| 1. |
- Atsawawaranunt, Kamolphat, et al.
(författare)
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The SISAL database : a global resource to document oxygen and carbon isotope records from speleothems
- 2018
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Ingår i: Earth System Science Data. - : Copernicus GmbH. - 1866-3508 .- 1866-3516. ; 10:3, s. 1687-1713
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Tidskriftsartikel (refereegranskat)abstract
- Stable isotope records from speleothems provide information on past climate changes, most particularly information that can be used to reconstruct past changes in precipitation and atmospheric circulation. These records are increasingly being used to provide "out-of-sample" evaluations of isotope-enabled climate models. SISAL (Speleothem Isotope Synthesis and Analysis) is an international working group of the Past Global Changes (PAGES) project. The working group aims to provide a comprehensive compilation of speleothem isotope records for climate reconstruction and model evaluation. The SISAL database contains data for individual speleothems, grouped by cave system. Stable isotopes of oxygen and carbon (delta O-18, delta C-13) measurements are referenced by distance from the top or bottom of the speleothem. Additional tables provide information on dating, including information on the dates used to construct the original age model and sufficient information to assess the quality of each data set and to erect a standardized chronology across different speleothems. The metadata table provides location information, information on the full range of measurements carried out on each speleothem and information on the cave system that is relevant to the interpretation of the records, as well as citations for both publications and archived data.
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| 2. |
- Cheng, Hai, et al.
(författare)
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Milankovitch theory and monsoon
- 2022
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Ingår i: The Innovation. - : Elsevier BV. - 2666-6758. ; 3:6
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Forskningsöversikt (refereegranskat)abstract
- The widely accepted “Milankovitch theory” explains insolation-induced waxing and waning of the ice sheets and their effect on the global climate on orbital timescales. In the past half century, however, the theory has often come under scrutiny, especially regarding its “100-ka problem.” Another drawback, but the one that has received less attention, is the “monsoon problem,” which pertains to the exclusion of monsoon dynamics in classic Milankovitch theory even though the monsoon prevails over the vast low-latitude (∼30° N to ∼30° S) region that covers half of the Earth's surface and receives the bulk of solar radiation. In this review, we discuss the major issues with the current form of Milankovitch theory and the progress made at the research forefront. We suggest shifting the emphasis from the ultimate outcomes of the ice volume to the causal relationship between changes in northern high-latitude insolation and ice age termination events (or ice sheet melting rate) to help reconcile the classic “100-ka problem.” We discuss the discrepancies associated with the characterization of monsoon dynamics, particularly the so-called “sea-land precession-phase paradox” and the “Chinese 100-ka problem.” We suggest that many of these discrepancies are superficial and can be resolved by applying a holistic “monsoon system science” approach. Finally, we propose blending the conventional Kutzbach orbital monsoon hypothesis, which calls for summer insolation forcing of monsoons, with Milankovitch theory to formulate a combined “Milankovitch-Kutzbach hypothesis” that can potentially explain the dual nature of orbital hydrodynamics of the ice sheet and monsoon systems, as well as their interplays and respective relationships with the northern high-latitude insolation and inter-tropical insolation differential.
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| 3. |
- Comas-Bru, Laia, et al.
