Matjaž Depolli, Manja Žebre, Uroš Stepišnik, Gregor Kosec
Abstract. In this paper, we present a reconstruction of climate conditions during the Last Glacial Maximum on a karst plateau Snežnik, which lies in Dinaric Mountains (southern Slovenia) and bears evidence of glaciation. The reconstruction merges geomorphological ice limits, classified as either clear or unclear, and a computer modelling approach based on the Parallel Ice Sheet Model (PISM). Based on extensive numerical experiments where we studied the agreements between simulated and geomorphological ice extent, we propose using a combination of a high-resolution precipitation model that accounts for orographic precipitation combined with a simple elevation-based temperature model. The geomorphological ice extent can be simulated with climate to be around 6 °C colder than the modern day and with a lower-than-modern-day amount of precipitation, which matches other state-of-the art climate reconstructions for the era. The results indicate that an orographic precipitation model is essential for the accurate simulation of the study area, with moist southern winds from the nearby Adriatic Sea having a predominant effect on the precipitation patterns. Finally, this study shows that transforming climate conditions towards wetter and warmer or drier and colder does not significantly change the conditions for glacier formation.
{"title":"Simulation of a former ice field with Parallel Ice Sheet Model – Snežnik study case","authors":"Matjaž Depolli, Manja Žebre, Uroš Stepišnik, Gregor Kosec","doi":"10.5194/cp-20-1471-2024","DOIUrl":"https://doi.org/10.5194/cp-20-1471-2024","url":null,"abstract":"Abstract. In this paper, we present a reconstruction of climate conditions during the Last Glacial Maximum on a karst plateau Snežnik, which lies in Dinaric Mountains (southern Slovenia) and bears evidence of glaciation. The reconstruction merges geomorphological ice limits, classified as either clear or unclear, and a computer modelling approach based on the Parallel Ice Sheet Model (PISM). Based on extensive numerical experiments where we studied the agreements between simulated and geomorphological ice extent, we propose using a combination of a high-resolution precipitation model that accounts for orographic precipitation combined with a simple elevation-based temperature model. The geomorphological ice extent can be simulated with climate to be around 6 °C colder than the modern day and with a lower-than-modern-day amount of precipitation, which matches other state-of-the art climate reconstructions for the era. The results indicate that an orographic precipitation model is essential for the accurate simulation of the study area, with moist southern winds from the nearby Adriatic Sea having a predominant effect on the precipitation patterns. Finally, this study shows that transforming climate conditions towards wetter and warmer or drier and colder does not significantly change the conditions for glacier formation.","PeriodicalId":10332,"journal":{"name":"Climate of The Past","volume":"24 1","pages":""},"PeriodicalIF":4.3,"publicationDate":"2024-07-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141568385","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}
Jessica Ng, Jeffrey Severinghaus, Ryan Bay, Delia Tosi
Abstract. The continuous ice core record extends 800 000 years into the past, covering the period of 100 000-year glacial cycles but not the transition from 40 000-year glacial cycles (the mid-Pleistocene transition, 1.2–0.7 million years ago). A primary goal of the International Partnerships in Ice Core Sciences is therefore to retrieve a 1.5-million-year-old continuous ice core, increasing our understanding of this major change in the climate system and thus of fundamental climate forcings and feedbacks. However, complex glacial processes, limited bedrock data, and young basal ice in previous cores necessitate careful reconnaissance studies before extracting a full core. Ice borehole optical logging reflects the ice dust content and may be used to date ice quickly and inexpensively if a reference record is known. Here we explore the relationship between ice dust records and well-dated marine dust records from sediment cores in the southern Atlantic and Pacific oceans, which lie along paths of dust sources to Antarctica. We evaluate how representative these records are of Antarctic dust both through the existing ice core record and during the older target age range, suggesting that a newly published 1.5-million-year record from Site U1537 near South America is likely the most robust predictor of the Oldest Ice dust signal. We then assess procedures for rapid dating of potential Oldest Ice sites, noting that the ability to detect dating errors is an essential feature. We emphasize that ongoing efforts to identify, recover, date, and interpret an Oldest Ice core should use care to avoid unfounded assumptions about the 40 kyr world based on the 100 kyr world.
