Mid-Holocene ITCZ migration: impacts on Hadley cell dynamics and terrestrial hydroclimate

Bian, Jianpu; Räisänen, Jouni; Seppä, Heikki

doi:https://doi.org/10.5194/egusphere-2024-3673

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https://doi.org/10.5194/egusphere-2024-3673

Preprints

13 Dec 2024

| 13 Dec 2024

Mid-Holocene ITCZ migration: impacts on Hadley cell dynamics and terrestrial hydroclimate

Jianpu Bian, Jouni Räisänen, and Heikki Seppä

Abstract. This study investigates the multiple changes of the Hadley cell (HC) in response to the northward migration of Intertropical Convergence Zone (ITCZ) and their combined influence on terrestrial hydrological cycle during the mid-Holocene, using simulations from the PMIP4-CMIP6 archive. Our results show that orbital forcing increased radiative heating in the Northern Hemisphere, shifting the ITCZ northward by 0.2° and 0.3° as a multi-model mean using two different precipitation metrics, which is consistent with proxy evidence of a slight northward shift during the mid-Holocene. This migration primarily drives the northward movement of the inner HC edge, resulting in a contracted and weakened northern HC, while the southern HC expands and intensifies. Specifically, the northern HC width contracted by 1.1° and 0.5°, with strength reductions of 3.7 % and 4.1 %, while the southern HC expanded by 1.2° and 0.6° and strengthened by 2.9 % and 1.8 %, according to the two stream- function metrics. Enhanced moisture eddy fluxes are a major contributor to increased terrestrial precipitation in the Northern Hemisphere, particularly in monsoonal regions, while Southern Hemisphere precipitation decreased due to evaporation and dynamic terms. Moist static energy (MSE) budget analysis reveals that stronger rising motion significantly promotes vertical MSE advection over land in the Northern Hemisphere, enhancing moist convection and precipitation, while reduced rising motion weakens vertical MSE advection in the Southern Hemisphere, suppressing moist convection and precipitation. Regionally, ITCZ migration and associated HC changes alter climate patterns with reduced Northern Hemisphere terrestrial aridity and drylands contraction, while the Southern Hemisphere has enhanced aridity and drylands expansion. Multiple proxies support these findings, indicating wetter Northern Hemisphere conditions and a drier Southern Hemisphere, although inconsistencies remain in Australia’s aridity pattern. Our results highlight the complex interactions among ITCZ migration, Hadley cell dynamics, global hydrological cycle, and terrestrial aridity during the mid-Holocene.

Received: 26 Nov 2024 – Discussion started: 13 Dec 2024

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Journal article(s) based on this preprint

14 Jul 2025

Mid-Holocene Intertropical Convergence Zone migration: connection with Hadley cell dynamics and impacts on terrestrial hydroclimate

Jianpu Bian, Jouni Räisänen, and Heikki Seppä

Clim. Past, 21, 1209–1233, https://doi.org/10.5194/cp-21-1209-2025,https://doi.org/10.5194/cp-21-1209-2025, 2025

