the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 24 May 2023
A missing link in the carbon cycle: phytoplankton light absorption under RCP scenarios
Abstract. Marine biota and biogeophysical mechanisms, such as phytoplankton light absorption, have attracted increasing attention in recent climate studies. Under global warming, the impact of phytoplankton on the climate system is expected to change. Previous studies analyzed the impact of phytoplankton light absorption under prescribed future atmospheric CO2 concentrations. However, the role of this biogeophysical mechanism under freely-evolving atmospheric CO2 concentration and future CO2 emissions remains unknown. To shed light on this research gap, we perform simulations with the EcoGEnIE Earth system model and prescribe CO2 emissions out to 2500 following the four Extended Concentration Pathways (ECP) scenarios, which for practical purpose we call RCP scenarios. Under all RCP scenarios, our results indicate that phytopankton light absorption weakens the biological carbon pump while it increases the surface chlorophyll, the sea surface temperature, the atmospheric CO2 concentrations and the atmospheric temperature. Under the RCP2.6, RCP4.5 and RCP6.0 scenarios, the magnitude of changes due to phytoplankton light absorption is similar. However, under the RCP8.5 scenario, the changes in the climate system are less pronounced due to temperature limitation of phytoplankton concentration, highlighting a reduced effect of phytoplankton light absorption under strong warming. Additionally, this work highlights the major role of phytoplankton light absorption on the climate system, suggesting highly uncertain feedbacks on the carbon cycle with uncertainties that maybe in the range of those known from the land biota.
-
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
(3570 KB)
-
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
- Preprint
(3570 KB) - Metadata XML
- BibTeX
- EndNote
- Final revised paper
Journal article(s) based on this preprint
Interactive discussion
Status: closed
-
RC1: 'Comment on egusphere-2023-921', Anonymous Referee #1, 30 Jun 2023
Review of the paper “A missing link in the carbon cycle: phytoplankton light absorption under RCP scenarios”
General comments
I have completed the review of the manuscript egusphere-2023-921. The manuscript shows some interesting results, somehow scientifically soundings. At the same time, I found that the manuscript has several issues that the Authors should address before a possible publication of their work. Thus, I asked major revisions for this work.
Major comments
- The manuscript shows several typos. See for example “phytopankton” at line 8. Please consider a strong editing of text.
- There is a lack in explaining the purpose and the methodology followed in the study.
- Along the text the Authors mention the “primary production”. Do you mean “net primary production” (gross pp minus respiration) or the gross pp? please specify since they are different things that can lead to a different interpretation of your outcomes.
- There is a lack in the manuscript in the description of the modeling tool and forcing adopted in the simulations. For example, I do not understand why using such old values for wind forcing (Trenberth; 1989) since you run long term simulations covered several centuries, eventually covered by CMIP models.
- I’m puzzled about the fact that chl-a is not transported by ocean currents. Is it your model result? Is it an assumption of the analysis or a constrain in your numerical simulations? Please explain better. Phytoplankton (and chl-a) could be considered a passive tracer (as it is in many coupled models). Thus, in marine environment it can transported by advection or diffusion processes.
- The explanation provided by the Authors related to the increase in the vertical velocity (see also my comment on Appendix D) looks to me weird (maybe I’m missing something in their reasoning and so please help me to understand). If someone warms/cools the upper/bottom of the water column I would expect an increase of the vertical stratification and thus lower vertical transport and vertical mixing (as predicted by several studies discussing the future climate projections). The Authors talk about an increase in the vertical velocity because of the difference in temperature. I do not think this is correct. Please explain better this point.
Specific comments
Line 2: I would say influence not impact.
Line 8-12: Please explain better how the light absorption would weaken the carbon pump.
Line 16-19: This part is not very clear and should go at the end of the introduction as purpose of the work.
