As anthropogenic impacts to both climate and freshwater resources continue to intensify in coming decades, an increasing number of lakes will experience carbon cycle perturbations. An examination of lakes that have experienced such perturbations for millennia can clarify the nature and severity of carbon cycle disturbances. Lakes precipitating carbonate minerals provide an opportunity to use measurements of both inorganic and organic carbon isotopes to detect the relationship between the inorganic and organic carbon cycles. We examine these dynamics among three lakes in Yunnan, China, which have been impacted by human activities for the last 1,500 years. We compare the period impacted by people to drying conditions and lowering lake levels during the middle Holocene, and more stable hydrologic conditions during the later Holocene, both of which are characterized by minimal anthropogenic influence. From 5,500 to 3,500 years BP, decreased precipitation, increased evaporation, and changes in vegetation drove increases in sediment carbon isotope values. Despite continued weakening of the Indian monsoon from 3,500 to 1,500 years BP, carbon isotopes values stabilized. Following anthropogenic manipulation of lake levels after 1,500 years BP, and despite differences in the magnitude of activities in the three catchments, a decrease in inorganic carbon isotopes without a parallel change in organic carbon isotopes is a pervasive feature in each system and a clear signature of human activity. We suggest possible drivers are an influx of dissolved inorganic carbon from either oxidized organic matter or dissolved carbonates from the watershed and/or the respiration of lake sediment organic matter.

As anthropogenic impacts to both the climate system and freshwater resources continue unabated and are expected to intensify in coming decades, an increasing number of lakes will experience carbon cycle perturbations. Lakes that have been experiencing such perturbations for millennia can clarify the nature and severity of carbon cycle disturbances as well as recoveries. In lakes with authigenic carbonate material, the use of both inorganic and organic carbon isotopes to detect the decoupling of the inorganic and organic carbon cycles has been underutilized. We summarize here the application of these methods to three lakes in Yunnan, China, which have been impacted by human activities for the last 1,500 years. Further we compare the results from this time period to the middle and late Holocene, both periods characterized by minimal anthropogenic influence. Decreased precipitation, increased evaporation, and changes in landscape vegetation drive changes observed in sediment carbon isotope compositions from 5,500 to 3,500 years BP. Stabilization of these factors from 3,500 to 1,500 years BP resulted in fairly consistent within-lake nutrient cycling. Following anthropogenic manipulation of lake levels after 1,500 years BP and despite differences in the magnitude of such activities, a pervasive feature in all of these lakes is the decoupling of the inorganic and organic carbon cycles, primarily driven by an influx of oxidized organic carbon from the watershed and/or the respiration of lake sediment organic matter. Carbon cycle decoupling persists into present-day for some lakes, illustrating the importance of considering historical, legacy activities.

To better understand how global and regional-scale climate has changed, high-resolution records for environmental changes are still needed in southwestern (SW) China during the Late Holocene epoch. This study presents a well-dated high-resolution diatom analysis from a 1.66-m-long sediment core taken from Lake Cuogeda (CGD) on the southeast (SE) edge of the Tibetan Plateau to document environmental changes over the past ∼4000 years. Diatom and other geochemical proxies show that, from 3850 to 3430 cal yr BP (before present, 0 BP=1950 AD, 1900 to 1480 BC), the environment of Lake CGD is acidic, oligotrophic, and enriched with humic acids. And the lake ice cover duration is short during this period. During 3430–1550 cal yr BP (1480 BC-400 AD), Lake CGD has less humic acid and a relatively high pH environment. The ice cover duration is longer, and the temperature drops during this period. Our multi-indicator recorded two environment fluctuations at ∼2800 cal yr BP (850 BC) and 2210–1950 cal yr BP (260 BC-0 AD). From 1550 to 3.6 cal yr BP (400–1946 AD), the lake ecosystem changed to a higher pH condition and had a prolonged freezing time. From 3.6 cal yr BP (1946 AD) to the present, Lake CGD’s water was acidic, with an environment of shorter duration of ice cover and stronger lake water turbulence. Comparisons between the CGD records and other climate reconstructions underscore the relevance of the CGD record for regional and global environments. Comparisons indicate that the environment evolution pattern of SW China during the Late Holocene was greatly affected by solar radiation and North Atlantic sea surface temperature.