Short summary

Jianpu Bian, Jouni Räisänen, and Heikki Seppä

Interactive discussion

Status: closed

RC1:
'Comment on egusphere-2024-3673', Anonymous Referee #1, 14 Jan 2025

Review of “Mid-Holocene ITCZ migration: impacts on Hadley cell dynamics and terrestrial hydroclimate” by Jianpu Bian, Jouni Räisänen, and Heikki Seppä.
This paper presents an analysis of the PMIP4 mid-Holocene (MH) simulations using a set of metrics to quantify changes in the ITCZ and Hadley Cell edge and extent. The paper also includes a broader discussion of the aridity and atmospheric circulation changes in the MH simulations and comparison with available proxy records. The paper is generally clearly written and describes the experiments and results thoroughly. There is a detailed comparison of different methods to define the Hadley Cell edge and strength and the MSE budget. The results will contribute to understanding of MH climate changes in climate model simulations. Overall the paper is a valuable contribution, presenting new and interesting results. I support publication subject to revisions addressing comments outlined below.
General comments:
My main concern is the focus on the annual mean changes. The key changes in the mid-Holocene are associated with seasonal shifts in insolation due to altered timing of perihelion, so that the seasonal mean anomalies will be larger and easier to interpret. Annual changes may involve offsetting summer and winter changes – for example, see Figure 6 of Brierley et al. (2020) mid-Holocene PMIP paper, where many changes in DJF and JJA precipitation are opposite in sign.
I suggest including analysis of the seasonal changes in addition to annual mean. As there is a clear seasonal change in insolation due to orbital changes, the resulting changes in atmospheric circulation and precipitation will be easier to interpret at seasonal time scales, e.g. for the summer monsoons in each hemisphere. It is also possible that MH minus PI Hadley cell changes will differ in Northern Hemisphere (NH) versus Southern Hemisphere (SH) winter given the strong seasonal orbital forcing anomalies.
There is also some apparent confusion regarding the annual mean insolation change due to orbital differences at 6ka relative to pre-industrial. For example, in the abstract it is stated that “orbital forcing increased radiative heating in the Northern Hemisphere” and at line 318, the paper mentions “increased solar radiation in the Northern Hemisphere driven by orbital forcing”. While this is true for the NH spring/summer, the paper presents annual mean results only.
Obliquity changes at 6ka cause annual mean heating at high latitudes versus tropics in both hemispheres, whereas precession of perihelion causes anomalies in seasonal heating in both NH and SH which cancel out for the annual average. It is therefore confusing to present annual mean results but refer to orbital increases in NH insolation and heating.
There may be an annual mean increase in NH temperature in some models – but there is no figure showing this, and it is not evident in the PMIP4 ensemble mean temperature as shown in Brierley et al. (2020) Figure 1: the NH is mainly cooler except for high northern latitudes. Given this, I cannot see how the results show “increased radiative heating in the Northern Hemisphere” for annual averages. Please clarify this.
Specific comments:
Abstract, line 16: Clarify that the wetter NH and drier SH is mainly over land. (Note that this also may vary when considering seasonal changes – see General Comment above).
Line 59: Use of bilinear interpolation – it is normally better to use conservative regridding for fields such as precipitation and mass streamfunction. Please confirm the choice of regridding does not significantly alter the results.
Line 130: As discussed in General Comment above, there would be some benefit to also including seasonal mean results, e.g. for DJF and JJA seasons.
Line 131: Make clear that you are comparing the CMIP6-PMIP4 PI simulations with observations here. This should also be stated in the caption for Figure 1.
Line 135: According to the legend, Figure 1c shows the multi-model median not the mean – if you are using this to argue that the multi-model mean should be used elsewhere, I suggest modify Figure 1c to show the multi-model mean not median.
Line 159-161: Note that some of the discussion in Reeves et al. (2013) of changes towards wetter/drier conditions is expressed relative to the early Holocene, not to the late Holocene or pre-industrial. It may also be worth including comparison with Petherick et al. (2013) paper about temperate Australian records:
Petherick, L., Bostock, H., Cohen, T. J., Fitzsimmons, K., Tibby, J., Fletcher, M. S., ... & Dosseto, A. (2013). Climatic records over the past 30 ka from temperate Australia–a synthesis from the Oz-INTIMATE workgroup. Quaternary Science Reviews, 74, 58-77.
Figure 1: (c) Caption should cite Adler et al. 2003 for GPCP. (f) Are different dot sizes significant? Explain in caption if so. I also suggest reversing the colour scheme as red is usually dry and blue is usually wet for precipitation anomaly plots.
Table 1: Table caption should be expanded to define all abbreviations used in table and distinguish between Method I and Method II – remind the reader how these differ (using streamfunction values at 500 hPa versus average over 200-900 hPa).
Line 167-168: The methods used to define the ITCZ location need to be briefly described in the Methods section, not just in the Supplement.
Figure 2: What are the red and blue line colours in (a) and (b) panels? Define in caption.
For panel c, either include full names (inner edge, southern edge etc.) or define the abbreviations in the figure caption: “southern edge of Hadley Cell (Edge_S)” etc.
Figure 3: Please either label the models on the x-axis of figures or ensure the order of models in the legend matches the order in the plots. Otherwise, any colour-blind reader will not be able to interpret this figure.
Line 196: Previous studies of global warming – clarify whether these are model or observational studies and whether focused on historical period or future projections or both.
Figure 4 a-f: It is difficult to distinguish the lines based on the colour alone. I suggest using different dot and dash patterns as well as different colours.
Section 4, paragraphs 2 and 3: In this section, you should also compare your results with D’Agostino et al. (2019) and (2020) studies on NH and SH monsoon changes in PMIP mid-Holocene simulations. These studies make use of MSE budget analysis so they are highly relevant. You may also want to mention these studies in the introduction in the section discussing the MH monsoon changes (lines 35-40).
D'Agostino, R., Bader, J., Bordoni, S., Ferreira, D., & Jungclaus, J. (2019). Northern Hemisphere monsoon response to mid‐Holocene orbital forcing and greenhouse gas‐induced global warming. Geophysical Research Letters, 46(3), 1591-1601.
D’Agostino, R., Brown, J. R., Moise, A., Nguyen, H., Dias, P. L. S., & Jungclaus, J. (2020). Contrasting southern hemisphere monsoon response: MidHolocene orbital forcing versus future greenhouse gas–induced global warming. Journal of Climate, 33(22), 9595-9613.
References:
Line 472: Publisher details missing from Nicholson book reference.

