bastien Y. Queste, Giorgio Dall’Olmo, Hugh J. Venables, Gerd Rohardt, Sharyn Ossebaar, Daniel Schuller, Sunke Trace-Kleeberg, and Dorothee C. E. Bakker
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AC2: 'Response to reviewer's comments', Elise Droste, 21 Jul 2022
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RC3: 'Comment on os-2022-19', Anonymous Referee #3, 12 Jun 2022
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AC3: 'Response to reviewer's comments', Elise Droste, 21 Jul 2022
Dear reviewer,
On behalf of all co-authors and myself, I'd like to thank you for your comments on our manuscript. Please find our responses in the attached document. We've included our responses to all other reviewers, to which we might have made references in our responses to your comments.
Best regards,
Elise Droste
Mario Hoppema, Melchor González-Dávila, Juana Magdalena Santana-Casiano, Bastien Y. Queste, Giorgio Dall’Olmo, Hugh J. Venables, Gerd Rohardt, Sharyn Ossebaar, Daniel Schuller, Sunke Trace-Kleeberg, and Dorothee C. E. Bakker
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AC3: 'Response to reviewer's comments', Elise Droste, 21 Jul 2022
Peer review completion
Interactive discussion
Status: closed
-
RC1: 'Comment on os-2022-19', Anonymous Referee #1, 29 Apr 2022
The authors have written an interesting case study that nicely demonstrates how sampling bias can influence marine observations in highly dynamic environments in Antarctic coastal waters. They illustrate this with carbonate chemistry observations from a single location over 1-2 days during two separate years. The authors attribute the observed physical and chemical oceanographic changes to tidally induced currents and mixing.
Figure 2 shows the expected tidal influence (from a model) alongside the measured currents using an ADCP. Based on this figure alone, it is a little difficult to determine to what extent the tide dominates the observed current movement during the observational period. This is mostly due to the compressed y-axis on panels A, B, G and H. I think the authors have tried to address this with Figure F1, but maybe a plot of the residual u and v component might be more helpful here, or perhaps a progressive vector diagram that shows the trajectory of a water parcel during each period? If tides really are dominant then the water parcel, of course, would pretty much end up back where it started. Although as the authors mentioned in Line 286, the net transport during the experimental period appears to be to the south/southeast. Which would imply a transport path against the prevailing coastal/Weddell Gyre current?
Admittedly, this is a minor point. Even if the tidal influence was not as significant, the sampling bias problems that the paper is highlighting would remain unchanged. Finally, the caption in Figure D1 incorrectly labels panels C and D.
-
AC1: 'Response to reviewer's comments', Elise Droste, 21 Jul 2022
Dear reviewer,
On behalf of all co-authors and myself, I'd like to thank you for your comments on our manuscript. Please find our responses in the attached document. We've included our responses to all other reviewers, to which we might have made references in our responses to your comments.
Best regards,
Elise Droste
Mario Hoppema, Melchor González-Dávila, Juana Magdalena Santana-Casiano, Bastien Y. Queste, Giorgio Dall’Olmo, Hugh J. Venables, Gerd Rohardt, Sharyn Ossebaar, Daniel Schuller, Sunke Trace-Kleeberg, and Dorothee C. E. Bakker
-
AC1: 'Response to reviewer's comments', Elise Droste, 21 Jul 2022
-
RC2: 'Comment on os-2022-19', Anonymous Referee #2, 21 May 2022
This study presents physical and biogeochemical measurements in a polynya and discusses variability and controlling factors during a complete tidal cycle in 2 different years in the eastern Weddell Sea. The data and discussions include using numerical output from a tidal model and considerations of snapshot sampling that may lead to biases and are an important contribution to marine carbonate chemistry, biogeochemical cycling and air-sea CO2 uptake in dynamic environments. The biogeochemical focus is DIC and TA and CO2 fluxes in the context of sea ice and tides. Calcium carbonate saturation for both aragonite and calcite are mentioned in the appendix figures but not really in the text. Some additional text in the Introduction and Methods is required to show how these variables were calculated, what they mean for these coastal polynya system and would put the results into greater context with regards the organisms found here. It would also be helpful to include more discussion of and reference to the theoretical lines drawn in Figure 5, whereby a short description of key processes that drive variability in the carbonate system in the Introduction would improve the understanding. Figure 3 green markers in panel A are difficult to see. Figure D1 panels C and D descriptions are reversed in the caption. Figure E1 interpretation would be assisted by marking depths of discrete samples in panels C and D to better compare to higher vertical resolution in panels A and B. There is assumption that the interpretation of biogeochemical data from the discrete samples is reliable as the physical variables from the high resolution CTD data, however additional processes such as primary production/respiration, location of a deep Chl maximum… would imprint additional variability particularly in the surface layer that is not captured by changing salinity and temperature (water mass) interactions. A comment in the text to consider this and consider adding references to support the statement that would complement the discussion. Figure G1 determining the difference between red dashed and dotted lines was difficult, perhaps a more striking difference would assist here (e.g. different colours). Aragonite saturation is mentioned here and would benefit from an introduction in the main text in terms of the definition and how it is determined, and relevance of the value depicted by the red line here, low value towards 1 relevant for calcifying organisms? Figure G2 calcite saturation is shown here, check consistency with Figure G1 and include definitions and how they are determined in the text.
-
AC2: 'Response to reviewer's comments', Elise Droste, 21 Jul 2022
Dear reviewer,
On behalf of all co-authors and myself, I'd like to thank you for your comments on our manuscript. Please find our responses in the attached document. We've included our responses to all other reviewers, to which we might have made references in our responses to your comments.
Best regards,
Elise Droste
Mario Hoppema, Melchor González-Dávila, Juana Magdalena Santana-Casiano, Bastien Y. Queste, Giorgio Dall’Olmo, Hugh J. Venables, Gerd Rohardt, Sharyn Ossebaar, Daniel Schuller, Sunke Trace-Kleeberg, and Dorothee C. E. Bakker
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AC2: 'Response to reviewer's comments', Elise Droste, 21 Jul 2022
-
RC3: 'Comment on os-2022-19', Anonymous Referee #3, 12 Jun 2022
-
AC3: 'Response to reviewer's comments', Elise Droste, 21 Jul 2022
Dear reviewer,
On behalf of all co-authors and myself, I'd like to thank you for your comments on our manuscript. Please find our responses in the attached document. We've included our responses to all other reviewers, to which we might have made references in our responses to your comments.
Best regards,
Elise Droste
Mario Hoppema, Melchor González-Dávila, Juana Magdalena Santana-Casiano, Bastien Y. Queste, Giorgio Dall’Olmo, Hugh J. Venables, Gerd Rohardt, Sharyn Ossebaar, Daniel Schuller, Sunke Trace-Kleeberg, and Dorothee C. E. Bakker
-
AC3: 'Response to reviewer's comments', Elise Droste, 21 Jul 2022
Peer review completion
Journal article(s) based on this preprint
Elise Sayana Droste et al.
Elise Sayana Droste et al.
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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
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