The reconstruction of human-driven ecosystem dynamics under the background of climate change is crucial for understanding past human-environment interactions and gaining insights into the evolution of aquatic ecosystems that are currently facing eutrophication. However, disentangling the effects of human activities from climate warming on lake ecosystem presents challenge due to limited knowledge of spatial and temporal response mechanisms of ecosystem evolution from climate-driven processes to those influenced by both climate and mild human intervention, and ultimately to those primarily driven by intense human activities. Here, we use diatom analysis of a sediment core from Dianchi Lake on the southeastern margin of the Tibetan Plateau to reconstruct environmental changes, with particular emphasis on the influences of climate, changing vegetation, and land-use on lake ecosystems. By comparing fossil diatom assemblages with previous reconstructions of vegetation and catchment processes, we demonstrate three successive stages of nutrient enrichment in Dianchi Lake over the past 20,000 years. The first major transition, occurring at the late glacial/Holocene boundary, witnessed an increase in nutrient inputs primarily driven by Holocene climate warming. The most pronounced nutrient enrichment, characterized by significant changes in diatom assemblages around 2.3 cal kyr BP, resulted from intensified agricultural cultivation. The arrival of the Han people to the Dianchi lake basin has been followed by extensive burning, land clearance, and increased soil erosion associated with agricultural production, marking the early detectable human impact on aquatic ecosystems since 2.3 cal kyr BP. Despite the eutrophication observed in Dianchi Lake in the last century, the long-term diatom record indicates that the lake ecosystem experienced abrupt state transformations as early as 2.3 cal kyr BP. The decline in water level due to dredging for flood control, coupled with intensified soil erosion and exposure of alluvial deposits during the period of 750-250 cal yr BP, triggered exceptionally low lake productivity and vegetation changes, indicating a collapse of the lake ecosystem due to intensified human impacts. This underscores the limnological effects of transitioning from predominantly agricultural practices to large-scale hydrological modifications for irrigation and agricultural development. The accelerated soil erosion and rapid water level decline since 2.3 cal kyr BP represent a tipping point for both the lake ecosystem and catchment vegetation, with significant implications for present-day land and lake degradation. To prevent further degradation of the lake and mitigate the impacts of climate warming, we propose: (1) enhancing lake ecosystem management through the promotion of diverse forests and crops within the landscape, and (2) fostering diverse cultural relationships between people and their water and land resources. Our study provides evidence that the impact of local anthropogenic activities on

Many Holocene paleoclimate records from the southeastern United States (SE US) have limited chronological constraints and/or low sedimentation rates and consequently low resolution; this presents challenges in discerning the relative importance of synoptic-scale drivers of past hydroclimate. In this study we summarize three lake sediment records that are uniquely located to test hypotheses regarding the importance of the Pacific North American (PNA) pattern and the North Atlantic Oscillation (NAO) over the last 5000 years. At Pigeon Marsh, Buck Pond, and Halls Pond, we used sedimentological (radiocarbon dating of transect cores), physical (grain size), geochemical (carbon and nitrogen ratios and isotopes), and biological (palynomorphs) proxies to reconstruct lake level and lake environment. Moderate lake and environmental changes occur around 2000 cal yr BP at Buck and Halls Pond, which is regionally consistent with other paleorecords and may suggest that the NAO was an important control. However, our results generally indicate fairly stable hydroclimate conditions up until historical European settlement when land clearance caused vegetational and lake hydrologic balance changes that were unprecedented in both magnitude and rate compared to the middle/late Holocene.

O-17-excess is a relatively new water isotope parameter that could potentially provide useful information about the hydrological cycle. Previous works focusing on O-17-excess in polar regions suggest that it primarily tracks moisture source relative humidity, but little is known about how to interpret O-17-excess data in lower latitudes. Here we present quasi-hourly triple oxygen isotope data of precipitation collected from two tropical cyclones in Texas and Louisiana in 2020 to understand the impacts of environmental and meteorological processes on the(17)O-excess of low-to mid-latitude precipitation. We find that at both hourly time scales and the event scale,O-17-excess is strongly correlated to changes in on-site rainfall intensity and relative humidity, which is consistent with the theory that the isotopic fraction at ion associated with rain re-evaporation lowers the(17)O-excess of the remaining droplet. In addition, although evaporative conditions at the moisture source region may also influence( 17)O-excess of water vapor transported to the precipitation site, their impacts are likely over printed by the post-condensation rain re-evaporation processes. Our results thus suggest that O-17-excess can be used as a proxy for local rather than source region evaporative conditions during tropical cyclones.

