TY - JOUR A1 - Sarr, Anta-Clarisse A1 - Donnadieu, Yannick A1 - Bolton, Clara T. A1 - Ladant, Jean-Baptiste A1 - Licht, Alexis A1 - Fluteau, Frédéric A1 - Laugié, Marie A1 - Tardif-Becquet, Delphine A1 - Dupont-Nivet, Guillaume T1 - Neogene South Asian monsoon rainfall and wind histories diverged due to topographic effects JF - Nature geoscience N2 - The drivers of the evolution of the South Asian Monsoon remain widely debated. An intensification of monsoonal rainfall recorded in terrestrial and marine sediment archives from the earliest Miocene (23-20 million years ago (Ma)) is generally attributed to Himalayan uplift. However, Indian Ocean palaeorecords place the onset of a strong monsoon around 13 Ma, linked to strengthening of the southwesterly winds of the Somali Jet that also force Arabian Sea upwelling. Here we reconcile these divergent records using Earth system model simulations to evaluate the interactions between palaeogeography and ocean-atmosphere dynamics. We show that factors forcing the South Asian Monsoon circulation versus rainfall are decoupled and diachronous. Himalayan and Tibetan Plateau topography predominantly controlled early Miocene rainfall patterns, with limited impact on ocean-atmosphere circulation. The uplift of the East African and Middle Eastern topography played a pivotal role in the establishment of the modern Somali Jet structure above the western Indian Ocean, while strong upwelling initiated as a direct consequence of the emergence of the Arabian Peninsula and the onset of modern-like atmospheric circulation. Our results emphasize that although elevated rainfall seasonality was probably a persistent feature since the India-Asia collision in the Paleogene, modern-like monsoonal atmospheric circulation only emerged in the late Neogene. Y1 - 2022 U6 - https://doi.org/10.1038/s41561-022-00919-0 SN - 1752-0894 SN - 1752-0908 VL - 15 IS - 4 SP - 314 EP - 319 PB - Nature Research CY - Berlin ER - TY - JOUR A1 - Barbolini, Natasha A1 - Woutersen, Amber A1 - Dupont-Nivet, Guillaume A1 - Silvestro, Daniele A1 - Tardif-Becquet, Delphine A1 - Coster, Pauline M. C. A1 - Meijer, Niels A1 - Chang, Cun A1 - Zhang, Hou-Xi A1 - Licht, Alexis A1 - Rydin, Catarina A1 - Koutsodendris, Andreas A1 - Han, Fang A1 - Rohrmann, Alexander A1 - Liu, Xiang-Jun A1 - Zhang, Y. A1 - Donnadieu, Yannick A1 - Fluteau, Frederic A1 - Ladant, Jean-Baptiste A1 - Le Hir, Guillaume A1 - Hoorn, M. Carina T1 - Cenozoic evolution of the steppe-desert biome in Central Asia JF - Science Advances N2 - The origins and development of the arid and highly seasonal steppe-desert biome in Central Asia, the largest of its kind in the world, remain largely unconstrained by existing records. It is unclear how Cenozoic climatic, geological, and biological forces, acting at diverse spatial and temporal scales, shaped Central Asian ecosystems through time. Our synthesis shows that the Central Asian steppe-desert has existed since at least Eocene times but experienced no less than two regime shifts, one at the Eocene-Oligocene Transition and one in the mid-Miocene. These shifts separated three successive "stable states," each characterized by unique floral and faunal structures. Past responses to disturbance in the Asian steppe-desert imply that modern ecosystems are unlikely to recover their present structures and diversity if forced into a new regime. This is of concern for Asian steppes today, which are being modified for human use and lost to desertification at unprecedented rates. Y1 - 2020 U6 - https://doi.org/10.1126/sciadv.abb8227 SN - 2375-2548 VL - 6 IS - 41 PB - American Association for the Advancement of Science CY - Washington ER - TY - JOUR A1 - Toumoulin, Agathe A1 - Tardif-Becquet, Delphine A1 - Donnadieu, Yannick A1 - Licht, Alexis A1 - Ladant, Jean-Baptiste A1 - Kunzmann, Lutz A1 - Dupont-Nivet, Guillaume T1 - Evolution of continental temperature seasonality from the Eocene greenhouse to the Oligocene icehouse BT - a model-data comparison JF - Climate of the past : an interactive open access journal of the European Geosciences Union N2 - At the junction of greenhouse and icehouse climate states, the Eocene-Oligocene Transition (EOT) is a key moment in Cenozoic climate history. While it is associated with severe extinctions and biodiversity turnovers on land, the role of terrestrial climate evolution remains poorly resolved, especially the associated changes in seasonality. Some paleobotanical and geochemical continental records in parts of the Northern Hemisphere suggest the EOT is associated with