{"title":"Evaluating marine dust records as templates for optical dating of Oldest Ice","authors":"Jessica Ng, Jeffrey Severinghaus, Ryan Bay, Delia Tosi","doi":"10.5194/cp-20-1437-2024","DOIUrl":"https://doi.org/10.5194/cp-20-1437-2024","url":null,"abstract":"Abstract. The continuous ice core record extends 800 000 years into the past, covering the period of 100 000-year glacial cycles but not the transition from 40 000-year glacial cycles (the mid-Pleistocene transition, 1.2–0.7 million years ago). A primary goal of the International Partnerships in Ice Core Sciences is therefore to retrieve a 1.5-million-year-old continuous ice core, increasing our understanding of this major change in the climate system and thus of fundamental climate forcings and feedbacks. However, complex glacial processes, limited bedrock data, and young basal ice in previous cores necessitate careful reconnaissance studies before extracting a full core. Ice borehole optical logging reflects the ice dust content and may be used to date ice quickly and inexpensively if a reference record is known. Here we explore the relationship between ice dust records and well-dated marine dust records from sediment cores in the southern Atlantic and Pacific oceans, which lie along paths of dust sources to Antarctica. We evaluate how representative these records are of Antarctic dust both through the existing ice core record and during the older target age range, suggesting that a newly published 1.5-million-year record from Site U1537 near South America is likely the most robust predictor of the Oldest Ice dust signal. We then assess procedures for rapid dating of potential Oldest Ice sites, noting that the ability to detect dating errors is an essential feature. We emphasize that ongoing efforts to identify, recover, date, and interpret an Oldest Ice core should use care to avoid unfounded assumptions about the 40 kyr world based on the 100 kyr world.","PeriodicalId":10332,"journal":{"name":"Climate of The Past","volume":"25 1","pages":""},"PeriodicalIF":4.3,"publicationDate":"2024-07-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141568384","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}
Rajmund Przybylak, Garima Singh, Przemysław Wyszyński, Andrzej Araźny, Konrad Chmist
Abstract. The thermal conditions of south-western Greenland in the second half of the 18th century were estimated using two unique series of meteorological observations. The first series (Neu-Herrnhut, 1 September 1767 to 22 July 1768, hereinafter 1767–1768) is the oldest long-term series of instrumental measurements of air temperature available for Greenland. The second (Godthaab, September 1784 to June 1792) contains the most significant and reliable data for Greenland for the study period. The quality-controlled and corrected data were used to calculate daily, monthly, seasonal and yearly means. The daily means were further used to calculate day-to-day temperature variability (DDTV), thermal seasons, growing degree days (GDDs), the air thawing index (ATI), positive degree days (PDDs) and air freezing index (AFI) degree days. Air temperature in Godthaab (now Nuuk) was, on average, warmer than the present day (1991–2020) in 1767–1768 and colder in 1784–1792. Compared to the early 20th-century Arctic warming (ETCAW) period, the data for the two sub-periods show that the late 18th century was as warm or even warmer. Except winter 1767/1768, winters and springs in the study period were longer, while summers and autumns were shorter than at present. The analysed climate indices usually did not exceed the maximum and minimum values from 1991–2020. Mean daily air temperature in the studied historical periods rarely exceed ±2 SD (standard deviation) of the long-term mean calculated for the contemporary period. Air temperature distribution was usually close to normal, in both historical and contemporary periods.
{"title":"Air temperature changes in SW Greenland in the second half of the 18th century","authors":"Rajmund Przybylak, Garima Singh, Przemysław Wyszyński, Andrzej Araźny, Konrad Chmist","doi":"10.5194/cp-20-1451-2024","DOIUrl":"https://doi.org/10.5194/cp-20-1451-2024","url":null,"abstract":"Abstract. The thermal conditions of south-western Greenland in the second half of the 18th century were estimated using two unique series of meteorological observations. The first series (Neu-Herrnhut, 1 September 1767 to 22 July 1768, hereinafter 1767–1768) is the oldest long-term series of instrumental measurements of air temperature available for Greenland. The second (Godthaab, September 1784 to June 1792) contains the most significant and reliable data for Greenland for the study period. The quality-controlled and corrected data were used to calculate daily, monthly, seasonal and yearly means. The daily means were further used to calculate day-to-day temperature variability (DDTV), thermal seasons, growing degree days (GDDs), the air thawing index (ATI), positive degree days (PDDs) and air freezing index (AFI) degree days. Air temperature in Godthaab (now Nuuk) was, on average, warmer than the present day (1991–2020) in 1767–1768 and colder in 1784–1792. Compared to the early 20th-century Arctic warming (ETCAW) period, the data for the two sub-periods show that the late 18th century was as warm or even warmer. Except winter 1767/1768, winters and springs in the study period were longer, while summers and autumns were shorter than at present. The analysed climate indices usually did not exceed the maximum and minimum values from 1991–2020. Mean daily air temperature in the studied historical periods rarely exceed ±2 SD (standard deviation) of the long-term mean calculated for the contemporary period. Air temperature distribution was usually close to normal, in both historical and contemporary periods.","PeriodicalId":10332,"journal":{"name":"Climate of The Past","volume":"41 1","pages":""},"PeriodicalIF":4.3,"publicationDate":"2024-07-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141568387","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 : 2024-07-05DOI: 10.5194/egusphere-2024-1845
Darrell Kaufman, Valérie Masson-Delmotte
Abstract. Rather than reverting to a dedicated paleoclimate chapter, knowledge about pre-industrial climate should be further integrated with other lines of evidence throughout the 7th assessment reports by the Intergovernmental Panel on Climate Change.
