Francesco Muschitiello, Marco Antonio Aquino-Lopez
Abstract. This study presents the first continuously measured transfer functions that quantify the age difference between the Greenland ice-core chronology 2005 (GICC05) and the U–Th timescale during the last glacial period. The transfer functions were estimated using an automated algorithm for Bayesian inversion that allows inferring a continuous and objective synchronization between Greenland ice-core and East Asian summer monsoon speleothem data, and a total of three transfer functions were inferred using independent ice-core records. The algorithm is based on an alignment model that considers prior knowledge of the GICC05 counting error but also samples synchronization scenarios that exceed the differential dating uncertainty of the annual-layer count in ice cores, which are currently hard to detect using conventional alignment techniques. The transfer functions are on average 48 % more precise than previous estimates and significantly reduce the absolute dating uncertainty of the GICC05 back to 48 kyr ago. The results reveal that GICCC05 is, on average, systematically younger than the U–Th timescale by 0.86 %. However, they also highlight that the annual-layer counting error is not strictly correlated over extended periods of time and that within the coldest Greenland Stadials the differential dating uncertainty is likely underestimated by up to ∼13 %. Importantly, the analysis implies for the first time that during the Last Glacial Maximum GICC05 may overcount ice layers by ∼10 % – a bias possibly attributable to a higher frequency of sub-annual layers due to changes in the seasonal cycle of precipitation and mode of dust deposition to the Greenland Ice Sheet. The new timescale transfer functions provide important constraints on the uncertainty surrounding the stratigraphic dating of the Greenland age scale and enable an improved chronological integration of ice cores as well as U–Th-dated and radiocarbon-dated paleoclimate records on a common timeline. The transfer functions are available as a Supplement to this study.
{"title":"Continuous synchronization of the Greenland ice-core and U–Th timescales using probabilistic inversion","authors":"Francesco Muschitiello, Marco Antonio Aquino-Lopez","doi":"10.5194/cp-20-1415-2024","DOIUrl":"https://doi.org/10.5194/cp-20-1415-2024","url":null,"abstract":"Abstract. This study presents the first continuously measured transfer functions that quantify the age difference between the Greenland ice-core chronology 2005 (GICC05) and the U–Th timescale during the last glacial period. The transfer functions were estimated using an automated algorithm for Bayesian inversion that allows inferring a continuous and objective synchronization between Greenland ice-core and East Asian summer monsoon speleothem data, and a total of three transfer functions were inferred using independent ice-core records. The algorithm is based on an alignment model that considers prior knowledge of the GICC05 counting error but also samples synchronization scenarios that exceed the differential dating uncertainty of the annual-layer count in ice cores, which are currently hard to detect using conventional alignment techniques. The transfer functions are on average 48 % more precise than previous estimates and significantly reduce the absolute dating uncertainty of the GICC05 back to 48 kyr ago. The results reveal that GICCC05 is, on average, systematically younger than the U–Th timescale by 0.86 %. However, they also highlight that the annual-layer counting error is not strictly correlated over extended periods of time and that within the coldest Greenland Stadials the differential dating uncertainty is likely underestimated by up to ∼13 %. Importantly, the analysis implies for the first time that during the Last Glacial Maximum GICC05 may overcount ice layers by ∼10 % – a bias possibly attributable to a higher frequency of sub-annual layers due to changes in the seasonal cycle of precipitation and mode of dust deposition to the Greenland Ice Sheet. The new timescale transfer functions provide important constraints on the uncertainty surrounding the stratigraphic dating of the Greenland age scale and enable an improved chronological integration of ice cores as well as U–Th-dated and radiocarbon-dated paleoclimate records on a common timeline. The transfer functions are available as a Supplement to this study.","PeriodicalId":10332,"journal":{"name":"Climate of The Past","volume":"17 1","pages":""},"PeriodicalIF":4.3,"publicationDate":"2024-06-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141508143","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Christian Pfister, Stefan Brönnimann, Andres Altwegg, Rudolf Brázdil, Laurent Litzenburger, Daniele Lorusso, Thomas Pliemon
Abstract. This study investigates the validity of wine must quality as an April-to-August temperature proxy between 1420 and 2019 based on expert ratings and quality measurements from Germany, Luxembourg, eastern France, and the Swiss Plateau. This is highly relevant as uncertainties remain on past climate variations during this period. The evidence was reviewed according to the best practice of historical climatology. Expert ratings tended to agree with Oechsle density measurements that gradually replaced them from the 1840s. A statistical model calibrated to predict wine must quality from climate data explains 75 % of the variance, underlining the potential value of wine must quality as a climate proxy. Premium crops were collected in years of early harvest involving high insolation during maturation, while poor crops resulted from very late harvests in cold and wet summers. An analysis of daily weather types for high- and low-quality years after 1763 shows marked differences. On a decadal timescale, the average quality was highest from 1470 to 1479, from 1536 to 1545, and from 1945 to 1954. Poor crops were collected in periods with prevailing cold and wet summers such as 1453 to 1466, 1485 to 1494, 1585 to 1614, 1685 to 1703, 1812 to 1821, and 1876 to 1936. In the period of enhanced warming after 1990, high quality became the rule.
