Meng Zuo, Yong Sun, Yan Zhao, Gilles Ramstein, Lin Ding, Tianjun Zhou
{"title":"South Asian summer monsoon enhanced by the uplift of the Iranian Plateau in Middle Miocene","authors":"Meng Zuo, Yong Sun, Yan Zhao, Gilles Ramstein, Lin Ding, Tianjun Zhou","doi":"10.5194/cp-20-1817-2024","DOIUrl":"https://doi.org/10.5194/cp-20-1817-2024","url":null,"abstract":"Abstract. The South Asian summer monsoon (SASM) significantly intensified during the Middle Miocene (17–12 Ma), but the driver of this change remains an open question. The uplift of the Himalaya (HM) and the Iranian Plateau (IP) and global CO2 variation are prominent factors among suggested drivers. Particularly, the impact of high CO2 levels on the Miocene SASM has been little studied, despite the wide range of reconstructed CO2 values around this period. Here we investigate their effects on the SASM using the fully coupled Ocean–Atmosphere Global Climate Model, CESM1.2, through a series of 12 sensitivity experiments. Our simulations show that the IP uplift plays a dominant role in the intensification of the SASM, mainly in the region around northwestern India. The effect of the HM uplift is confined to the range of the HM and its vicinity, producing orographic precipitation change. The topography forcing overall out-competes CO2 variation in driving the intensification of the SASM. In the case of extremely strong CO2 variation, the effects of these two factors are comparable in the core SASM region, while in the western region, the topographic forcing is still the dominant driver. We propose a thermodynamical process linking the uplift of the IP and the enhanced SASM through the release of latent heat. When compared with reconstructions, the simulated response of SASM to the IP uplift is in good agreement with observed precipitation and wind field, while the effects of the HM uplift and CO2 variation are inadequate to interpret the proxies.","PeriodicalId":10332,"journal":{"name":"Climate of The Past","volume":"14 1","pages":""},"PeriodicalIF":4.3,"publicationDate":"2024-08-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142190415","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}
Dhanushka Devendra, Natalia Szymańska, Magdalena Łącka, Małgorzata Szymczak-Żyła, Magdalena Krajewska, Maciej M. Telesiński, Marek Zajączkowski
{"title":"Postglacial environmental changes in the northwestern Barents Sea caused by meltwater outbursts","authors":"Dhanushka Devendra, Natalia Szymańska, Magdalena Łącka, Małgorzata Szymczak-Żyła, Magdalena Krajewska, Maciej M. Telesiński, Marek Zajączkowski","doi":"10.5194/cp-2024-52","DOIUrl":"https://doi.org/10.5194/cp-2024-52","url":null,"abstract":"<strong>Abstract.</strong> The last deglaciation was marked by abrupt shifts between cold and warm states reflecting an integrated response to the gradually increasing summer insolation at northern latitudes, changing ocean circulation, and the retreat of the Northern Hemisphere ice sheets. In this study, we present new multiproxy reconstructions of water mass properties and sea surface characteristics from a sediment core from the northwestern Barents Sea (Kveithola) representing the last 14,700 years. Our reconstruction documents four sediment-laden meltwater pulses between 14,700 and 8,200 cal years BP based on biomarkers, stable isotopes, and sedimentological parameters. Deglacial processes primarily cause these meltwater pulses and are possibly supplemented with paleo-lake outbursts, paleo-tsunami currents, or a combination of at least one of these, are characterized by sudden drops in sea surface temperatures, increased sea ice formation, increased terrigenous supply, and a limited influence of Atlantic Water in the northwestern Barents Sea. The influence of the Storegga tsunami, which occurred around the 8,200 cal years BP cooling event likely reached and redistributed the sediment in Kveithola. Strong coarsening of the northwestern Barents shelf was observed after 3,500 years, which might be related to a stronger Atlantic Water inflow from the west across the bank leading to winnowing.","PeriodicalId":10332,"journal":{"name":"Climate of The Past","volume":"14 1","pages":""},"PeriodicalIF":4.3,"publicationDate":"2024-08-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142190407","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}
Katharina D. Six, Uwe Mikolajewicz, Gerhard Schmiedl