(författare)
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Evaluating model outputs using integrated global speleothem records of climate change since the last glacial
- 2019
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Ingår i: Climate of the Past. - : Copernicus GmbH. - 1814-9324 .- 1814-9332. ; 15:4, s. 1557-1579
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Tidskriftsartikel (refereegranskat)abstract
- Although quantitative isotope data from speleothems has been used to evaluate isotope-enabled model simulations, currently no consensus exists regarding the most appropriate methodology through which to achieve this. A number of modelling groups will be running isotope-enabled palaeoclimate simulations in the framework of the Coupled Model Intercomparison Project Phase 6, so it is timely to evaluate different approaches to using the speleothem data for data-model comparisons. Here, we illustrate this using 456 globally distributed speleothem delta O-18 records from an updated version of the Speleothem Isotopes Synthesis and Analysis (SISAL) database and palaeoclimate simulations generated using the ECHAM5-wiso isotope-enabled atmospheric circulation model. We show that the SISAL records reproduce the first-order spatial patterns of isotopic variability in the modern day, strongly supporting the application of this dataset for evaluating model-derived isotope variability into the past. However, the discontinuous nature of many speleothem records complicates the process of procuring large numbers of records if data-model comparisons are made using the traditional approach of comparing anomalies between a control period and a given palaeoclimate experiment. To circumvent this issue, we illustrate techniques through which the absolute isotope values during any time period could be used for model evaluation. Specifically, we show that speleothem isotope records allow an assessment of a model's ability to simulate spatial isotopic trends. Our analyses provide a protocol for using speleothem isotope data for model evaluation, including screening the observations to take into account the impact of speleothem mineralogy on delta O-18 values, the optimum period for the modern observational baseline and the selection of an appropriate time window for creating means of the isotope data for palaeo-time-slices.
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| 4. |
- Tian, Ye, et al.
(författare)
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Holocene climate change in southern Oman deciphered by speleothem records and climate model simulations
- 2023
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Ingår i: Nature Communications. - 2041-1723. ; 14:1
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Tidskriftsartikel (refereegranskat)abstract
- Qunf Cave oxygen isotope (& delta;O-18(c)) record from southern Oman is one of the most significant of few Holocene Indian summer monsoon cave records. However, the interpretation of the Qunf & delta;O-18(c) remains in dispute. Here we provide a multi-proxy record from Qunf Cave and climate model simulations to reconstruct the Holocene local and regional hydroclimate changes. The results indicate that besides the Indian summer monsoon, the North African summer monsoon also contributes water vapor to southern Oman during the early to middle Holocene. In principle, Qunf & delta;O-18(c) values reflect integrated oxygen-isotope fractionations over a broad moisture transport swath from moisture sources to the cave site, rather than local precipitation amount alone, and thus the Qunf & delta;O-18(c) record characterizes primary changes in the Afro-Asian monsoon regime across the Holocene. In contrast, local climate proxies appear to suggest an overall slightly increased or unchanged wetness over the Holocene at the cave site. Southern Oman speleothem oxygen isotope and multi-proxy data reveal diverse changes in the Afro-Indian summer monsoon circulations and local hydroclimate conditions during the Holocene, confirming climate model simulations.
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| 5. |
- Wei, Guohui, et al.
(författare)
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Photothermal catalytic activity and mechanism of LaNixCo1-xO3(0 <= x <= 1) perovskites for CO2 reduction to CH4 and CH3OH with H2O
- 2019
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Ingår i: Materials Research Express. - : IOP Publishing. - 2053-1591. ; 6:8
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Tidskriftsartikel (refereegranskat)abstract
- A series of LaNixCo1-xO3 perovskites were synthesized by sol-gel combustion method, the photothermal catalysis of CO2 and H2O into CH4 and CH3OH was investigated systematically. The crystal structure, surface area, oxygen vacancies, band structures and catalytic performance of LaNixCo1-xO3 perovskites were characterized thoroughly in order to understand the design principle of the material for such a photothermal catalysis of CO2 and H2O. With the change of x value, the best catalytic performance was achieved at x = 0.4 and the accumulated yield of CH4 and CH3OH can reach 678.57, 20.83 mu molg(-1) in 6 h, which were 3.4 and 3.8, 1.9 and 2.2 times of that of two end composition, LaCoO3 and LaNiO3 under the same condition. For LaNi0.4Co0.6O3, the surface area reached a maximum concentration of oxygen vacancy while the band gap reached a minimum of 1.42 eV. It is evident that the formation of solid solution between LaMO3 (M = transition metals) compounds can be a general strategy for the new catalyst design.
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| 6. |
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- 2019
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Tidskriftsartikel (refereegranskat)
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