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Recent climate and environment over the Tibetan Plateau (TP) have undergone significant changes, dominated by variations in the Westerlies and the Indian summer monsoon. However, long‐term shifts in atmospheric circulation during the transitional seasons are still lacking. Here we investigate the modern distribution of Tsuga pollen over the central‐western TP and confirm it as an indicator of variable atmospheric circulation in spring. By combining our Tsuga record from Taro Co with existing records in the Tsuga pollen source area, we suggest that a potential particle transport pathway from the southern slope of the Himalayas to the interior of the plateau appeared in the spring of the late Holocene. Our results show that the springtime atmospheric circulation over the southwestern TP during the early and late Holocene is closely related to the substantial remnants of ice sheets at northern high latitudes and the frequency of El Niño events, respectively. Plain Language Summary: The spring climate over the Tibetan Plateau (TP) is undergoing significant changes that yield profound impacts on environmental changes such as variations in vegetation phenology and alpine treeline. Knowledge of long‐term variations in atmospheric circulation during spring can improve the understanding of current climatic and environmental change and the projection of future variability. In this paper, we use an exotic pollen grain, which can be transported long distances in the air, as an indicator to trace the variability of spring atmospheric circulation over the TP. The results indicate that the spring meridional atmospheric circulation from the southern slope of the TP to its interior has been enhanced in the last four thousand years, which is mainly influenced by the frequency of El Niño events. Key Points: Spring atmospheric circulation change over the southwestern Tibetan Plateau (TP) during Holocene is reconstructedMeridional atmospheric circulation in spring over the southwestern TP is strengthened in the late HoloceneHigh‐(low‐) latitude forcing mainly influence the variations in spring atmospheric circulation during the early (late) Holocene [ABSTRACT FROM AUTHOR]

The North American Monsoon (NAM) is a critical component of the hydrologic cycle in southwestern North America. However, our understanding of the long‐term evolution of this monsoon system is incomplete due to a paucity of long‐term paleoclimatic records from the core and periphery of the NAM domain. C. Routson et al. (2022, https://doi.org/10.1029/2022gl099772) leverage a new compilation of Holocene proxy records to generate a new composite index of NAM evolution over the Holocene. They identify a relationship between NAM strength and the latitudinal temperature gradient over the Holocene. The authors suggest that shifts in the strength of the westerlies altered NAM convection via ventilation, a process whereby the large‐scale circulation imports low moist entropy air into the monsoon domain. These results highlight the importance of paleoclimatic records, especially from past "warm" intervals, for generating new insights about the evolution of regional monsoons. Plain Language Summary: The North American Monsoon is a circulation that brings summer rain to regions of the US southwest and western Mexico. Despite the fact that this circulation provides a majority of the precipitation in many parts of the arid southwest, we do not fully understand the factors that govern long‐term changes in this monsoon. A new paper by C. Routson et al. (2022, https://doi.org/10.1029/2022gl099772) uses proxy indicators of past summer rainfall, stretching from Central America to Arizona, to reconstruct changes in the monsoon over the geologic epoch known as the Holocene, or the last 11,000 years of Earth history. The results of this study suggest that Holocene changes in the temperature difference between the equator to pole, known as the "latitudinal temperature gradient," exerted an important influence over monsoon strength in the southwest. This has implications for the future of the summer monsoon, especially as the high latitudes of the northern hemisphere are expected to warm in the future. Key Point: The strength North American Monsoon tracks changes in the position of the midlatitude westerlies over the Holocene [ABSTRACT FROM AUTHOR]

The englacial stratigraphic architecture of internal reflection horizons (IRHs) as imaged by ice‐penetrating radar (IPR) across ice sheets reflects the cumulative effects of surface mass balance, basal melt, and ice flow. IRHs, considered isochrones, have typically been traced in interior, slow‐flowing regions. Here, we identify three distinctive IRHs spanning the Institute and Möller catchments that cover 50% of West Antarctica's Weddell Sea Sector and are characterized by a complex system of ice stream tributaries. We place age constraints on IRHs through their intersections with previous geophysical surveys tied to Byrd Ice Core and by age‐depth modeling. We further show where the oldest ice likely exists within the region and that Holocene ice‐dynamic changes were limited to the catchment's lower reaches. The traced IRHs from this study have clear potential to nucleate a wider continental‐scale IRH database for validating ice sheet models. Plain Language Summary: Ice‐penetrating radar is widely used to measure the thickness of ice sheets, critical to assessments of global sea level rise potential. This technique also captures reflections from chemical contrasts within the ice sheet, caused by the atmospheric deposition of conductive impurities, known as "internal reflection horizons" (IRHs) that can be traced over large distances. As these deposits are laid down in distinct events, most IRHs are isochronous age tracers and contain valuable information on past ice sheet processes. In this paper we trace and place age constraints on stratigraphic horizons across a large portion of the West Antarctic Ice Sheet, including regions where fast ice flow has disrupted the ice sheet stratigraphy. The resulting data set allows us to identify where the oldest ice is buried in the study region and provides evidence that flow of the ice sheet interior has been stable during the Holocene. Our results can be used to test the performance of ice sheet models, which seek to simulate the response of ice sheets to long‐term environmental change. Key Points: We measure and date individual isochronal radar internal reflection horizons across the Weddell Sea sector of the West Antarctic Ice SheetHorizons dated to 1.9–3.2, 3.5–6.0, and 4.6–8.1 ka are widespread and linked to previous radar surveys of the Ross and Amundsen Sea sectorsThese form the basis for a wider database of ice sheet architecture for validating and calibrating ice sheet models of West Antarctica [ABSTRACT FROM AUTHOR]