{"title":"600 years of wine must quality and April to August temperatures in western Europe 1420–2019","authors":"Christian Pfister, Stefan Brönnimann, Andres Altwegg, Rudolf Brázdil, Laurent Litzenburger, Daniele Lorusso, Thomas Pliemon","doi":"10.5194/cp-20-1387-2024","DOIUrl":"https://doi.org/10.5194/cp-20-1387-2024","url":null,"abstract":"Abstract. This study investigates the validity of wine must quality as an April-to-August temperature proxy between 1420 and 2019 based on expert ratings and quality measurements from Germany, Luxembourg, eastern France, and the Swiss Plateau. This is highly relevant as uncertainties remain on past climate variations during this period. The evidence was reviewed according to the best practice of historical climatology. Expert ratings tended to agree with Oechsle density measurements that gradually replaced them from the 1840s. A statistical model calibrated to predict wine must quality from climate data explains 75 % of the variance, underlining the potential value of wine must quality as a climate proxy. Premium crops were collected in years of early harvest involving high insolation during maturation, while poor crops resulted from very late harvests in cold and wet summers. An analysis of daily weather types for high- and low-quality years after 1763 shows marked differences. On a decadal timescale, the average quality was highest from 1470 to 1479, from 1536 to 1545, and from 1945 to 1954. Poor crops were collected in periods with prevailing cold and wet summers such as 1453 to 1466, 1485 to 1494, 1585 to 1614, 1685 to 1703, 1812 to 1821, and 1876 to 1936. In the period of enhanced warming after 1990, high quality became the rule.","PeriodicalId":10332,"journal":{"name":"Climate of The Past","volume":"44 1","pages":""},"PeriodicalIF":4.3,"publicationDate":"2024-06-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141508142","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract. The 8.2 ka event has been extensively investigated as a remarkable single event but rarely considered as a part of multi-centennial climatic evolution. Here, we present absolutely dated speleothem multi-proxy records spanning 9.0–7.9 ka from Beijing in North China, near the northern limit of the East Asian summer monsoon (EASM) and thus sensitive to climate change, to provide evidence of the intensified multi-decadal climatic oscillations since 8.52 ka. Three extreme excursions characterized by inter-decadal consecutive δ18O excursions exceeding ±1σ are identified from 8.52 ka in our speleothem record. The earlier two are characterized by enriched 18O at ∼8.50 and 8.20 ka, respectively, suggesting a prolonged arid event, which is supported by the positive trend in δ13C values, increased trace element ratios, and lower growth rate. Following the 8.2 ka event, an excessive rebound immediately emerges in our δ18O and trace element records but moderate in the δ13C, probably suggesting pluvial conditions and nonlinear response of the local ecosystem. Following two similar severe droughts at 8.50 and 8.20 ka, the different behavior of δ13C suggests the recovering degree of resilient ecosystem responding to different rebounded rainfall intensity. A comparison with other high-resolution records suggests that the two droughts–one pluvial pattern between 8.52 and 8.0 ka is of global significance instead of being a regional phenomenon, and is causally linked to the slowdown and acceleration of the Atlantic Meridional Overturning Circulation that was further dominated by the freshwater injections in the North Atlantic.
摘要。8.2 ka事件作为一个显著的单一事件已被广泛研究，但很少被视为多世纪气候演变的一部分。这里，我们展示了华北地区北京的9.0-7.9 ka绝对年代的岩浆多代记录，这些记录靠近东亚夏季季风（EASM）的北部界限，因此对气候变化非常敏感，为8.52 ka以来加剧的多年代气候振荡提供了证据。在我们的岩浆记录中发现了自 8.52 ka 以来的三次极端偏移，其特征是年代际连续的 δ18O 偏差超过 ±1σ。前两次分别在 8.50 ka 和 8.20 ka 出现 18O 富集，表明这是一次长期的干旱事件，δ13C 值的正向变化趋势、微量元素比率的增加以及较低的生长率都证明了这一点。在 8.2 ka 事件之后，我们的δ18O 和微量元素记录中立即出现了过度反弹，但δ13C 值却有所缓和，这可能表明了当地生态系统的冲积条件和非线性反应。在 8.50 ka 和 8.20 ka 两次类似的严重干旱之后，δ13C 的不同表现表明了生态系统对不同的降雨强度反弹的恢复程度。与其他高分辨率记录的比较表明，8.52 和 8.0 ka 之间的 "两旱一涝 "模式具有全球意义，而非区域现象，它与大西洋经向翻转环流的减缓和加速有因果关系，而北大西洋的淡水注入进一步主导了大西洋经向翻转环流。
