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- Axelsson, Josefine, 1992-
(författare)
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Interglacial climates in proxies and models : Utilizing sampled oxygen isotopes and model simulations to understand past Indian summer monsoon variability
- 2024
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The study of Earth's climate system, including the mechanisms driving monsoon systems, is a key area of research within environmental sciences. Monsoons, vital for billions of people, are complex atmospheric phenomena influenced by various global factors, including orbital changes and natural climate variability. Among monsoon systems, the Indian summer Monsoon (ISM) is of particular interest due to its significant impact on the South Asian climate, agriculture, and water resources. Despite extensive study, comprehending the ISM's historical variability and its future implications remains a challenge. Utilizing natural archives like speleothems, along with stable water isotopes from precipitation and advanced climate model simulations, this thesis aims to decipher the ISM's responses to natural forcings across key interglacial periods—the Last Interglacial and the Holocene.Our findings indicate that the ISM's strength is critically influenced by slight variations in orbital configurations, leading to significant shifts in monsoon patterns. Our research also highlights the dual influence of local geographical features and distant atmospheric conditions on the ISM's annual variability. Most notably, we observed discrepancies between δ18O values obtained from isotope-enabled climate models and those derived from speleothems. This insight indicates that the models need refinement to accurately mirror the complexities observed in the proxy records and that the uncertainty parameter in speleothem records needs to be improved.The alignment between proxy and model data is crucial for a more accurate reconstruction of past climates and for enhancing the predictive capabilities of future monsoon behavior under changing climatic conditions. By advancing our knowledge of the ISM's past, we are better equipped to anticipate its future. To achieve that, this thesis stresses the importance of bridging the gap between proxy data insights and climate model simulations. This would not only enrich our historical climate knowledge but also inform future climate projections, highlighting the indispensable role of interdisciplinary research in climate science challenges.
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| 2. |
- Lin, Fangyuan, 1996-, et al.
(författare)
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Seasonal to decadal variations of precipitation oxygen isotopes in northern China linked to the moisture source
- 2024
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Ingår i: npj Climate and Atmospheric Science. - 2397-3722. ; 7
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Tidskriftsartikel (refereegranskat)abstract
- A precise characterization of moisture source and transport dynamics over the inland margins of monsoonal China is crucial for understanding the climatic significance of precipitation oxygen isotope (δ18Op) variability preserved in the regional proxy archives. Here, we use a general circulation model with an embedded water-tagging module to quantify the role of moisture dynamics on the seasonal to decadal variations of δ18Op in northern China. Our data indicate that during the non-monsoon season, the δ18Op variability is dominated by the temperature effect. Conversely, in the summer monsoon season, the moisture contributions from the low-latitude land areas (LLA), the Pacific Ocean (PO), and the North Indian Ocean (NIO) override the temperature effect and influence the summer δ18Op. Intensified upstream convection along the NIO moisture transport pathway results in a more negative summer δ18Op compared to moisture transported from the PO and LLA regions. Our analysis shows a decadal shift in summer δ18Op around the mid-1980s, marking changes in the relative contribution of oceanic moisture from PO and NIO in response to changes in the atmospheric circulation patterns influenced by the Pacific Decadal Oscillation. We suggest that such decadal-scale δ18Op variability can be recorded in the natural archives from the region, which can provide valuable insights into understanding past climate variability.
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