The desiccation (extreme drying) of rivers has important implications for the broader Earth System. However, the desiccation history and its linkage to climate are rarely known for numerous major river systems, primarily due to difficulties in recognizing desiccation events from available stratigraphic records. Here, using a combination of geochemical techniques (major and rare‐earth element geochemistry, detrital zircon geochronology, and optically stimulated luminescence dating), we demonstrate that the Yellow River, which maintains the highest sediment load on Earth, became desiccated during the Last Glacial Maximum at approximately 20 thousand years ago. This finding implies that transportation of sediments and dissolved constituents to the oceans via the Yellow River may have decreased substantially or ceased during glacials, which would have ramifications for ocean chemistry and biology. Furthermore, our work highlights the importance of desiccated riverbed sediments as potential dust sources during glacial periods, a finding that is different from what is observed today. Plain Language Summary: Understanding the characteristics of major rivers is important for better constraining changes in the Earth System. Based on new geochemical data, we find that during the period dominated by overall drier and colder climate conditions ∼20,000 years ago, water flow in the upper reaches of the Yellow River was reduced to the point that flow effectively ceased downstream of the Hetao Basin. In other words, the Yellow River was no longer a perennial river between the upper and middle‐low reaches until re‐integrating ∼10,000–5,000 years ago. Moreover, we demonstrate that surface processes related to the Yellow River system are substantially different between colder‐drier and warmer‐wetter intervals, at least for the last ∼40 thousand years, and we suggest caution when using modern observations to infer regional environments and geomorphology related to rivers during colder‐drier periods. Key Points: Provenance changes at the outlet of the Hetao Basin indicate the desiccation and re‐integration of the upper Yellow River over the last ∼40 kaPaleo‐lake shorelines and geochemical proxies confirm that the west Hetao Basin contained the terminal lake for the desiccated Yellow RiverClimate‐river feedbacks across glacial‐interglacial cycles have implications for constraining terrestrial‐marine source‐to‐sink processes [ABSTRACT FROM AUTHOR]

Dating of the Tibetan ice cores is often challenging with great uncertainties. The significant age difference between the Guliya ice core (∼760 ka [thousand years]) and other Tibetan ice cores (Holocene origin) necessitates new approaches to resolve the inconsistency. Here, we present the atmospheric O2δ18O (δ18Oatm) profile of the 216.6 m Chongce ice core. Our data suggest that post depositional alterations significantly changed δ18Oatm. We reject samples with melt layers, and reconstruct the δ18Oatm values with two extreme correction approaches: a minimum isotopic correction based on gas loss fractionation, and a maximum isotopic correction based on respiration fractionation. We consequently estimate the age range of the Chongce ice core to be 2.763–7.192 ka at the depth of 215.14 m, and ∼3–9.799 ka at the depth of 215.61 m. Our work provides an independent line of evidence for the Holocene origin of the Chongce ice core. Plain Language Summary: Dating of the Tibetan ice cores is often challenging with great uncertainties, mainly due to rapid thinning at the ice core bottom sections. There is a significant difference between the published ages of the Tibetan Guliya ice core (∼760,000 yr) and those of other Tibetan ice cores, all of which were confined to the Holocene (∼10,000 yr). The direct distance between the Guliya and Chongce ice core drilling sites is only ∼30 km. Here, we present the gas chronology based on the 18O/16O isotopes of trapped air O2 for the Chongce ice core. We apply corrections to eliminate the isotopic fractionations caused by post depositional alterations. The dating results based on the trapped air 18O/16O constrain the maximum age for the Chongce bottom ice to be within 9.799 ka at 215.61 m, indicating that the Chongce ice core is of Holocene origin. Key Points: We present the profile of δ18O of paleoatmospheric O2 and its implied gas chronology of a Tibetan ice coreThe trapped air δ18O synchronization with the Antarctic Siple Dome ice core yields an upper age limit of 9.799 kaThe age deduced from the trapped air δ18O confirms the Holocene origin of the Chongce ice core [ABSTRACT FROM AUTHOR]

