Rachel T. So, T. Lowenstein, E. Jagniecki, J. Tierney, S. Feakins
Great Salt Lake (GSL), Utah, is a hypersaline terminal lake in the Great Basin, and the remnant of the late glacial Lake Bonneville. Holocene hydroclimate variations cannot be interpreted from the shoreline record, but instead can be investigated by proxies archived in the sediments. GLAD1‐GSL00‐1B was cored in 2000 and recently dated by radiocarbon for the Holocene section with the top 11 m representing ∼7 ka to present. Sediment samples every 30 cm (∼220 years) were studied for the full suite of microbial membrane lipids, including those responsive to temperature and salinity. The Archaeol and Caldarchaeol Ecometric (ACE) index detects the increase in lipids of halophilic archaea, relative to generalists, as salinity increases. We find Holocene ACE values ranged from 81 to 98, which suggests persistent hypersalinity with <50 g/L variability across 7.2 ka. The temperature proxy, MBTʹ5Me, yields values similar to modern mean annual air temperature for months above freezing (MAF = 15.7°C) over the last 5.5 ka. Several glycerol dialkyl glycerol tetraether metrics show a step shift in microbial communities and limnology at 5.5 ka. Extended archaeol detects elevated salinity during the regional mid‐Holocene drought, not readily detected in the ACE record that is often near the upper limit of the index. We infer that the mid‐Holocene GSL was shallower and saltier than the late Holocene. The current drying may be returning the lake to conditions not seen since the mid‐Holocene.
{"title":"Holocene Water Balance Variations in Great Salt Lake, Utah: Application of GDGT Indices and the ACE Salinity Proxy","authors":"Rachel T. So, T. Lowenstein, E. Jagniecki, J. Tierney, S. Feakins","doi":"10.1029/2022PA004558","DOIUrl":"https://doi.org/10.1029/2022PA004558","url":null,"abstract":"Great Salt Lake (GSL), Utah, is a hypersaline terminal lake in the Great Basin, and the remnant of the late glacial Lake Bonneville. Holocene hydroclimate variations cannot be interpreted from the shoreline record, but instead can be investigated by proxies archived in the sediments. GLAD1‐GSL00‐1B was cored in 2000 and recently dated by radiocarbon for the Holocene section with the top 11 m representing ∼7 ka to present. Sediment samples every 30 cm (∼220 years) were studied for the full suite of microbial membrane lipids, including those responsive to temperature and salinity. The Archaeol and Caldarchaeol Ecometric (ACE) index detects the increase in lipids of halophilic archaea, relative to generalists, as salinity increases. We find Holocene ACE values ranged from 81 to 98, which suggests persistent hypersalinity with <50 g/L variability across 7.2 ka. The temperature proxy, MBTʹ5Me, yields values similar to modern mean annual air temperature for months above freezing (MAF = 15.7°C) over the last 5.5 ka. Several glycerol dialkyl glycerol tetraether metrics show a step shift in microbial communities and limnology at 5.5 ka. Extended archaeol detects elevated salinity during the regional mid‐Holocene drought, not readily detected in the ACE record that is often near the upper limit of the index. We infer that the mid‐Holocene GSL was shallower and saltier than the late Holocene. The current drying may be returning the lake to conditions not seen since the mid‐Holocene.","PeriodicalId":54239,"journal":{"name":"Paleoceanography and Paleoclimatology","volume":" ","pages":""},"PeriodicalIF":3.5,"publicationDate":"2023-05-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48920748","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}
In the North Atlantic, relatively coarse grained sediments can be found periodically throughout sediment cores spanning the Last Glacial Period. These sediments were rafted by icebergs released from the Laurentide Ice Sheet (LIS) in so‐called Heinrich Events. These “Heinrich Layers” coincide with records of global climate change, suggesting that the impact of these events was propagated beyond the North Atlantic. In order to best understand the climate context and significance of Heinrich Events, it is important to constrain the mechanism for their release from the LIS and the nature of the ice sheet itself. One approach for investigating the source of Heinrich Events is to understand the sediment load of icebergs involved, information that would inform interpretations of how those icebergs were produced. By simulating Heinrich Events in a high resolution global climate model (20–40 times the resolution of previous studies), this work investigates the processes involved in the deposition of Heinrich Layers in the North Atlantic. In these simulations, the same volume of sediment is distributed differently through the same volume of icebergs, producing profoundly different sediment records. Due to the high resolution of the model, these simulated sedimentary layers can be inspected in great detail, revealing nuances of the deposit. Only when sediment is distributed throughout the entire iceberg does the model produce a sediment pattern in agreement with observations, yet icebergs with this sediment distribution are not observed in the modern‐day.