Citation: https://doi.org/10.5194/egusphere-2024-3673-RC1
- AC1: 'Reply on RC1', Jianpu Bian, 06 Mar 2025
  
  The point-to-point reply file was uploaded in the form of supplement
  
  Citation: https://doi.org/10.5194/egusphere-2024-3673-AC1
RC2:
'Comment on egusphere-2024-3673', Anonymous Referee #2, 16 Jan 2025
terrestrial hydroclimate”
By Bian et al.
Overview:
This study investigates the effects of the northward migration of the Intertropical Convergence Zone (ITCZ) on the Hadley cell and global hydrological patterns during the mid-Holocene, around 6,000 years ago. This period, known as the "Green Sahara," experienced significant climatic changes, with increased precipitation in typically arid regions. The study utilizes simulations from the PMIP4-CMIP6 archive to analyze shifts in the ITCZ and changes in Hadley cell characteristics, revealing a contraction and weakening of the northern Hadley cell and an expansion and strengthening of the southern cell. These dynamics contributed to wetter conditions in the Northern Hemisphere and drier conditions in the Southern Hemisphere. This study underscores the complex interactions among orbital forcing, ITCZ migration, Hadley cell dynamics, and terrestrial aridity during the mid-Holocene. While climate models provide valuable insights, recognizing their limitations and the uncertainties in simulations and reconstructions is crucial. Continued research and model development are necessary to enhance our understanding of past climate changes and their implications for future climate scenarios. In general, I find the paper is well written and could be published after revision.
My main concerns:
What are the new findings of the study? The change of Hadley cell, ITCZ, and precipitation patterns in the Mid-Holocene were well reported in previous studies, and especially the Mid-Holocene ITCZ migration and precipitation patterns have been reported in the authors’ previous published paper of Bian et al. (2024). Maybe the moisture static energy budget could be interesting to understand the dynamics of changes in Hadley cells. The author should clearly state what is new in the introduction.

Bian, J., Räisänen, J. Mid-holocene changes in the global ITCZ: meridional structure and land–sea rainfall differences. Clim Dyn 62, 10683–10701 (2024). https://doi.org/10.1007/s00382-024-07470-1
Why is the ITCZ migration leading to the change of Hadley Cells? It could also be the Hadley cell leads the ITCZ migration. Where I can see the evidence of ITCZ migration leading to the changes in Hadley Cells?

The asymmetry responses of Hadley Cells in the Northern Hemisphere and Southern Hemisphere are interesting. It would be great if the authors could show a more dynamic understanding of the asymmetry responses, especially more focus on the moisture static energy budget in the revision.

In most of the analysis, this study uses multiple model ensemble mean, I am wondering whether there are any models and realizations that could better capture the reconstructed precipitation patterns, or how different the simulated precipitation patterns change among different models. For example, does a model with a larger Hadley Cell northward shifting and intensifying show more precipitation increases in the Northern Hemisphere extropical monsoon regions? I think some more discussions on the model uncertainties might further help to understand the dynamic links between the large-scale circulation change and precipitation patterns.
Citation: https://doi.org/10.5194/egusphere-2024-3673-RC2
- AC2: 'Reply on RC2', Jianpu Bian, 06 Mar 2025
  