The source and seasonality of rainfall in southern Arabia during the early‐ to mid‐Holocene and preceding humid periods are controversial because fossil lacustrine sediments provide solely indirect information on the amount of rainfall. Hydrogen and oxygen isotope measurements on fluid inclusion water trapped in Holocene and Pleistocene stalagmites from Hoti Cave in Northern Oman are direct indicators of the isotopic composition of paleoprecipitation. Isotope values of fluid inclusions formed during peak interglacial periods plot along monsoonal water lines and are indicative of a southern monsoonal moisture source. The last monsoon‐dominated period lasting from ∼10,100 to 6,300 years before present was terminated within a few decades in southeastern Arabia. The subsequent reduction in rainfall amount and change from predominantly summer to predominantly winter rainfall had a profound impact on human communities living in this area and triggered migration from inland to coastal areas where resources were more abundant. Plain Language Summary: During the Quaternary period, the Arabian Peninsula experienced short intervals of enhanced rainfall, turning the Arabian Desert into a savannah‐type landscape with abundant lakes and wetlands. These intervals are well‐documented in lake sediments and cave deposits throughout Arabia, whereas the source of rainfall is uncertain. Ancient rainwater trapped in fluid inclusions in stalagmites from Hoti Cave, Northern Oman, allows us to determine moisture source changes over the last 350,000 years before present. Using new analytical methods to extract the water from fluid inclusions and measure its hydrogen and oxygen isotopic composition, we are able to show that greatly enhanced rainfall was caused by an intensification and greater northward extension of the African and Indian monsoons into Arabia. For the last humid period between ∼10,500 and 6,300 years before present, stalagmites from Hoti Cave reveal an abrupt termination of the monsoon‐dominated period, a sharp decline in precipitation and change from a summer‐ to winter‐dominated rainfall regime in southeastern Arabia. As a result, human communities were severely affected by this major climatic change and forced to migrate from inland to coastal areas, where water and resources were more abundant. Key Points: Hydrogen and oxygen isotopes in fluid inclusions in stalagmites from Hoti Cave, Northern Oman, reveal changes in the source of rainfallRainfall during the early and middle Holocene originated from the Indian Ocean and was associated with the Indian summer monsoonA change in the seasonality and reduction in rainfall at ∼6,300 years before present had a profound impact on communities in Northern Oman [ABSTRACT FROM AUTHOR]

Insolation changes play an important role in driving monsoon changes at orbital time scales. One key issue that has remained outstanding is whether the Asian monsoon is driven by local insolation from the Northern Hemisphere (NH) or remote insolation from the Southern Hemisphere (SH) at orbital band. Here, we perform a set of sensitivity experiments to quantify the impacts of local and remote insolation changes on the Afro‐Asian summer monsoon at 11 ka BP relative to the present. We show that the Afro‐Asian summer monsoon is overwhelmingly driven by the precession induced local insolation change in the tropical‐subtropical NH. The insolation from NH high latitudes also affects the Afro‐Asian summer monsoon. In contrast, the insolation from SH plays a negligible role. Our model experiments support the idea that the Afro‐Asian summer monsoon are driven predominantly by the direct forcing of NH low latitudes summer insolation for the Holocene. Plain Language Summary: The Afro‐Asian summer monsoon response to solar insolation has been studied extensively both in observation evidences and model simulations. However, whether the Afro‐Asian summer monsoon is driven by local insolation from the Northern Hemisphere (NH) and remote insolation from the Southern Hemisphere (SH) still remains an open question. This work, for the first time, systematically isolates local and remote insolation impacts on Afro‐Asian summer monsoon using insolation from 11 ka BP. Our study suggests that the Afro‐Asian summer monsoon is driven by local precession insolation change. The increased local summer insolation at 11 ka increases the land‐sea thermal contrast, migrating the subcloud moist static energy maximum and westerly jet northward. These processes lead to a belt of increased monsoon precipitation stretching from North Africa eastward into South and East Asia, resulting in enhanced monsoon circulation and precipitation. The remote insolation from NH high latitude can also drives the incremental Afro‐Asian summer monsoon precipitation but the magnitude is much smaller compared with local effect. The insolation from SH has negligible role. Our model experiments support the idea that NH summer monsoons are driven predominantly by the direct forcing of NH low latitudes summer insolation for the Holocene. Key Points: The first study to completely isolate the local and remote insolation effect on Afro‐Asian summer monsoon at geological timeThe Afro‐Asian summer monsoon during Holocene is driven by local precession forcing in the tropical‐subtropical Northern HemisphereThe "latent heat" hypothesis is not supported by this study [ABSTRACT FROM AUTHOR]