a marked cooling in winter, leading to the development of more pronounced seasons (i.e., an increase in the mean annual range of temperature, MATR). However, the MATR increase has been barely studied by climate models and large uncertainties remain on its origin, geographical extent and impact. In order to better understand and describe temperature seasonality changes between the middle Eocene and the early Oligocene, we use the Earth system model IPSL-CM5A2 and a set of simulations reconstructing the EOT through three major climate forcings: pCO(2) decrease (1120, 840 and 560 ppm), the Antarctic ice-sheet (AIS) formation and the associated sea-level decrease. Our simulations suggest that pCO(2) lowering alone is not sufficient to explain the seasonality evolution described by the data through the EOT but rather that the combined effects of pCO(2) , AIS formation and increased continentality provide the best data-model agreement.pCO(2) decrease induces a zonal pattern with alternating increasing and decreasing seasonality bands particularly strong in the northern high latitudes (up to 8 degrees C MATR increase) due to sea-ice and surface albedo feedback. Conversely, the onset of the AIS is responsible for a more constant surface albedo yearly, which leads to a strong decrease in seasonality in the southern midlatitudes to high latitudes (> 40 degrees S). Finally, continental areas that emerged due to the sea-level lowering cause the largest increase in seasonality and explain most of the global heterogeneity in MATR changes (1MATR) patterns. The Delta MATR patterns we reconstruct are generally consistent with the variability of the EOT biotic crisis intensity across the Northern Hemisphere and provide insights on their underlying mechanisms. Y1 - 2022 U6 - https://doi.org/10.5194/cp-18-341-2022 SN - 1814-9324 SN - 1814-9332 VL - 18 IS - 2 SP - 341 EP - 362 PB - Copernicus CY - Göttingen ER - TY - JOUR A1 - Tardif-Becquet, Delphine A1 - Fluteau, Frédéric A1 - Donnadieu, Yannick A1 - Le Hir, Guillaume A1 - Ladant, Jean-Baptiste A1 - Sepulchre, Pierre A1 - Licht, Alexis A1 - Poblete, Fernando A1 - Dupont-Nivet, Guillaume T1 - The origin of Asian monsoons BT - a modelling perspective JF - Climate of the Past N2 - The Cenozoic inception and development of the Asian monsoons remain unclear and have generated much debate, as several hypotheses regarding circulation patterns at work in Asia during the Eocene have been proposed in the few last decades. These include (a) the existence of modern-like monsoons since the early Eocene; (b) that of a weak South Asian monsoon (SAM) and little to no East Asian monsoon (EAM); or (c) a prevalence of the Intertropical Convergence Zone (ITCZ) migrations, also referred to as Indonesian-Australian monsoon (I-AM). As SAM and EAM are supposed to have been triggered or enhanced primarily by Asian palaeogeographic changes, their possible inception in the very dynamic Eocene palaeogeographic context remains an open question, both in the modelling and field-based communities. We investigate here Eocene Asian climate conditions using the IPSL-CM5A2 (Sepulchre et al., 2019) earth system model and revised palaeogeographies. Our Eocene climate simulation yields atmospheric circulation patterns in Asia substantially different from modern conditions. A large high-pressure area is simulated over the Tethys ocean, which generates intense low tropospheric winds blowing southward along the western flank of the proto-Himalayan-Tibetan plateau (HTP) system. This low-level wind system blocks, to latitudes lower than 10 degrees N, the migration of humid and warm air masses coming from the Indian Ocean. This strongly contrasts with the modern SAM, during which equatorial air masses reach a latitude of 20-25 degrees N over India and southeastern China. Another specific feature of our Eocene simulation is the widespread subsidence taking place over northern India in the midtroposphere (around 5000 m), preventing deep convective updraught that would transport water vapour up to the condensation level. Both processes lead to the onset of a broad arid region located over northern India and over the HTP. More humid regions of high seasonality in precipitation encircle this arid area, due to the prevalence of the Intertropical Convergence Zone (ITCZ) migrations (or Indonesian-Australian monsoon, I-AM) rather than monsoons. Although the existence of this central arid region may partly result from the specifics of our simulation (model dependence and palaeogeographic uncertainties) and has yet to