  The point-to-point reply file was uploaded in the form of supplement
  
  Citation: https://doi.org/10.5194/egusphere-2024-3673-AC2

Interactive discussion

Status: closed

RC1:
'Comment on egusphere-2024-3673', Anonymous Referee #1, 14 Jan 2025

Review of “Mid-Holocene ITCZ migration: impacts on Hadley cell dynamics and terrestrial hydroclimate” by Jianpu Bian, Jouni Räisänen, and Heikki Seppä.
This paper presents an analysis of the PMIP4 mid-Holocene (MH) simulations using a set of metrics to quantify changes in the ITCZ and Hadley Cell edge and extent. The paper also includes a broader discussion of the aridity and atmospheric circulation changes in the MH simulations and comparison with available proxy records. The paper is generally clearly written and describes the experiments and results thoroughly. There is a detailed comparison of different methods to define the Hadley Cell edge and strength and the MSE budget. The results will contribute to understanding of MH climate changes in climate model simulations. Overall the paper is a valuable contribution, presenting new and interesting results. I support publication subject to revisions addressing comments outlined below.
General comments:
My main concern is the focus on the annual mean changes. The key changes in the mid-Holocene are associated with seasonal shifts in insolation due to altered timing of perihelion, so that the seasonal mean anomalies will be larger and easier to interpret. Annual changes may involve offsetting summer and winter changes – for example, see Figure 6 of Brierley et al. (2020) mid-Holocene PMIP paper, where many changes in DJF and JJA precipitation are opposite in sign.
I suggest including analysis of the seasonal changes in addition to annual mean. As there is a clear seasonal change in insolation due to orbital changes, the resulting changes in atmospheric circulation and precipitation will be easier to interpret at seasonal time scales, e.g. for the summer monsoons in each hemisphere. It is also possible that MH minus PI Hadley cell changes will differ in Northern Hemisphere (NH) versus Southern Hemisphere (SH) winter given the strong seasonal orbital forcing anomalies.
There is also some apparent confusion regarding the annual mean insolation change due to orbital differences at 6ka relative to pre-industrial. For example, in the abstract it is stated that “orbital forcing increased radiative heating in the Northern Hemisphere” and at line 318, the paper mentions “increased solar radiation in the Northern Hemisphere driven by orbital forcing”. While this is true for the NH spring/summer, the paper presents annual mean results only.
Obliquity changes at 6ka cause annual mean heating at high latitudes versus tropics in both hemispheres, whereas precession of perihelion causes anomalies in seasonal heating in both NH and SH which cancel out for the annual average. It is therefore confusing to present annual mean results but refer to orbital increases in NH insolation and heating.
There may be an annual mean increase in NH temperature in some models – but there is no figure showing this, and it is not evident in the PMIP4 ensemble mean temperature as shown in Brierley et al. (2020) Figure 1: the NH is mainly cooler except for high northern latitudes. Given this, I cannot see how the results show “increased radiative heating in the Northern Hemisphere” for annual averages. Please clarify this.
Specific comments:
Abstract, line 16: Clarify that the wetter NH and drier SH is mainly over land. (Note that this also may vary when considering seasonal changes – see General Comment above).
Line 59: Use of bilinear interpolation – it is normally better to use conservative regridding for fields such as precipitation and mass streamfunction. Please confirm the choice of regridding does not significantly alter the results.
Line 130: As discussed in General Comment above, there would be some benefit to also including seasonal mean results, e.g. for DJF and JJA seasons.
Line 131: Make clear that you are comparing the CMIP6-PMIP4 PI simulations with observations here. This should also be stated in the caption for Figure 1.
Line 135: According to the legend, Figure 1c shows the multi-model median not the mean – if you are using this to argue that the multi-model mean should be used elsewhere, I suggest modify Figure 1c to show the multi-model mean not median.
Line 159-161: Note that some of the discussion in Reeves et al. (2013) of changes towards wetter/drier conditions is expressed relative to the early Holocene, not to the late Holocene or pre-industrial. It may also be worth including comparison with Petherick et al. (2013) paper about temperate Australian records:
Petherick, L., Bostock, H., Cohen, T. J., Fitzsimmons, K., Tibby, J., Fletcher, M. S., ... & Dosseto, A. (2013). Climatic records over the past 30 ka from temperate Australia–a synthesis from the Oz-INTIMATE workgroup. Quaternary Science Reviews, 74, 58-77.
Figure 1: (c) Caption should cite Adler et al. 2003 for GPCP. (f) Are different dot sizes significant? Explain in caption if so. I also suggest reversing the colour scheme as red is usually dry and blue is usually wet for precipitation anomaly plots.
Table 1: Table caption should be expanded to define all abbreviations used in table and distinguish between Method I and Method II – remind the reader how these differ (using streamfunction values at 500 hPa versus average over 200-900 hPa).
Line 167-168: The methods used to define the ITCZ location need to be briefly described in the Methods section, not just in the Supplement.
Figure 2: What are the red and blue line colours in (a) and (b) panels? Define in caption.
For panel c, either include full names (inner edge, southern edge etc.) or define the abbreviations in the figure caption: “southern edge of Hadley Cell (Edge_S)” etc.
Figure 3: Please either label the models on the x-axis of figures or ensure the order of models in the legend matches the order in the plots. Otherwise, any colour-blind reader will not be able to interpret this figure.
Line 196: Previous studies of global warming – clarify whether these are model or observational studies and whether focused on historical period or future projections or both.
Figure 4 a-f: It is difficult to distinguish the lines based on the colour alone. I suggest using different dot and dash patterns as well as different colours.
Section 4, paragraphs 2 and 3: In this section, you should also compare your results with D’Agostino et al. (2019) and (2020) studies on NH and SH monsoon changes in PMIP mid-Holocene simulations. These studies make use of MSE budget analysis so they are highly relevant. You may also want to mention these studies in the introduction in the section discussing the MH monsoon changes (lines 35-40).
D'Agostino, R., Bader, J., Bordoni, S., Ferreira, D., & Jungclaus, J. (2019). Northern Hemisphere monsoon response to mid‐Holocene orbital forcing and greenhouse gas‐induced global warming. Geophysical Research Letters, 46(3), 1591-1601.
D’Agostino, R., Brown, J. R., Moise, A., Nguyen, H., Dias, P. L. S., & Jungclaus, J. (2020). Contrasting southern hemisphere monsoon response: MidHolocene orbital forcing versus future greenhouse gas–induced global warming. Journal of Climate, 33(22), 9595-9613.
References:
Line 472: Publisher details missing from Nicholson book reference.