The forcing of multicentennial climate variability in the Western Pacific Warm Pool (WPWP) region is not fully understood. Here, we generated 6‐kyr‐long continuous charcoal records from five peatlands in Borneo. Every several hundred years, peaks of charcoal influx were identified in the composite record, indicating that the peatlands repeatedly experienced dry conditions and wildfires. Major fire events were identified at ∼5.4, 4.7, 4.4, 3.7, 3.2, 2.7, 2.4, 2.2, 1.7, 1.1, 0.6, and 0.3 ka. Most of these coincided with the maxima of Borneo speleothem δ18O and occurred in the high solar activity periods following the solar minima. This suggests that the higher solar activity decreased rainfall, increasing dryness and wildfire frequency. This result challenges the hypothesis that high solar activity intensifies atmospheric convection in the WPWP area. Plain Language Summary: The charcoal influx in peat sequences shed light on the wildfire history in northern Borneo during the last 6,000 years. The sequences indicate peaks of charcoal influx every several hundred years, suggesting that the peatlands repeatedly experienced dry conditions and wildfires. The major fire events occurred in the high solar activity period after the solar activity was at a minimum. This suggests that the climate was drier when the solar activity was stronger. This result challenges the idea that high solar activity induces more rainfall in the tropical Western Pacific area. Key Points: Charcoal influx in peats was evaluated to understand wildfire history and climate change in northern BorneoThe charcoal record showed that fire events occurred every several hundred years in response to changes in solar activityMajor fire events occurred in the high solar activity periods following the preceding solar minima [ABSTRACT FROM AUTHOR]

Wildfire activity is an important activity in evolution of vegetation and carbon cycling. Whether wet weather will suppress wildfire or promote them by increasing fuel reserves during the Holocene is not clear. We obtained a record of black carbon from a sediment core spanning the last 14.8 kyr from Gonghai Lake, in North China. There is a close relationship between the timing of wildfire activity and vegetation development driven by the East Asian summer monsoon intensity. On a millennial timescales, wet climatic conditions provide a sufficient biofuels reserve, in the same period wildfire increase; thus, the regional potential biofuels reserve is shown to be an important controlling of regional wildfire activity in the monsoon region of China, under natural conditions. We infer that with the strengthening of Asian summer monsoon caused by global warming, the wildfire carbon emission in Asian monsoon region may increase in the future. Plain Language Summary: Much attention has been paid to the response of wildfire activity to climate change. Understanding the past history of wildfires and their triggering factors may help us to mitigate the effects of future wildfires. Our study of the black carbon record of the sediments from an alpine lake (Gonghai Lake) in North China indicates that the level of biofuels (mainly woody vegetation) was the main control on the intensity of wildfire on a millennial timescales over the past ∼14,800 yr. When the climate was wetter, more biofuels were available as a result of increased biomass storage, wildfires were more intense with a relatively stable ignition probability. So, climate trends that favor vegetation development will lead to a higher intensity of wildfire and carbon emission in the Asian monsoon region in the future, with the strengthening of Asian summer monsoon caused by global warming. Key Points: The variation of wildfire and summer monsoon is consistent on the millennial scale, wet climate drives wildfire enhancingBiofuels reserve has controlled wildfire for the Holocene in Asian summer monsoon regionStronger monsoons caused by global warming would increase wildfire carbon emission [ABSTRACT FROM AUTHOR]

The Ross Sea has the world's largest marine protected area. Modified Circumpolar Deep Water (MCDW) has significant effects on physical and biological processes in the Ross Sea. Totally 13 penguin ornithogenic sediment profiles were collected from Inexpressible Island, Ross Sea, and the Cd/P ratios were used as a proxy of MCDW intrusion, enabling to reconstruct the variability of MCDW intrusion into the Ross Sea during the past 6,000 years. During the intervals of ∼0.7–1.6 and ∼2.8–6.0 kyr BP, enhanced MCDW intrusion increased the heat supply which warmed the surface water and reduced the coastal sea ice concentration. By contrast, reduced MCDW intrusion during ∼1.6–2.8 kyr BP caused a decrease in the penguin population via restricting food supply and/or increasing sea ice concentration. Thus, changes in MCDW were responsible for driving millennial changes in sea ice and penguin population in the Ross Sea. Plain Language Summary: Modified Circumpolar Deep Water (MCDW) has important impacts on physical and biological processes in the Ross Sea. Although high‐resolution spatiotemporal records of MCDW intrusion into the modern Ross Sea have been obtained using various methods, the intrusion of this water mass into the Ross Sea during the Holocene has not previously been reconstructed. Here, we use measurements of the Cd/P ratio in ornithogenic sediments to reconstruct the variability of the intrusion of the MCDW into the Ross Sea during the past 6,000 years. MCDW intrusion was enhanced during the intervals of ∼0.7–1.6 and ∼2.8–6.0 kyr BP, when the resulting increased heat supply warmed the surface water and reduced the concentration of coastal sea ice. By contrast, when MCDW intrusion was reduced during ∼1.6–2.8 kyr BP, the resulting restriction of the food supply and/or increased coastal sea ice concentration caused a decrease in the penguin population. Our results demonstrate that the Cd/P ratio can be used as a proxy of MCDW intrusion and that changes in the intrusion of the MCDW were responsible for driving millennial‐scale changes in sea ice and the penguin population in the Ross Sea. Key Points: Cd/P profiles from ornithogenic sediments can be used as a proxy of Modified Circumpolar Deep Water (MCDW) intrusionReconstruction of MCDW intrusion in the Ross Sea during the past 6,000 yearsMCDW intrusion drives millennial changes in sea ice concentration and penguin population in the Ross Sea [ABSTRACT FROM AUTHOR]