be confirmed by proxy records, most of the observational evidence for Eocene monsoons are located in the highly seasonal transition zone between the arid area and the more humid surroundings. We thus suggest that a zonal arid climate prevailed over Asia before the initiation of monsoons that most likely occurred following Eocene palaeogeographic changes. Our results also show that precipitation seasonality should be used with caution to infer the presence of a monsoonal circulation and that the collection of new data in this arid area is of paramount importance to allow the debate to move forward. KW - earth system model KW - early eocene KW - tibetan plateau KW - climate-change KW - oligocene climate KW - summer monsoon KW - global monsoon KW - ice sheet KW - part 1 KW - China Y1 - 2020 U6 - https://doi.org/10.5194/cp-16-847-2020 SN - 1814-9332 SN - 1814-9324 VL - 16 IS - 3 SP - 847 EP - 865 PB - Copernicus Publications CY - Göttingen ER - TY - GEN A1 - Tardif-Becquet, Delphine A1 - Fluteau, Frédéric A1 - Donnadieu, Yannick A1 - Le Hir, Guillaume A1 - Ladant, Jean-Baptiste A1 - Sepulchre, Pierre A1 - Licht, Alexis A1 - Poblete, Fernando A1 - Dupont-Nivet, Guillaume T1 - The origin of Asian monsoons BT - a modelling perspective T2 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe N2 - The Cenozoic inception and development of the Asian monsoons remain unclear and have generated much debate, as several hypotheses regarding circulation patterns at work in Asia during the Eocene have been proposed in the few last decades. These include (a) the existence of modern-like monsoons since the early Eocene; (b) that of a weak South Asian monsoon (SAM) and little to no East Asian monsoon (EAM); or (c) a prevalence of the Intertropical Convergence Zone (ITCZ) migrations, also referred to as Indonesian-Australian monsoon (I-AM). As SAM and EAM are supposed to have been triggered or enhanced primarily by Asian palaeogeographic changes, their possible inception in the very dynamic Eocene palaeogeographic context remains an open question, both in the modelling and field-based communities. We investigate here Eocene Asian climate conditions using the IPSL-CM5A2 (Sepulchre et al., 2019) earth system model and revised palaeogeographies. Our Eocene climate simulation yields atmospheric circulation patterns in Asia substantially different from modern conditions. A large high-pressure area is simulated over the Tethys ocean, which generates intense low tropospheric winds blowing southward along the western flank of the proto-Himalayan-Tibetan plateau (HTP) system. This low-level wind system blocks, to latitudes lower than 10 degrees N, the migration of humid and warm air masses coming from the Indian Ocean. This strongly contrasts with the modern SAM, during which equatorial air masses reach a latitude of 20-25 degrees N over India and southeastern China. Another specific feature of our Eocene simulation is the widespread subsidence taking place over northern India in the midtroposphere (around 5000 m), preventing deep convective updraught that would transport water vapour up to the condensation level. Both processes lead to the onset of a broad arid region located over northern India and over the HTP. More humid regions of high seasonality in precipitation encircle this arid area, due to the prevalence of the Intertropical Convergence Zone (ITCZ) migrations (or Indonesian-Australian monsoon, I-AM) rather than monsoons. Although the existence of this central arid region may partly result from the specifics of our simulation (model dependence and palaeogeographic uncertainties) and has yet to be confirmed by proxy records, most of the observational evidence for Eocene monsoons are located in the highly seasonal transition zone between the arid area and the more humid surroundings. We thus suggest that a zonal arid climate prevailed over Asia before the initiation of monsoons that most likely occurred following Eocene palaeogeographic changes. Our results also show that precipitation seasonality should be used with caution to infer the presence of a monsoonal circulation and that the collection of new data in this arid area is of paramount importance to allow the debate to move forward. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1436 KW - earth system model KW - early eocene KW - tibetan plateau KW - climate-change KW - oligocene climate KW - summer monsoon KW - global monsoon KW - ice sheet KW - part 1 KW - China Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-516770 SN - 1866-8372 IS - 1436 ER -