{"title":"A series of climate oscillations around 8.2 ka revealed through multi-proxy speleothem records from North China","authors":"Pengzhen Duan, Hanying Li, Zhibang Ma, Jingyao Zhao, Xiyu Dong, Ashish Sinha, Peng Hu, Haiwei Zhang, Youfeng Ning, Guangyou Zhu, Hai Cheng","doi":"10.5194/cp-20-1401-2024","DOIUrl":"https://doi.org/10.5194/cp-20-1401-2024","url":null,"abstract":"Abstract. The 8.2 ka event has been extensively investigated as a remarkable single event but rarely considered as a part of multi-centennial climatic evolution. Here, we present absolutely dated speleothem multi-proxy records spanning 9.0–7.9 ka from Beijing in North China, near the northern limit of the East Asian summer monsoon (EASM) and thus sensitive to climate change, to provide evidence of the intensified multi-decadal climatic oscillations since 8.52 ka. Three extreme excursions characterized by inter-decadal consecutive δ18O excursions exceeding ±1σ are identified from 8.52 ka in our speleothem record. The earlier two are characterized by enriched 18O at ∼8.50 and 8.20 ka, respectively, suggesting a prolonged arid event, which is supported by the positive trend in δ13C values, increased trace element ratios, and lower growth rate. Following the 8.2 ka event, an excessive rebound immediately emerges in our δ18O and trace element records but moderate in the δ13C, probably suggesting pluvial conditions and nonlinear response of the local ecosystem. Following two similar severe droughts at 8.50 and 8.20 ka, the different behavior of δ13C suggests the recovering degree of resilient ecosystem responding to different rebounded rainfall intensity. A comparison with other high-resolution records suggests that the two droughts–one pluvial pattern between 8.52 and 8.0 ka is of global significance instead of being a regional phenomenon, and is causally linked to the slowdown and acceleration of the Atlantic Meridional Overturning Circulation that was further dominated by the freshwater injections in the North Atlantic.","PeriodicalId":10332,"journal":{"name":"Climate of The Past","volume":"13 1","pages":""},"PeriodicalIF":4.3,"publicationDate":"2024-06-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141513624","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-06-25DOI: 10.5194/egusphere-2024-1754
Markus Adloff, Aurich Jeltsch-Thömmes, Frerk Pöppelmeier, Thomas F. Stocker, Fortunat Joos
Abstract. Atmospheric CO2 concentrations changed over ice age cycles due to net exchange fluxes between land, ocean, ocean sediments, atmosphere, and the lithosphere. Marine sediment and ice cores preserved biogeochemical evidence of these carbon transfers, which resulted from sensitivities of the various carbon reservoirs to climate forcing, many of which remain poorly understood. Numerical studies proved the potential of several physical and biogeochemical processes to impact atmospheric CO2 under steady-state glacial conditions. Yet, it is unclear how much they affected carbon cycling during transient changes of repeated glacial cycles, and what role burial and release of sedimentary organic and inorganic carbon and nutrients played. Addressing this uncertainty, we produced a simulation ensemble of various physical and biogeochemical carbon cycle forcings over the repeated glacial inceptions and terminations of the last 780 kyr with the Bern3D Earth system model of intermediate complexity including dynamic marine sediments. This ensemble allows for assessing transient carbon cycle changes due to these different forcings and gaining a process-based understanding of the associated carbon fluxes and isotopic shifts in a continuously perturbed Earth system. We present results of the simulated Earth system dynamics in the non-equilibrium glacial cycles and a comparison with multiple proxy time series. In our simulations the ocean inventory changed by 200–1400 GtC and the atmospheric inventory by 1–150 GtC over the last deglaciation. DIC changes differ by a factor of up to 28 between simulations with and without interactive sediments, while CO2 changes in the atmosphere are at most four times larger when interactive sediments are simulated. Simulations with interactive sediments show no clear correlations between DIC or nutrient concentrations and atmospheric CO2 change, highlighting the likely need for multi-proxy analyses to understand global carbon cycle changes during glacial cycles in practice. Starting transient simulations with an interglacial geologic carbon cycle balance causes isotopic drifts that require several 100 kyr to overcome, and needs to be considered when designing spin-up strategies.
摘要。由于陆地、海洋、海洋沉积物、大气和岩石圈之间的净交换通量，大气中的二氧化碳浓度在冰期周期中发生了变化。海洋沉积物和冰岩芯保存了这些碳转移的生物地球化学证据，这些证据来自各种碳库对气候作用力的敏感性，其中有许多仍然知之甚少。数值研究证明，在稳态冰川条件下，一些物理和生物地球化学过程有可能对大气中的二氧化碳产生影响。然而，目前还不清楚这些过程在冰川周期的瞬时变化中对碳循环的影响程度，也不清楚沉积有机碳和无机碳以及营养物质的埋藏和释放所起的作用。为了解决这一不确定性，我们利用包括动态海洋沉积物在内的中等复杂度 Bern3D 地球系统模型，对过去 780 千年冰川期的反复起始和终止过程中的各种物理和生物地球化学碳循环作用力进行了模拟组合。通过这种集合可以评估这些不同作用力导致的瞬时碳循环变化，并对持续扰动的地球系统中相关的碳通量和同位素变化获得基于过程的理解。我们介绍了非平衡冰川周期中地球系统动态变化的模拟结果，并与多个代用时间序列进行了比较。在我们的模拟中，海洋存量在上一次冰川期变化了 200-1400 GtC，大气存量变化了 1-150 GtC。在有交互沉积物和没有交互沉积物的模拟中，DIC 的变化最多相差 28 倍，而在有交互沉积物的模拟中，大气中 CO2 的变化最多相差四倍。有交互沉积物的模拟结果显示，DIC 或营养物质浓度与大气中 CO2 变化之间没有明显的相关性，这突出表明在实践中可能需要进行多代理分析，以了解冰川周期中全球碳循环的变化。用冰期地质碳循环平衡开始瞬态模拟会导致同位素漂移，需要几百kyr才能克服，因此在设计自旋策略时需要加以考虑。