The integrated effects of ocean‐atmosphere dynamics on the temperature evolution in the western North Pacific marginal seas have remained elusive. In order to study mechanisms controlling southern Yellow Sea (YS) temperature changes, bottom water temperature (BWT) changes were reconstructed for the last 8.8 kyr by using the TEXL86 index, which archives temperature signal of the winter season Yellow Sea Warm Current. Our results reveal a series of abrupt multi‐centennial to millennial scale BWT changes (∼1°C), superimposed on a gradual long‐term cooling (>3°C) trend starting from ∼5 ka to the present. The YS BWT changes are positively correlated with subsurface water temperature changes in the Western Pacific Warm Pool (WPWP). The Western Pacific Warm Pool subsurface water cooling signal was most likely transmitted by the Kuroshio Current into the southern YS, highlighting the role of WPWP in influencing thermodynamics of the extratropical regions during the Holocene. Plain Language Summary: The Yellow Sea (YS) is a semi‐closed marginal sea located in the northwestern Pacific Ocean. During the winter season, the Yellow Sea Warm Current (YSWC) is driven by northwesterly winds, flowing into the southern YS along the west flank of the central trough. The YSWC, a continuation of the Kuroshio Current, brings warm equatorial Pacific water into the YS, leading to milder winters in the surrounding coastal cities compared with other cities on the same latitude in China. The YSWC is sensitive to changes in ocean‐atmosphere dynamics. However, its evolution during the Holocene is not well understood. We reconstruct the winter season temperature changes of the YSWC during the last 8.8 kyr. We found warm temperatures during the mid‐Holocene (8.8‐5 ka) and a gradual cooling trend over the last 5 kyr, which coincides with subsurface water temperature changes in the Western Pacific Warm Pool (WPWP). We suggest that the tropical subsurface water temperature changes of the WPWP are most likely transmitted via the Kuroshio Current into the YS. Our results shed new light on our understanding of the role played by the WPWP water masses in regulating subtropical ocean dynamics and climate during the mid‐to‐late Holocene. Key Points: The temperature evolution of the winter season Yellow Sea Warm Current was reconstructed over the past 8.8 kyrAbrupt multi‐centennial to millennial scale changes are superimposed on a gradual cooling trend starting from ∼5 ka to the presentWestern Pacific Warm Pool subsurface water cooling signal was transmitted by the Kuroshio Current into the southern Yellow Sea [ABSTRACT FROM AUTHOR]

Here we present, to date, the highest‐resolved (~5 years) and most precisely dated Holocene monsoon climate reconstruction for the western Chinese Loess Plateau based on five replicated stalagmite δ18O records from Wuya Cave, eastern Gansu, China. Our record suggests the wettest period occurred between 10,500 and 6,600 a BP in this region. After this period, the amplitude of Asian summer monsoon decadal‐scale variability progressively increased likely in response to increasing ENSO frequency since the middle Holocene. Our study reveals similar asymmetric centennial‐scale double‐plunging structures of the 8.2, 5.5, and 2.8 ka events in the western Chinese Loess Plateau, suggesting a possible role of solar activity whose impact was amplified around 8.2 ka BP by the meltwater flood. In contrast, the 4.2 ka event exhibit gradually declining monsoon rainfall with centennial‐ to decadal‐scale fluctuations. Key Points: A 5 year‐resolved Holocene Asian summer monsoon record was reconstructed for the western Loess Plateau based on speleothemsThe wettest period occurred between 10,500 and 6,600 a BP, after that, the amplitude of decadal‐scale monsoon variability increasedSimilar structures were observed during the 8.2, 5.5, and 2.8 ka weak monsoon events, which are different from the 4.2 ka event [ABSTRACT FROM AUTHOR]

The East Asian summer monsoon and winter monsoon (EASM and EAWM) are two important components of the East Asian monsoon system. However, the relationship between the two components during the Holocene remains debated in the observation. Here, we use a set of simulations in CCSM3 to investigate the EASM‐EAWM relation across different timescales during the Holocene. It is shown that the intensities of EASM and EAWM are positively correlated at orbital timescale but negatively correlated from millennial down to multidecadal timescales. The positive correlation at orbital timescales is forced by the seasonal insolation forcing, while the negative correlation at millennial and shorter timescales is caused mainly by the internal variability of the Atlantic Meridional Overturning Circulation (AMOC) and the subsequent teleconnection to East Asia via land‐sea thermal contrast. Plain Language Summary: The East Asian summer monsoon (EASM) and East Asian winter monsoon (EAWM) are important factors that affect regional climate. However, it has remained controversial whether EASM and EAWM vary in‐phase or out of phase in the Holocene. Our simulations show that EASM correlates with EAWM positively at orbital timescale due to the seasonal precessional forcing but negatively correlated from multidecadal to millennial timescales because of the impact of the Atlantic Meridional Overturning Circulation (AMOC). Key Points: Anticorrelations are found in EASM and EAWM variations from multidecadal to millennial timescales during the HoloceneThe negative EASM‐EAWM relation is likely caused by the AMOC [ABSTRACT FROM AUTHOR]

