the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 22 Aug 2024
Surface CO2 Gradients Challenge Conventional CO2 Emission Quantification in Lentic Water Bodies under Calm Conditions
Abstract. Lakes are hotspots of inland carbon cycling and are important sources of greenhouse gases (GHGs), such as carbon dioxide (CO2). The significant role of CO2 in global carbon cycle makes quantifying its emission from various ecosystems, including lakes and reservoirs, important for developing strategies to mitigate climate change. The thin boundary layer method is a common approach to calculate CO2 fluxes from CO2 measurements in both the water and the air, and wind speed. However, one assumption for the TBL method is a homogeneous CO2 concentration between the measurement depth and the water surface, where gas exchange takes place. This assumption might not be true under calm conditions, when microstratification below the surface slows vertical exchange of gases. We used a floating outdoor laboratory to monitor CO2 concentrations in 5 cm and 25 cm depth, CO2 concentration in the air, wind speed, and water temperature profiles for one week in Bautzen Reservoir, Germany. While we found homogeneous CO2 concentrations in the two depths during wind speeds above 3 m s-1, there was a vertical gradient observed during wind still nights. The concentrations observed temporally ranged from undersaturation to supersaturation in 25 cm and 5 cm, respectively. Fluxes calculated from the measured concentrations therefore would change from negative to positive, depending on the measurement depth. Simultaneous Eddy Covariance measurements showed that even the measurements close to the surface underestimated the actual CO2 concentration. Oxygen measurements support our hypothesis that respirational processes at the water surface cause a temporal CO2 concentration gradient from the surface to the underlying water. Until now, the depth of CO2 measurements has not been questioned, as long as measurements were done in the upper mixed layer and close to the surface. Our results provide evidence that representative measurements of CO2 in the water strongly depend on depth and time of measurements.
-
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.
-
Preprint
(1953 KB)
-
Supplement
(284 KB)
-
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
- Preprint
(1953 KB) - Metadata XML
-
Supplement
(284 KB) - BibTeX
- EndNote
- Final revised paper
Journal article(s) based on this preprint
Interactive discussion
Status: closed
-
RC1: 'Comment on egusphere-2024-2550', Mariana Ribas-Ribas, 03 Sep 2024
The manuscript titled "Surface CO2 Gradients Challenge Conventional CO2 Emission Quantification in Lentic Water Bodies under Calm Conditions" by Patrick Aurich et al. presents an insightful study on CO2 dynamics in the near-surface layer of the Bautzen Reservoir. I think the first author is a PhD student, and I would like to extend my congratulations to him, recognizing the complexity and difficulty of this research.
The manuscript benefits from a high temporal and spatial resolution dataset, and the analysis provides valuable insights worthy of publication. However, I think the manuscript requires further development and refinement before it is ready for publication. As I am not concerned with remaining anonymous (and I can’t remain anonymous given the nature of my comments 😊), I have attached my detailed feedback in the accompanying PDF document.
I look forward to reviewing the revised version of this manuscript.
- AC1: 'Reply on RC1', Patrick Aurich, 29 Oct 2024
-
RC2: 'Comment on egusphere-2024-2550', Anonymous Referee #2, 08 Oct 2024
This is a very relevant study as it points to one of the major concerns of the traditional methods to estimate air-water CO2 exchange, the assumption of constant concentration of CO2 in the water. The experiment and data are interesting and well worth publishing. I, however, think that a substantial revision with rewriting and reanalysis is required.
Below are some comments and suggestions, I will not comment much on language, but I think a thorough revision of the writing is necessary as well.
General comments of the introduction:
There exists a range of literature on the role of lakes in the carbon cycle, and this part should be updated base on more and more recent literature. Please look at the papers by Golub et al and Guseva et al for a range of suggested papers.
I think the ambition to look at 5 and 25 cm are good, but the major gradient is closer to the surface, please have a more thorough discussion on this aspect.
Line 35: There are several EC sites worldwide (see Golub and Guseva).
Line 50 to 55: The cooling induced convection and the impact on the gas exchange is very important here (in particularly when seeing the strong diurnal cycle in the result section) and should be further discussed also in the introduction. There exists a range of literature from seas and lakes (Rutgersson and Smedman, 2010, Podgrajsek et al 2015, Eugster et al, 2003, 2023; Heiskanen 2014, Andersson et al 2017)
Line 75: The study of Rudeberg is interesting and well discusses how spatial and temporal variations influences the flux. It is, however, limited to chambers. Other studies use EC-fluxes (Rutgersson et al, Dong et al).
I think the limitations of chambers in relation to EC should be further discussed (se for example Podgrajsek et al 2014).
The surrounding areas is considered unimportant, please ale note the possibility of non-local effects (eeg Esters et al).