{"title":"Rapid communication: Distribute paleoscience information across the next IPCC reports","authors":"Darrell Kaufman, Valérie Masson-Delmotte","doi":"10.5194/egusphere-2024-1845","DOIUrl":"https://doi.org/10.5194/egusphere-2024-1845","url":null,"abstract":"<strong>Abstract.</strong> Rather than reverting to a dedicated paleoclimate chapter, knowledge about pre-industrial climate should be further integrated with other lines of evidence throughout the 7th assessment reports by the Intergovernmental Panel on Climate Change.","PeriodicalId":10332,"journal":{"name":"Climate of The Past","volume":"16 1","pages":""},"PeriodicalIF":4.3,"publicationDate":"2024-07-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141549656","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 : 2024-07-04DOI: 10.5194/egusphere-2024-1992
Arnaud Nicolas, Gesine Mollenhauer, Johannes Lachner, Konstanze Stübner, Maylin Malter, Jutta Wollenburg, Hendrik Grotheer, Florian Adolphi
Abstract. Establishing accurate chronological frameworks is imperative for reliably identifying lead-lag dynamics within the climate system and enabling meaningful inter-comparisons across diverse paleoclimate proxy records over long time periods. Robust age models provide a solid temporal foundation for establishing correlations between paleoclimate records. One of the primary challenges in constructing reliable radiocarbon-based chronologies in the marine environment is to determine the regional marine radiocarbon reservoir age correction. Calculations of the local marine reservoir effect (ΔR) can be acquired using 14C-independent dating methods, such as synchronization with other well-dated archives. The cosmogenic radionuclide 10Be offers such a synchronization tool. Its atmospheric production rate is controlled by the global changes in the cosmic ray influx, caused by variations in solar activity and geomagnetic field strength. The resulting fluctuations in the meteoric deposition of 10Be are preserved in sediments and ice cores and can thus be utilized for their synchronization. In this study, for the first time, we use the authigenic 10Be/9Be record of a Laptev Sea sediment core for the period 8–14 kyr BP and synchronize it with the 10Be records from absolutely dated ice cores. Based on the resulting absolute chronology, a benthic ΔR value of +345 ± 60 14C years was estimated for the Laptev Sea, which corresponds to a marine reservoir age of 848 ± 90 14C years. The ΔR value was used to refine the age-depth model for core PS2458-4, establishing it as a potential reference chronology for the Laptev Sea. We also compare the calculated ΔR value with modern estimates from the literature and discuss its implications for the age-depth model.
{"title":"Precise dating of deglacial Laptev Sea sediments via 14C and authigenic 10Be/9Be – assessing local 14C reservoir ages","authors":"Arnaud Nicolas, Gesine Mollenhauer, Johannes Lachner, Konstanze Stübner, Maylin Malter, Jutta Wollenburg, Hendrik Grotheer, Florian Adolphi","doi":"10.5194/egusphere-2024-1992","DOIUrl":"https://doi.org/10.5194/egusphere-2024-1992","url":null,"abstract":"<strong>Abstract.</strong> Establishing accurate chronological frameworks is imperative for reliably identifying lead-lag dynamics within the climate system and enabling meaningful inter-comparisons across diverse paleoclimate proxy records over long time periods. Robust age models provide a solid temporal foundation for establishing correlations between paleoclimate records. One of the primary challenges in constructing reliable radiocarbon-based chronologies in the marine environment is to determine the regional marine radiocarbon reservoir age correction. Calculations of the local marine reservoir effect (ΔR) can be acquired using <sup>14</sup>C-independent dating methods, such as synchronization with other well-dated archives. The cosmogenic radionuclide <sup>10</sup>Be offers such a synchronization tool. Its atmospheric production rate is controlled by the global changes in the cosmic ray influx, caused by variations in solar activity and geomagnetic field strength. The resulting fluctuations in the meteoric deposition of <sup>10</sup>Be are preserved in sediments and ice cores and can thus be utilized for their synchronization. In this study, for the first time, we use the authigenic <sup>10</sup>Be/<sup>9</sup>Be record of a Laptev Sea sediment core for the period 8–14 kyr BP and synchronize it with the <sup>10</sup>Be records from absolutely dated ice cores. Based on the resulting absolute chronology, a benthic ΔR value of +345 ± 60 <sup>14</sup>C years was estimated for the Laptev Sea, which corresponds to a marine reservoir age of 848 ± 90 <sup>14</sup>C years. The ΔR value was used to refine the age-depth model for core PS2458-4, establishing it as a potential reference chronology for the Laptev Sea. We also compare the calculated ΔR value with modern estimates from the literature and discuss its implications for the age-depth model.","PeriodicalId":10332,"journal":{"name":"Climate of The Past","volume":"9 1","pages":""},"PeriodicalIF":4.3,"publicationDate":"2024-07-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141552823","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}
Fredrik Charpentier Ljungqvist, Bo Christiansen, Lea Schneider, Peter Thejll
Abstract. In central and southern Europe, grapevine is a climate-sensitive agricultural product of large economic importance, both in historical times and today. We systematically investigated the climatic impact, focusing on volcanic-forced abrupt cooling, on two long annual records of wine production quantity (spanning 1444–1786) from the Moselle Valley in present-day Luxembourg, close to the northern limit of viticulture in Europe. We present a consistent picture of the impact of volcanic eruptions on wine production through climate. To this end, we applied superposed epoch analysis – an appropriate method for detecting episodic signals in non-stationary time-series – in combination with a bootstrap procedure to estimate the statistical significance. We also assessed the long-term relationship between different annual and seasonal climate parameters and wine production in the Moselle Valley. Robust and highly significant wine production declines occurred in the years immediately following major volcanic events. Warmer, and to a lesser extent drier, climate condition had a moderately strong, but persistent, positive effect on wine production. We also find a volcanic cooling signature in spring and summer in temperature reconstructions. However, the detected volcanic signature in the Moselle Valley wine production is considerably stronger than the one found for Central Europe in tree-ring data and is instead more akin to the strong volcanic signature present in Fennoscandian tree-ring series. On the basis of our findings, we encourage further compilation, publication, and analyses of additional wine production series containing unique biological and climatic information.
{"title":"Strong volcanic-induced climatic shocks on historical Moselle wine production","authors":"Fredrik Charpentier Ljungqvist, Bo Christiansen, Lea Schneider, Peter Thejll","doi":"10.5194/cp-2024-41","DOIUrl":"https://doi.org/10.5194/cp-2024-41","url":null,"abstract":"<strong>Abstract.</strong> In central and southern Europe, grapevine is a climate-sensitive agricultural product of large economic importance, both in historical times and today. We systematically investigated the climatic impact, focusing on volcanic-forced abrupt cooling, on two long annual records of wine production quantity (spanning 1444–1786) from the Moselle Valley in present-day Luxembourg, close to the northern limit of viticulture in Europe. We present a consistent picture of the impact of volcanic eruptions on wine production through climate. To this end, we applied superposed epoch analysis – an appropriate method for detecting episodic signals in non-stationary time-series – in combination with a bootstrap procedure to estimate the statistical significance. We also assessed the long-term relationship between different annual and seasonal climate parameters and wine production in the Moselle Valley. Robust and highly significant wine production declines occurred in the years immediately following major volcanic events. Warmer, and to a lesser extent drier, climate condition had a moderately strong, but persistent, positive effect on wine production. We also find a volcanic cooling signature in spring and summer in temperature reconstructions. However, the detected volcanic signature in the Moselle Valley wine production is considerably stronger than the one found for Central Europe in tree-ring data and is instead more akin to the strong volcanic signature present in Fennoscandian tree-ring series. On the basis of our findings, we encourage further compilation, publication, and analyses of additional wine production series containing unique biological and climatic information.","PeriodicalId":10332,"journal":{"name":"Climate of The Past","volume":"12 1","pages":""},"PeriodicalIF":4.3,"publicationDate":"2024-07-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141549657","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}
Yurui Zhang, Hans Renssen, Heikki Seppä, Zhen Li, Xingrui Li
Abstract. The Arctic stratospheric polar vortex (PV) is a key driver of winter weather, and has been found playing role in winter climate variability and its predictability in Eurasia and North America on inter-annual and decadal time scales. However, to what extent this relationship also plays a role in driving climate variability on glacial-interglacial time scales is still unknown. Here, by systematically analysing PV changes in four sets of PMIP4 simulations for the last glacial maximum (LGM) and the pre-industrial (PI), we explore how the PV changed during the glacial climate and how it influenced climate variability. Our results show that under LGM conditions, the PV stretched toward the Laurentide ice sheet, which resulted in a less stable ellipse shape that increased the possibility of cold air outbreaks into mid-latitudes. During the LGM, this stretched PV pushed cold Arctic air further equatorward, increasing winter climate variability over the more (southward) southern mid-latitudes. In particular, this strengthened winter cooling over the mid-latitudes beyond the coverage of the Laurentide ice sheet (unlike summer). PV-induced temperature variability also explains the inter-model spread, as removing the PV variation from the model results reduces the inter-model spread by up to 5 °C over mid-latitude Eurasia. These results highlight the critical role of PV in connecting the polar region and mid-latitudes on glacial-interglacial time scales. These connections are reminiscent of intra-seasonal stratosphere–troposphere coupling.
{"title":"Stretched polar vortex increases mid-latitude climate variability during the Last Glacial Maximum","authors":"Yurui Zhang, Hans Renssen, Heikki Seppä, Zhen Li, Xingrui Li","doi":"10.5194/cp-2024-46","DOIUrl":"https://doi.org/10.5194/cp-2024-46","url":null,"abstract":"<strong>Abstract.</strong> The Arctic stratospheric polar vortex (PV) is a key driver of winter weather, and has been found playing role in winter climate variability and its predictability in Eurasia and North America on inter-annual and decadal time scales. However, to what extent this relationship also plays a role in driving climate variability on glacial-interglacial time scales is still unknown. Here, by systematically analysing PV changes in four sets of PMIP4 simulations for the last glacial maximum (LGM) and the pre-industrial (PI), we explore how the PV changed during the glacial climate and how it influenced climate variability. Our results show that under LGM conditions, the PV stretched toward the Laurentide ice sheet, which resulted in a less stable ellipse shape that increased the possibility of cold air outbreaks into mid-latitudes. During the LGM, this stretched PV pushed cold Arctic air further equatorward, increasing winter climate variability over the more (southward) southern mid-latitudes. In particular, this strengthened winter cooling over the mid-latitudes beyond the coverage of the Laurentide ice sheet (unlike summer). PV-induced temperature variability also explains the inter-model spread, as removing the PV variation from the model results reduces the inter-model spread by up to 5 °C over mid-latitude Eurasia. These results highlight the critical role of PV in connecting the polar region and mid-latitudes on glacial-interglacial time scales. These connections are reminiscent of intra-seasonal stratosphere–troposphere coupling.","PeriodicalId":10332,"journal":{"name":"Climate of The Past","volume":"52 1","pages":""},"PeriodicalIF":4.3,"publicationDate":"2024-07-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141549658","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 : 2024-07-04DOI: 10.5194/egusphere-2024-1915
Szabina Karancz, Lennart J. de Nooijer, Bas van der Wagt, Marcel T. J. van der Meer, Sambuddha Misra, Rick Hennekam, Zeynep Erdem, Julie Lattaud, Negar Haghipour, Stefan Schouten, Gert-Jan Reichart
Abstract. Upwelling regions are dynamic systems where relatively cold, nutrient- and CO2-rich waters reach to the surface from the deep. CO2 sink or source properties of these regions are dependent not only on the dissolved inorganic carbon content of the upwelled waters, but also on the efficiency of the biological carbon pump that provides constraint on the drawdown of pCO2 in the surface waters. The Benguela Upwelling System (BUS) is a major upwelling region with one of the most productive marine ecosystems today. However, contrasting signals reported on the variation in upwelling intensities based on, for instance, foraminiferal and radiolarian indices from this region over the last glacial cycle indicate that a complete understanding of (local) changes is currently lacking. To reconstruct changes in the CO2 history of the Northern Benguela upwelling region over the last 27 ka BP, we used a box core (64PE450-BC6) and piston core (64PE450-PC8) from the Walvis Ridge. Here, we apply various temperature and pCO2-proxies, representing both surface (UKʹ 37,δ13C of alkenones) and intermediate depth (Mg/Ca, B/Ca, S/Mg, δ11B in planktonic foraminiferal shells) processes. Reconstructed pCO2 records suggest enhanced storage of carbon at depth during the last glacial maximum. The offset between δ13C of planktonic (high δ13C) and benthic foraminifera (low δ13C) suggests an evidence of a more efficient biological carbon pump, potentially fuelled by remote and local iron supply through aeolian transport and dissolution in the shelf regions, effectively preventing release of the stored glacial CO2.
{"title":"Glacial-interglacial contrasts in the marine inorganic carbon chemistry of the Benguela Upwelling System","authors":"Szabina Karancz, Lennart J. de Nooijer, Bas van der Wagt, Marcel T. J. van der Meer, Sambuddha Misra, Rick Hennekam, Zeynep Erdem, Julie Lattaud, Negar Haghipour, Stefan Schouten, Gert-Jan Reichart","doi":"10.5194/egusphere-2024-1915","DOIUrl":"https://doi.org/10.5194/egusphere-2024-1915","url":null,"abstract":"<strong>Abstract.</strong> Upwelling regions are dynamic systems where relatively cold, nutrient- and CO<sub>2</sub>-rich waters reach to the surface from the deep. CO<sub>2</sub> sink or source properties of these regions are dependent not only on the dissolved inorganic carbon content of the upwelled waters, but also on the efficiency of the biological carbon pump that provides constraint on the drawdown of <em>p</em>CO<sub>2 </sub>in the surface waters. The Benguela Upwelling System (BUS) is a major upwelling region with one of the most productive marine ecosystems today. However, contrasting signals reported on the variation in upwelling intensities based on, for instance, foraminiferal and radiolarian indices from this region over the last glacial cycle indicate that a complete understanding of (local) changes is currently lacking. To reconstruct changes in the CO<sub>2</sub> history of the Northern Benguela upwelling region over the last 27 ka BP, we used a box core (64PE450-BC6) and piston core (64PE450-PC8) from the Walvis Ridge. Here, we apply various temperature and <em>p</em>CO<sub>2</sub>-proxies, representing both surface (U<sup>Kʹ </sup><sub>37</sub>,<sub> </sub>δ<sup>13</sup>C of alkenones) and intermediate depth (Mg/Ca, B/Ca, S/Mg, δ<sup>11</sup>B in planktonic foraminiferal shells) processes. Reconstructed <em>p</em>CO<sub>2</sub> records suggest enhanced storage of carbon at depth during the last glacial maximum. The offset between δ<sup>13</sup>C of planktonic (high δ<sup>13</sup>C) and benthic foraminifera (low δ<sup>13</sup>C) suggests an evidence of a more efficient biological carbon pump, potentially fuelled by remote and local iron supply through aeolian transport and dissolution in the shelf regions, effectively preventing release of the stored glacial CO<sub>2</sub>.","PeriodicalId":10332,"journal":{"name":"Climate of The Past","volume":"56 1","pages":""},"PeriodicalIF":4.3,"publicationDate":"2024-07-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141552822","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}
Sina Panitz, Michael Rogerson, Jack Longman, Nick Scroxton, Tim J. Lawson, Tim C. Atkinson, Vasile Ersek, James Baldini, Lisa Baldini, Stuart Umbo, Mahjoor A. Lone, Gideon M. Henderson, Sebastian F. M. Breitenbach
Abstract. Reconstructing the spatio-temporal dynamics of glaciations and permafrost largely relies on surface deposits, and is therefore a challenge for every glacial older than the last due to erosion. Consequently, glaciations and permafrost remain poorly constrained worldwide before c. 30 ka. Since speleothems (carbonate cave deposits) form from drip water and generally indicate the absence of an ice sheet and permafrost, we evaluate how speleothem growth phases defined by U-series dates align with past glacial-interglacial cycles. Further, we make the first systematic comparison of the spatial distribution of speleothem dates with independent reconstructions of the history of the British-Irish Ice Sheet (BIIS) to test how well geomorphologic ice reconstructions are replicated in the cave record. The frequency distribution of 1,020 U-series dates based on three different dating methods between 300 and 5 ka shows statistically significant periods of speleothem growth during the last interglacial and several interstadials during the last glacial. A pronounced decline in speleothem growth coincides with the Last Glacial Maximum, before broad reactivation during deglaciation and into the Holocene. Spatio-temporal patterns in speleothem growth between 31 and 15 ka agree well with the surface-deposit-based reconstruction of the last BIIS. In data-rich regions, such as northern England, ice dynamics are well-replicated in the cave record, which provide additional evidence about the spatio-temporal distribution of permafrost dynamics. Beyond the Last Glacial Maximum, the distribution of speleothem dates across the British Isles offers the opportunity to improve chronological constraints on past ice sheet variability, with evidence for a highly dynamic Scottish ice sheet during the last glacial. The results provide independent evidence of ice distribution complementary to studies of surface geomorphology and geology, and the potential to extend reconstructions into permafrost and earlier glacial cycles. Whilst undersampling is currently the main limitation for speleothem-based ice and permafrost reconstruction even in relatively well-sampled parts of the British Isles, we show that speleothem dates obtained using modern mass spectrometry techniques reveal a higher spatio-temporal resolution of glacial-interglacial cycles and glacial extent than previously possible. Further study of leads and lags in speleothem growth compared to surface deposition may provide new insights into landscape-scale dynamics during ice sheet growth and retreat.