Arctic summer temperatures mostly cooled over the last ~7 kyr, owing to decreasing summer insolation. However, knowledge of the winter season is limited in the Arctic paleoclimate literature. Here we develop a composite record of δ18O from ice wedges—a winter precipitation archive—to reconstruct changes in winter climate in the northwestern Canadian Arctic since ~7.4 kyr b2k. Our record shows a long‐term δ18O enrichment (+(0.14 ± 0.10)‰ kyr−1), suggesting winter temperatures increased since the mid‐Holocene, a finding that is corroborated by reconstructions from the Siberian Arctic. Winter warming over the last ~7 kyr is consistent with increasing winter insolation and greenhouse gas forcing. This study provides some of the first insights on the sensitivity of winter temperatures in the Canadian Arctic to past, and potentially future, climate forcings, and contributes to a more seasonally holistic understanding of the Arctic system. Plain Language Summary: The history of climate change during the last 11,700 years, a period known as the Holocene Epoch, has been traditionally studied using natural climate proxies such as tree rings or pollen in the sedimentary record. Such records allow us to better understand past climate variability in response to changing greenhouse gas concentrations, solar radiation, and other boundary conditions. However, most traditional climate proxies are biological and sensitive mainly to growing‐season conditions, whereas changes in cold‐season conditions are not well described in the literature. This is especially true in the Arctic where recent climate warming has been most pronounced in the winter season, but few cold‐season‐specific proxy records are available. In this study, we develop a ~7,400‐year record of the δ18O isotope composition of relict ice wedges in the northwestern Canadian Arctic, a proxy type that is specifically sensitive to cold‐season conditions. We observe a long‐term increase in ice‐wedge δ18O over the past ~7,400 years, indicating warming winter temperatures since the mid‐Holocene. This warming corresponds to increasing winter solar radiation and greenhouse gas concentrations and is in agreement with recent reports from ice wedges in the Siberian Arctic. Key Points: Ice‐wedge δ18O reveals an enrichment trend over the last ~7.4 kyrThe enrichment reflects a long‐term winter warming trend, coinciding with increasing winter insolation and greenhouse gas forcingThis record provides key insights on winter Holocene climate not previously described by other records in this region [ABSTRACT FROM AUTHOR]

Arctic climate is uniquely sensitive to ongoing warming. The feedbacks that drive this amplified response remain insufficiently quantified and misrepresented in model scenarios of future warming. Comparison with paleotemperature reconstructions from past warm intervals can help close this gap. The Early Holocene (11.7–8.2 ka BP) is an important target because Arctic temperatures were warmer than today. This study presents centennially resolved summer temperature reconstructions from three Svalbard lakes. We show that Early Holocene temperatures fluctuated between the coldest and warmest extremes of the past 12 ka, exceeding the range of instrumental observations and future projections. Peak warmth occurred ~10 ka BP, with temperatures 7 °C warmer than today due to high radiative forcing and intensified inflow of warm Atlantic waters. Between 9.5 and 8 ka BP, temperatures dropped in response to freshwater fluxes from melting ice. Facing similar mechanisms, our findings may provide insight into the near‐future response of Arctic climate. Plain Language Summary: The Arctic warms much faster than the global average. This amplified response can trigger feedbacks that affect the trajectory of future change. In areas formerly covered by ice, darker open water or rocks reflect less solar heat, enhancing warming. However, freshwater from melting ice may slow ocean circulation, leading to cooling. The climate impact of these mechanisms remain insufficiently understood, restricting efforts to predict future change. To reduce uncertainty, our research uses geological information from the most recent past period when the Arctic was warmer than the present, the Early Holocene, which lasted from 11,700 to 8,200 years ago. We analyzed fats from algae preserved in Svalbard lakes that yield information about past summer temperatures. Our findings show that the Early Holocene was characterized by the coldest and warmest extremes experienced since the last Ice Age. During peak warmth, summer temperatures were 7 °C warmer than today as more solar radiation and warm water reached the Arctic. However, Early Holocene warming was much slower than today. But warming was interrupted when freshwater pulses from melting Ice Sheets lowered temperatures. As we face a warmer Arctic with a melting Greenland Ice Sheet, our findings provide a rare window into the region's future. Key Points: Temperatures exceeded instrumental and projected values ~10 ka BP as reinvigorating ocean circulation compounded radiative forcingTemperatures drop ~9.5–8 ka BP as the impact of freshwater from the melting Laurentide Ice Sheet overwhelms warmingFirst terrestrial evidence from the Nordic Seas of surface cooling in response to the meltwater‐driven 9.3 and 8.2 ka climate events [ABSTRACT FROM AUTHOR]