{"title":"Sediment fluxes dominate glacial-interglacial changes in ocean carbon inventory: results from factorial simulations over the past 780,000 years","authors":"Markus Adloff, Aurich Jeltsch-Thömmes, Frerk Pöppelmeier, Thomas F. Stocker, Fortunat Joos","doi":"10.5194/egusphere-2024-1754","DOIUrl":"https://doi.org/10.5194/egusphere-2024-1754","url":null,"abstract":"<strong>Abstract.</strong> Atmospheric CO<sub>2</sub> concentrations changed over ice age cycles due to net exchange fluxes between land, ocean, ocean sediments, atmosphere, and the lithosphere. Marine sediment and ice cores preserved biogeochemical evidence of these carbon transfers, which resulted from sensitivities of the various carbon reservoirs to climate forcing, many of which remain poorly understood. Numerical studies proved the potential of several physical and biogeochemical processes to impact atmospheric CO<sub>2</sub> under steady-state glacial conditions. Yet, it is unclear how much they affected carbon cycling during transient changes of repeated glacial cycles, and what role burial and release of sedimentary organic and inorganic carbon and nutrients played. Addressing this uncertainty, we produced a simulation ensemble of various physical and biogeochemical carbon cycle forcings over the repeated glacial inceptions and terminations of the last 780 kyr with the Bern3D Earth system model of intermediate complexity including dynamic marine sediments. This ensemble allows for assessing transient carbon cycle changes due to these different forcings and gaining a process-based understanding of the associated carbon fluxes and isotopic shifts in a continuously perturbed Earth system. We present results of the simulated Earth system dynamics in the non-equilibrium glacial cycles and a comparison with multiple proxy time series. In our simulations the ocean inventory changed by 200–1400 GtC and the atmospheric inventory by 1–150 GtC over the last deglaciation. DIC changes differ by a factor of up to 28 between simulations with and without interactive sediments, while CO<sub>2</sub> changes in the atmosphere are at most four times larger when interactive sediments are simulated. Simulations with interactive sediments show no clear correlations between DIC or nutrient concentrations and atmospheric CO<sub>2</sub> change, highlighting the likely need for multi-proxy analyses to understand global carbon cycle changes during glacial cycles in practice. Starting transient simulations with an interglacial geologic carbon cycle balance causes isotopic drifts that require several 100 kyr to overcome, and needs to be considered when designing spin-up strategies.","PeriodicalId":10332,"journal":{"name":"Climate of The Past","volume":"1 1","pages":""},"PeriodicalIF":4.3,"publicationDate":"2024-06-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141513627","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract. Glacial terminations are marked by a re-organisation of the different components of the climate system. In particular, rapid ice sheet disintegration leads to multiple complex feedback loops that are still poorly understood. To further investigate this aspect, we use here a fully coupled Northern Hemisphere ice sheet–climate model to perform numerical experiments of the last two glacial terminations. We show that even if the first-order climate trajectory is similar for the two terminations, the difference in terms of solar insolation leads to important changes for the ice sheet–climate system. Warmer temperatures during the penultimate termination are compatible with higher sea level during the last interglacial period with respect to the Holocene. We simulate a last interglacial Greenland contribution to sea level rise of about 2 m of sea level equivalent. We also simulate warmer subsurface Southern Ocean, compatible with an additional contribution from the Antarctic ice sheet. In addition, even without considering freshwater flux to the ocean resulting from ice sheet melting, the two terminations display different Atlantic overturning circulation sensitivity, this circulation being more prone to collapses during the penultimate termination. Finally, with additional sensitivity experiments we show that, for the two terminations, the Northern Hemisphere insolation is the main driver for the ice sheet retreat even if vegetation changes have also to be taken into account to simulate the full deglaciation. Conversely, even though it impacts the temperature, greenhouse gas concentration change alone does not explain the amplitude of ice sheet retreat and only modulates its timing.