Line 25-35. There is a dependence of the projections for the net primary production on the parametrization adopted and how they are influenced by the temperature. In the Mediterranean sea there is an extensive review on this topic by Richon et al., 2019 and Reale et al., 2022. Please consider to add a sentence about.
Line 33-35: how? Please explain
Line 38 and line 55: On what? Please explain
Line 68 e Fig.2: The RCP scenarios do not “describe possible future climate system” but hypothetical temporal evolution of greenhouse gases emission in the atmosphere. Please correct this statement and the caption.
Line 81-82-89: What do you mean with “association”, “intermediate” and “related to climate processes”?
Figure: is there a coupler managing the exchange of fields (arrows) among the components of the modeling tools? Please specify
Line 101: I see that the purpose of the work is not to validate your simulations but please add some quantitative information to your discussion (under/over estimation is too generic).
Line 123: Why do not you consider Nitrate? Please specify.
Line 145: DIC as nutrient sounds to me weird since it involves different chemical species (CO2aq, HCO3, CO3 and so on). Could you please add some references or explain better this point?
Line 169: What are the criteria to choose the sixth layer as limit for light?
Line 196: Why just one year (2050) instead of the entire period?
Line 200: It would be nice to see the spatial distribution of these differences that could explain the differences among the different scenarios instead of a single value that is meaningless
Line 226: I do not think that chl-a is a climate variable
Line 229: How? Please explain
Line 230-235: see my major point 6
Line 266: what do you mean with underestimation of the oceanic circulation?
Line 269: What do you mean “The missing….model setup”. Please explain
Line 274-276: Please rephrase.
Line 342-342: Not clear. Please rephrase
Appendix D: It would be better to have a map to show the global distribution of this quantity. Maybe the results in the Chilean area could be associated with La Nina/El nino pattern. Did you check that?
Citation: https://doi.org/10.5194/egusphere-2023-921-RC1 -
AC2: 'Reply on RC1', Rémy Asselot, 12 Oct 2023
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2023/egusphere-2023-921/egusphere-2023-921-AC2-supplement.pdf
-
RC2: 'Comment on egusphere-2023-921', Anonymous Referee #2, 26 Jul 2023
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2023/egusphere-2023-921/egusphere-2023-921-RC2-supplement.pdf
-
AC1: 'Reply on RC2', Rémy Asselot, 12 Oct 2023
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2023/egusphere-2023-921/egusphere-2023-921-AC1-supplement.pdf
-
AC1: 'Reply on RC2', Rémy Asselot, 12 Oct 2023
Interactive discussion
Status: closed
-
RC1: 'Comment on egusphere-2023-921', Anonymous Referee #1, 30 Jun 2023
Review of the paper “A missing link in the carbon cycle: phytoplankton light absorption under RCP scenarios”
General comments
I have completed the review of the manuscript egusphere-2023-921. The manuscript shows some interesting results, somehow scientifically soundings. At the same time, I found that the manuscript has several issues that the Authors should address before a possible publication of their work. Thus, I asked major revisions for this work.
Major comments
- The manuscript shows several typos. See for example “phytopankton” at line 8. Please consider a strong editing of text.
- There is a lack in explaining the purpose and the methodology followed in the study.
- Along the text the Authors mention the “primary production”. Do you mean “net primary production” (gross pp minus respiration) or the gross pp? please specify since they are different things that can lead to a different interpretation of your outcomes.
- There is a lack in the manuscript in the description of the modeling tool and forcing adopted in the simulations. For example, I do not understand why using such old values for wind forcing (Trenberth; 1989) since you run long term simulations covered several centuries, eventually covered by CMIP models.
- I’m puzzled about the fact that chl-a is not transported by ocean currents. Is it your model result? Is it an assumption of the analysis or a constrain in your numerical simulations? Please explain better. Phytoplankton (and chl-a) could be considered a passive tracer (as it is in many coupled models). Thus, in marine environment it can transported by advection or diffusion processes.