Independent inference of the Asian winter monsoon (AWM), albeit achieved at several sparse sites, has reached no consensus for its variability through the Holocene. A sediment core from the northern coast of the South China Sea (SCS) was utilized to analyze organic biomarkers at (bi‐)decadal resolution, unveiling how SCS oceanic conditions fingerprint the AWM signal. Generally, alkenone sea surface temperature (SST) record, resembling the temporal structures of integrated tropical SST over the past 7,500 years, shows abnormal cool temperatures (up to ~4 °C) during the Little Ice Age and between ~1,200 and 2,500 years BP, when windborne terrigenous hopane compounds experienced considerable increases superimposed on a general increasing trend. Our results, together with augmented SST gradient between the SCS coast and open ocean, consistently suggest AWM strengthening toward the late Holocene. An intensified AWM during cold intervals like the Little Ice Age would have provided strong positive feedback to enhance coastal cooling. Plain Language Summary: Reconstructions of the Holocene Asian winter monsoon (AWM) history from terrestrial proxies are not only limited but also opposite, with both strengthening and weakening trends as reported. This study sheds additional insight into this controversy by analyzing the organic geochemistry of a sediment core at the northern coast of the South China Sea, where oceanic conditions such as sea surface temperature intensively interact with the AWM. We observed substantial surface cooling and a remarkable increase in terrestrial‐sourced hopane content concurrently toward the late Holocene, with the maximum taking place during the Little Ice Age and between 1,200 and 2,500 years ago. Together with enhanced temperature contrast between the coast and open ocean, our results clearly demonstrate an overall intensification of the Holocene AWM toward the present, antiphased with Asian summer monsoon changes. Key Points: Bi‐decadal alkenone SST changes at the northern SCS coast over the past ~7,500 yearsSharp increase in flux of terrestrial‐sourced hopane compounds during cool intervalsStrengthened winter monsoon toward the late Holocene, particularly at the LIA [ABSTRACT FROM AUTHOR]

We report a new high‐resolution Holocene 10Be record from Huguangyan Maar Lake in subtropical‐tropical South China, aimed to detect the atmospheric 10Be production signal in low‐latitude regions. After minimizing climatic effects by regression analyses between 10Be concentration and climatic proxies from the same archive, we successfully distinguished variations in geomagnetic field intensity and solar activity using 2,000‐year low‐ and high‐pass filtering, respectively, of the residual 10Be record (a proxy of the atmospheric 10Be production rate). The resulting 10Be‐derived record of geomagnetic field intensity is generally comparable with geomagnetic models, and the solar‐modulated 10Be signal shows significant correlations with solar activity proxies. The preservation of 10Be production signal in the sediments of this low‐latitude maar lake highlights the largely unexplored potential as well as limitations of 10Be as a tool to reconstruct variations in solar activity and geomagnetic field intensity. Plain Language Summary: The atmospheric production rate of cosmogenic 10Be depends on the cosmic ray flux penetrating the atmosphere, a process that is mainly controlled by the geomagnetic field strength and solar activity. The geomagnetic imprint on 10Be has been well established in previous studies of ice cores and marine sediments. The relationship between solar activity and 10Be has also been studied in ice cores and high‐latitude lakes. Here we for the first time present a high‐resolution 10Be record from Huguangyan Maar Lake in subtropical‐tropical South China over the Holocene. We successfully separated the atmospheric 10Be production signal from climatic effects that contribute to up to ~52% of the variance in 10Be concentration. After eliminating the climatic effects, variations in both geomagnetic field intensity and solar activity signals were reconstructed from the residual 10Be record, using 2,000‐year low pass, and high‐pass filtering, respectively. The geomagnetic‐ and solar‐modulated 10Be production signals are evaluated by comparisons with independent records. This result unambiguously indicates that the 10Be‐derived solar activity signal at a low‐latitude subtropical site can be obtained, even when the 10Be signal is dominated by regional climate, in our case, accounting for up to ~65% of the variance in the record during the early‐middle Holocene. Key Points: We for the first time report on a multidecadal to centennial‐scale 10Be record throughout the Holocene in subtropical‐tropical South ChinaWe separated atmospheric 10Be production signal from regional environmental effects that account for ~52% of variance in 10Be concentrationGeomagnetic‐ and solar‐derived 10Be signals were reconstructed by 2,000‐year low‐ and high‐pass filtering, respectively, of the residual record [ABSTRACT FROM AUTHOR]

The hazards posed by infrequent major floods to communities along the Susquehanna River and the ecological health of Chesapeake Bay remain largely unconstrained due to the short length of streamgage records. Here we develop a history of high‐flow events on the Susquehanna River during the late Holocene from flood deposits contained in MD99‐2209, a sediment core recovered in 26 m of water from Chesapeake Bay near Annapolis, Maryland, United States. We identify coarse‐grained deposits left by Hurricane Agnes (1972) and the Great Flood of 1936, as well as during three intervals that predate instrumental flood records (~1800–1500, 1300–1100, and 400–0 CE). Comparison to sedimentary proxy data (pollen and ostracode Mg/Ca ratios) from the same core site indicates that prehistoric flooding on the Susquehanna often accompanied cooler‐than‐usual winter/spring temperatures near Chesapeake Bay—typical of negative phases of the North Atlantic Oscillation and conditions thought to foster hurricane landfalls along the East Coast. Plain Language Summary: Despite the vulnerability of many mid‐Atlantic cities to flooding, including Washington D.C., few long‐term records exist to assess the risks posed by extreme, infrequent, storm events. Here we document recent and prehistoric floods on the Susquehanna River, which has the largest watershed on the U.S. Eastern Seaboard, using sediment cores collected from Chesapeake Bay. Our analysis finds that much of the Susquehanna's observed centennial‐millennial scale flood variability may be driven by the frequency of hurricane landfalls along the U.S. East Coast. Key Points: Recent and prehistoric flood deposits are recorded in Chesapeake Bay sedimentsFlood frequency is higher during negative phases of the North Atlantic OscillationNegative NAO conditions may increase hurricane landfalls along the U.S. East Coast [ABSTRACT FROM AUTHOR]

