the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 04 Sep 2026
Holocene hydroclimatic reorganization and prehistoric settlement response in the East Asian summer monsoon transition zone
Abstract. Holocene hydroclimatic changes in the East Asian monsoon region were spatially heterogeneous, but their timing and driving mechanisms within the monsoon transition zone remain insufficiently constrained. Here, we present a multi-proxy biomarker record from Nansi Lake, eastern China, to reconstruct Holocene hydroclimatic variability in this sensitive monsoon transition belt. The record indicates relatively dry conditions during the early Holocene, a pronounced humid interval during the middle Holocene, and generally drier but more variable conditions during the late Holocene. This pattern is broadly consistent with the middle-Holocene moisture maximum recorded in northern China, but contrasts with central-sector records characterized by wetter early and late Holocene conditions and drier mid-Holocene. Beyond this latitudinal contrast, proxy records across the monsoon transition zone reveal a longitudinal hydroclimatic gradient, with peak Holocene humidity generally delayed from west to east. This eastward delay may have been modulated by changes in El Niño activity and regional topographic effects on monsoon moisture transport. Furthermore, comparison with archaeological site distributions suggests that this hydroclimatic reorganization was accompanied by an eastward shift in prehistoric settlement density within the transition zone. These findings highlight the spatial complexity of Holocene hydroclimatic change in monsoon transition regions and provide a long-term perspective on landscape–human interactions under changing moisture regimes.
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CC1: 'Comment on egusphere-2026-4480', Giacomo Medici, 18 Sep 2026
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AC1: 'Reply on CC1', Can Zhang, 31 Oct 2026
CC1: 'Comment on egusphere-2026-4480', Giacomo Medici.
General comments
Very good research on the past climate. Please, follow my specific comments to improve your manuscript.
Response: We thank the commentator for the encouraging assessment and constructive suggestions. We have broadened the context, clarified the lake and groundwater setting, separated Results from Discussion, and revised the figures and captions. Items that require original analytical or graphical metadata are identified explicitly below.
Specific comments
Lines 52-107. Enlarge the views of this good papers beyond the Holocene climate and speleothems.
Response: Thank you for this suggestion. We have added a longer glacial–interglacial perspective using the loess rainfall record of Beck et al. (2018), and a short example of pre-Quaternary paleokarst research (Medici et al., 2026). We also explain the complementary information provided by speleothems, lakes, peat, and loess.
Lines 60-61. Measurements of oxygen-isotope records on speleothems. Please, insert recent literature on this topic:
- Dayem, K.E., Molnar, P., Battisti, D.S., Roe, G.H. 2010. Lessons learned from oxygen isotopes in modern precipitation applied to interpretation of speleothem records of paleoclimate from eastern Asia. Earth and Planetary Science Letters, 295(1-2), 219-230.
- Medici, G., Marianelli, D., Cornacchia, I., Gori, F., Brandano, M. 2026. Multi-disciplinary approach to paleokarst occurrence in the Eocene–Oligocene succession of the Apulia Carbonate Platform (Salento, Italy). Facies, 72(2), 17.
Response: Thank. We verified both publications and added them. Dayem et al. (2010) is used to emphasize that speleothem δ18O can reflect moisture source, transport pathway, seasonality, and upstream rainout rather than simply local precipitation amount. Medici et al. (2026) is cited in the broader context of karst/paleokarst archives and meteoric-water/groundwater processes over longer geological timescales.
Line 101-107. Very good to specify general goal, and specific objectives at the end of the introduction.
Response: Thank you for this positive comment.
Line 112. “hydrologically connected”. Please, provide more information on the flow in the sub-surface and the hydraulic connections between the lakes.
Response: Thank you for your helpful suggestion. We apologize that our previous wording may have caused some ambiguity. We have clarified that the four modern sub-lakes form a connected surface-water system, and added regional groundwater information from Yan et al. (2025). We separately summarize the regional shallow-groundwater setting and note that local lake–groundwater exchange can occur along permeable basin margins.
Line 112. Provide information on the lithology of the aquifer.
Response: Thank you for this useful suggestion. Following the reviewer’s suggestion, we added a concise description of the regional aquifer lithology. Shallow groundwater is mainly hosted in Quaternary porous silt–sand–gravel sediments, while karst/fracture aquifers occur in surrounding carbonate-bearing uplands.
Lines 112-123. Provide information on the nature of the lake sediments.
Response: Thank you for this comment. We added a lithological summary based directly on the core description and Figure 2b. The sequence is dominated by sandy silt, silt, and clayey silt, with systematic color changes down-core.
Lines 120-123. What about evolution of Air Temperature and Precipitation over time?
Response: Thank you for suggestion. We therefore added instrumental evidence showing significant warming in annual temperature from 1960 to present, an abrupt annual-mean temperature increases around 1985, and no significant long-term trend in annual precipitation. We also added the rainfall analysis showing strong decadal variability and step changes around 1974 and 2002.
Line 174-359. Large mixing between results and interpretation.
Response: Thank you for this important structural suggestion. We have separated the descriptive observations from interpretation. Section 3 now presents lithology and chronology, n-alkane distributions and index patterns. Proxy meaning, hydrological interpretation, mechanisms and human influences are addressed in Section 4.
Line 359. What about inserting a separate discussion?
Response: We sincerely thank the reviewer for this helpful suggestion. We agree that the previous manuscript mixed the presentation of results with their interpretation. Accordingly, we have reorganized the manuscript by separating the Results and Discussion sections.
Figures and tables
Figure 1. Increase graphic resolution. Coordinates are difficult to read.
Response: We revised Figure 1 by separating and vertically stacking the two map panels at substantially larger display size.
Figure 2. Graph Depth vs 210Pbx too small. I suggest to create a separate figure.
Response: Thank you for this practical suggestion. The radionuclide inset has been removed from the age–depth figure and presented as a separate.
