The Changing Annual Cycle of Sea Surface Temperature

In recent decades, many research efforts focused on global climate change, multidecadal, decadal, interannual variability, and the increasing extreme events of sea surface temperature. In contrast, the continuous evolution of the reference frame, the annual cycle of SST used to quantify the aforementioned variability and changes, has long been overlooked, resulting in difficulties in under- standing the underlying physical mechanisms responsible for these variability and changes. This study strives to bridge this gap on the changes in SST annual cycle. By devising a running correlation-based method, the seasons such as summer and winter are characterized as a period of varying SST rather than an exact timing and the phase and amplitude of non-sinusoidal annually evolving SST annual cycle is quantified. It is revealed that the varying phases of summer or winter are more closely linked to multidecadal SST variability than to long- term climate change, with the former reaching 3.0 day/decade. Moreover, the changes in amplitude are well-explained by the distinct variation of summer and winter SST. Both the systematic shift of the phase and alterations in the annual cycle shape contribute to the phase changes which explain up to 1.2 K of monthly SST anomaly with respect to climatological annual cycle on multidecadal timescale. The variation of surface wind stress is found as an important driver of phase shift of SST annual cycle. Furthermore, it is evident that the SST annual cycle in CMIP6 historical simulations experience notable bias compared with that in ERA5 SST for both phase and summer/winter SST. The low-frequency variability is often overshadowed by substantial high-frequency part or, in some cases, underestimated in models. The oversensitivity of modeled SST to anthropogenic forcing significantly contributes to these results. A well-simulated temperature annual cycle is required for more realistic feedback mechanisms and interactions between regional climates.

Grantor dc:publisher

Florida State University

Year dc:date

2024

Contributors dc:contributor

• Yang, Fucheng (author)
• Wu, Zhaohua (professor directing dissertation)
• Zhu, Lingjiong (university representative)
• Atwood, Alyssa Regine (committee member)
• Cai, Ming, 1957- (committee member)
• Misra, Vasubandhu, 1970- (committee member)
• Florida State University (degree granting institution)
• College of Arts and Sciences (degree granting college)
• Department of Earth, Ocean, and Atmospheric Science (degree granting department)

• Atmospheric sciences

Language dc:language

English

Identifier

fsu:927806
iid: Yang_fsu_0071E_18532

OAI identifier oai:identifier

oai:diginole.lib.fsu.edu:fsu_927806