Quantitative reconstruction of past climate plays an important role in understanding global and regional climate changes and validating climate models. Although some important progress has been made in quantitative paleoclimate reconstructions based on terrestrial records in the Indian summer monsoon region, high-resolution quantitative studies spanning the last similar to 20 ka are still relatively sparse with differing results. This study presents high-resolution quantitative variations in mean temperature of the coldest month (MTCM, the first controlling factor of the regional vegetation), mean annual temperature (MAT, the second controlling factor), and mean annual precipitation (MAP) from Lake Tengchongqinghai in southwestern China, based on an updated modern pollen dataset and the fossil pollen record spanning the last 18.5 ka. The results show that temperature and precipitation increased gradually from 18.5 ka, and peaked from 7.2 to 4.5 ka when MAT was on average 1.0 degrees C higher than the modern observational value (14.5 degrees C), corresponding to the mid-Holocene thermal maximum (HTM), and then decreased gradually. The total reconstructed ranges are between-2.2 and 9.2 degrees C for MTCM, 7.7 and 17.2 degrees C for MAT, and 840 and 1300 mm for MAP. On top of this overall climate trend, seven abrupt cold and dry events were detected during the periods of 16.2-14.8 ka, 12.8-11.5 ka, similar to 11.1 ka, 9.1-8.4 ka, similar to 7.7 ka, 4.3-3.7 ka, and 0.68-0.009 ka (1270-1950 CE). The results of this quantitative reconstruction were validated by both statistical and ecological evaluations. We conclude that the trend of climatic change since 18.5 ka in this study area was primarily driven by June, July, August, and September solar insolation and changes in radiative forcing and greenhouse gas concentrations. The abrupt changes may be caused by changes in the Atlantic meridional overturning circulation, solar activity, the position of the Intertropical Convergence Zone, and volcanic activity.

目前对中晚全新世人类活动和环境之间相互作用的认识还不全面.中国东部长江中下游地区巢湖C1钻孔为研究5100cal. a BP以来的植被演替、气候变化、人类活动和东亚夏季风演化提供了良好载体.基于放射性碳测年、孢粉和炭屑记录以及磁化率、中值粒径和总磷等指标分析,本文获得以下结果:巢湖西湖区在2080～730cal.a BP期间存在沉积间断,该现象在长江中下游多数湖泊中都有发生.研究区常绿、落叶阔叶混交林从3650cal. a BP开始逐渐衰退,到至少730cal. a BP后逐渐被次生松林取代;首次强烈的人类活动和植被破坏出现在大约2520cal. a BP.人类居住地从滨湖湿地（在2520～2080cal. a BP期间）扩展到远离湖泊的高海拔地区（在2080～400cal.a BP期间）,再返回滨湖一带以开垦湿地和湖泊（自400cal. a BP之后）.夏季风强度自4300cal. a BP以来呈现逐渐衰退的趋势,在5100～3650cal. a BP期间经历了百年尺度的波动.夏季日照的减少、热带辐合带（ITCZ）的南移以及厄尔尼诺与南方涛动（ENSO）可能在大范围内控制了东亚夏季风强度和区域气候变化.

Our knowledge about the interaction between human activities and the environment in the middle-late Holocene remains incomplete. Core C1 in Lake Chaohu from the middle and lower reaches of Yangtze River (MLYR), eastern China, provides an opportunity to investigate vegetation and climate changes, human activities, and East Asian summer monsoon (EASM) evolution since 5100 cal. yr BP. These variables are assessed based on radiocarbon dating, pollen and charcoal records, and magnetic susceptibility ( χ lf ), median grain size and TP. Results reveal a hiatus in sedimentation between 2080 and 730 cal. yr BP in the western part of Lake Chaohu, which is common in most lakes in the MLYR. Evergreen and deciduous broadleaved mixed forest retreated gradually after 3650 cal. yr BP, and was replaced by secondary Pinus forest after at least 730 cal. yr BP. Intense agricultural activities and vegetation clearance are first detected at 2520 cal. yr BP. Human settlements expanded from the lake front wetlands (during the period 2520–2080 cal. yr BP) to remote high-altitude areas (2080–100 cal. yr BP), and then returned to the lake front to reclaim the wetlands and lake (after 400 cal. yr BP). A gradual trend of recessional EASM strength from 4300 cal. yr BP and centennial-scale variations of EASM during the period 5100–3650 cal. yr BP are revealed. The reduction of summer insolation, southward shift of the ITCZ, and El Niño Southern Oscillation may control the intensity of EASM and climate on a large regional scale.