Figure 7. Increase the graphic resolution. The coordinates are difficult to read.
Response: Thank you for this suggestion. The six KDE panels have been rearranged.
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AC1: 'Reply on CC1', Can Zhang, 31 Oct 2026
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RC1: 'Comment on egusphere-2026-4480', Anonymous Referee #1, 20 Sep 2026
This manuscript presents an n-alkane record from a 2.45m sediment core from Nansi Lake, Shandong, reconstructing Holocene hydroclimatic changes in the East Asian summer monsoon transition zone and linking them to spatiotemporal changes in archaeological site density. The topic is of clear scientific significance. The Holocene precipitation pattern in the monsoon transition zone has long been debated, and reliable quantitative or semi-quantitative reconstructions from southwestern Shandong have been lacking; the Nansi Lake record helps fill this spatial gap. The attempt to link hydroclimatic reorganization with the eastward shift in prehistoric settlement density is also novel. The analytical work is generally sound, and the paper is well structured. I therefore recommend minor revision, subject to the authors addressing the following points, particularly the influence of late Holocene human activity on the sedimentary record and a series of detailed issues in the text, figures, and references.
The influence of late Holocene human activity on the sedimentary record requires explicit treatment. This is my main substantive concern. Nansi Lake is located in a densely populated region with a long history of human occupation, and the late Holocene interval in particular is characterized by intensive anthropogenic disturbance. The paper uses n-alkane proxies (Paq, C23/C31, LPTP) to infer effective moisture and lake water depth, and interprets the late Holocene decline and increased variability in these proxies as reflecting drier and less stable hydrological conditions with enhanced terrestrial input. However, this interpretation does not adequately consider the possibility that human activities, rather than, or in addition to climate drove the observed proxy changes. An additional discussion should be added to claim it.
L31–34 (Abstract): The abstract should specify which proxies were used and what they indicate in terms of hydrological and wet-dry changes.
L53: “its”should be changed to “EASM”; “has” should be changed to “have”.
L55: “EASM” should be changed to “East Asia”.
L56: useful.
L62–64: Monsoon circulation indicates monsoon intensity; it would be better to use one consistent term throughout.
L120: Figure 1c is missing from the figure.
L147: “gentle N2” — please clarify or revise.
L148: Was the saponified treatment performed at room temperature? Please specify.
L149–150: “extracted”? “separated” may be more accurate.
L155: “for 60 min?” — please confirm and clarify.
L157: The full name of “LPTP” should be spelled out at first occurrence.
L143–160: Was an internal standard used? Please specify.
L149, 160, 173, 176, 177, 180, 185, etc.: The “n” in “n-alkane” should be italicized. This needs to be corrected throughout the manuscript.
L196–197, 206: Terms such as “early Holocene” and “late Holocene” should be defined chronologically.
Figure 1: Panels 1c and 1d are missing from the figure, although they are mentioned in the caption. The figure and caption are inconsistent.
Figures 4 and 5: The proxies and units need to be clearly labeled. For example, the y-axis for Nansi Lake is the Paq parameter, not lake water depth. For pollen-based precipitation reconstructions, the units are not indicated.
Figure 6: The caption indicates summer precipitation patterns, but the color bar on the right appears to show standardized relative precipitation anomalies. This should be clarified.
Figure 7: The text in the figure is too small to read. Please enlarge it.
Citation: https://doi.org/10.5194/egusphere-2026-4480-RC1 -
AC2: 'Reply on RC1', Can Zhang, 31 Oct 2026
RC1: 'Comment on egusphere-2026-4480', Anonymous Referee #1.
This manuscript presents an n-alkane record from a 2.45m sediment core from Nansi Lake, Shandong, reconstructing Holocene hydroclimatic changes in the East Asian summer monsoon transition zone and linking them to spatiotemporal changes in archaeological site density. The topic is of clear scientific significance. The Holocene precipitation pattern in the monsoon transition zone has long been debated, and reliable quantitative or semi-quantitative reconstructions from southwestern Shandong have been lacking; the Nansi Lake record helps fill this spatial gap. The attempt to link hydroclimatic reorganization with the eastward shift in prehistoric settlement density is also novel. The analytical work is generally sound, and the paper is well structured. I therefore recommend minor revision, subject to the authors addressing the following points, particularly the influence of late Holocene human activity on the sedimentary record and a series of detailed issues in the text, figures, and references.
Response: We thank the referee for the careful assessment and constructive recommendations.
The influence of late Holocene human activity on the sedimentary record requires explicit treatment. This is my main substantive concern. Nansi Lake is located in a densely populated region with a long history of human occupation, and the late Holocene interval in particular is characterized by intensive anthropogenic disturbance. The paper uses n-alkane proxies (Paq, C23/C31, LPTP) to infer effective moisture and lake water depth, and interprets the late Holocene decline and increased variability in these proxies as reflecting drier and less stable hydrological conditions with enhanced terrestrial input. However, this interpretation does not adequately consider the possibility that human activities, rather than, or in addition to climate drove the observed proxy changes. An additional discussion should be added to claim it.
Response: We sincerely thank the reviewer for raising this important point. We agree that the previous version placed too much emphasis on the hydroclimatic interpretation of the late-Holocene changes in the n-alkane proxies and did not sufficiently consider the potential influence of human activities. We have therefore added a specific discussion in Section 4.1 and incorporated two additional references (Lin et al., 2024; Zhang et al., 2025) to support this interpretation. Recent paleolimnological evidence from Nansi Lake shows that hydrological regulation, water diversion, and pollution substantially altered aquatic macrophyte communities, including prolonged declines in macrophyte abundance (Zhang et al., 2025). In addition, n-alkane records from Erhai Lake demonstrate that intensified deforestation and agricultural cultivation can enhance catchment soil erosion, increase terrestrial organic-matter input, and reduce the relative contribution of aquatic-plant-derived organic matter (Lin et al., 2024). Accordingly, we now interpret the late-Holocene decline and increased variability in Paq, C23/C31, and LPTP as reflecting the combined effects of hydroclimatic variability and anthropogenic disturbance, rather than as a purely climate-driven signal.