Section 2.4: Please do not name the routines used. If this is important explain what they do to the data (if this paper is read in 10 years’ time, it might be impossible to understand as now written). The name of the routines could be in an appendix, if the authors consider it important information.
Results:
In Figure 1 you show a really nice diurnal cycle, with significant gradients during night-time, this is explained by the phytoplankton activity, but you really should consider the effect of physical processes with a strong waterside convection during night-time. This is seen during low winds, when the convection is found to dominate.
Andersson, A., E. Falck, A. Sjöblom, N. Kljun, E. Sahlée, A. M. Omar, and A. Rutgersson (2017), Air-sea gas transfer in high Arctic fjords, Geophys. Res. Lett., 44, doi:10.1002/2016GL072373.
Dong et al 2021, https://doi.org/10.5194/acp-21-8089-2021
Esters L, Rutgersson A, Nilsson E and Sahlee E 2020 Non-local impacts on eddy-covariance air-lake CO2 fluxes Bound.-Layer Meteorol. 178 283–300
Eugster W et al 2003 CO2 exchange between air and water in an arctic Alaskan and midlatitude Swiss lake: importance of convective mixing J. Geophys. Res. 108 4362
Eugster W, DelSontro T, Shaver G R and Kling G W 2020 Interannual, summer, and diel variability of CH4 and CO2 effluxes from Toolik Lake, Alaska, during the ice-free periods 2010–2015 Environ. Sci.: Process. Impacts 22 2181–98
Golub et al., 2023 Diel, seasonal, and inter-annual variation in carbon dioxide effluxes from lakes and reservoirs, Environ. Res. Lett. 18 034046, https://doi.org/10.1088/1748-9326/acb834
Heiskanen J J, Mammarella I, Haapanala S, Pumpanen J, Vesala T, Macintyre S and Ojala A 2014 Effects of cooling and internal wave motions on gas transfer coefficients in a boreal lake Tellus B 66 22827
Guseva, S., etal , 2023. Bulk Transfer Coefficients Estimated from Eddy-Covariance Measurements over Lakes and Reservoirs. J Geophys Res.-Atmospheres, 128, e2022JD037219, doi:10.1029/2022JD037219. https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2022JD037219
Podgrajsek E, Sahlée E and Rutgersson A 2015 Diel cycle of lake-air CO2 flux from a shallow lake and the impact of waterside convection on the transfer velocity J. Geophys. Res. 120 29–38
Rutgersson A. and Smedman, A. Enhancement of CO2 transfer velocity due to water-side convection, J. Marine Syst., 80, 125-134,. 2010
Rutgersson, A., M. Norman, B. Schneider, H. Pettersson, E. , Sahlée. The annual cycle of carbon-dioxide and parameters influencing the air-sea carbon exchange in the Baltic Proper. J. Mar. Syst., 74, 381-394. 2008
Citation: https://doi.org/10.5194/egusphere-2024-2550-RC2 - AC2: 'Reply on RC2', Patrick Aurich, 29 Oct 2024
Interactive discussion
Status: closed
-
RC1: 'Comment on egusphere-2024-2550', Mariana Ribas-Ribas, 03 Sep 2024
The manuscript titled "Surface CO2 Gradients Challenge Conventional CO2 Emission Quantification in Lentic Water Bodies under Calm Conditions" by Patrick Aurich et al. presents an insightful study on CO2 dynamics in the near-surface layer of the Bautzen Reservoir. I think the first author is a PhD student, and I would like to extend my congratulations to him, recognizing the complexity and difficulty of this research.
The manuscript benefits from a high temporal and spatial resolution dataset, and the analysis provides valuable insights worthy of publication. However, I think the manuscript requires further development and refinement before it is ready for publication. As I am not concerned with remaining anonymous (and I can’t remain anonymous given the nature of my comments 😊), I have attached my detailed feedback in the accompanying PDF document.
I look forward to reviewing the revised version of this manuscript.
- AC1: 'Reply on RC1', Patrick Aurich, 29 Oct 2024
-
RC2: 'Comment on egusphere-2024-2550', Anonymous Referee #2, 08 Oct 2024
This is a very relevant study as it points to one of the major concerns of the traditional methods to estimate air-water CO2 exchange, the assumption of constant concentration of CO2 in the water. The experiment and data are interesting and well worth publishing. I, however, think that a substantial revision with rewriting and reanalysis is required.
Below are some comments and suggestions, I will not comment much on language, but I think a thorough revision of the writing is necessary as well.
General comments of the introduction:
There exists a range of literature on the role of lakes in the carbon cycle, and this part should be updated base on more and more recent literature. Please look at the papers by Golub et al and Guseva et al for a range of suggested papers.