Legacy pollution research has established that over the past 3000 years, mining and metallurgical activities have resulted in widespread deposition of lead (Pb) pollution. However, there is still a limited understanding of how humans have impacted the long-term cycling of Pb in the environment. We present a 4,000-year lake sediment Pb isotope record from Laguna Roya, northwestern Iberia, that identifies and quantifies the predominant sources of atmospheric Pb pollution. For the first time, Pb isotopic compositions of ancient slag samples dated (∼600 BCE–200 CE) from a mining district in the southwest of the Iberian Peninsula are compared to Pb isotope ratios of Pb pollution deposited contemporaneously in lake sediments. In addition, literature Pb isotope ratios of ores from mining regions throughout Iberia are compared with those of leaded gasoline and coal to identify additional sources of anthropogenic Pb. Deposition of atmospheric Pb pollution begins after 950 BCE, and until 1750 CE, the Pb isotopic composition most resembles the southwestern slag deposits, containing a mixture of Pb ores from southeast Iberia (up to 36%) and southwest Iberia (∼74%). Between 1750 and 1960 CE, Pb pollution is attributed to Pb mining in southcentral Iberia. After 1960 CE, the dominant Pb pollution source (∼85%) is again metal refining in southwestern Iberia, and only ∼15% is from leaded gasoline. Provenance and reconstruction of the temporal and spatial distribution of legacy Pb pollution further our understanding of how humans have affected the biogeochemical cycle of this toxic element in the environment over time.

El Niño Southern Oscillation (ENSO) is a periodic disruption of coupled oceanic-atmospheric conditions in the tropical Pacific, which changes global precipitation regimes. One area strongly affected by positive (el Niño) phases is the Pacific Coast of South America. The specific effects of ENSO on Andean ecological communities have received little attention, however. We examine vegetation gross primary productivity (GPP) on Peru's north coast arid-lands during a recent (2016–2017) el Niño, using a time series of Sentinel 2 imagery. By comparing GPP time-series in three agricultural subregions and three endemic desert vegetation communities, we demonstrate that levels of primary productivity in desert regions during ENSO-positive phases meet or exceed thresholds of adjacent agricultural lands. These results, the first that quantify and spatialize changing GPP between ENSO-neutral and ENSO-positive phases for South American arid-land biomes, both outline the scale and distribution of the el Niño effects on terrestrial ecosystems and highlight the resulting opportunities for human inhabitants. The dramatic changes to endemic vegetation on the normally hyperarid coastal desert of Peru revealed by reconstructed GPP suggest that periodic el Niño precipitation plays a critical role in arid land ecodynamics by enhancing establishment, green growth, and seedbank development. These findings improve our understanding of ENSO's net effects and highlight the roles of abrupt climate events in the arid land ecology of NW South America.

There is much debate regarding the temporal and spatial pattern of hydroclimate variations on the Tibetan Plateau during the Holocene, focusing especially on the dipolar pattern of precipitation and moisture between the southern and northern regions, on multiple timescales. Modern observations reveal that the delta O-18 in precipitation is an integrated tracer of the atmospheric processes of the Indian summer monsoon (ISM), the East Asian summer monsoon (EASM), and the westerlies, which dominate the climate of the Tibetan Plateau. Here, we summarize and compare 20 Holocene lacustrine authigenic carbonate delta O-18 records from lakes distributed across the Tibetan Plateau. After carefully considering the potential effects of temperature, evaporation, site elevation, meltwater supply, and moisture sources, we eliminate their influences on the isotopic composition of Tibetan lakes, and suggest that the long-term variations of the lacustrine delta O-18 records were dominated by the moisture sources. The delta O-18 values of the lake sediments in the central and western Tibetan Plateau increased since the early Holocene, which agrees with the trend of delta O-18 in speleothem records from the plateau, as well as with the variations of monsoon precipitation reconstructions for the region. Overall, this evidence indicates the substantial influence of the monsoon in the abovementioned regions. However, the delta O-18 records from lakes in the northeastern Tibetan Plateau show a decreasing trend during the second half of the Holocene (after similar to 5 ka), highlighting the operation of a different hydrological process, with enhanced moisture availability, in the regions. It has been suggested that the increased contribution from westerlies-derived moisture in the nonmonsoon season, with depleted delta O-18 (e.g., from melting snow or frozen soil in spring), is responsible for such variations. We propose that the interplay between the Asian summer monsoon and the westerlies was the major control of the hydroclimatic variations on the Tibetan Plateau during the Holocene, which led to the dipolar pattern of moisture variation between the northeastern Tibetan Plateau and other parts of the plateau, on the multi-millennial timescales during the Holocene.