Citation: https://doi.org/10.5194/egusphere-2024-3673-RC1
- AC1: 'Reply on RC1', Jianpu Bian, 06 Mar 2025
  
  The point-to-point reply file was uploaded in the form of supplement
  
  Citation: https://doi.org/10.5194/egusphere-2024-3673-AC1
RC2:
'Comment on egusphere-2024-3673', Anonymous Referee #2, 16 Jan 2025
terrestrial hydroclimate”
By Bian et al.
Overview:
This study investigates the effects of the northward migration of the Intertropical Convergence Zone (ITCZ) on the Hadley cell and global hydrological patterns during the mid-Holocene, around 6,000 years ago. This period, known as the "Green Sahara," experienced significant climatic changes, with increased precipitation in typically arid regions. The study utilizes simulations from the PMIP4-CMIP6 archive to analyze shifts in the ITCZ and changes in Hadley cell characteristics, revealing a contraction and weakening of the northern Hadley cell and an expansion and strengthening of the southern cell. These dynamics contributed to wetter conditions in the Northern Hemisphere and drier conditions in the Southern Hemisphere. This study underscores the complex interactions among orbital forcing, ITCZ migration, Hadley cell dynamics, and terrestrial aridity during the mid-Holocene. While climate models provide valuable insights, recognizing their limitations and the uncertainties in simulations and reconstructions is crucial. Continued research and model development are necessary to enhance our understanding of past climate changes and their implications for future climate scenarios. In general, I find the paper is well written and could be published after revision.
My main concerns:
What are the new findings of the study? The change of Hadley cell, ITCZ, and precipitation patterns in the Mid-Holocene were well reported in previous studies, and especially the Mid-Holocene ITCZ migration and precipitation patterns have been reported in the authors’ previous published paper of Bian et al. (2024). Maybe the moisture static energy budget could be interesting to understand the dynamics of changes in Hadley cells. The author should clearly state what is new in the introduction.

Bian, J., Räisänen, J. Mid-holocene changes in the global ITCZ: meridional structure and land–sea rainfall differences. Clim Dyn 62, 10683–10701 (2024). https://doi.org/10.1007/s00382-024-07470-1
Why is the ITCZ migration leading to the change of Hadley Cells? It could also be the Hadley cell leads the ITCZ migration. Where I can see the evidence of ITCZ migration leading to the changes in Hadley Cells?

The asymmetry responses of Hadley Cells in the Northern Hemisphere and Southern Hemisphere are interesting. It would be great if the authors could show a more dynamic understanding of the asymmetry responses, especially more focus on the moisture static energy budget in the revision.