The middle to late Holocene (8,200 years ago to present) in the Arctic is characterized by cooling temperatures and the regrowth and advance of glaciers. Whether this Neoglaciation was a threshold response to linear cooling, or was driven by a regional or Arctic‐wide acceleration of cooling, is unknown. Here we examine the largest‐yet‐compiled multiproxy database of Arctic Holocene temperature change, along with model simulations, to investigate regional and Arctic‐wide increases in cooling rate, the synchronicity of Neoglacial onset, and the observed and simulated rates of temperature change. We find little support for an Arctic‐wide onset of Neoglacial cooling but do find intervals when regions experienced rapid increases in long‐term cooling rate, both in the observations and in climate model simulations. In the model experiments, Neoglacial cooling is associated with indirectly forced millennial‐scale variability in meridional heat transport superposed on the long‐term decline of summer insolation. Plain Language Summary: Arctic summer temperatures have decreased for the past 8,000 years, before rapidly warming over the past century. As temperatures cooled, glaciers that had melted began to regrow throughout the Arctic, a phenomenon and a time interval known as Neoglaciation. This study seeks to understand the nature of this cooling and whether or not this indicates a tipping point in the climate system. Specifically, we use a large database of records from ice cores, lakes, ocean sediment, and more paleoclimate archives to detect patterns of cooling. We investigate these patterns, and climate model simulations, to determine what parts of the Arctic experienced Neoglaciation at the same time, how rapidly it cooled, and what climate models indicate about the causes of cooling. We find that the Arctic did not cool simultaneously, but different regions cooled at different times and that the climate models perform well when simulating both the timing and amount of Arctic cooling. Key Points: The onset of Neoglaciation is regional and driven by nonlinear increases in regional coolingModel simulations suggest that cooling onsets are linked to Atlantic Meridional Overturning CirculationObserved and simulated rates of late Holocene cooling in the Arctic are remarkably similar [ABSTRACT FROM AUTHOR]

Arctic precipitation is predicted to increase this century, with dramatic consequences for high‐latitude systems. Observations remain spatiotemporally limited, hampering determination of the forcings causing wetter Arctic conditions, although two mechanisms have been proposed: enhanced local evaporation and greater poleward atmospheric moisture transport. Here a subcentennial‐resolution multiproxy lake sediment record from western Greenland sheds light on these mechanisms. Cool summers throughout the Northern Hemisphere and in western Greenland 9 to 8 ka are associated with aridity in this region, via reductions in local evaporation and in meridional moisture gradients, which suppressed poleward moisture transport. Summers became more humid starting 8.1 ka, mainly due to increased evaporation from warmer Arctic seas but also to increased poleward moisture transport caused by hemispheric warming. This record provides independent support for predictions of both enhanced local evaporation and increased poleward moisture transport causing wetter Arctic summers in step with global ocean and atmosphere warming. Plain Language Summary: As the Arctic warms, it is getting wetter. This change can amplify warming worldwide by causing more plants to grow and decompose, releasing heat‐trapping gases into the atmosphere. Sparse modern weather records in the Arctic make it difficult to pinpoint the forces causing increased rainfall, but scientists are debating two theories: (1) More water evaporates from warm, ice‐free Arctic seas, and then falls locally as precipitation, or (2) as Earth warms, humidity rises more at lower latitudes, creating an imbalance that draws moist air up into the drier Arctic. Our research turns to history for insights. We show that in western Greenland, summers became cooler and drier about 9,000 years ago, coinciding with a drop in moisture imported from lower latitudes. Then, around 8,000 years ago, the region warmed rapidly and summers got wetter. A rise in both local evaporation and incoming moisture from lower latitudes may have fueled this change, according to our interpretation of geologic records. Our study suggests that both processes may contribute to a future, wetter Arctic. In addition, we advance scientific inquiry by using a recently developed technique, analysis of the hydrogen isotopes of ancient precipitation, to examine prehistoric humidity and precipitation trends that previously eluded investigation. Key Points: Coastal western Greenland summers became cooler and more arid 9,000 to 8,000 years agoWetter summers 8,000 years ago were synchronous with warming on western Greenland and throughout Northern HemispherePrecipitation isotopes show wetter summers caused by increased local evaporation and increased poleward moisture transport [ABSTRACT FROM AUTHOR]