Contaminated legacy sediments contribute to modern pollution loadings, particularly trace metals. These contributions are challenging to quantify as metal histories reconstructed from sediment records cannot be easily divided into legacy and concurrent contamination. In particular, the contribution from re-mobilization and delivery of legacy metals stored in catchment soil, colluvial, and fluvial environments are rarely considered or quantified when interpreting sediment records. Here, extended records of metals accumulation for a set of three lakes in Yunnan, China are compared with endmember chemistries using Monte Carlo-Markov Chain mixing models to help identify source contributions to the sediments. This approach allows attribution of metals transported by atmospheric and fluvial mechanisms in a region with a history of mining and metallurgy spanning millennia. These analyses reveal distinct source mixtures and demonstrate the sensitivity of lake records to basin sediment dynamics. In particular, substantial proportions of elevated metal concentrations in these lake systems seem to arise from soil contributions more than from atmospheric deposition of smelting emissions. The largest soil contributions seem to be in Erhai, a lake with erosion prone soils closely "connected" to the lake. Moreover, these invesigations illustrate the potential for mixing approaches to accommodate and clarify uncertainties in metal source and extraction as differences in extraction efficiency can be incorporated into source uncertainty estimates. Ultimately, these approaches emphasize the need to account for fluvial metal transport in interpretation of sediment histories.

Although Holocene-scale trends in Indian Summer Monsoon (ISM) variability have been well-established, manifestations and drivers of centennial-and multi-decadal-scale variability are still debated. Additionally, the extent to which proxies reflect abrupt climatic changes rather than proxy-specific thresholds is unclear. To address these questions, we summarize a 9200-year record from Yilong Lake in Yunnan China using multiple proxies including oxygen and carbon isotopes of authigenic calcite as well as Ti/Al ratio to characterize lake hydrologic balance and catchment erosion, respectively. We compare these results to two other well-studied nearby lakes on the Yunnan Plateau. At all three lakes, the Holocene-scale waning of the ISM is evident, but punctuated by abrupt shifts indicative of lower precipitation and/or greater evaporation at 7900, 5500, and 4500 cal yr B.P. We suggest that a shift to a positive mean-state of the Indian Ocean Dipole lasting multiple centuries can account for these events, with possible moderating influence from El Nin tilde o Southern Oscillation. After 1500 cal yr B.P., Yilong oxygen isotopes shift to less negative values as a result of human manipulation of hydrologic balance, coincident with the deposition of a red clay layer from catchment erosion. These results are similar to other Yunnan lakes although the intensity of anthropogenic management of Yilong's hydrologic bal-ance is substantially smaller than at the other regional lakes. These results underscore the diversity of anthro-pogenic impacts to lakes, even ones that are only a few kilometers apart, and demonstrate spatiotemporal differences in freshwater resource use.

Our understanding of the climatic teleconnections that drove ice-age cycles has been limited by a paucity of well-dated tropical records of glaciation that span several glacial–interglacial intervals. Glacial deposits offer discrete snapshots of glacier extent but cannot provide the continuous records required for detailed interhemispheric comparisons. By contrast, lakes located within glaciated catchments can provide continuous archives of upstream glacial activity, but few such records extend beyond the last glacial cycle. Here a piston core from Lake Junín in the uppermost Amazon basin provides the first, to our knowledge, continuous, independently dated archive of tropical glaciation spanning 700,000 years. We find that tropical glaciers tracked changes in global ice volume and followed a clear approximately 100,000-year periodicity. An enhancement in the extent of tropical Andean glaciers relative to global ice volume occurred between 200,000 and 400,000 years ago, during sustained intervals of regionally elevated hydrologic balance that modified the regular approximately 23,000-year pacing of monsoon-driven precipitation. Millennial-scale variations in the extent of tropical Andean glaciers during the last glacial cycle were driven by variations in regional monsoon strength that were linked to temperature perturbations in Greenland ice cores 1 ; these interhemispheric connections may have existed during previous glacial cycles.

South American arid lands present unique constellations of climatic risk to their human inhabitants, due to volatile events that can create markedly different hydroclimate conditions over interannual–centennial scales. However, a main driver of such volatility – the El Niño/Southern Oscillation (ENSO) – occurs with semiregular periodicity. Paleoclimatic and archeological evidence indicate not only that the strength and periodicity of ENSO patterns have changed over the late-Holocene, but their impacts were likely recognized, adapted to, and perhaps capitalized upon by agriculturalists employing adaptive risk strategies. We examine relationships over the last 1.3 kyr between ENSO periodicity, ecological transitions, and archeological settlement in Peru’s Chicama Valley through a coupled paleohydroclimate and agroecology model. We reconstruct periods when ENSO-like conditions dominated past hydroclimates and present a quantitative, spatially-explicit analysis of ecological productivity during modern ENSO-positive hydroclimate conditions. We show that archeological settlement patterns are sensitive to these transformations and reflect efforts to capitalize on expanded agroecological niches. Such expanded niches potentially offset the adverse impacts and risks associated with abrupt ENSO climate events. These results suggest archeological communities were aware of ENSO risk and managed productive strategies accordingly, highlighting the importance of a risk calculus that considers the net ecological effects of climate events.

Continuous lacustrine records of the Indian Summer Monsoon (ISM) that span the Pleistocene-Holocene transition to the present are relatively rare, yet crucial to providing context to future changes in hydroclimate. We summarize here a 17,000 year continuous multi-proxy record of hydroclimate and primary productivity from Lake Dian in the central Yunnan Province of China. Analysis of sediment composition, opal, carbon to nitrogen ratios, carbon and nitrogen stable isotope ratios, and magnetic susceptibility (MS) are used to identify four distinct units in the sediment record. Unit I sediments from 17,000 to 11,500 years BP are characterized by high MS and uniformly low organic and opal content interrupted by a decrease in MS during the Bolling-Allerod indicating the influence of the North Atlantic on the ISM. We interpret this to reflect cold, dry, and windy conditions during the transition out of the Last Glacial Maximum. Unit II from 11,500 to 5000 years BP is marked by a pronounced decrease in MS, increase in opal, and decrease in delta C-13(org) of organic carbon driven by peak warmth and wet conditions increasing productivity. Unit III from 5000 to 1800 years BP shows further increases in primary productivity, marked by lower carbon to nitrogen ratios and carbonate precipitation, possibly driven by a drop in lake level. A period of aridity is in wide agreement with a number of other records from the region. Unit IV from 1800 years BP to present is dominated by anthropogenic impacts and hallmark signs of catchment soil erosion and cultural eutrophication. Our interpretations of the Dian sediment record agree well with previous palynological work and add a new dimension to our understanding of lake hydrology and productivity over the past 17,000 years.

Over the past few decades, the δ18O records of ice wedges have been used to estimate late Quaternary winter air temperatures. This study first reviews the development of ice wedges and the potential isotopic fractionation that takes place from snow deposition to formation of ice veinlets. Then, based on the high resolution analysis of ice wedges from the Eureka Sound Lowland (Ellesmere and Axel Heiberg Islands), we evaluate the effect of sampling depth and edge effects on the δ18O records and compare a composite δ18O time-series of ice wedges to the Holocene 25-yr annual and 20-yr winter δ18O records of the nearby Agassiz Ice Cap. Radiocarbon ages of dissolved organic carbon in ice wedges showed that cracking occurs mostly near the center of the wedge, but age reversals were observed. Covariance analysis showed that two δ18O profiles collected at the same depth had high noise (c. 70–80 % uncorrelated parts). Additionally, ice wedge mean δ18O records showed a decreasing trend with depth, likely due Rayleigh fractionation during freezing of residual water in the crack. Finally, the composite δ18O time-series of ice wedges and δ18O records of the Agassiz Ice Cap showed a similar Holocene cooling trend, however the wedges δ18O records had a higher degree of variability throughout the Holocene (∼4 ‰ versus ∼2 ‰ in the Agassiz records). The higher variability in the wedge is attributed to the timing of meltwater infiltrating the wedge crack over the growth period, which from the onset to termination of snowmelt, is in the order of 3–6‰. The study highlights that, if to be used as a centennial-millennial scale proxy, ice wedges should be sampled near the surface where δ18O records would be less affected by in situ freezing and plugging, and veinlets should be dated directly and smoothed to remove the local random variance.