the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 25 Jun 2025
Combined water table and temperature dynamics control CO2 emission estimates from drained peatlands under rewetting and climate change scenarios
Abstract. This study integrates process-based hydrological modeling and empirical CO2 flux modeling at a daily temporal resolution to evaluate how peatland hydrology influence CO2 emissions under scenarios of rewetting and climate change.
Following the calibration of a three-dimensional transient groundwater flow model for a peat-dominated catchment, daily groundwater table dynamics were simulated to represent hydrological conditions in drained peat soils. These simulations were coupled with an empirical CO2 flux model, developed from a comprehensive daily dataset of groundwater table depth, temperature, and soil CO2 flux measurements. The empirical CO2 flux model captures a clear temperature-dependent response of soil CO2 emissions to variations in groundwater table depth.
By applying this coupled modeling framework, we quantified CO2 emissions at daily timescales. The results demonstrate that incorporating both temperature sensitivity and high-resolution temporal variability in water level significantly influences projections of CO2 fluxes. Especially the co-occurrence of elevated air temperature and low groundwater table significantly influence CO2 emissions under scenarios of rewetting and climate change. These insights highlight the importance of including changing climate conditions in future peatland management strategies for emission inventories.
The study illustrates the value of combining detailed hydrological simulations with emission models. It also emphasizes the need for detailed monitoring of greenhouse gas emissions across multiple sites and the development of robust empirical models that can be generalized and spatially upscaled.
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Status: closed
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RC1: 'Comment on egusphere-2025-2503', Anonymous Referee #1, 10 Sep 2025
- AC1: 'Reply on RC1', Tanja Denager, 14 Nov 2025
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RC2: 'Comment on egusphere-2025-2503', Anonymous Referee #2, 31 Oct 2025
The authors have done hydrological modelling of peatland WTD and its impacts on CO2 fluxes in current and future climates under different rewetting scenarios. Overall the study is well conducted and clearly represented. The study is highly topical considering the importance of peatland ecosystems in GHG budgets and the open questions still surrounding them. I only have a few minor comments on the manuscript.
1. Concerning the rewetting scenarios: Are there actual management practices, that can focus the rewetting seasonally? I am only aware of the more nature-based methods, such as ditch-blocking. I appreciate that discussing actual, real-life management practices is not the point of this manuscript but it would perhaps be helpful to somewhere explain how these scenarios used here relate to real life, as your findings rather strongly suggest that considering the seasonal variation in rewetting is important.
2. Choosing one RCP is understandable considering the amount of variables that are already present in the study. I do not suggest that you introduce a milder climate scenario here but I think it would be good to acknowledge in the discussion that this is the scenario leading to strongest impacts of climate change. This is particularly relevant for your manuscript, as you assess the cascading impacts of two climate-related variables. It would be highly interesting to know (perhaps in a future paper) if this relationship of WTD and Ta cancelling each other out is visible in other climate change scenarios, or would the influence of one overpower the other.
3. Throughout the paper, you refer to the ground surface as "terrain", i.e. on L63 and L129. Is there a particular reason why you don't just say "surface"? I'm not sure I've ever heard this use of the term terrain, and at least for me, this was somewhat confusing.
4. I would advise on renaming the two future time periods as "mid-century" (or something like that" and "end of century". Distant future, to me at least, seems to be something further in the future than within my own lifespan, and since your simulation covers this century, it seems like a much clearer choice to refer to that.
Fig.3: Could you make the lines within the legend a little thicker, so that it is clear which line (blue or black) is referring to modelled and measured values?
Finally, while the language is generally very good, I would advise a thorough read-through of the manuscript, or employing the help of a proof-reader. I have listed below some parts that need refining, but I did not conduct a thorough language check.
L70. Do not account for neither: double negative.
L85: Sentence starting with "For example through..." is not a full sentence.
L91: field-scale, not field scale
L113: Should this be "continuous", not "contiguous"?
L126: This probably should be "automatically", not "automatic"
L306: There is no need to say "such as rewetting", since this is the only management practice discussed in this paper.
L311-313: This is a confusing sentence.
L657: "In 2023, CO₂ emissions from drained organic soils in croplands and grasslands was estimated to
accounted for 6.7% of Denmark's total emissions" --> "was estimated to have accounted for"L687: "Such nature-based solutions are not likely to reduce..."
Citation: https://doi.org/10.5194/egusphere-2025-2503-RC2 - AC2: 'Reply on RC2', Tanja Denager, 14 Nov 2025
Status: closed
-
RC1: 'Comment on egusphere-2025-2503', Anonymous Referee #1, 10 Sep 2025
The manuscript presents a well-structured and scientifically sound study with valuable findings on the prediction of CO₂ emissions from peatlands under warming climate and rewetting scenarios. The modeling approach and discussion are generally well executed. I recommend the authors consider the following minor revisions to improve clarity and consistency:
- Lines 63–66: The sentence is difficult to follow due to the use of both WTD and groundwater level, which change in opposite directions. Please consider reformulating the sentence using only WTD.