{"title":"Modelling Mediterranean ocean biogeochemistry of the Last Glacial Maximum","authors":"Katharina D. Six, Uwe Mikolajewicz, Gerhard Schmiedl","doi":"10.5194/cp-20-1785-2024","DOIUrl":"https://doi.org/10.5194/cp-20-1785-2024","url":null,"abstract":"Abstract. We present results of simulations performed with a physical–biogeochemical ocean model of the Mediterranean Sea for the Last Glacial Maximum (LGM) and analyse the differences in physical and biochemical states between the historical period and the LGM. Long-term simulations with an Earth system model based on ice sheet reconstructions provide the necessary atmospheric forcing data, oceanic boundary conditions at the entrance to the Mediterranean Sea, and river discharge to the entire basin. Our regional model accounts for changes in bathymetry due to ice sheet volume changes, reduction in atmospheric CO2 concentration, and an adjusted aeolian dust and iron deposition. The physical ocean state of the Mediterranean during the LGM shows a reduced baroclinic water exchange at the Strait of Gibraltar, a more sluggish zonal overturning circulation, and the relocation of intermediate and deep-water-formation areas – all in line with estimates from palaeo-sediment records or previous modelling efforts. Most striking features of the biogeochemical realm are a reduction in the net primary production, an accumulation of nutrients below the euphotic zone, and an increase in the organic matter deposition at the seafloor. This seeming contradiction of increased organic matter deposition and decreased net primary production challenges our view of possible changes in surface biological processes during the LGM. We attribute the origin of a reduced net primary production to the interplay of increased stability of the upper water column, changed zonal water transport at intermediate depths, and lower water temperatures, which slow down all biological processes during the LGM. Cold water temperatures also affect the remineralisation rates of organic material, which explains the simulated increase in the organic matter deposition, which is in good agreement with sediment proxy records. In addition, we discuss changes in an artificial tracer which captures the surface ocean temperature signal during organic matter production. A shifted seasonality of the biological production in the LGM leads to a difference in the recording of the climate signal by this artificial tracer of up to 1 K. This could be of relevance for the interpretation of proxy records like, e.g., alkenones. Our study not only provides the first consistent insights into the biogeochemistry of the glacial Mediterranean Sea but will also serve as the starting point for transient simulations of the last deglaciation.","PeriodicalId":10332,"journal":{"name":"Climate of The Past","volume":"21 1","pages":""},"PeriodicalIF":4.3,"publicationDate":"2024-08-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141945918","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}
Meike D. W. Scherrenberg, Constantijn J. Berends, Roderik S. W. van de Wal
{"title":"Late Pleistocene glacial terminations accelerated by proglacial lakes","authors":"Meike D. W. Scherrenberg, Constantijn J. Berends, Roderik S. W. van de Wal","doi":"10.5194/cp-20-1761-2024","DOIUrl":"https://doi.org/10.5194/cp-20-1761-2024","url":null,"abstract":"Abstract. During the glacial cycles of the past 800 000 years, Eurasia and North America were periodically covered by large ice sheets, causing up to 100 m of sea-level change. While Late Pleistocene glacial cycles typically lasted 80 000–120 000 years, the termination phases were completed in only 10 000 years. During these glacial terminations, the North American and Eurasian ice sheets retreated, which created large proglacial lakes in front of the ice-sheet margin. Proglacial lakes accelerate deglaciation as they facilitate the formation of ice shelves at the southern margins of the North American and Eurasian ice sheets. These ice shelves are characterized by basal melting, low surface elevations, and negligible friction at the base. Here, we use an ice-sheet model to quantify the (combined) effects of proglacial lakes on Late Pleistocene glacial terminations by examining their interplay with glacial isostatic adjustment (GIA) and basal sliding. We find that proglacial lakes accelerate the deglaciation of ice sheets mainly because there is an absence of basal friction underneath ice shelves. If friction underneath grounded ice is applied to floating ice, full deglaciation is postponed by a few millennia, resulting in more ice remaining during interglacial periods and no extensive ice shelves forming. Additionally, the large uncertainty in melt rates underneath lacustrine ice shelves translates to an uncertainty in the timing of the termination of up to a millennium. Proglacial lakes are created by depressions in the landscape that remain after an ice sheet has retreated. The depth, size, and timing of proglacial lakes depend on the rate of bedrock rebound. We find that if bedrock rebounds within a few centuries (rather than a few millennia), the mass loss rate of the ice sheet is substantially reduced. This is because fast bedrock rebound prevents the formation of extensive proglacial lakes. Additionally, a decrease in ice thickness is partly compensated for by faster bedrock rebound, resulting in a higher surface elevation; lower temperatures; and a higher surface mass balance, which delays deglaciation. We find that a very long bedrock relaxation time does not substantially affect terminations, but it may lead to a delayed onset of the next glacial period. This is because inception regions, such as northwestern Canada, remain below sea level throughout the preceding interglacial period.","PeriodicalId":10332,"journal":{"name":"Climate of The Past","volume":"1 1","pages":""},"PeriodicalIF":4.3,"publicationDate":"2024-08-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141945917","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":"A novel explainable deep learning framework for reconstructing South Asian palaeomonsoons","authors":"Kieran M. R. Hunt, Sandy P. Harrison","doi":"10.5194/egusphere-2024-2128","DOIUrl":"https://doi.org/10.5194/egusphere-2024-2128","url":null,"abstract":"<strong>Abstract.