- The explanation provided by the Authors related to the increase in the vertical velocity (see also my comment on Appendix D) looks to me weird (maybe I’m missing something in their reasoning and so please help me to understand). If someone warms/cools the upper/bottom of the water column I would expect an increase of the vertical stratification and thus lower vertical transport and vertical mixing (as predicted by several studies discussing the future climate projections). The Authors talk about an increase in the vertical velocity because of the difference in temperature. I do not think this is correct. Please explain better this point.
Specific comments
Line 2: I would say influence not impact.
Line 8-12: Please explain better how the light absorption would weaken the carbon pump.
Line 16-19: This part is not very clear and should go at the end of the introduction as purpose of the work.
Line 25-35. There is a dependence of the projections for the net primary production on the parametrization adopted and how they are influenced by the temperature. In the Mediterranean sea there is an extensive review on this topic by Richon et al., 2019 and Reale et al., 2022. Please consider to add a sentence about.
Line 33-35: how? Please explain
Line 38 and line 55: On what? Please explain
Line 68 e Fig.2: The RCP scenarios do not “describe possible future climate system” but hypothetical temporal evolution of greenhouse gases emission in the atmosphere. Please correct this statement and the caption.
Line 81-82-89: What do you mean with “association”, “intermediate” and “related to climate processes”?
Figure: is there a coupler managing the exchange of fields (arrows) among the components of the modeling tools? Please specify
Line 101: I see that the purpose of the work is not to validate your simulations but please add some quantitative information to your discussion (under/over estimation is too generic).
Line 123: Why do not you consider Nitrate? Please specify.
Line 145: DIC as nutrient sounds to me weird since it involves different chemical species (CO2aq, HCO3, CO3 and so on). Could you please add some references or explain better this point?
Line 169: What are the criteria to choose the sixth layer as limit for light?
Line 196: Why just one year (2050) instead of the entire period?
Line 200: It would be nice to see the spatial distribution of these differences that could explain the differences among the different scenarios instead of a single value that is meaningless
Line 226: I do not think that chl-a is a climate variable
Line 229: How? Please explain
Line 230-235: see my major point 6
Line 266: what do you mean with underestimation of the oceanic circulation?
Line 269: What do you mean “The missing….model setup”. Please explain
Line 274-276: Please rephrase.
Line 342-342: Not clear. Please rephrase
Appendix D: It would be better to have a map to show the global distribution of this quantity. Maybe the results in the Chilean area could be associated with La Nina/El nino pattern. Did you check that?
Citation: https://doi.org/10.5194/egusphere-2023-921-RC1 -
AC2: 'Reply on RC1', Rémy Asselot, 12 Oct 2023
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2023/egusphere-2023-921/egusphere-2023-921-AC2-supplement.pdf
-
RC2: 'Comment on egusphere-2023-921', Anonymous Referee #2, 26 Jul 2023
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2023/egusphere-2023-921/egusphere-2023-921-RC2-supplement.pdf
-
AC1: 'Reply on RC2', Rémy Asselot, 12 Oct 2023
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2023/egusphere-2023-921/egusphere-2023-921-AC1-supplement.pdf
-
AC1: 'Reply on RC2', Rémy Asselot, 12 Oct 2023
Peer review completion
Journal article(s) based on this preprint
Viewed
| HTML | XML | Total | BibTeX | EndNote | |
|---|---|---|---|---|---|
| 333 | 149 | 39 | 521 | 30 | 26 |
- HTML: 333
- PDF: 149
- XML: 39
- Total: 521
- BibTeX: 30
- EndNote: 26
Viewed (geographical distribution)
| Country | # | Views | % |
|---|
| Total: | 0 |
| HTML: | 0 |
| PDF: | 0 |
| XML: | 0 |
- 1
Rémy Asselot
Frank Lunkeit
Philip Holden
Inga Hense
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
- Preprint
(3570 KB) - Metadata XML