{"title":"Investigating similarities and differences of the penultimate and last glacial terminations with a coupled ice sheet–climate model","authors":"Aurélien Quiquet, Didier M. Roche","doi":"10.5194/cp-20-1365-2024","DOIUrl":"https://doi.org/10.5194/cp-20-1365-2024","url":null,"abstract":"Abstract. Glacial terminations are marked by a re-organisation of the different components of the climate system. In particular, rapid ice sheet disintegration leads to multiple complex feedback loops that are still poorly understood. To further investigate this aspect, we use here a fully coupled Northern Hemisphere ice sheet–climate model to perform numerical experiments of the last two glacial terminations. We show that even if the first-order climate trajectory is similar for the two terminations, the difference in terms of solar insolation leads to important changes for the ice sheet–climate system. Warmer temperatures during the penultimate termination are compatible with higher sea level during the last interglacial period with respect to the Holocene. We simulate a last interglacial Greenland contribution to sea level rise of about 2 m of sea level equivalent. We also simulate warmer subsurface Southern Ocean, compatible with an additional contribution from the Antarctic ice sheet. In addition, even without considering freshwater flux to the ocean resulting from ice sheet melting, the two terminations display different Atlantic overturning circulation sensitivity, this circulation being more prone to collapses during the penultimate termination. Finally, with additional sensitivity experiments we show that, for the two terminations, the Northern Hemisphere insolation is the main driver for the ice sheet retreat even if vegetation changes have also to be taken into account to simulate the full deglaciation. Conversely, even though it impacts the temperature, greenhouse gas concentration change alone does not explain the amplitude of ice sheet retreat and only modulates its timing.","PeriodicalId":10332,"journal":{"name":"Climate of The Past","volume":"114 1","pages":""},"PeriodicalIF":4.3,"publicationDate":"2024-06-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141508144","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-06-25DOI: 10.5194/egusphere-2024-1566
Thamizharasan Sakthivel, Prosenjit Ghosh, Ravi Bhushan, Harsh Raj, Ankur J. Dabhi, Ajay Shivam, Senthilnathan D
Abstract. Warmer Sea Surface Temperature (SST) in the Bay of Bengal (BoB) is crucial for driving deep atmospheric convection, facilitating low-level south-westerly winds, and enhancing moisture transport, thereby intensifying South Asian Summer Monsoon (SASM) rainfall over South Asia. However, the specific impact of BoB SST on SASM rainfall during the Glacial-Interglacial periods remains poorly understood. In this study, we reconstructed SST and evaporation versus rainfall variability over the past 31 kiloyears by simultaneously analyzing the carbonate clumped isotopes and stable oxygen isotopic composition of surface-dwelling planktic foraminifera Globigerinoides ruber from the Central West BoB (CWBoB), a key moisture source region. Additionally, cloud cover index was inferred from the abundance ratio of planktic foraminifera Globigerina bulloides to Neogloboquadrina dutertrei. Our SST reconstruction reveals an 8 °C variability over the past 31 kyr, coinciding with shifts in the G. bulloides to N. dutertrei ratio during the Last Glacial period and deglaciation, suggesting SST regulation by variable cloud cover. The increase in SST from the Early Holocene is attributed to CO2 radiative forcing. The stable oxygen isotope of seawater δ18Osw strongly aligns with a proxy record of SASM wind intensity, indicating that changes in wind patterns drive the variable evaporation versus rainfall dynamics over CWBoB. Furthermore, we examined the temporal variation in SASM continental runoff and rainfall to the Northern BoB (NBoB) by assessing changes in δ18Osw (∆18Osw), a proxy for Sea Surface Salinity (ΔSSS), between the NBoB and CWBoB. Our analysis revealed a significant relationship between SASM rainfall and SST in the CWBoB, indicating a sensitivity of 0.9±0.1 psu drop in ΔSSS across the NBoB per 1 °C rise in SST. These findings enhance our understanding of the relationship between CWBoB SST and SASM rainfall, highlighting the intricate dynamics of monsoon variability and paving the way for improved predictability of SASM rainfall patterns.
{"title":"Sea Surface Temperature over the Bay of Bengal: A key driver for South Asian Summer Monsoon rainfall during past 31 kiloyears","authors":"Thamizharasan Sakthivel, Prosenjit Ghosh, Ravi Bhushan, Harsh Raj, Ankur J. Dabhi, Ajay Shivam, Senthilnathan D","doi":"10.5194/egusphere-2024-1566","DOIUrl":"https://doi.org/10.5194/egusphere-2024-1566","url":null,"abstract":"<strong>Abstract.</strong> Warmer Sea Surface Temperature (SST) in the Bay of Bengal (BoB) is crucial for driving deep atmospheric convection, facilitating low-level south-westerly winds, and enhancing moisture transport, thereby intensifying South Asian Summer Monsoon (SASM) rainfall over South Asia. However, the specific impact of BoB SST on SASM rainfall during the Glacial-Interglacial periods remains poorly understood. In this study, we reconstructed SST and evaporation versus rainfall variability over the past 31 kiloyears by simultaneously analyzing the carbonate clumped isotopes and stable oxygen isotopic composition of surface-dwelling planktic foraminifera <em>Globigerinoides ruber</em> from the Central West BoB (CWBoB), a key moisture source region. Additionally, cloud cover index was inferred from the abundance ratio of planktic foraminifera <em>Globigerina bulloides</em> to <em>Neogloboquadrina dutertrei</em>. Our SST reconstruction reveals an 8 °C variability over the past 31 kyr, coinciding with shifts in the <em>G. bulloides to N. dutertrei</em> ratio during the Last Glacial period and deglaciation, suggesting SST regulation by variable cloud cover. The increase in SST from the Early Holocene is attributed to CO<sub>2</sub> radiative forcing. The stable oxygen isotope of seawater δ<sup>18</sup>O<sub>sw</sub> strongly aligns with a proxy record of SASM wind intensity, indicating that changes in wind patterns drive the variable evaporation versus rainfall dynamics over CWBoB. Furthermore, we examined the temporal variation in SASM continental runoff and rainfall to the Northern BoB (NBoB) by assessing changes in δ<sup>18</sup>O<sub>sw</sub> (∆<sup>18</sup>O<sub>sw</sub>), a proxy for Sea Surface Salinity (ΔSSS), between the NBoB and CWBoB. Our analysis revealed a significant relationship between SASM rainfall and SST in the CWBoB, indicating a sensitivity of 0.9±0.1 psu drop in ΔSSS across the NBoB per 1 °C rise in SST. These findings enhance our understanding of the relationship between CWBoB SST and SASM rainfall, highlighting the intricate dynamics of monsoon variability and paving the way for improved predictability of SASM rainfall patterns.","PeriodicalId":10332,"journal":{"name":"Climate of The Past","volume":"34 1","pages":""},"PeriodicalIF":4.3,"publicationDate":"2024-06-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141513626","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Wenxu Du, Dawei Lv, Zhihui Zhang, Munira Raji, Cuiyu Song, Luojing Wang, Zekuan Li, Kai Cao, Ruoxiang Yuan, Yuzhuang Sun
