Defense
Student: Marie Fernanda Massarico Cardoso
Program: Meteorology
Title: "Teleconnections between ENSO and Antarctic Sea Ice using 3D Wavelets in clustered regions"
Advisor: Prof. Dr. Ricardo de Camargo
Judging Comitee:
- Prof. Dr. Ricardo de Camargo - IAG/USP (Chair and Advisor)
- Profa. Dra. Rosmerí Porfírio da Rocha - IAG/USP
- Prof. Dr. Luciano Ponzi Pezzi - OBT/INPE (videoconferência)
- Prof. Dr. Francisco Eliseu Aquino - UFRGS (videoconferência)
- Profa. Dra. Camila Bertoletti Carpenedo - UFPR (videoconferência)
Other Members:
- Profa. Dra. Natália Pillar da Silva - IAG/USP
- Prof. Dr. Pedro Leite da Silva Dias - IAG/USP
- Prof. Dr. Ronald Buss de Souza - CPTEC/INPE
- Profa. Dra. Ana Cristina Pinto de Almeida Palmeira - IGeo/UFRJ
- Profa. Dra. Claudia Klose Parise - UFMA
Abstract:
The spatial heterogeneity of Antarctic sea ice variability and its modulation by large-scale climate variability modes constitute central elements for understanding Southern Hemisphere climate dynamics. This work aimed to objectively characterize the spatio-temporal structure of Antarctic sea ice variability and investigate the intensity, scale, and non-stationarity of teleconnections between the El Niño-Southern Oscillation and sea ice concentrations across different sectors of the Southern Ocean. Daily sea ice concentration series derived from passive microwave sensors (1978-2023) and four ENSO indices representative of different equatorial Pacific regions (1982-2022) were used. Regionalization was based on hierarchical and non-hierarchical clustering techniques applied to 37 statistical features, identifying 19 homogeneous sub-regions according to multiple variability criteria. Time-frequency analysis employed continuous wavelet transform, cross-wavelet transform, and wavelet coherence to quantify covariability, shared power, and phase relationships across spectral bands ranging from intermonthly to interdecadal scales. Results demonstrate that the Bellingshausen-Amundsen sector constitutes the core of response to remote ENSO forcing, with interannual coherence exceeding 0.80, persistent antiphase relationships (approximately +120 degrees) over four decades, and up to 38% of interannual variance explained by central-western Pacific indices. Pronounced bimodal distributions in this sector indicate alternation between concentration regimes modulated by ENSO phase through the Pacific-South American pattern and anomalies in the Amundsen Sea Low. Coupling operates simultaneously via direct atmospheric forcing — meridional advection of sensible heat — and indirect oceanic modulation — intrusions of Circumpolar Deep Water onto continental shelves. Progressive intensification of coherence from approximately 0.65 (1982-1992) to approximately 0.75 (2012-2022) indicates non-stationarity of the teleconnection, potentially associated with long-term changes in the polar ocean-atmosphere system. Persistence of elevated coherence in intradecadal and interdecadal bands reveals the role of subsurface oceanic memory in maintaining anomalies beyond the scale of individual events. These results provide a quantitative basis for identifying fast-response sectors, persistence mechanisms, and prioritizing seasonal to interannual climate predictability systems in polar regions.
Keywords: Antarctic sea ice, Teleconnections, ENSO, Wavelet, Cluster analysis