摘要重建冰川和永久冻土的时空动态主要依赖于地表沉积物，因此，由于侵蚀作用，每一个比上一个冰川更早的冰川都面临着挑战。因此，大约 30 ka 年之前的全球冰川和永久冻土仍然难以确定。由于岩浆（碳酸盐洞穴沉积物）是由滴水形成的，通常表明当时没有冰盖和永久冻土，因此我们评估了根据 U 系列日期确定的岩浆生长阶段与过去冰川-间冰期周期的一致性。此外，我们还首次系统地比较了岩浆化石日期的空间分布与英国-爱尔兰冰盖（BIIS）历史的独立重建，以检验冰盖地貌重建在洞穴记录中的复制情况。根据三种不同的测年方法，从 300 ka 到 5 ka 的 1020 个 U 系列日期的频率分布来看，上一个间冰期和上一个冰期的几个间冰期都出现了具有统计意义的岩浆生长期。在末次冰川极盛时期，岩浆体的增长出现了明显的下降，之后在脱冰期和全新世出现了广泛的恢复。31 ka 到 15 ka 之间岩浆生长的时空模式与基于地表沉积重建的上一个 BIIS 非常吻合。在数据丰富的地区，如英格兰北部，冰的动态在洞穴记录中得到了很好的复制，这为永冻土动态的时空分布提供了更多证据。在末次冰川极盛期之后，英伦三岛的岩浆化石日期分布为改进对过去冰盖变化的年代学限制提供了机会，有证据表明苏格兰冰盖在末次冰川期高度动态。研究结果提供了冰层分布的独立证据，补充了地表地貌和地质研究，并有可能将重建工作扩展到永久冻土和早期冰川周期。虽然目前取样不足是基于岩浆化石的冰和永久冻土重建的主要限制因素，即使在不列颠群岛取样相对较好的地区也是如此，但我们的研究表明，利用现代质谱技术获得的岩浆化石日期揭示了冰川-间冰期周期和冰川范围的更高时空分辨率，这在以前是不可能实现的。与地表沉积相比，对岩浆生长的领先和滞后的进一步研究可能会为冰盖生长和消退期间的地貌尺度动态提供新的见解。
{"title":"Spatio-temporal dynamics of speleothem growth and glaciation in the British Isles","authors":"Sina Panitz, Michael Rogerson, Jack Longman, Nick Scroxton, Tim J. Lawson, Tim C. Atkinson, Vasile Ersek, James Baldini, Lisa Baldini, Stuart Umbo, Mahjoor A. Lone, Gideon M. Henderson, Sebastian F. M. Breitenbach","doi":"10.5194/cp-2024-48","DOIUrl":"https://doi.org/10.5194/cp-2024-48","url":null,"abstract":"<strong>Abstract.</strong> Reconstructing the spatio-temporal dynamics of glaciations and permafrost largely relies on surface deposits, and is therefore a challenge for every glacial older than the last due to erosion. Consequently, glaciations and permafrost remain poorly constrained worldwide before c. 30 ka. Since speleothems (carbonate cave deposits) form from drip water and generally indicate the absence of an ice sheet and permafrost, we evaluate how speleothem growth phases defined by U-series dates align with past glacial-interglacial cycles. Further, we make the first systematic comparison of the spatial distribution of speleothem dates with independent reconstructions of the history of the British-Irish Ice Sheet (BIIS) to test how well geomorphologic ice reconstructions are replicated in the cave record. The frequency distribution of 1,020 U-series dates based on three different dating methods between 300 and 5 ka shows statistically significant periods of speleothem growth during the last interglacial and several interstadials during the last glacial. A pronounced decline in speleothem growth coincides with the Last Glacial Maximum, before broad reactivation during deglaciation and into the Holocene. Spatio-temporal patterns in speleothem growth between 31 and 15 ka agree well with the surface-deposit-based reconstruction of the last BIIS. In data-rich regions, such as northern England, ice dynamics are well-replicated in the cave record, which provide additional evidence about the spatio-temporal distribution of permafrost dynamics. Beyond the Last Glacial Maximum, the distribution of speleothem dates across the British Isles offers the opportunity to improve chronological constraints on past ice sheet variability, with evidence for a highly dynamic Scottish ice sheet during the last glacial. The results provide independent evidence of ice distribution complementary to studies of surface geomorphology and geology, and the potential to extend reconstructions into permafrost and earlier glacial cycles. Whilst undersampling is currently the main limitation for speleothem-based ice and permafrost reconstruction even in relatively well-sampled parts of the British Isles, we show that speleothem dates obtained using modern mass spectrometry techniques reveal a higher spatio-temporal resolution of glacial-interglacial cycles and glacial extent than previously possible. Further study of leads and lags in speleothem growth compared to surface deposition may provide new insights into landscape-scale dynamics during ice sheet growth and retreat.","PeriodicalId":10332,"journal":{"name":"Climate of The Past","volume":"24 1","pages":""},"PeriodicalIF":4.3,"publicationDate":"2024-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141508141","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 : 2024-06-28DOI: 10.5194/egusphere-2024-1862
Chenzhi Li, Anne Dallmeyer, Jian Ni, Manuel Chevalier, Matteo Willeit, Andrei A. Andreev, Xianyong Cao, Laura Schild, Birgit Heim, Ulrike Herzschuh
Abstract. We present a global megabiome reconstruction for 43 timeslices at 500-year intervals throughout the last 21,000 years based on an updated and thus currently most extensive global taxonomically and temporally standardized fossil pollen dataset of 3,691 records. The evaluation with modern potential natural vegetation distributions yields an agreement of ~80 %, suggesting a high degree of reliability of the pollen-based megabiome reconstruction. With its high temporal and spatial resolution, this reconstruction is ideally suited for the evaluation of paleo-simulations from Earth System Models (ESMs). As an example, we compare the reconstruction with an ensemble of six different biomized simulations based on transient vegetation simulations performed by ESMs. The global spatiotemporal patterns of megabiomes estimated by the simulation ensemble and reconstructions are generally consistent, i.e., from glacial non-forest megabiomes to Holocene forest megabiomes, in line with the general climate warming trend and continental ice-sheet retreat. The shift to a global spatial megabiome distribution similar to today’s took place during the early Holocene. At a global scale over the last 21,000 years, the deviations between the reconstruction and the simulation ensemble are (a) largest during the Last Glacial Maximum and early deglaciation periods, mainly due to different estimates of tundra in the circum-Arctic areas and the Tibetan Plateau; and (b) moderate during the Holocene, mainly due to different estimates of non-forest megabiomes in relatively semi-arid zones such as North Africa and the Mediterranean that increases over time. To some extent, these mismatches could be attributed to systematic model biases in the simulated climate, as well as to the different plant representations and low taxonomic resolution of pollen in the reconstructions.
{"title":"Global biome changes over the last 21,000 years inferred from model-data comparisons","authors":"Chenzhi Li, Anne Dallmeyer, Jian Ni, Manuel Chevalier, Matteo Willeit, Andrei A. Andreev, Xianyong Cao, Laura Schild, Birgit Heim, Ulrike Herzschuh","doi":"10.5194/egusphere-2024-1862","DOIUrl":"https://doi.org/10.5194/egusphere-2024-1862","url":null,"abstract":"<strong>Abstract.</strong> We present a global megabiome reconstruction for 43 timeslices at 500-year intervals throughout the last 21,000 years based on an updated and thus currently most extensive global taxonomically and temporally standardized fossil pollen dataset of 3,691 records. The evaluation with modern potential natural vegetation distributions yields an agreement of ~80 %, suggesting a high degree of reliability of the pollen-based megabiome reconstruction. With its high temporal and spatial resolution, this reconstruction is ideally suited for the evaluation of paleo-simulations from Earth System Models (ESMs). As an example, we compare the reconstruction with an ensemble of six different biomized simulations based on transient vegetation simulations performed by ESMs. The global spatiotemporal patterns of megabiomes estimated by the simulation ensemble and reconstructions are generally consistent, i.e., from glacial non-forest megabiomes to Holocene forest megabiomes, in line with the general climate warming trend and continental ice-sheet retreat. The shift to a global spatial megabiome distribution similar to today’s took place during the early Holocene. At a global scale over the last 21,000 years, the deviations between the reconstruction and the simulation ensemble are (a) largest during the Last Glacial Maximum and early deglaciation periods, mainly due to different estimates of tundra in the circum-Arctic areas and the Tibetan Plateau; and (b) moderate during the Holocene, mainly due to different estimates of non-forest megabiomes in relatively semi-arid zones such as North Africa and the Mediterranean that increases over time. To some extent, these mismatches could be attributed to systematic model biases in the simulated climate, as well as to the different plant representations and low taxonomic resolution of pollen in the reconstructions.","PeriodicalId":10332,"journal":{"name":"Climate of The Past","volume":"8 1","pages":""},"PeriodicalIF":4.3,"publicationDate":"2024-06-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141513623","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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