L31–34 (Abstract): The abstract should specify which proxies were used and what they indicate in terms of hydrological and wet-dry changes.
Response: We sincerely thank the reviewer for this helpful suggestion. In response, we have revised the Abstract to explicitly specify the sedimentary n-alkane indices (Paq, C23/C31, and LPTP) and clarify their significance in reflecting changes in organic-matter sources and lake hydrological conditions. We have also refined the description of Holocene wet–dry variations to make the findings clearer and more precise.
L53: “its”should be changed to “EASM”; “has” should be changed to “have”.
Response: We sincerely thank the reviewer for pointing out these errors. We have revised the manuscript accordingly by replacing “its” with “EASM” and “has” with “have”.
L55: “EASM” should be changed to “East Asia”.
Response: We appreciate the reviewer's helpful suggestion. We have revised the manuscript accordingly by replacing “EASM” with “East Asia”.
L56: useful.
Response: We appreciate the reviewer's helpful suggestion. We have revised the wording to “useful” as suggested.
L62–64: Monsoon circulation indicates monsoon intensity; it would be better to use one consistent term throughout.
Response: We appreciate the reviewer's helpful suggestion. We have revised the relevant text to consistently use “monsoon intensity”.
L120: Figure 1c is missing from the figure.
Response: Thanks. We have added the missing panel (c) to Figure 1 and revised the figure accordingly.
L147: “gentle N2”— please clarify or revise.
Response: Thanks. We have revised the description of the lipid extraction procedure to explicitly state that the total lipid extract was concentrated under a stream of nitrogen gas (N₂) before saponification.
L148: Was the saponified treatment performed at room temperature? Please specify.
Response: We appreciate the reviewer's helpful comment. The saponification was performed at room temperature. We have revised Section 2.3 to explicitly specify the reaction temperature.
L149–150: “extracted”? “separated” may be more accurate.
Response: We thank the reviewer for this helpful suggestion. We agree that “separated” is more appropriate in this context and have revised the wording accordingly.
L155: “for 60 min?” — please confirm and clarify.
Response: We thank the reviewer for this comment. We confirm that the final GC oven temperature was maintained at 310 °C for 60 min, consistent with the analytical procedure described by Sun et al. (2023). We have revised Section 2.3 to clarify the temperature program.
L157: The full name of “LPTP” should be spelled out at first occurrence.
Response: We appreciate the reviewer's helpful suggestion. We have added the full name of LPTP at its first occurrence in the manuscript, followed by the abbreviation in parentheses.
L143–160: Was an internal standard used? Please specify.
Response: We thank the reviewer for this important comment. No internal standard was used in our analysis. Instead, an external C16 standard was employed for n-alkane quantification, following the method described by Sun et al. (2023). We have revised Section 2.3 to clarify the quantification procedure.
L149, 160, 173, 176, 177, 180, 185, etc.: The “n” in “n-alkane” should be italicized. This needs to be corrected throughout the manuscript.
Response: We sincerely thank the reviewer for this helpful correction. We have carefully checked the entire manuscript and italicized the “n” in all occurrences of “n-alkane” to ensure consistent formatting throughout the text.
L196–197, 206: Terms such as “early Holocene” and “late Holocene” should be defined chronologically.
Response: We sincerely thank the reviewer for this valuable comment. We have revised the manuscript to explicitly define the chronological boundaries of the early, middle, and late Holocene at their first occurrence and ensured consistent use of these terms throughout the manuscript.
Figure 1: Panels 1c and 1d are missing from the figure, although they are mentioned in the caption. The figure and caption are inconsistent.
Response: We thank the reviewer for this comment. We have added the missing panels (c) to Figure 1 to ensure consistency between the figure and its caption.
Figures 4 and 5: The proxies and units need to be clearly labeled. For example, the y-axis for Nansi Lake is the Paq parameter, not lake water depth. For pollen-based precipitation reconstructions, the units are not indicated.
Response: We thank the reviewer for this comment. We have revised Figures 4 and 5 to clearly label the proxies and their corresponding units.
Figure 6: The caption indicates summer precipitation patterns, but the color bar on the right appears to show standardized relative precipitation anomalies. This should be clarified.
Response: Thanks. We have revised the caption of Figure 6 to clarify that the spatial patterns represent standardized summer precipitation anomalies. We have also specified that the color bar represents Z-scores (dimensionless), with positive and negative values indicating above- and below-average summer precipitation, respectively.
Figure 7: The text in the figure is too small to read. Please enlarge it.
Response: Thanks. We have enlarged the text and labels in Figure 7 to improve readability and ensure that all information is clearly presented.
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AC2: 'Reply on RC1', Can Zhang, 31 Oct 2026
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RC2: 'Comment on egusphere-2026-4480', Anonymous Referee #2, 14 Oct 2026
Comment on EGUSPHERE-2026-4480
Title: Holocene hydroclimatic reorganization and prehistoric settlement response in the East Asian summer monsoon transition zone
Authors: Xiaoshuang Sun, Rui Han, Mengyi Yang, Jinliang Liu, Tianlong Yan, Xin Mao, Can Zhang
This study reconstructs Holocene regional precipitation variability based on organic geochemical proxies from a 2.45-m sediment core collected from Nansi Lake, Shandong Province, China. The results indicate relatively high precipitation during the middle to late Holocene (6000-2500 cal yr BP), in contrast to relatively dry conditions during the early and late Holocene. The authors further compare this record with published Holocene precipitation records from different latitudinal and longitudinal sectors of the East Asian monsoon region. In terms of latitudinal patterns, the precipitation evolution at Nansi Lake is broadly consistent with that of northern China but exhibits an opposite trend to that of the middle and lower reaches of the Yangtze River. In terms of longitudinal patterns, the authors suggest that the timing of peak precipitation progressively shifts from west to east, with earlier peaks in the western part and later peaks in the eastern part of the monsoon marginal zone. Furthermore, by comparing the longitudinal differences in the timing of peak precipitation with the probability density distributions of archaeological sites, the authors propose that the spatial distribution of prehistoric settlements may have been influenced by the eastward progression of peak precipitation and may have exhibited a similar spatiotemporal migration pattern.
