Diagnosing CMIP6 sea surface temperature variability in the Indo-Pacific warm pool

Sasaki, Maile

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https://hdl.handle.net/2142/127169 Copy

Description

Title

Diagnosing CMIP6 sea surface temperature variability in the Indo-Pacific warm pool

Author(s)

Sasaki, Maile

Issue Date

2024-10-31

Director of Research (if dissertation) or Advisor (if thesis)

Proistosescu, Cristian

Committee Member(s)

• Conroy, Jessica
• Zhang, Gan

Department of Study

Climate Meteorology & Atm Sci

Discipline

Atmospheric Sciences

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

M.S.

Degree Level

Thesis

Keyword(s)

Climate Variability, Tropical Variability, Pattern Effect, Interdecadal Climate Variability, Climate Feedbacks, Climate Change, Climate Dynamics, Internal and Forced Variability, CMIP6, CESM

Abstract

In recent decades, sea surface temperatures (SSTs) in the eastern tropical Pacific have been observed to be cooling, while the western Indo-Pacific warm pool has been experiencing intensified warming. However, models in the Coupled Model Intercomparison Project phase 6 (CMIP6) have been unable to recreate this warming pattern. They indicate an even warming pattern over most of the earth, with intensified warming in the eastern tropical Pacific where we see cooling today. Understanding the cause for this discrepancy is made difficult by the fact that we currently do not have a good understanding of the mechanisms that control decadal scale variability in the tropical Pacific. Here we focus on understanding how climate models handle internal climate variability. Climate models in CMIP6 seem to agree that interdecadal surface air temperature variability is very muted in tropical areas of ascent, and therefore high precipitation. As a result, climate change is disproportionately increasing the temperature variability in the warm pool and along the Intertropical Convergence Zone and South Pacific Convergence Zone. Across CMIP6 models, the strength of ascent is positively correlated with the signal to noise ratio of forced response to unforced variability. We use a simple Hasselmann model to partition SST variability into contributions from forcing and feedback terms for both oceanic and atmospheric heat fluxes. We find that the suppressed variability in tropical regions of ascent is related to strong horizontal transport damping of SST anomalies.

Graduation Semester

2024-12

Type of Resource

Thesis

Handle URL

https://hdl.handle.net/2142/127169

Copyright and License Information

Copyright 2024 Maile Sasaki

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