</strong> We present novel explainable deep learning techniques for reconstructing South Asian palaeomonsoon rainfall over the last 500 years, leveraging long instrumental precipitation records and palaeoenvironmental datasets from South and East Asia to build two types of model: dense neural networks ('timeline models') and convolutional neural networks (CNNs). The timeline models are trained individually on seven regional rainfall datasets and while they capture decadal-scale variability and significant droughts, they underestimate interannual variability. The CNNs, designed to account for spatial relationships in both predictor and target, demonstrate higher skill in reconstructing rainfall patterns and produce robust spatiotemporal reconstructions. The 19th and 20th centuries were characterised by marked inter-annual variability in the monsoon, but earlier periods were characterised by more decadal- to centennial-scale oscillations. Multidecadal droughts occurred in the mid-seventeenth and nineteenth centuries, while much of the eighteenth century (particularly the early part of the century) was characterised by above-average monsoon precipitation. Extreme droughts tend to be concentrated in south and west India and often coincide with recorded famines. By applying explainability techniques, we show that the models make use of both local hydroclimate and synoptic-scale dynamical relationships. Our findings offer insights into the historical variability of the Indian summer monsoon and highlight the potential of deep learning techniques in palaeoclimate reconstruction.","PeriodicalId":10332,"journal":{"name":"Climate of The Past","volume":"1 1","pages":""},"PeriodicalIF":4.3,"publicationDate":"2024-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141945919","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}
Marco Gaetani, Gabriele Messori, Francesco S. R. Pausata, Shivangi Tiwari, M. Carmen Alvarez Castro, Qiong Zhang
{"title":"Mid-Holocene climate at mid-latitudes: assessing the impact of Saharan greening","authors":"Marco Gaetani, Gabriele Messori, Francesco S. R. Pausata, Shivangi Tiwari, M. Carmen Alvarez Castro, Qiong Zhang","doi":"10.5194/cp-20-1735-2024","DOIUrl":"https://doi.org/10.5194/cp-20-1735-2024","url":null,"abstract":"Abstract. During the first half of the Holocene (11 000 to 5000 years ago), the Northern Hemisphere experienced a strengthening of the monsoonal regime, with climate reconstructions robustly suggesting a greening of the Sahara region. Palaeoclimate archives also show that this so-called African humid period (AHP) was accompanied by changes in climate conditions at middle to high latitudes. However, inconsistencies still exist in reconstructions of the mid-Holocene (MH) climate at mid-latitudes, and model simulations provide limited support in reducing these discrepancies. In this paper, a set of simulations performed using a climate model are used to investigate the hitherto unexplored impact of Saharan greening on mid-latitude atmospheric circulation during the MH. Numerical simulations show Saharan greening has a year-round impact on the main circulation features in the Northern Hemisphere, especially during boreal summer (when the African monsoon develops). Key findings include a westward shift in the global Walker Circulation, leading to modifications in the North Atlantic jet stream in summer and the North Pacific jet stream in winter. Furthermore, Saharan greening modifies atmospheric synoptic circulation over the North Atlantic, enhancing the effect of orbital forcing on the transition of the North Atlantic Oscillation phase from predominantly positive to negative in winter and summer. Although the prescription of vegetation in the Sahara does not improve the proxy–model agreement, this study provides the first constraint on the influence of Saharan greening on northern mid-latitudes, opening new opportunities for understanding MH climate anomalies in regions such as North America and Eurasia.","PeriodicalId":10332,"journal":{"name":"Climate of The Past","volume":"76 1","pages":""},"PeriodicalIF":4.3,"publicationDate":"2024-08-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141946019","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}
Uwe Mikolajewicz, Marie-Luise Kapsch, Clemens Schannwell, Katharina D. Six, Florian A. Ziemen, Meike Bagge, Jean-Philippe Baudouin, Olga Erokhina, Veronika Gayler, Volker Klemann, Virna L. Meccia, Anne Mouchet, Thomas Riddick
{"title":"Deglaciation and abrupt events in a coupled comprehensive atmosphere–ocean–ice sheet–solid earth model","authors":"Uwe Mikolajewicz, Marie-Luise Kapsch, Clemens Schannwell, Katharina D. Six, Florian A. Ziemen, Meike Bagge, Jean-Philippe Baudouin, Olga Erokhina, Veronika Gayler, Volker Klemann, Virna L. Meccia, Anne Mouchet, Thomas Riddick","doi":"10.5194/cp-2024-55","DOIUrl":"https://doi.org/10.5194/cp-2024-55","url":null,"abstract":"<strong>Abstract.</strong> During the last 20,000 years the climate of the earth has changed from a state much colder than today with large ice sheets in North America and Northwest Eurasia to its present state. The fully-interactive simulation of this transition represents a hitherto unsolved challenge for state-of-the-art climate models. We use a novel coupled comprehensive atmosphere–ocean–vegetation– ice sheet–solid earth model to simulate the transient climate evolution from the last glacial maximum to preindustrial times. The model considers dynamical changes of the glacier mask, land–sea mask and river routing. An ensemble of transient model simulations successfully captures the main features of the last deglaciation, as depicted by proxy estimates. In addition, our model simulates a series of abrupt climate changes, which can be attributed to different drivers. Abrupt cooling events during the glacial and the first half of the deglaciation are caused by Heinrich-event like ice-sheet surges, which are part of the model generated internal variability. We show that the timing of these surges depends on the initial state and the model parameters. Abrupt events during the second half of the deglaciation are caused by a long-term shift in the sign of the Arctic freshwater budget, changes in river routing and/or the opening of ocean passages.","PeriodicalId":10332,"journal":{"name":"Climate of The Past","volume":"50 1","pages":""},"PeriodicalIF":4.3,"publicationDate":"2024-08-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141946017","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":"Northern Hemisphere ice sheets and ocean interactions during the last glacial period in a coupled ice sheet-climate model","authors":"Louise Abot, Aurélien Quiquet, Claire Waelbroeck","doi":"10.5194/cp-2024-51","DOIUrl":"https://doi.org/10.5194/cp-2024-51","url":null,"abstract":"<strong>Abstract.</strong> This study examines the interactions between the Northern Hemisphere ice sheets and the ocean during the last glacial period. We explore the consequences of an ocean subsurface warming on ice sheet dynamics and the associated feedbacks, using the climate model of intermediate complexity iLOVECLIM coupled with the ice sheet model GRISLI. Our study shows that amplified oceanic basal melt rates lead to significant freshwater release from both increased calving and basal melt fluxes. Inland, dynamic thinning occurs over the Eurasian and Iceland ice sheets, leading to destabilization, while the coasts of Greenland and the eastern part of the Laurentide ice sheet are thickening. There, the increased oceanic basal melt rates lead to a reduction in the thickness of the ice shelves and the ice flow at the grounding line, resulting in upstream accumulation. Nevertheless, the influx of fresh water temporarily increases sea-ice extent, reduces convection in the Labrador Sea, weakens the Atlantic meridional overturning circulation, lowers surface temperatures in the Northern Hemisphere and increases the subsurface temperatures in the Nordic Seas. The release of cold and fresh water leads to a decrease in ice sheet discharge (negative feedback) for the Greenland and Eurasian ice sheets. The Laurentide ice sheet is rather stable due to low background temperatures and salinity at shelf drafts in the Baffin Bay and Labrador Sea in the model. Still, we show that we are able to trigger a grounding line retreat by imposing ad-hoc oceanic melt rates (10 m/yr). However, continental ice loss stops as soon as we halt the perturbation. This study emphasizes the complex feedback mechanisms at the ocean-ice sheet interface, stressing the necessity for more accurately constrained model results to enhance our understanding of past changes and the predictions of future ice sheet behaviour and sea level rise.","PeriodicalId":10332,"journal":{"name":"Climate of The Past","volume":"31 1","pages":""},"PeriodicalIF":4.3,"publicationDate":"2024-08-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141946016","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":"Documentary evidence of urban droughts and their impact in the eastern Netherlands: the cases of Deventer and Zutphen, 1500–1795","authors":"Dániel Johannes Moerman","doi":"10.5194/cp-20-1721-2024","DOIUrl":"https://doi.org/10.5194/cp-20-1721-2024","url":null,"abstract":"Abstract. Compared to other parts of Europe, very little is known about pre-instrumental drought periods in the Netherlands. Existing reconstructions are based primarily on data from England, France, and Germany, while more local studies on drought and its impact are still absent. This article thus aims to expand our knowledge of droughts in the Netherlands between 1500 and 1795 by focusing specifically on drought in an urban context to provide a more precise and local idea of the impact and severity of drought. The main case studies are cities in the eastern part of the country, Deventer and Zutphen. Both cities lay in relatively close proximity to each other and share similar geological and hydrological conditions, as well as extensive archives that can be used to gather documentary data regarding historical drought periods. The three primary aims of the article are (1) to examine the potential use of documentary data from the city archives of Deventer and Zutphen for historical drought reconstruction; (2) to establish droughts for both cities on the basis of the year and month or season in which they took place, as well as ranking the droughts according to the impact-based Historical Severity Drought Scale (HSDS); and (3) to compare the data from this analysis with those from other indices. In the end, the article strengthens the need to focus on documentary data from local case studies regarding drought, not only to provide more precise local reconstructions of drought severity compared to regional studies, but also to take into account the long-term effects on urban waterscapes and the provisioning of fresh water.","PeriodicalId":10332,"journal":{"name":"Climate of The Past","volume":"216 1","pages":""},"PeriodicalIF":4.3,"publicationDate":"2024-08-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141881733","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}
Justin Gérard, Loïc Sablon, Jarno J. C. Huygh, Anne-Christine Da Silva, Alexandre Pohl, Christian Vérard, Michel Crucifix
{"title":"Exploring the mechanisms of Devonian oceanic anoxia: impact of ocean dynamics, palaeogeography and orbital forcing","authors":"Justin Gérard, Loïc Sablon, Jarno J. C. Huygh, Anne-Christine Da Silva, Alexandre Pohl, Christian Vérard, Michel Crucifix","doi":"10.5194/egusphere-2024-1983","DOIUrl":"https://doi.org/10.5194/egusphere-2024-1983","url":null,"abstract":"<strong>Abstract.</strong> The Devonian is a warmer-than-present geological period spanning from 419 to 359 million years ago (Ma) characterized by multiple identified ocean anoxic/hypoxic events. Despite decades of extensive investigation, no consensus has been reached regarding the drivers of these anoxic events. While growing geological evidence has demonstrated a temporal correlation between astronomical forcing and anoxia during this period, underlying physical mechanisms remain unknown, hence questioning causality. Here, we perform multiple sensitivity experiments, using an Earth system model of intermediate complexity (cGENIE), to isolate the influences of specific Devonian climate and palaeogeography components on ocean oxygen levels, contributing to the better understanding of the intricate interplay of factors preconditioning the ocean to anoxia. We quantify the impact of continental configuration, ocean-atmosphere biogeochemistry (global mean oceanic PO<sub>4</sub> concentration and atmospheric pO<sub>2</sub>), climatic forcing (pCO<sub>2</sub>) and astronomical forcing on background oceanic circulation and oxygenation during the Devonian. Our results indicate that continental configuration is crucial for Devonian ocean anoxia, significantly influencing ocean circulation and oxygen levels while consistently modulating the effects of other Devonian climate components such as oceanic PO<sub>4</sub> concentration, atmospheric pO<sub>2</sub> and pCO<sub>2</sub>, and orbital forcing. The evolution of continental configuration provides a plausible explanation for the increased frequency of ocean anoxic events identified during the Middle and Late Devonian periods, as it contributed to the expansion of oxygen-depleted zones. Our simulations also show that both the decreased atmospheric pO<sub>2</sub> and increased oceanic PO<sub>2</sub> concentration exacerbate ocean anoxia, consistent with established knowledge. The variation of pCO<sub>2</sub> reveals a wide range of ocean dynamics patterns, including stable oscillations, multiple convection cells, multistability and hysteresis; all leading to significant variations of the ocean oxygen levels, therefore strongly impacting the preconditioning of the ocean to anoxia. Furthermore, multistability and important hysteresis (particularly slow ocean time response) offer different mechanisms to account for the prolonged duration of some ocean anoxic events. Finally, we found that astronomical forcing substantially impacts ocean anoxia by altering ocean circulation and oxygen solubility, with obliquity consistently emerging as the primary orbital parameter driving ocean oxygen variations.","PeriodicalId":10332,"journal":{"name":"Climate of The Past","volume":"34 1","pages":""},"PeriodicalIF":4.3,"publicationDate":"2024-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141866171","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}