Abstract. The Carboniferous, an important coal-forming period in geological history, was characterized by extensive vegetation and high oxygen levels. Numerous wildfire evidence suggests that high frequency of wildfire occurred at that time, specifically in peatlands. However, the control mechanisms for changes in wildfire activity in peatlands during this period are still not clearly understood. In this study, evidence from the Gzhelian in the Ordos Basin, such as the inertinite/vitrinite (I/V) ratio, indicated the existence of different frequencies of wildfire activity at that time. The CaO/MgO and CaO/MgO • Al2O3 climate indicators revealed that high-frequency wildfires mainly occur in warm and humid climates. Based on former age constraints, we deduced that orbital cycles (long eccentricity) controlled the climate influence on peatland wildfires during the Gzhelian. When eccentricity was high, abundant sunshine and frequent rainfall led to warmer and more humid peatlands. The latter environments were more favourable for vegetation development, leading to increased fuel loads, which in turn led to more frequent wildfires. Moreover, the Gzhelian global wildfire records, showed that evidence of wildfire during this period was mainly located in areas with abundant tropical vegetation, supporting the view that wildfire activity during this period was mainly controlled by the fuel loads. Although Hg could be produced by peatland wildfires, but our results show that Hg was mainly from frequent volcanic activity during this period.
{"title":"Orbital-scale climate dynamics impacts on Gzhelian peatland wildfire activity in the Ordos Basin","authors":"Wenxu Du, Dawei Lv, Zhihui Zhang, Munira Raji, Cuiyu Song, Luojing Wang, Zekuan Li, Kai Cao, Ruoxiang Yuan, Yuzhuang Sun","doi":"10.5194/cp-2024-42","DOIUrl":"https://doi.org/10.5194/cp-2024-42","url":null,"abstract":"<strong>Abstract.</strong> The Carboniferous, an important coal-forming period in geological history, was characterized by extensive vegetation and high oxygen levels. Numerous wildfire evidence suggests that high frequency of wildfire occurred at that time, specifically in peatlands. However, the control mechanisms for changes in wildfire activity in peatlands during this period are still not clearly understood. In this study, evidence from the Gzhelian in the Ordos Basin, such as the inertinite/vitrinite (I/V) ratio, indicated the existence of different frequencies of wildfire activity at that time. The CaO/MgO and CaO/MgO • Al<sub>2</sub>O<sub>3</sub> climate indicators revealed that high-frequency wildfires mainly occur in warm and humid climates. Based on former age constraints, we deduced that orbital cycles (long eccentricity) controlled the climate influence on peatland wildfires during the Gzhelian. When eccentricity was high, abundant sunshine and frequent rainfall led to warmer and more humid peatlands. The latter environments were more favourable for vegetation development, leading to increased fuel loads, which in turn led to more frequent wildfires. Moreover, the Gzhelian global wildfire records, showed that evidence of wildfire during this period was mainly located in areas with abundant tropical vegetation, supporting the view that wildfire activity during this period was mainly controlled by the fuel loads. Although Hg could be produced by peatland wildfires, but our results show that Hg was mainly from frequent volcanic activity during this period.","PeriodicalId":10332,"journal":{"name":"Climate of The Past","volume":"410 1","pages":""},"PeriodicalIF":4.3,"publicationDate":"2024-06-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141508145","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Annika V. Herbert, Simon G. Haberle, Suzette G. A. Flantua, Ondrej Mottl, Jessica L. Blois, John W. Williams, Adrian George, Geoff S. Hope
Abstract. The Indo-Pacific Pollen Database (IPPD) is the brainchild of the late Professor Geoffrey Hope, who gathered pollen records from across the region to ensure their preservation for future generations of palaeoecologists. This noble aim is now being fulfilled by integrating the IPPD into the online Neotoma Palaeoecology Database, making this compilation available for public use. Here we explore the database in depth and suggest directions for future research. The IPPD comprises 226 fossil pollen records, most postdating 20 ka, but some extending as far back as 50 ka or further. Over 80 % of the records are Australian, with a fairly even distribution between the different Australian geographical regions, the notable exception being Western Australia, which is only represented by 3 records. The records are also well distributed in modern climate space, the largest gap being in drier regions due to preservation issues. However, many of the records contain few samples or have fewer than 5 chronology control points, such as radiocarbon, luminescence or Pb-210 for the younger sequences. Average sedimentation rate for the whole database, counted as years per cm, is 64.8 yr/cm, with 61 % of the records having a rate of less than 50 yr/cm. The highest sedimentation rate by geographical region occurs on Australia’s east coast, while the lowest rates are from the Western Pacific. Overall, Australia has a higher sedimentation rate than the rest of the Indo-Pacific region. The IPPD offers many exciting research opportunities, such as examination of human impact on regional vegetation, contrasting first human arrival and colonisation, and assessment of rates of vegetation change during the Holocene. Merging the IPPD into Neotoma also facilitates inclusion of data from the Indo-Pacific region into global syntheses.
{"title":"The Indo-Pacific Pollen Database – a Neotoma constituent database","authors":"Annika V. Herbert, Simon G. Haberle, Suzette G. A. Flantua, Ondrej Mottl, Jessica L. Blois, John W. Williams, Adrian George, Geoff S. Hope","doi":"10.5194/cp-2024-44","DOIUrl":"https://doi.org/10.5194/cp-2024-44","url":null,"abstract":"<strong>Abstract.</strong> The Indo-Pacific Pollen Database (IPPD) is the brainchild of the late Professor Geoffrey Hope, who gathered pollen records from across the region to ensure their preservation for future generations of palaeoecologists. This noble aim is now being fulfilled by integrating the IPPD into the online Neotoma Palaeoecology Database, making this compilation available for public use. Here we explore the database in depth and suggest directions for future research. The IPPD comprises 226 fossil pollen records, most postdating 20 ka, but some extending as far back as 50 ka or further. Over 80 % of the records are Australian, with a fairly even distribution between the different Australian geographical regions, the notable exception being Western Australia, which is only represented by 3 records. The records are also well distributed in modern climate space, the largest gap being in drier regions due to preservation issues. However, many of the records contain few samples or have fewer than 5 chronology control points, such as radiocarbon, luminescence or Pb-210 for the younger sequences. Average sedimentation rate for the whole database, counted as years per cm, is 64.8 yr/cm, with 61 % of the records having a rate of less than 50 yr/cm. The highest sedimentation rate by geographical region occurs on Australia’s east coast, while the lowest rates are from the Western Pacific. Overall, Australia has a higher sedimentation rate than the rest of the Indo-Pacific region. The IPPD offers many exciting research opportunities, such as examination of human impact on regional vegetation, contrasting first human arrival and colonisation, and assessment of rates of vegetation change during the Holocene. Merging the IPPD into Neotoma also facilitates inclusion of data from the Indo-Pacific region into global syntheses.","PeriodicalId":10332,"journal":{"name":"Climate of The Past","volume":"30 1","pages":""},"PeriodicalIF":4.3,"publicationDate":"2024-06-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141513573","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-06-19DOI: 10.5194/egusphere-2024-1691
Stuart Umbo, Franziska Lechleitner, Thomas Opel, Sevasti Modestou, Tobias Braun, Anton Vaks, Gideon Henderson, Pete Scott, Alexander Osintzev, Alexandr Kononov, Irina Adrian, Yuri Dublyansky, Alena Giesche, Sebastian Breitenbach
Abstract. The Miocene provides an excellent climatic analogue for near future anthropogenic warming, with atmospheric CO2 concentrations and global average temperatures similar to those projected for the coming century. However, the magnitude of Miocene Arctic warming remains unclear due to the scarcity of reliable proxy data. Here we use stable oxygen isotope and trace element analyses, alongside clumped isotope and fluid inclusion palaeothermometry of speleothems to reconstruct palaeo-environmental conditions near the Siberian Arctic coast during the late Tortonian (8.68 ± 0.09 Ma). Stable oxygen isotope records suggest warmer than present temperatures. This is supported by temperature estimates based on clumped isotopes and fluid inclusions giving mean annual air temperatures between +6.6 and +11.1 °C, compared with -12.3 °C today. Trace elements records reveal a highly seasonal hydrological environment. Our estimate of >18 °C of Arctic warming supports the wider consensus of a warmer-than-present Miocene and provides a rare paleo-analogue for future Arctic amplification under high emissions scenarios. The reconstructed increase in mean surface temperature far exceeds those projected in fully coupled global climate models, even under extreme emissions scenarios. Given that climate models have consistently underestimated the extent of recent Arctic amplification, our proxy data suggest Arctic warming may exceed current projections. If Arctic warming by 2100 matches our late Miocene estimates, it would have large-scale impacts on global climate, including extensive thawing of Siberian permafrost – a vast fossil carbon store.