In most of the analysis, this study uses multiple model ensemble mean, I am wondering whether there are any models and realizations that could better capture the reconstructed precipitation patterns, or how different the simulated precipitation patterns change among different models. For example, does a model with a larger Hadley Cell northward shifting and intensifying show more precipitation increases in the Northern Hemisphere extropical monsoon regions? I think some more discussions on the model uncertainties might further help to understand the dynamic links between the large-scale circulation change and precipitation patterns.
Citation: https://doi.org/10.5194/egusphere-2024-3673-RC2
- AC2: 'Reply on RC2', Jianpu Bian, 06 Mar 2025
  
  The point-to-point reply file was uploaded in the form of supplement
  
  Citation: https://doi.org/10.5194/egusphere-2024-3673-AC2

Peer review completion

AR: Author's response | RR: Referee report | ED: Editor decision | EF: Editorial file upload

ED: Reconsider after major revisions (07 Mar 2025) by Laurie Menviel

AR by Jianpu Bian on behalf of the Authors (08 Mar 2025) Author's response Author's tracked changes Manuscript

ED: Referee Nomination & Report Request started (10 Mar 2025) by Laurie Menviel

RR by Anonymous Referee #2 (11 Apr 2025)

Suggestions for revision or reasons for rejection

Review of “Mid-Holocene ITCZ migration: Connection with Hadley cell dynamics and impacts on terrestrial hydroclimate”
By Bian et al.
I have previously reviewed the manuscript, and the authors have conducted substantial analysis to address the reviewers' concerns and enhance the study's novelty. They have largely revised the manuscript, making the storyline clearer and easier to follow. I find the paper interesting and valuable for publication. However, it still requires some revisions, as some of our concerns have not been fully addressed.
1. A clear knowledge gap needs to be clearly defined at the beginning of the introduction. The current introduction is not efficient at this point. I must say I only capture such a piece of information in the main context of lines 275-279. It would be very helpful if the author could write one or two sentences to address the question “What is new for the present study?”.
2. In the abstract also in the conclusion, the authors have a strong statement of “Orbital forcing during the mid-Holocene does not directly drive the hemispheric asymmetry in annual atmospheric radiation balance.” Why? The orbital forcing initialed all the changes in the solar radiation, and thereafter, drove changes in atmospheric circulation and further enhanced the hemispheric asymmetry in annual atmospheric radiation balance. Could you please make it more specific? What do you mean by “directly drive the hemispheric asymmetry in annual atmospheric radiation balance”? Maybe I just missed some key figures or results in the manuscript.
3. The discussion in the conclusion section of lines 538-556 is very interesting and important. I take the conclusion that “the contributions from transient and stationary eddies are not negligible in mid-Holocene”, as a key new finding of the present study. However, the discussion here only provides reviews on the debate on the importance of eddy fluxes from previous studies. I would suggest the authors add some findings from your results. What do we learn from your analysis in the mid-Holocene? You have done a comprehensive dynamic analysis to draw a conclusion here.
4. Figure 4 requires efforts to improve, and the same for Figure 6. There are busy figures. The colors and marks make the figures difficult to read. In the legend, the change in precipitation is solid red, but it is dash red in the figure, and the change in P-E is solid blue, but it is dash blue in the figure. My suggestions would be to only use different colors for the terms, darker and thick lines for the key information of the figure, and lighter colors for the less important information.

Hide

ED: Publish subject to minor revisions (review by editor) (14 Apr 2025) by Laurie Menviel

AR by Jianpu Bian on behalf of the Authors (17 Apr 2025) Author's response Author's tracked changes Manuscript

ED: Publish subject to technical corrections (27 Apr 2025) by Laurie Menviel

AR by Jianpu Bian on behalf of the Authors (27 Apr 2025) Author's response Manuscript

Journal article(s) based on this preprint

14 Jul 2025

Mid-Holocene Intertropical Convergence Zone migration: connection with Hadley cell dynamics and impacts on terrestrial hydroclimate

Jianpu Bian, Jouni Räisänen, and Heikki Seppä

Clim. Past, 21, 1209–1233, https://doi.org/10.5194/cp-21-1209-2025,https://doi.org/10.5194/cp-21-1209-2025, 2025

Short summary

Jianpu Bian, Jouni Räisänen, and Heikki Seppä

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Jianpu Bian, Jouni Räisänen, and Heikki Seppä

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This research examines the impact of the global ITCZ northward migration on Hadley cell dynamics and terrestrial hydroclimate during the mid-Holocene. Our results reveal that the ITCZ shift caused a contraction and weakening of the northern Hadley cell and an expansion and intensification of the southern cell. These changes led to increased precipitation in the Northern Hemisphere and decreased precipitation in the Southern Hemisphere, altering regional aridity patterns.


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