{"title":"Modeling the Production of Heinrich Layers With a Sediment‐Enabled Iceberg Model","authors":"M. Fendrock, A. Condron, D. McGee","doi":"10.1029/2022PA004583","DOIUrl":"https://doi.org/10.1029/2022PA004583","url":null,"abstract":"In the North Atlantic, relatively coarse grained sediments can be found periodically throughout sediment cores spanning the Last Glacial Period. These sediments were rafted by icebergs released from the Laurentide Ice Sheet (LIS) in so‐called Heinrich Events. These “Heinrich Layers” coincide with records of global climate change, suggesting that the impact of these events was propagated beyond the North Atlantic. In order to best understand the climate context and significance of Heinrich Events, it is important to constrain the mechanism for their release from the LIS and the nature of the ice sheet itself. One approach for investigating the source of Heinrich Events is to understand the sediment load of icebergs involved, information that would inform interpretations of how those icebergs were produced. By simulating Heinrich Events in a high resolution global climate model (20–40 times the resolution of previous studies), this work investigates the processes involved in the deposition of Heinrich Layers in the North Atlantic. In these simulations, the same volume of sediment is distributed differently through the same volume of icebergs, producing profoundly different sediment records. Due to the high resolution of the model, these simulated sedimentary layers can be inspected in great detail, revealing nuances of the deposit. Only when sediment is distributed throughout the entire iceberg does the model produce a sediment pattern in agreement with observations, yet icebergs with this sediment distribution are not observed in the modern‐day.","PeriodicalId":54239,"journal":{"name":"Paleoceanography and Paleoclimatology","volume":" ","pages":""},"PeriodicalIF":3.5,"publicationDate":"2023-05-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43369120","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}
V. Taylor, T. Westerhold, S. Bohaty, J. Backman, T. Jones, K. Edgar, K. Egan, M. Lyle, H. Pälike, U. Röhl, J. Zachos, P. Wilson
The major Cenozoic shift from a shallow (∼3–4 km) to deep (∼4.5 km) calcite compensation depth (CCD) occurred at the Eocene‐Oligocene Transition (∼34 Ma), suggesting a strong relationship between calcium carbonate (CaCO3) cycling and Antarctic glaciation. However, the linkages between these two events are debated. Here we present new records of bulk sediment stable isotope and carbonate composition from a depth transect of sites in the low‐latitude Pacific Ocean and one site from the South Atlantic Ocean, together with a new benthic foraminiferal stable isotope record (δ13Cb and δ18Ob) from the Pacific where the sedimentary sequence is most expanded. Our records reveal a short‐lived (∼3,000 Kyr) CCD shoaling event closely associated with a negative carbon isotope excursion in the latest Eocene. This event is immediately followed by CCD deepening which occurs in two rapid (∼40 Kyr‐long) steps. Our data show that the first of these deepening steps represents recovery from the latest Eocene shoaling event while the second was closely associated with a rapid increase in δ18Ob and shows a distinctive over‐deepening and settling pattern to >5 and 4.4 km, respectively. These results, together with good agreement between Pacific and South Atlantic records, strongly suggest that the carbon cycle was perturbed globally shortly before the inception of Antarctic glaciation. Once large‐scale Antarctic glaciation was initiated, rapid further change in global seawater chemistry triggered transitory deep ocean carbonate burial fluxes far exceeding their early Oligocene steady state values.
{"title":"Transient Shoaling, Over‐Deepening and Settling of the Calcite Compensation Depth at the Eocene‐Oligocene Transition","authors":"V. Taylor, T. Westerhold, S. Bohaty, J. Backman, T. Jones, K. Edgar, K. Egan, M. Lyle, H. Pälike, U. Röhl, J. Zachos, P. Wilson","doi":"10.1029/2022PA004493","DOIUrl":"https://doi.org/10.1029/2022PA004493","url":null,"abstract":"The major Cenozoic shift from a shallow (∼3–4 km) to deep (∼4.5 km) calcite compensation depth (CCD) occurred at the Eocene‐Oligocene Transition (∼34 Ma), suggesting a strong relationship between calcium carbonate (CaCO3) cycling and Antarctic glaciation. However, the linkages between these two events are debated. Here we present new records of bulk sediment stable isotope and carbonate composition from a depth transect of sites in the low‐latitude Pacific Ocean and one site from the South Atlantic Ocean, together with a new benthic foraminiferal stable isotope record (δ13Cb and δ18Ob) from the Pacific where the sedimentary sequence is most expanded. Our records reveal a short‐lived (∼3,000 Kyr) CCD shoaling event closely associated with a negative carbon isotope excursion in the latest Eocene. This event is immediately followed by CCD deepening which occurs in two rapid (∼40 Kyr‐long) steps. Our data show that the first of these deepening steps represents recovery from the latest Eocene shoaling event while the second was closely associated with a rapid increase in δ18Ob and shows a distinctive over‐deepening and settling pattern to >5 and 4.4 km, respectively. These results, together with good agreement between Pacific and South Atlantic records, strongly suggest that the carbon cycle was perturbed globally shortly before the inception of Antarctic glaciation. Once large‐scale Antarctic glaciation was initiated, rapid further change in global seawater chemistry triggered transitory deep ocean carbonate burial fluxes far exceeding their early Oligocene steady state values.","PeriodicalId":54239,"journal":{"name":"Paleoceanography and Paleoclimatology","volume":" ","pages":""},"PeriodicalIF":3.5,"publicationDate":"2023-05-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48259401","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}
{"title":"Issue Information","authors":"","doi":"10.1002/palo.21175","DOIUrl":"https://doi.org/10.1002/palo.21175","url":null,"abstract":"No abstract is available for this article.","PeriodicalId":54239,"journal":{"name":"Paleoceanography and Paleoclimatology","volume":" ","pages":""},"PeriodicalIF":3.5,"publicationDate":"2023-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47821860","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}
K. Gariboldi, J. Pike, E. Malinverno, C. Di Celma, Anna Gionacada, G. Bianucci
The detailed study of diatom laminations conducted by means of backscattered electron imaging serves as tool to unravel details of past ocean dynamics. In this paper we apply this method to the analysis of the diatomites of Cerro Los Quesos, Upper Miocene Pisco Fm, Peru. Numerous studies have been conducted on the Pisco Fm; however, a focus on its paleoceanographic significance is still lacking. In this work, we provide information on the oceanographic setting in the area at the time of diatomites deposition. The high abundance of deep‐living Coscinodiscus laminae, proceeded by either a mixed lamina or a terrigenous one, let us hypothesize a deep position of the thermocline during the deposition of the Pisco diatomites; together with the scarcity of Chaetoceros Hyalochaete spp. resting spores, this evidence confutes the belief that equals high biogenic silica content in marine sediments with enhanced upwelling. Conversely, the depositional setting of the Pisco Fm diatomites is more similar to what is known as “permanent El Niño” (or “El Padre”) state, meaning a constant weakened upwelling (or upwelling of nutrients‐poor waters). Climate modeling warns that an increase in atmospheric CO2 may lead to this mean state in the near future. Thanks to this study we also obtained refined information on the diatomites sedimentations rates. The comparison of the Pisco diatomites sedimentation rates with those of Quaternary diatomites gave strength to the hypothesis that the formation of the vertebrate Lagerstätte may have been enhanced, among others, by the so‐called “impact‐burial” mechanism.
通过背散射电子成像对硅藻叠层进行的详细研究是解开过去海洋动力学细节的工具。本文将该方法应用于秘鲁上中新世皮斯科组Cerro Los Quesos硅藻的分析。对皮斯科组进行了大量研究；然而，对其古海洋意义的关注仍然缺乏。在这项工作中，我们提供了硅藻沉积时该地区的海洋学环境信息。由混合薄层或陆生薄层形成的高丰度深层生活的Coscinodisco薄层，让我们假设了在Pisco硅藻沉积过程中温跃层的深层位置；再加上透明毛犀属休眠孢子的稀缺性，这一证据证实了海洋沉积物中生物二氧化硅含量高，上升流增强的观点。相反，皮斯科组硅藻的沉积环境更类似于所谓的“永久厄尔尼诺”（或“El Padre”）状态，即持续减弱的上升流（或营养不良水域的上升流）。气候模型警告说，大气中二氧化碳的增加可能在不久的将来导致这种平均状态。由于这项研究，我们还获得了关于硅藻沉积速率的精确信息。Pisco硅藻沉积速率与第四纪硅藻沉积速率的比较有力地支持了脊椎动物Lagerstätte的形成可能通过所谓的“撞击-埋藏”机制而增强的假设。
{"title":"Paleoceanographic Implications of Diatom Seasonal Laminations in the Upper Miocene Pisco Formation (Ica Desert, Peru) and Their Clues on the Development of the Pisco Fossil‐Lagerstätte","authors":"K. Gariboldi, J. Pike, E. Malinverno, C. Di Celma, Anna Gionacada, G. Bianucci","doi":"10.1029/2022PA004566","DOIUrl":"https://doi.org/10.1029/2022PA004566","url":null,"abstract":"The detailed study of diatom laminations conducted by means of backscattered electron imaging serves as tool to unravel details of past ocean dynamics. In this paper we apply this method to the analysis of the diatomites of Cerro Los Quesos, Upper Miocene Pisco Fm, Peru. Numerous studies have been conducted on the Pisco Fm; however, a focus on its paleoceanographic significance is still lacking. In this work, we provide information on the oceanographic setting in the area at the time of diatomites deposition. The high abundance of deep‐living Coscinodiscus laminae, proceeded by either a mixed lamina or a terrigenous one, let us hypothesize a deep position of the thermocline during the deposition of the Pisco diatomites; together with the scarcity of Chaetoceros Hyalochaete spp. resting spores, this evidence confutes the belief that equals high biogenic silica content in marine sediments with enhanced upwelling. Conversely, the depositional setting of the Pisco Fm diatomites is more similar to what is known as “permanent El Niño” (or “El Padre”) state, meaning a constant weakened upwelling (or upwelling of nutrients‐poor waters). Climate modeling warns that an increase in atmospheric CO2 may lead to this mean state in the near future. Thanks to this study we also obtained refined information on the diatomites sedimentations rates. The comparison of the Pisco diatomites sedimentation rates with those of Quaternary diatomites gave strength to the hypothesis that the formation of the vertebrate Lagerstätte may have been enhanced, among others, by the so‐called “impact‐burial” mechanism.","PeriodicalId":54239,"journal":{"name":"Paleoceanography and Paleoclimatology","volume":" ","pages":""},"PeriodicalIF":3.5,"publicationDate":"2023-04-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49665499","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}
R. Sulzbach, V. Klemann, G. Knorr, H. Dobslaw, H. Dümpelmann, G. Lohmann, M. Thomas
This study addresses the evolution of global tidal dynamics since the Last Glacial Maximum focusing on the extraction of tidal levels that are vital for the interpretation of geologic sea‐level markers. For this purpose, we employ a truly‐global barotropic ocean tide model which considers the non‐local effect of Self‐Attraction and Loading. A comparison to a global tide gauge data set for modern conditions yields agreement levels of 65%–70%. As the chosen model is data‐unconstrained, and the considered dissipation mechanisms are well understood, it does not have to be re‐tuned for altered paleoceanographic conditions. In agreement with prior studies, we find that changes in bathymetry during glaciation and deglaciation do exert critical control over the modeling results with minor impact by ocean stratification and sea ice friction. Simulations of 4 major partial tides are repeated in time steps of 0.5–1 ka and augmented by 4 additional partial tides estimated via linear admittance. These are then used to derive time series from which the tidal levels are determined and provided as a global data set conforming to the HOLSEA format. The modeling results indicate a strengthened tidal resonance by M2, but also by O1, under glacial conditions, in accordance with prior studies. Especially, a number of prominent changes in local resonance conditions are identified, that impact the tidal levels up to several meters difference. Among other regions, resonant features are predicted for the North Atlantic, the South China Sea, and the Arctic Ocean.
{"title":"Evolution of Global Ocean Tide Levels Since the Last Glacial Maximum","authors":"R. Sulzbach, V. Klemann, G. Knorr, H. Dobslaw, H. Dümpelmann, G. Lohmann, M. Thomas","doi":"10.1029/2022PA004556","DOIUrl":"https://doi.org/10.1029/2022PA004556","url":null,"abstract":"This study addresses the evolution of global tidal dynamics since the Last Glacial Maximum focusing on the extraction of tidal levels that are vital for the interpretation of geologic sea‐level markers. For this purpose, we employ a truly‐global barotropic ocean tide model which considers the non‐local effect of Self‐Attraction and Loading. A comparison to a global tide gauge data set for modern conditions yields agreement levels of 65%–70%. As the chosen model is data‐unconstrained, and the considered dissipation mechanisms are well understood, it does not have to be re‐tuned for altered paleoceanographic conditions. In agreement with prior studies, we find that changes in bathymetry during glaciation and deglaciation do exert critical control over the modeling results with minor impact by ocean stratification and sea ice friction. Simulations of 4 major partial tides are repeated in time steps of 0.5–1 ka and augmented by 4 additional partial tides estimated via linear admittance. These are then used to derive time series from which the tidal levels are determined and provided as a global data set conforming to the HOLSEA format. The modeling results indicate a strengthened tidal resonance by M2, but also by O1, under glacial conditions, in accordance with prior studies. Especially, a number of prominent changes in local resonance conditions are identified, that impact the tidal levels up to several meters difference. Among other regions, resonant features are predicted for the North Atlantic, the South China Sea, and the Arctic Ocean.","PeriodicalId":54239,"journal":{"name":"Paleoceanography and Paleoclimatology","volume":" ","pages":""},"PeriodicalIF":3.5,"publicationDate":"2023-04-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49351073","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}
C. Leland, R. D’Arrigo, N. Davi, K. J. Anchukaitis, L. Andreu‐Hayles, T. Porter, T. Galloway, M. Mant, G. Wiles, R. Wilson, S. Beaulieu, R. Oelkers, B. Gaglioti, M. Rao, E. Reid, T. Nixon
Two large volcanic eruptions contributed to extreme cold temperatures during the early 1800s, one of the coldest phases of the Little Ice Age. While impacts from the massive 1815 Tambora eruption in Indonesia are relatively well‐documented, much less is known regarding an unidentified volcanic event around 1809. Here, we describe the spatial extent, duration, and magnitude of cold conditions following this eruption in northwestern North America using a high‐resolution network of tree‐ring records that capture past warm‐season temperature variability. Extreme and persistent cold temperatures were centered around the Gulf of Alaska, the adjacent Wrangell‐St Elias Mountains, and the southern Yukon, while cold anomalies diminished with distance from this core region. This distinct spatial pattern of temperature anomalies suggests that a weak Aleutian Low and conditions similar to a negative phase of the Pacific Decadal Oscillation could have contributed to regional cold extremes after the 1809 eruption.
19世纪初，两次大型火山爆发导致了极端寒冷的气温，这是小冰期最寒冷的时期之一。虽然1815年印度尼西亚坦博拉火山大规模喷发的影响被记录得相对较好，但关于1809年左右的一次不明火山事件，人们所知甚少。在这里，我们使用树木年轮记录的高分辨率网络来描述北美西北部火山喷发后寒冷条件的空间范围、持续时间和程度，这些记录捕获了过去暖季的温度变化。极端和持续的低温以阿拉斯加湾、邻近的Wrangell - St Elias山脉和育空南部为中心，而寒冷异常随着距离该核心区域的距离而减弱。这种明显的温度异常空间模式表明，弱阿留申低气压和类似于太平洋年代际涛动负相位的条件可能导致了1809年火山喷发后的区域极端寒冷。
{"title":"A Spatiotemporal Assessment of Extreme Cold in Northwestern North America Following the Unidentified 1809 CE Volcanic Eruption","authors":"C. Leland, R. D’Arrigo, N. Davi, K. J. Anchukaitis, L. Andreu‐Hayles, T. Porter, T. Galloway, M. Mant, G. Wiles, R. Wilson, S. Beaulieu, R. Oelkers, B. Gaglioti, M. Rao, E. Reid, T. Nixon","doi":"10.1029/2022PA004581","DOIUrl":"https://doi.org/10.1029/2022PA004581","url":null,"abstract":"Two large volcanic eruptions contributed to extreme cold temperatures during the early 1800s, one of the coldest phases of the Little Ice Age. While impacts from the massive 1815 Tambora eruption in Indonesia are relatively well‐documented, much less is known regarding an unidentified volcanic event around 1809. Here, we describe the spatial extent, duration, and magnitude of cold conditions following this eruption in northwestern North America using a high‐resolution network of tree‐ring records that capture past warm‐season temperature variability. Extreme and persistent cold temperatures were centered around the Gulf of Alaska, the adjacent Wrangell‐St Elias Mountains, and the southern Yukon, while cold anomalies diminished with distance from this core region. This distinct spatial pattern of temperature anomalies suggests that a weak Aleutian Low and conditions similar to a negative phase of the Pacific Decadal Oscillation could have contributed to regional cold extremes after the 1809 eruption.","PeriodicalId":54239,"journal":{"name":"Paleoceanography and Paleoclimatology","volume":" ","pages":""},"PeriodicalIF":3.5,"publicationDate":"2023-04-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48923214","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}
