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Deciphering the deglacial evolution of water isotope and climate in the Northern Hemisphere

He, Chengfei
http://orcid.org/0000-0003-1453-9691
http://rave.ohiolink.edu/etdc/view?acc_num=osu1620739423120004

Abstract Details

2021, Doctor of Philosophy, Ohio State University, Atmospheric Sciences.
The climate change during the last deglaciation is characterized by several abrupt fluctuations, notably the Heinrich Stadial 1 (HS1, ~18-14.5 ka), Bølling-Allerød (BA, 14.5-12.9 ka), and Younger Dryas (YD, 12.9-11.7 ka). These abrupt events as well as long-term climate variability are well preserved in stable water isotope (𝛿18𝑂) proxies over Asia and Greenland. Yet, some long-standing puzzles regarding the evolution of the water isotopes and their implications to the climate remains not well understood. In particular, the absence of the onset signal of the HS1 cold event around 18 ka in Greenland ice core oxygen isotope 𝛿18𝑂 records appears to be inconsistent with other climate proxies around the globe that do show a clear HS1 onset; the mechanism and hydroclimate implication of highly coherent speleothem 𝛿18𝑂c (𝛿18𝑂 in stalactite) across the Asian monsoon regions remain a subject of debates. To decipher the evolution of water isotope and climate in the last deglaciation, an isotope-enabled Transient Climate Experiment (iTRACE) of global climate and water isotopes in a state-of-the-art isotope-enabled Earth system model is conducted. The iTRACE successfully reproduces the oxygen-isotope evolutions across the pan-Asia and Greenland in the last deglaciation. It is found that the oxygen-isotope evolution is determined by a compensation between accumulation effect associated with summer-winter precipitation contrast, and water isotopic composition effect associated with oxygen-isotope in rainfall. Over Greenland, the isotopic composition effect plays a dominant role during the much of the deglacial time, while the opposite accumulation effect becomes comparable around the onset of HS1 that produces a muted onset in ice core 𝛿18𝑂. Further investigation suggests that the deglacial ice-core isotope variability is mainly modulated by the sea ice extent in the North Atlantic that controls moisture and energy supply to Greenland. Across the Asian monsoon regions, the 𝛿18𝑂c variability is entirely dominated by the isotopic composition effect, which is ultimately determined by upstream moisture source over Indian Ocean. Perturbations of the Indian Ocean rainfall from the variation of Atlantic Meridional Overturning Circulation (AMOC) and solar insolation enrich or deplete the monsoon flow and yield a coherently widespread 𝛿18𝑂c response in downstream Asian monsoon regions. Accompanied by the uniform oxygen isotope signal, a continental-scale hydroclimate footprint is identified in the summer monsoon, consistent with recently developed hydroclimate proxies in South China. This footprint is characterized by a dipole response in East China and a consistent response between North China and South Asia, with a decreased rainfall in North China and South Asia as well as an increased rainfall in South China. The footprint results from migration of high-level westerly jet related to meridional temperature gradients and low-level monsoon flow related to land-sea thermal contrast, which is further reinforced by atmospheric “Silk Road” teleconnection. Besides the summer monsoon, a dramatic change of deglacial autumn monsoon is also detected in South China. The autumn monsoon, consistent with local moisture proxy and comparable with the summer monsoon, results from convergence between anomalous northerly wind and anomalous southerly wind associated with an anticyclone at Western North Pacific, both of which are responses to the slowdown of the AMOC.
Zhengyu Liu (Advisor)
Lonnie Thompson (Committee Member)
David Bromwich (Committee Member)
Bryan Mark (Committee Member)
Atmospheric Sciences; Oceanography; Paleoclimate Science

Recommended Citations

Citations

  • He, C. (2021). Deciphering the deglacial evolution of water isotope and climate in the Northern Hemisphere [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1620739423120004

    APA Style (7th edition)

  • He, Chengfei. Deciphering the deglacial evolution of water isotope and climate in the Northern Hemisphere. 2021. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1620739423120004.

    MLA Style (8th edition)

  • He, Chengfei. "Deciphering the deglacial evolution of water isotope and climate in the Northern Hemisphere." Doctoral dissertation, Ohio State University, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=osu1620739423120004

    Chicago Manual of Style (17th edition)

osu1620739423120004
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