{"title":"Speleothem evidence for late Miocene extreme Arctic amplification – an analogue for near future anthropogenic climate change?","authors":"Stuart Umbo, Franziska Lechleitner, Thomas Opel, Sevasti Modestou, Tobias Braun, Anton Vaks, Gideon Henderson, Pete Scott, Alexander Osintzev, Alexandr Kononov, Irina Adrian, Yuri Dublyansky, Alena Giesche, Sebastian Breitenbach","doi":"10.5194/egusphere-2024-1691","DOIUrl":"https://doi.org/10.5194/egusphere-2024-1691","url":null,"abstract":"<strong>Abstract.</strong> The Miocene provides an excellent climatic analogue for near future anthropogenic warming, with atmospheric CO<sub>2</sub> concentrations and global average temperatures similar to those projected for the coming century. However, the magnitude of Miocene Arctic warming remains unclear due to the scarcity of reliable proxy data. Here we use stable oxygen isotope and trace element analyses, alongside clumped isotope and fluid inclusion palaeothermometry of speleothems to reconstruct palaeo-environmental conditions near the Siberian Arctic coast during the late Tortonian (8.68 ± 0.09 Ma). Stable oxygen isotope records suggest warmer than present temperatures. This is supported by temperature estimates based on clumped isotopes and fluid inclusions giving mean annual air temperatures between +6.6 and +11.1 °C, compared with -12.3 °C today. Trace elements records reveal a highly seasonal hydrological environment. Our estimate of >18 °C of Arctic warming supports the wider consensus of a warmer-than-present Miocene and provides a rare paleo-analogue for future Arctic amplification under high emissions scenarios. The reconstructed increase in mean surface temperature far exceeds those projected in fully coupled global climate models, even under extreme emissions scenarios. Given that climate models have consistently underestimated the extent of recent Arctic amplification, our proxy data suggest Arctic warming may exceed current projections. If Arctic warming by 2100 matches our late Miocene estimates, it would have large-scale impacts on global climate, including extensive thawing of Siberian permafrost – a vast fossil carbon store.","PeriodicalId":10332,"journal":{"name":"Climate of The Past","volume":"73 1","pages":""},"PeriodicalIF":4.3,"publicationDate":"2024-06-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141513629","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract. As a crucial geological, climatic, and ecological boundary in the southeastern margin of the Tibetan Plateau (SEMTP), the topographic evolution of the Diancang Shan (DCS) remains unclear due to the lack of direct constraints on its paleoelevation. Here, we quantitatively reconstructed changes in annual mean temperature (ANNT) based on palynological data from the terrestrial Dasongping section (~7.6–1.8 Ma) in the Dali Basin, located at the northeastern margin of the DCS in Yunnan Province, China. Integrating the thermochronological data from the eastern and southern margins of DCS, we have clarified the paleotopographic evolution of DCS during this period: the paleoelevation of DCS likely exceeded 2000 meters above sea level (m a.s.l.) due to initial normal faulting at ~7.6 Ma, possibly comparable to the current average elevation (~2200 m a.s.l.) of surrounding Dali Basin region. Significant growth occurred between ~5.0 Ma and ~3.5 Ma, with at least ~1000 meters uplift gain in the northern segment and up to ~2000 meters in the southern segment of DCS, caused by the intensification of normal faulting activities. Finally, the northern segment of DCS reached the elevation of ~3500 m a.s.l. after ~1.8 Ma. Our findings suggest that the quantitively ANNT reconstruction, combined with thermochronological and sedimentary data, can significantly improve constraint on the paleotopographic evolution of DCS.
摘要。滇仓山是青藏高原东南缘重要的地质、气候和生态边界，由于缺乏古高程的直接约束，滇仓山的地形演化至今仍不清楚。在此，我们根据位于中国云南省滇苍山东北缘大理盆地陆相大松坪剖面（约7.6-1.8 Ma）的古乐彩网学数据，定量重建了年平均温度（ANNT）的变化。综合大理盆地东缘和南缘的热年代学数据，我们明确了这一时期大理盆地的古地形演化：大理盆地的古海拔高度在〜7.6Ma时由于最初的正断层作用可能超过了2000米，可能与大理盆地周边地区目前的平均海拔（〜2200米）相当。在~5.0Ma至~3.5Ma期间，由于正断层活动的加剧，DCS北段出现了至少~1000米的隆起，南段则高达~2000米。最后，DCS 北段在 ~1.8 Ma 之后达到 ~3500 m a.s.l.的海拔高度。我们的研究结果表明，将 ANNT 定量重建与热时学和沉积学数据相结合，可以显著改善对 DCS 古地形演化的约束。
{"title":"Rapid topographic growth of the Diancang Shan, southeastern margin of the Tibetan Plateau since 5.0–3.5 Ma","authors":"Chunxia Zhang, Haibin Wu, Xiuli Zhao, Yunkai Deng, Yunxia Jia, Wenchao Zhang, Shihu Li, Chenglong Deng","doi":"10.5194/cp-2024-43","DOIUrl":"https://doi.org/10.5194/cp-2024-43","url":null,"abstract":"<strong>Abstract.</strong> As a crucial geological, climatic, and ecological boundary in the southeastern margin of the Tibetan Plateau (SEMTP), the topographic evolution of the Diancang Shan (DCS) remains unclear due to the lack of direct constraints on its paleoelevation. Here, we quantitatively reconstructed changes in annual mean temperature (<em>ANNT</em>) based on palynological data from the terrestrial Dasongping section (~7.6–1.8 Ma) in the Dali Basin, located at the northeastern margin of the DCS in Yunnan Province, China. Integrating the thermochronological data from the eastern and southern margins of DCS, we have clarified the paleotopographic evolution of DCS during this period: the paleoelevation of DCS likely exceeded 2000 meters above sea level (m a.s.l.) due to initial normal faulting at ~7.6 Ma, possibly comparable to the current average elevation (~2200 m a.s.l.) of surrounding Dali Basin region. Significant growth occurred between ~5.0 Ma and ~3.5 Ma, with at least ~1000 meters uplift gain in the northern segment and up to ~2000 meters in the southern segment of DCS, caused by the intensification of normal faulting activities. Finally, the northern segment of DCS reached the elevation of ~3500 m a.s.l. after ~1.8 Ma. Our findings suggest that the quantitively <em>ANNT</em> reconstruction, combined with thermochronological and sedimentary data, can significantly improve constraint on the paleotopographic evolution of DCS.","PeriodicalId":10332,"journal":{"name":"Climate of The Past","volume":"346 1","pages":""},"PeriodicalIF":4.3,"publicationDate":"2024-06-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141508146","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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