Dissertation/Thesis Abstract

El Niño Tropical Pacific Mean State Interaction Under Anthropogenic Global Warming
by Lemmon, Danielle Elizabeth, Ph.D., University of Colorado at Boulder, 2020, 142; 28031703
Abstract (Summary)

El Niño-Southern Oscillation (ENSO) is well established to modify and be modified by the tropical Pacific (TP) mean state. Additionally, the influence of anthropogenic global warming (AGW) on the TP mean state remains uncertain. To explore the impact of anthropogenic global warming (AGW) on El Niño – mean state interaction, three scientific chapters are presented which 1. quantify and examine sea surface temperature (SST) observations to show changing El Niño diversity over past decades, supporting studies that show an increase in unique Central Pacific (CP) El Niño events vs non-unique Eastern Pacific (EP) events, and positing that CP events are generally more unique than EP events, 2. simulate the results from the presented El Niño diversity framework using an atmospheric general circulation model (AGCM) to show stronger Walker Circulation (WC) as mechanism for TP-AGW adjustment; and this could perpetuate more La Madre mean state changes through thermocline feedbacks as part of a larger CP El Niño – La Madre mean state feedback, and 3. investigate past and future El Niño teleconnections using an AGCM to simulate TP SST paleo-reconstructions over the Plio-Pliestocene (Wycech et al., 2020) as an analog for El Niño under El Padre AGW TP mean state adjustment, showing overlap between simulated modern and Pliocene El Niño teleconnections and suggesting that El Niño teleconnections under El Padre mean state changes may be more stronger and more sensitive to El Niño diversity. The present thesis is focused on El Niño diversity and TP mean state interaction, though the importance of La Niña diversity is discussed as important for past and future ENSO – mean state interaction. Thus, I explore diverse El Niño – TP mean state interaction under the larger posited theory of ENSO – mean state interaction, along with considerations for the uncertain impact of AGW.

Indexing (document details)
Advisor: Karnauskas, Kristopher B.
Commitee: Capotondi, Antonietta, Marchitto, Thomas, Han, Weiqing, Alexander, Michael
School: University of Colorado at Boulder
Department: Atmospheric and Oceanic Sciences
School Location: United States -- Colorado
Source: DAI-B 82/3(E), Dissertation Abstracts International
Subjects: Climate Change, Paleoclimate Science, Atmospheric sciences
Keywords: El Niño, ENSO diversity, Global warming, Pliocene, Tropical Pacific
Publication Number: 28031703
ISBN: 9798672149462
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