Speleothem oxygen isotope records (δ18O) of tropical South American rainfall in the late Quaternary show a zonal “South American Precipitation Dipole” (SAPD). The dipole is characterized by opposing east‐west precipitation anomalies compared to the present—wetter in the east and drier in the west at the mid‐Holocene (∼7 ka), and drier in the east and wetter in the west at the Last Glacial Maximum (∼21 ka). However, the SAPD remains enigmatic because it is expressed differently in western versus eastern δ18O records and isotope‐enabled climate model simulations usually misrepresent the magnitude and/or spatial pattern of δ18O change. Here, we address the SAPD enigma in two parts. First, we re‐interpret the δ18O data to account for upwind rainout effects that are known to be pervasive in tropical South America, but are not always considered in Quaternary paleoclimate studies. Our revised interpretation reconciles the δ18O data with cave infiltration and other proxy records, and indicates that the centroid of tropical South American rainfall has migrated zonally over time. Second, using an energy balance model of tropical atmospheric circulation, we hypothesize that zonal migration of the precipitation centroid can be explained by regional energy budget shifts, such as changing Saharan albedo associated with the African Humid Period, that have not been modeled in previous SAPD studies. This hypothesis of a migrating precipitation centroid presents a new framework for interpreting δ18O records from tropical South America and may help explain the zonal rainfall anomalies that predate the late Quaternary.
{"title":"The Zonal Patterns in Late Quaternary Tropical South American Precipitation","authors":"T. Kukla, M. Winnick, M. Laguë, Z. Xia","doi":"10.1029/2022PA004498","DOIUrl":"https://doi.org/10.1029/2022PA004498","url":null,"abstract":"Speleothem oxygen isotope records (δ18O) of tropical South American rainfall in the late Quaternary show a zonal “South American Precipitation Dipole” (SAPD). The dipole is characterized by opposing east‐west precipitation anomalies compared to the present—wetter in the east and drier in the west at the mid‐Holocene (∼7 ka), and drier in the east and wetter in the west at the Last Glacial Maximum (∼21 ka). However, the SAPD remains enigmatic because it is expressed differently in western versus eastern δ18O records and isotope‐enabled climate model simulations usually misrepresent the magnitude and/or spatial pattern of δ18O change. Here, we address the SAPD enigma in two parts. First, we re‐interpret the δ18O data to account for upwind rainout effects that are known to be pervasive in tropical South America, but are not always considered in Quaternary paleoclimate studies. Our revised interpretation reconciles the δ18O data with cave infiltration and other proxy records, and indicates that the centroid of tropical South American rainfall has migrated zonally over time. Second, using an energy balance model of tropical atmospheric circulation, we hypothesize that zonal migration of the precipitation centroid can be explained by regional energy budget shifts, such as changing Saharan albedo associated with the African Humid Period, that have not been modeled in previous SAPD studies. This hypothesis of a migrating precipitation centroid presents a new framework for interpreting δ18O records from tropical South America and may help explain the zonal rainfall anomalies that predate the late Quaternary.","PeriodicalId":54239,"journal":{"name":"Paleoceanography and Paleoclimatology","volume":" ","pages":""},"PeriodicalIF":3.5,"publicationDate":"2023-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45392946","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}
Once a year we take the opportunity to thank the reviewers whose difficult, important work is never sufficiently recognized. Three years into the COVID-19 pandemic, reviewers continued to show deep resolve to support their community, by providing thorough, timely reviews aiming to improve manuscripts, while simultaneously dealing with very difficult personal and professional circumstances. Without their intense, robust, and helpful attention, all the science we do would be diminished. Matthew and Ulla would like to express their gratitude and appreciation for your efforts this year and their hope for improvement in 2023 and beyond. Thank you to the 339 reviewers who submitted 473 reviews in the journal last year. Individuals in italics provided three or more reviews for Paleoceanography and Paleoclimatology during the year. Abbott, April Abell, Jordan Acosta, Rene Paul Agnini, Claudia Ai, Xuyuan Allen, Katherine Anagnostou, Eleni Anchukaitis, Kevin Anderson, Robert Arbic, Brian Archer, David Arreguín-Rodríguez, Gabriela Atwood, Alyssa Babila, Tali Baker, Paul Bakker, Pepijn Barron, John Barth, Aaron Bassinot, Franck Batenburg, Sietske Baumgartner, Aly Belanger, Christina Berenice, Sophie Bhattacharya, Tripti
{"title":"Thank You to Our 2022 Peer Reviewers","authors":"M. Huber, U. Röhl","doi":"10.1029/2023pa004653","DOIUrl":"https://doi.org/10.1029/2023pa004653","url":null,"abstract":"Once a year we take the opportunity to thank the reviewers whose difficult, important work is never sufficiently recognized. Three years into the COVID-19 pandemic, reviewers continued to show deep resolve to support their community, by providing thorough, timely reviews aiming to improve manuscripts, while simultaneously dealing with very difficult personal and professional circumstances. Without their intense, robust, and helpful attention, all the science we do would be diminished. Matthew and Ulla would like to express their gratitude and appreciation for your efforts this year and their hope for improvement in 2023 and beyond. Thank you to the 339 reviewers who submitted 473 reviews in the journal last year. Individuals in italics provided three or more reviews for Paleoceanography and Paleoclimatology during the year. Abbott, April Abell, Jordan Acosta, Rene Paul Agnini, Claudia Ai, Xuyuan Allen, Katherine Anagnostou, Eleni Anchukaitis, Kevin Anderson, Robert Arbic, Brian Archer, David Arreguín-Rodríguez, Gabriela Atwood, Alyssa Babila, Tali Baker, Paul Bakker, Pepijn Barron, John Barth, Aaron Bassinot, Franck Batenburg, Sietske Baumgartner, Aly Belanger, Christina Berenice, Sophie Bhattacharya, Tripti","PeriodicalId":54239,"journal":{"name":"Paleoceanography and Paleoclimatology","volume":" ","pages":""},"PeriodicalIF":3.5,"publicationDate":"2023-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48952393","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}
Mengli Chen, P. Martin, H. Ren, Run Zhang, D. Samanta, Yi-Chi Chen, K. Hughen, K. Phan, S. Vo, N. Goodkin
Climate change impacts ocean nutrient availability and will likely alter the marine food web. While climate models predict decreased average ocean productivity, the extent of these changes, especially in the marginal seas upon which large human populations depend, is not well understood. Here, we reconstructed changes in seawater phosphate concentration and nitrate source over the past 400 years, which reveals a more than 50% decline in residence time of seawater phosphate, and 8%–48% decline in subsurface nitrogen supply following the coldest period of Little Ice Age. Our data indicates a link between surface ocean nutrient supply and the East Asian Summer Monsoon strength in an economically important marginal sea. As climate models predict that the East Asian Summer monsoon will strengthen in the future, our study implies that surface ocean primary productivity may increase in the South China Sea, contrary to the predicted decrease in global average ocean productivity.
{"title":"Enhanced Monsoon‐Driven Upwelling in Southeast Asia During the Little Ice Age","authors":"Mengli Chen, P. Martin, H. Ren, Run Zhang, D. Samanta, Yi-Chi Chen, K. Hughen, K. Phan, S. Vo, N. Goodkin","doi":"10.1029/2022PA004546","DOIUrl":"https://doi.org/10.1029/2022PA004546","url":null,"abstract":"Climate change impacts ocean nutrient availability and will likely alter the marine food web. While climate models predict decreased average ocean productivity, the extent of these changes, especially in the marginal seas upon which large human populations depend, is not well understood. Here, we reconstructed changes in seawater phosphate concentration and nitrate source over the past 400 years, which reveals a more than 50% decline in residence time of seawater phosphate, and 8%–48% decline in subsurface nitrogen supply following the coldest period of Little Ice Age. Our data indicates a link between surface ocean nutrient supply and the East Asian Summer Monsoon strength in an economically important marginal sea. As climate models predict that the East Asian Summer monsoon will strengthen in the future, our study implies that surface ocean primary productivity may increase in the South China Sea, contrary to the predicted decrease in global average ocean productivity.","PeriodicalId":54239,"journal":{"name":"Paleoceanography and Paleoclimatology","volume":" ","pages":""},"PeriodicalIF":3.5,"publicationDate":"2023-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46482628","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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