I think the ambition to look at 5 and 25 cm are good, but the major gradient is closer to the surface, please have a more thorough discussion on this aspect.
Line 35: There are several EC sites worldwide (see Golub and Guseva).
Line 50 to 55: The cooling induced convection and the impact on the gas exchange is very important here (in particularly when seeing the strong diurnal cycle in the result section) and should be further discussed also in the introduction. There exists a range of literature from seas and lakes (Rutgersson and Smedman, 2010, Podgrajsek et al 2015, Eugster et al, 2003, 2023; Heiskanen 2014, Andersson et al 2017)
Line 75: The study of Rudeberg is interesting and well discusses how spatial and temporal variations influences the flux. It is, however, limited to chambers. Other studies use EC-fluxes (Rutgersson et al, Dong et al).
I think the limitations of chambers in relation to EC should be further discussed (se for example Podgrajsek et al 2014).
The surrounding areas is considered unimportant, please ale note the possibility of non-local effects (eeg Esters et al).
Section 2.4: Please do not name the routines used. If this is important explain what they do to the data (if this paper is read in 10 years’ time, it might be impossible to understand as now written). The name of the routines could be in an appendix, if the authors consider it important information.
Results:
In Figure 1 you show a really nice diurnal cycle, with significant gradients during night-time, this is explained by the phytoplankton activity, but you really should consider the effect of physical processes with a strong waterside convection during night-time. This is seen during low winds, when the convection is found to dominate.
Andersson, A., E. Falck, A. Sjöblom, N. Kljun, E. Sahlée, A. M. Omar, and A. Rutgersson (2017), Air-sea gas transfer in high Arctic fjords, Geophys. Res. Lett., 44, doi:10.1002/2016GL072373.
Dong et al 2021, https://doi.org/10.5194/acp-21-8089-2021
Esters L, Rutgersson A, Nilsson E and Sahlee E 2020 Non-local impacts on eddy-covariance air-lake CO2 fluxes Bound.-Layer Meteorol. 178 283–300
Eugster W et al 2003 CO2 exchange between air and water in an arctic Alaskan and midlatitude Swiss lake: importance of convective mixing J. Geophys. Res. 108 4362
Eugster W, DelSontro T, Shaver G R and Kling G W 2020 Interannual, summer, and diel variability of CH4 and CO2 effluxes from Toolik Lake, Alaska, during the ice-free periods 2010–2015 Environ. Sci.: Process. Impacts 22 2181–98
Golub et al., 2023 Diel, seasonal, and inter-annual variation in carbon dioxide effluxes from lakes and reservoirs, Environ. Res. Lett. 18 034046, https://doi.org/10.1088/1748-9326/acb834
Heiskanen J J, Mammarella I, Haapanala S, Pumpanen J, Vesala T, Macintyre S and Ojala A 2014 Effects of cooling and internal wave motions on gas transfer coefficients in a boreal lake Tellus B 66 22827
Guseva, S., etal , 2023. Bulk Transfer Coefficients Estimated from Eddy-Covariance Measurements over Lakes and Reservoirs. J Geophys Res.-Atmospheres, 128, e2022JD037219, doi:10.1029/2022JD037219. https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2022JD037219
Podgrajsek E, Sahlée E and Rutgersson A 2015 Diel cycle of lake-air CO2 flux from a shallow lake and the impact of waterside convection on the transfer velocity J. Geophys. Res. 120 29–38
Rutgersson A. and Smedman, A. Enhancement of CO2 transfer velocity due to water-side convection, J. Marine Syst., 80, 125-134,. 2010
Rutgersson, A., M. Norman, B. Schneider, H. Pettersson, E. , Sahlée. The annual cycle of carbon-dioxide and parameters influencing the air-sea carbon exchange in the Baltic Proper. J. Mar. Syst., 74, 381-394. 2008
Citation: https://doi.org/10.5194/egusphere-2024-2550-RC2 - AC2: 'Reply on RC2', Patrick Aurich, 29 Oct 2024
Peer review completion
Journal article(s) based on this preprint
Viewed
| HTML | XML | Total | Supplement | BibTeX | EndNote | |
|---|---|---|---|---|---|---|
| 285 | 86 | 286 | 657 | 38 | 25 | 22 |
- HTML: 285
- PDF: 86
- XML: 286
- Total: 657
- Supplement: 38
- BibTeX: 25
- EndNote: 22
Viewed (geographical distribution)
| Country | # | Views | % |
|---|
| Total: | 0 |
| HTML: | 0 |
| PDF: | 0 |
| XML: | 0 |
- 1
Uwe Spank
Matthias Koschorreck
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
- Preprint
(1953 KB) - Metadata XML
-
Supplement
(284 KB) - BibTeX
- EndNote
- Final revised paper