Overall, this study provides a valuable Holocene paleoclimate record from the Shandong Peninsula and attempts to explore the potential influence of hydroclimatic changes on prehistoric human activities. However, the manuscript has several substantial shortcomings regarding the formulation of the scientific questions, the reliability of the chronological framework, the interpretation of the mechanisms driving precipitation changes, and the evidence supporting the proposed relationship between precipitation variability and archaeological site distributions. Some of the major conclusions are not adequately supported by the available data. Therefore, I recommend “major revision” before the manuscript can be considered for publication.
General Comments:
- The scientific questions and overall research focus need to be more clearly defined. The authors frame their study around the uncertainties surrounding the evolution of monsoon intensity and its driving mechanisms in the East Asian monsoon marginal zone during the Holocene. However, numerous studies over the past decade have systematically investigated Holocene precipitation variability and its driving mechanisms in this region (e.g., Chen et al., 2015). Consequently, the distinction between the scientific questions addressed in this study and those explored in previous research remains unclear. Furthermore, the observed eastward delay in the timing of peak precipitation across the monsoon marginal zone may be influenced by multiple climatic factors, including westerly circulation, Subtropical High position and typhoon activity, rather than being directly attributable to changes in the East Asian summer monsoon. Framing the study primarily in terms of East Asian summer monsoon evolution may therefore obscure the central scientific questions and make it difficult to distinguish the novel contributions of this work from previous studies. The authors should reconsider the overall research focus, clearly articulate the key scientific questions, and highlight the new insights provided by the Nansi Lake record and its regional comparisons.
- The literature review in the Introduction lacks a sufficiently focused discussion of previous research, and the research rationale needs to be better established. The Introduction primarily emphasizes the spatial heterogeneity of Holocene precipitation across the East Asian monsoon region and provides a relatively broad overview of previous studies. However, the research progress concerning the monsoon marginal zone between central and northern China, particularly its hydroclimatic evolution, longitudinal precipitation gradients, and potential driving mechanisms, is insufficiently discussed. In addition, the manuscript attempts to investigate the relationship between regional hydroclimatic changes and the distribution of prehistoric archaeological sites, yet the Introduction provides little discussion of previous studies, the significance of this research direction, or the outstanding questions that remain unresolved. The authors should place greater emphasis on the study region and the central scientific questions, provide a more systematic review of previous research on Holocene hydroclimatic variability in the monsoon marginal zone and its potential implications for prehistoric human activities, and clearly identify the knowledge gaps that this study aims to address. This would help establish a stronger rationale for the study and clarify its potential contributions.
- The reliability of the chronological framework and the substantial changes in sedimentation rates require further justification. According to the chronological framework established by the authors, approximately 1.4 m of sediment accumulated during the past 2,000 years, whereas only about 1 m accumulated over the preceding 7,000 years (9000-2000 cal yr BP). This indicates a substantial difference in sedimentation rates between the two intervals, which requires further explanation in the context of the depositional environment of the study area. The authors should clarify the possible causes of these differences and discuss how historical changes in regional hydrology, including potential shifts relative to ancient Yellow River, may have affected depositional stability and sedimentary continuity. Furthermore, given the well-developed drainage network, shallow water depth, and potential reservoir effects associated with different dating materials, the accuracy of the current chronological framework remains uncertain. The authors should provide more robust evidence supporting the reliability of the chronology, taking into account the characteristics of dated materials, radiocarbon results, and regional geological and hydrological contexts. They should also assess how chronological uncertainties may influence the reconstructed precipitation history, especially the inferred timing of precipitation maxima.
- The mechanisms driving precipitation variability are insufficiently explored, and some interpretations lack a clear causal link to the reconstructed precipitation patterns. The authors compare variations in El Niño intensity with longitudinal precipitation differences across the monsoon marginal zone. However, the current analysis remains largely descriptive and does not adequately explain how ENSO events may influence the spatial distribution of precipitation through changes in atmospheric circulation and moisture transport. In particular, changes in the position and intensity of the western North Pacific subtropical high (WNPSH) may play an important role in modulating monsoon moisture transport and rain-belt migration, and their potential contribution to the observed longitudinal precipitation differences deserves further consideration. Moreover, the authors should draw on relevant previous studies to investigate the potential mechanisms linking ENSO variability to regional precipitation patterns. Figure 6 compares precipitation patterns during two modern periods, but these differences cannot be attributed to El Niño activity alone. More importantly, modern ENSO events and Holocene ENSO variability may differ in terms of temporal scales and background climatic conditions. Therefore, variations in Holocene ENSO intensity alone may not adequately explain the longitudinal differences in the timing of peak precipitation. In addition, the authors suggest that stronger monsoon circulation allowed moisture to pass rapidly across the eastern plains, whereas subsequent monsoon weakening increased rainfall persistence in the eastern sector. However, the physical basis for these contrasting precipitation responses is not sufficiently explained. Furthermore, some records indicate relatively humid conditions or enhanced hydrological activity in parts of the western and central transition zone during the middle to late Holocene (e.g., Li et al., 2023; Liu et al., 2025; Xiao et al., 2026), despite the overall weakening trend of the East Asian summer monsoon. The authors should consider the potential roles of westerly circulation, the East Asian summer monsoon, the WNPSH, ENSO, and regional topography, and clarify how these factors may interact to produce the observed longitudinal precipitation differences. More importantly, the relative roles of these factors should be discussed in a physically consistent manner, rather than inferring causal relationships solely from similarities or differences between time series.
- The proposed relationship between the eastward shift in peak precipitation and the spatial distribution of archaeological sites is insufficiently supported. The authors attempt to link the progressive eastward delay in peak precipitation across the monsoon marginal zone to the probability density distribution of regional archaeological sites, suggesting that changes in the timing and spatial patterns of peak precipitation may have influenced the distribution of prehistoric settlements. However, Fig. 7 does not reveal a clear or continuous west-to-east migration pattern in the distribution of archaeological sites. Instead, the figure also shows a pronounced north-south shift in their spatial distribution. Therefore, directly linking the eastward shift in peak precipitation to changes in archaeological site density appears somewhat tenuous. Furthermore, the spatial distribution of archaeological sites is influenced not only by climatic and hydrological conditions but also by various other factors, including topography, land resources, agricultural development, and sociocultural dynamics. The authors should critically reassess whether the available evidence is sufficient to support their interpretation and discuss the relationship between precipitation variability and archaeological site distributions more cautiously. In the absence of more direct evidence, the relevant conclusions should be appropriately tempered, and the observed spatiotemporal correspondence between precipitation changes and archaeological site distributions should not be interpreted as evidence of a causal relationship.
Specific Comments:
- There are two part 3.3 (lines 228, 284).
- Line 56: The word “useful” contains a spelling error. Please correct it and remove the unnecessary space.
- The in-text citations are not consistently ordered by publication year or authors’ surnames. Please carefully check and revise the order of all citations throughout the manuscript in accordance with the journal’s formatting requirements.
- The authors should explicitly define the chronological boundaries of the early, middle, and late Holocene. The interval of 6000-2500 cal yr BP should not be broadly classified as the middle Holocene without a clear justification. Please specify the adopted Holocene subdivision scheme and apply it consistently throughout the text and figures.
- Abbreviations and indices such as LPTP and Paq should be fully defined and briefly explained at their first occurrence in the main text to ensure clarity for readers.
- 5: Given the emphasis on longitudinal differences in precipitation variability, I suggest revising the color scheme of the curves. Curves representing the same geographical sector (eastern, central, or western) should use similar color tones to facilitate the visual distinction between regions and improve the readability of the figure.
- The reference Li et al. (2023b) is listed in the reference section but does not appear to have a corresponding citation in the main text. Please check and correct this inconsistency.
- The section titled “Influence of Longitudinal Hydroclimatic Variability on Prehistoric Human Settlement Patterns” should be numbered 3.4.
- The pronounced dry interval around 5000 cal yr BP indicated by the n-alkane record deserves further attention. The authors should discuss this event in greater detail, drawing on other proxy records and regional paleoclimate reconstructions to evaluate its climatic significance and possible driving mechanisms.
Citation: https://doi.org/10.5194/egusphere-2026-4480-RC2 -
AC3: 'Reply on RC2', Can Zhang, 31 Oct 2026
RC2: 'Comment on egusphere-2026-4480', Anonymous Referee #2
This study reconstructs Holocene regional precipitation variability based on organic geochemical proxies from a 2.45-m sediment core collected from Nansi Lake, Shandong Province, China. The results indicate relatively high precipitation during the middle to late Holocene (6000-2500 cal yr BP), in contrast to relatively dry conditions during the early and late Holocene. The authors further compare this record with published Holocene precipitation records from different latitudinal and longitudinal sectors of the East Asian monsoon region. In terms of latitudinal patterns, the precipitation evolution at Nansi Lake is broadly consistent with that of northern China but exhibits an opposite trend to that of the middle and lower reaches of the Yangtze River. In terms of longitudinal patterns, the authors suggest that the timing of peak precipitation progressively shifts from west to east, with earlier peaks in the western part and later peaks in the eastern part of the monsoon marginal zone. Furthermore, by comparing the longitudinal differences in the timing of peak precipitation with the probability density distributions of archaeological sites, the authors propose that the spatial distribution of prehistoric settlements may have been influenced by the eastward progression of peak precipitation and may have exhibited a similar spatiotemporal migration pattern.
Overall, this study provides a valuable Holocene paleoclimate record from the Shandong Peninsula and attempts to explore the potential influence of hydroclimatic changes on prehistoric human activities. However, the manuscript has several substantial shortcomings regarding the formulation of the scientific questions, the reliability of the chronological framework, the interpretation of the mechanisms driving precipitation changes, and the evidence supporting the proposed relationship between precipitation variability and archaeological site distributions. Some of the major conclusions are not adequately supported by the available data. Therefore, I recommend “major revision” before the manuscript can be considered for publication.
Response: We sincerely thank the reviewer for the thorough evaluation of our manuscript and the constructive comments and suggestions. We acknowledge the concerns raised regarding the scientific questions, chronological framework, driving mechanisms, and interpretation of the relationship between hydroclimatic changes and prehistoric settlements. We will carefully address each comment and revise the manuscript accordingly to improve its scientific rigor and clarity.
General Comments:
- The scientific questions and overall research focus need to be more clearly defined. The authors frame their study around the uncertainties surrounding the evolution of monsoon intensity and its driving mechanisms in the East Asian monsoon marginal zone during the Holocene. However, numerous studies over the past decade have systematically investigated Holocene precipitation variability and its driving mechanisms in this region (e.g., Chen et al., 2015). Consequently, the distinction between the scientific questions addressed in this study and those explored in previous research remains unclear. Furthermore, the observed eastward delay in the timing of peak precipitation across the monsoon marginal zone may be influenced by multiple climatic factors, including westerly circulation, Subtropical High position and typhoon activity, rather than being directly attributable to changes in the East Asian summer monsoon. Framing the study primarily in terms of East Asian summer monsoon evolution may therefore obscure the central scientific questions and make it difficult to distinguish the novel contributions of this work from previous studies. The authors should reconsider the overall research focus, clearly articulate the key scientific questions, and highlight the new insights provided by the Nansi Lake record and its regional comparisons.
Response: We sincerely thank the reviewer for this important and constructive comment. We agree that the scientific questions and novel contributions of our study should be more clearly defined. In response, we have revised the Introduction to better distinguish our study from previous research. We now place greater emphasis on the contribution of the Nansi Lake record to understanding regional hydroclimatic variability, particularly the longitudinal differences in the timing of Holocene humid periods across the monsoon transition zone. We also agree that these spatial differences cannot be attributed solely to changes in EASM intensity. Accordingly, we have expanded the discussion of potential driving mechanisms to consider additional atmospheric processes, including changes in the Western Pacific Subtropical High, the midlatitude westerly jet, and tropical cyclone activity. We have further acknowledged the uncertainties associated with these mechanisms and the need for additional paleoclimate evidence and climate model simulations.
- The literature review in the Introduction lacks a sufficiently focused discussion of previous research, and the research rationale needs to be better established.The Introduction primarily emphasizes the spatial heterogeneity of Holocene precipitation across the East Asian monsoon region and provides a relatively broad overview of previous studies. However, the research progress concerning the monsoon marginal zone between central and northern China, particularly its hydroclimatic evolution, longitudinal precipitation gradients, and potential driving mechanisms, is insufficiently discussed. In addition, the manuscript attempts to investigate the relationship between regional hydroclimatic changes and the distribution of prehistoric archaeological sites, yet the Introduction provides little discussion of previous studies, the significance of this research direction, or the outstanding questions that remain unresolved. The authors should place greater emphasis on the study region and the central scientific questions, provide a more systematic review of previous research on Holocene hydroclimatic variability in the monsoon marginal zone and its potential implications for prehistoric human activities, and clearly identify the knowledge gaps that this study aims to address. This would help establish a stronger rationale for the study and clarify its potential contributions.
Response: We thank the reviewer for this constructive comment. We have revised the Introduction to provide a more focused and systematic review of previous studies on Holocene hydroclimatic variability in the East Asian monsoon transition zone, with particular attention to regional hydroclimatic differences, longitudinal variations in the timing of humid periods, and their potential climatic controls. We have also expanded the discussion of previous research on the relationships between hydroclimatic changes and prehistoric settlement patterns, highlighting the remaining knowledge gaps. These revisions clarify the rationale for this study, the specific scientific questions addressed, and the contributions of the Nansi Lake record to understanding regional hydroclimatic variability and prehistoric human–environment interactions.
- The reliability of the chronological framework and the substantial changes in sedimentation rates require further justification. According to the chronological framework established by the authors, approximately 1.4 m of sediment accumulated during the past 2,000 years, whereas only about 1 m accumulated over the preceding 7,000 years (9000-2000 cal yr BP). This indicates a substantial difference in sedimentation rates between the two intervals, which requires further explanation in the context of the depositional environment of the study area. The authors should clarify the possible causes of these differences and discuss how historical changes in regional hydrology, including potential shifts relative to ancient Yellow River, may have affected depositional stability and sedimentary continuity. Furthermore, given the well-developed drainage network, shallow water depth, and potential reservoir effects associated with different dating materials, the accuracy of the current chronological framework remains uncertain. The authors should provide more robust evidence supporting the reliability of the chronology, taking into account the characteristics of dated materials, radiocarbon results, and regional geological and hydrological contexts. They should also assess how chronological uncertainties may influence the reconstructed precipitation history, especially the inferred timing of precipitation maxima.
Response: We thank the reviewer for constructive suggestion.
First, we calculated approximate interval-averaged linear sedimentation rates based on the midpoints of the calibrated radiocarbon age ranges and the corresponding depth intervals. These estimates have been added to Table 1 and discussed in Section 3.1. The results indicate substantial variability in apparent sediment accumulation, with relatively higher rates in the upper part of the core and lower rates in the deeper sequence.
Second, we have expanded the discussion of historical hydrological changes associated with Yellow River flooding and channel shifts in the section addressing late-Holocene human and hydrological influences. Previous studies indicate that these changes affected the configuration and hydrology of Nansi Lake, particularly during approximately the past millennium, and may have altered sediment delivery, hydrological connectivity, and the relative contributions of aquatic and terrestrial organic matter to lake sediments (Shen et al., 2000; Zhang et al., 1999). Therefore, the Yellow River and human activities are considered potential influences on the younger part of the sedimentary record, while their influence on the Holocene sedimentary record as a whole is likely to have been more limited. Please refer to the second paragraph of section 4.1 for details.
Third, the chronological framework is based on five stratigraphically ordered AMS radiocarbon dates from organic sediment samples, with calibrated ages spanning approximately 1.1–8.9 ka cal yr BP, combined with a Bacon age–depth model. The primary objective of this study is to reconstruct millennial-scale hydroclimatic variability at Nansi Lake, as clarified in Section 2.2.
Regarding the potential radiocarbon reservoir effect, because all five dated samples consist of organic sediment, age offsets associated with reservoir effects cannot be completely excluded. We will continue to investigate this issue in future research.
Finally, the primary aim of this study is to reconstruct millennial-scale hydroclimatic variability and identify relatively wet intervals during the Holocene, rather than to determine the precise timing of individual precipitation maxima. The existing age–depth model provides chronological constraints for evaluating broad hydroclimatic patterns, including the relatively humid interval at approximately 6000–2500 cal yr BP. Nevertheless, we acknowledge that chronological uncertainties may affect the precise timing of individual transitions and comparisons of peak timing among regional records.
- The mechanisms driving precipitation variability are insufficiently explored, and some interpretations lack a clear causal link to the reconstructed precipitation patterns. The authors compare variations in El Niño intensity with longitudinal precipitation differences across the monsoon marginal zone. However, the current analysis remains largely descriptive and does not adequately explain how ENSO events may influence the spatial distribution of precipitation through changes in atmospheric circulation and moisture transport. In particular, changes in the position and intensity of the western North Pacific subtropical high (WNPSH) may play an important role in modulating monsoon moisture transport and rain-belt migration, and their potential contribution to the observed longitudinal precipitation differences deserves further consideration. Moreover, the authors should draw on relevant previous studies to investigate the potential mechanisms linking ENSO variability to regional precipitation patterns. Figure 6 compares precipitation patterns during two modern periods, but these differences cannot be attributed to El Niño activity alone. More importantly, modern ENSO events and Holocene ENSO variability may differ in terms of temporal scales and background climatic conditions. Therefore, variations in Holocene ENSO intensity alone may not adequately explain the longitudinal differences in the timing of peak precipitation. In addition, the authors suggest that stronger monsoon circulation allowed moisture to pass rapidly across the eastern plains, whereas subsequent monsoon weakening increased rainfall persistence in the eastern sector. However, the physical basis for these contrasting precipitation responses is not sufficiently explained. Furthermore, some records indicate relatively humid conditions or enhanced hydrological activity in parts of the western and central transition zone during the middle to late Holocene (e.g., Li et al., 2023; Liu et al., 2025; Xiao et al., 2026), despite the overall weakening trend of the East Asian summer monsoon. The authors should consider the potential roles of westerly circulation, the East Asian summer monsoon, the WNPSH, ENSO, and regional topography, and clarify how these factors may interact to produce the observed longitudinal precipitation differences. More importantly, the relative roles of these factors should be discussed in a physically consistent manner, rather than inferring causal relationships solely from similarities or differences between time series.
Response: We sincerely thank the reviewer for this insightful and constructive comment. We appreciate the reviewer's suggestion to further clarify the physical mechanisms underlying the longitudinal differences in Holocene precipitation across the monsoon transition zone.
First, we have amended the discussion of the relationship between ENSO variability and the spatial distribution of Holocene precipitation. Previous studies have suggested that ENSO-related changes in the position and circulation characteristics of the WPSH may influence monsoon moisture transport and the location of the precipitation belt, thereby contributing to regional differences in precipitation (Rao et al., 2016; Li et al., 2023; Liu et al., 2025). Based on these studies, we have further discussed the longitudinal hydroclimatic differences across the transition zone in relation to reconstructed Holocene ENSO variability, particularly the contrasting precipitation patterns before ~6500 cal yr BP and during ~6500–2500 cal yr BP.
Second, we have incorporated additional evidence concerning the potential influence of the WPSH on longitudinal precipitation differences. Wu et al. (2021) documented an east–west asymmetry in Holocene precipitation across the Chinese Loess Plateau and suggested, based on PMIP3 climate simulations, that the westward extension of the WPSH may have contributed to this spatial pattern. This finding provides a relevant physical perspective for interpreting the longitudinal differences identified in our study. In addition, we have revised the discussion of modern precipitation patterns during 1951–1978 and 1979–1992 (Fig. 6) by considering the north–south displacement of the WPSH and the associated changes in East Asian summer monsoon circulation (Ding et al., 2008). These observations are now used to illustrate the relationship between atmospheric circulation and the spatial redistribution of precipitation, rather than attributing the observed differences solely to El Niño activity.
Third, to provide a broader perspective on the possible driving mechanisms, we have additionally considered changes in the position and orientation of the midlatitude westerly jet (Herzschuh et al., 2019) and the potential contribution of tropical cyclones to regional precipitation, including their modulation by ENSO variability (Zhang et al., 2018).
We thank the reviewer again for this valuable suggestion, which has helped us improve the interpretation of the regional hydroclimatic patterns.
- The proposed relationship between the eastward shift in peak precipitation and the spatial distribution of archaeological sites is insufficiently supported. The authors attempt to link the progressive eastward delay in peak precipitation across the monsoon marginal zone to the probability density distribution of regional archaeological sites, suggesting that changes in the timing and spatial patterns of peak precipitation may have influenced the distribution of prehistoric settlements. However, Fig. 7 does not reveal a clear or continuous west-to-east migration pattern in the distribution of archaeological sites. Instead, the figure also shows a pronounced north-south shift in their spatial distribution. Therefore, directly linking the eastward shift in peak precipitation to changes in archaeological site density appears somewhat tenuous. Furthermore, the spatial distribution of archaeological sites is influenced not only by climatic and hydrological conditions but also by various other factors, including topography, land resources, agricultural development, and sociocultural dynamics. The authors should critically reassess whether the available evidence is sufficient to support their interpretation and discuss the relationship between precipitation variability and archaeological site distributions more cautiously. In the absence of more direct evidence, the relevant conclusions should be appropriately tempered, and the observed spatiotemporal correspondence between precipitation changes and archaeological site distributions should not be interpreted as evidence of a causal relationship.
Response: We sincerely thank the reviewer for this valuable and constructive comment. We appreciate the reviewer's suggestion to further clarify the relationship between Holocene precipitation variability and the spatial distribution of archaeological sites. In response, we have revised the relevant discussion to provide a more comprehensive interpretation of their spatiotemporal correspondence and the potential factors influencing prehistoric settlement patterns.
First, we have refined the interpretation of the archaeological site density maps (Fig. 7). The revised text emphasizes changes in the spatial concentration of archaeological sites across the monsoon transition zone, rather than focusing solely on a continuous eastward migration of settlements. In particular, the KDE maps show increasingly prominent archaeological site concentrations in the eastern sector during 4000–2000 cal yr BP (Fig. 7e, f), broadly consistent with the later occurrence of maximum humidity in this region. This spatial correspondence remains an important finding of our study.
Second, we have strengthened the discussion of the potential relationship between hydroclimatic variability and prehistoric settlement development. In the revised manuscript, we discuss how changes in moisture availability may have affected water resources, agricultural productivity, and settlement suitability. For example, relatively humid conditions in the eastern sector during approximately 6000–2500 cal yr BP may have favored the development of river–lake environments, wetlands, and agricultural land, thereby providing favorable conditions for prehistoric settlement expansion.
Third, we have further considered the roles of regional topography, land resources, agricultural practices, and sociocultural development in shaping archaeological site distributions. These factors may have interacted with hydroclimatic variability and contributed to the complex spatial patterns of prehistoric settlement.
Accordingly, the revised discussion retains the broad spatial correspondence between the eastward delay in Holocene humidity maxima and changes in archaeological site concentrations, while interpreting hydroclimatic variability as one of several contributing factors to prehistoric settlement reorganization.
We thank the reviewer again for this helpful suggestion, which has improved the interpretation of the relationship between Holocene hydroclimatic variability and prehistoric human settlement patterns.
Specific Comments:
- There are two part 3.3 (lines 228, 284).
Response: Thank you for pointing out this numbering error. We have corrected the section numbering in the revised manuscript to ensure consistency throughout the text.
- Line 56: The word “useful” contains a spelling error. Please correct it and remove the unnecessary space.
Response: We thank the reviewer for this helpful suggestion. The spelling error in “useful” has been corrected, and the unnecessary space has been removed in the revised manuscript.
- The in-text citations are not consistently ordered by publication year or authors’ surnames. Please carefully check and revise the order of all citations throughout the manuscript in accordance with the journal’s formatting requirements.
Response: We appreciate the reviewer’s careful attention to the citation formatting. We have carefully checked and standardized the order of all in-text citations throughout the manuscript, arranging them alphabetically by the first authors’ surnames in accordance with the journal’s formatting requirements.
- The authors should explicitly define the chronological boundaries of the early, middle, and late Holocene. The interval of 6000-2500 cal yr BP should not be broadly classified as the middle Holocene without a clear justification. Please specify the adopted Holocene subdivision scheme and apply it consistently throughout the text and figures.
Response: We sincerely thank the reviewer for this important suggestion. We have carefully revised the relevant descriptions throughout the manuscript and figure captions to ensure consistent use of chronological terminology, while preserving the hydroclimatic phases identified in the Nansi Lake record.
- Abbreviations and indices such as LPTP and Paq should be fully defined and briefly explained at their first occurrence in the main text to ensure clarity for readers.
Response: We appreciate the reviewer’s helpful suggestion. We have provided the full definitions of LPTP and Paq at their first occurrence in the main text, together with brief explanations of their meanings and applications in interpreting sedimentary organic matter sources and hydroclimatic variability.
- 5: Given the emphasis on longitudinal differences in precipitation variability, I suggest revising the color scheme of the curves. Curves representing the same geographical sector (eastern, central, or western) should use similar color tones to facilitate the visual distinction between regions and improve the readability of the figure.
Response: We thank the reviewer for this constructive suggestion. We have revised the color scheme of Fig. 5 by using similar color tones for precipitation records from the same geographical sector (western, central, or eastern). This adjustment improves the visual distinction among regions and facilitates comparison of longitudinal precipitation variability across the monsoon transition zone.
- The reference Li et al. (2023b) is listed in the reference section but does not appear to have a corresponding citation in the main text. Please check and correct this inconsistency.
Response: Thanks. We have checked and corrected the inconsistency involving Li et al. (2023b) and ensured consistency between the in-text citations and the reference list in the revised manuscript.
- The section titled “Influence of Longitudinal Hydroclimatic Variability on Prehistoric Human Settlement Patterns” should be numbered 3.4.
Response: Thanks. We have corrected the section numbering.
- The pronounced dry interval around 5000 cal yr BP indicated by the n-alkane record deserves further attention. The authors should discuss this event in greater detail, drawing on other proxy records and regional paleoclimate reconstructions to evaluate its climatic significance and possible driving mechanisms.
Response: We sincerely thank the reviewer for this insightful suggestion. We also noted the pronounced dry interval around 5000 cal yr BP in the n-alkane record. However, the absence of nearby chronological control points introduces considerable uncertainty in the precise timing of this event. Therefore, we have focused primarily on the long-term hydroclimatic trends in this study rather than interpreting individual fluctuations. We acknowledge the potential significance of this dry interval and will investigate it further in future studies with improved chronological constraints and additional proxy evidence.
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General comments
Very good research on the past climate. Please, follow my specific comments to improve your manuscript.
Specific comments
Lines 52-107. Enlarge the views of this good papers beyond the Holocene climate and speleothems.
Lines 60-61. Measurements of oxygen-isotope records on speleothems. Please, insert recent literature on this topic:
- Dayem, K.E., Molnar, P., Battisti, D.S., Roe, G.H. 2010. Lessons learned from oxygen isotopes in modern precipitation applied to interpretation of speleothem records of paleoclimate from eastern Asia. Earth and Planetary Science Letters, 295(1-2), 219-230.
- Medici, G., Marianelli, D., Cornacchia, I., Gori, F., Brandano, M. 2026. Multi-disciplinary approach to paleokarst occurrence in the Eocene–Oligocene succession of the Apulia Carbonate Platform (Salento, Italy). Facies, 72(2), 17.
Line 101-107. Very good to specify general goal, and specific objectives at the end of the introduction.
Line 112. “hydrologically connected”. Please, provide more information on the flow in the sub-surface and the hydraulic connections between the lakes.
Line 112. Provide information on the lithology of the aquifer.
Lines 112-123. Provide information on the nature of the lake sediments.
Lines 120-123. What about evolution of Air Temperature and Precipitation over time?
Line 174-359. Large mixing between results and interpretation.
Line 359. What about inserting a separate discussion?
Figures and tables
Figure 1. Increase graphic resolution. Coordinates are difficult to read.
Figure 2. Graph Depth vs 210Pbx too small. I suggest to create a separate figure.
Figure 7. Increase the graphic resolution. The coordinates are difficult to read.