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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Status: open (until 30 Oct 2026)
- CC1: 'Comment on egusphere-2026-4480', Giacomo Medici, 18 Sep 2026 reply
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RC1: 'Comment on egusphere-2026-4480', Anonymous Referee #1, 20 Sep 2026
reply
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 -
RC2: 'Comment on egusphere-2026-4480', Anonymous Referee #2, 14 Oct 2026
reply
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
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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.