- Lines 70–71: Correct the double negative in “not … neither ... nor.”
- Table S3: Please define the variables Alpha, N, L, and Kint.
- Line 201: The term KGEWTD is not defined—please add a definition.
- Line 203: To maintain consistency with other objective functions, consider using subscripts for q_head_amp.
- Lines 215–217: It is unclear how the objective functions are combined, given their differing ranges and optimal values. Please clarify the methodology.
- Tables S3 and S4: Both tables present water retention parameters for peat, but with differing values. Could you explain the reason for this discrepancy?
- Line 287: Remove the unnecessary line break.
- Line 433: The temperature sensitivity of soil fCO₂ is commonly reported as non-linear. While the selected model and alternatives are well addressed in the discussion, I’m curious—did you explore temperature sensitivity within WTD bins? The model appears to miss many of the observed high fCO₂ values; perhaps a non-linear temperature dependence could improve performance?
- Lines 479–487: While I understand the need to limit fCO₂, the rationale behind the chosen thresholds (WTD 62.5 cm and Tair 25°C) is unclear. I expect hese values to strongly influence the comparison of modeled fluxes for extreme years (Lines 516–517). Please elaborate.
- Lines 488–491: The statement that “both CO₂ flux models exclusively account for the CO₂ emissions from the peat soil” is misleading. The Annual model includes NEBC, and thus GPP, as discussed earlier in the manuscript. GPP is also used as a reason for downscaling the daily model for fCO₂. Please revise this statement for accuracy.
- Figure 6: Consider combining panels c and d, as they contain overlapping information.
- Discussion: The section is generally well structured. However, it would benefit from additional citations, e.g., regarding the advantages of hydrological models and process-based emission models.
Citation: https://doi.org/10.5194/egusphere-2025-2503-RC1 - AC1: 'Reply on RC1', Tanja Denager, 14 Nov 2025
-
RC2: 'Comment on egusphere-2025-2503', Anonymous Referee #2, 31 Oct 2025
The authors have done hydrological modelling of peatland WTD and its impacts on CO2 fluxes in current and future climates under different rewetting scenarios. Overall the study is well conducted and clearly represented. The study is highly topical considering the importance of peatland ecosystems in GHG budgets and the open questions still surrounding them. I only have a few minor comments on the manuscript.
1. Concerning the rewetting scenarios: Are there actual management practices, that can focus the rewetting seasonally? I am only aware of the more nature-based methods, such as ditch-blocking. I appreciate that discussing actual, real-life management practices is not the point of this manuscript but it would perhaps be helpful to somewhere explain how these scenarios used here relate to real life, as your findings rather strongly suggest that considering the seasonal variation in rewetting is important.
2. Choosing one RCP is understandable considering the amount of variables that are already present in the study. I do not suggest that you introduce a milder climate scenario here but I think it would be good to acknowledge in the discussion that this is the scenario leading to strongest impacts of climate change. This is particularly relevant for your manuscript, as you assess the cascading impacts of two climate-related variables. It would be highly interesting to know (perhaps in a future paper) if this relationship of WTD and Ta cancelling each other out is visible in other climate change scenarios, or would the influence of one overpower the other.
3. Throughout the paper, you refer to the ground surface as "terrain", i.e. on L63 and L129. Is there a particular reason why you don't just say "surface"? I'm not sure I've ever heard this use of the term terrain, and at least for me, this was somewhat confusing.
4. I would advise on renaming the two future time periods as "mid-century" (or something like that" and "end of century". Distant future, to me at least, seems to be something further in the future than within my own lifespan, and since your simulation covers this century, it seems like a much clearer choice to refer to that.
Fig.3: Could you make the lines within the legend a little thicker, so that it is clear which line (blue or black) is referring to modelled and measured values?
Finally, while the language is generally very good, I would advise a thorough read-through of the manuscript, or employing the help of a proof-reader. I have listed below some parts that need refining, but I did not conduct a thorough language check.
L70. Do not account for neither: double negative.
L85: Sentence starting with "For example through..." is not a full sentence.
L91: field-scale, not field scale
L113: Should this be "continuous", not "contiguous"?
L126: This probably should be "automatically", not "automatic"
L306: There is no need to say "such as rewetting", since this is the only management practice discussed in this paper.
L311-313: This is a confusing sentence.
L657: "In 2023, CO₂ emissions from drained organic soils in croplands and grasslands was estimated to
accounted for 6.7% of Denmark's total emissions" --> "was estimated to have accounted for"L687: "Such nature-based solutions are not likely to reduce..."
Citation: https://doi.org/10.5194/egusphere-2025-2503-RC2 - AC2: 'Reply on RC2', Tanja Denager, 14 Nov 2025
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The manuscript presents a well-structured and scientifically sound study with valuable findings on the prediction of CO₂ emissions from peatlands under warming climate and rewetting scenarios. The modeling approach and discussion are generally well executed. I recommend the authors consider the following minor revisions to improve clarity and consistency: