Teleconnection between Antarctic sea ice variability and Indian summer monsoon / Siti Syairah Atiqah Azhar

Siti Syairah Atiqah , Azhar (2023) Teleconnection between Antarctic sea ice variability and Indian summer monsoon / Siti Syairah Atiqah Azhar. PhD thesis, Universiti Malaya.

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Abstract

Teleconnection between the Antarctic sea ice and the tropical climate has become an important issue in recent years, particularly among scientists and researchers. Further investigating the subject, this study examines the teleconnection between the Antarctic sea ice extent in the Indian Ocean sector and the Indian summer monsoon rainfall. It utilises reanalysis, satellite and in-situ observation data, and model output from the coupled model Intercomparison project phase 5 (CMIP5) from 1979 to 2013. The study is divided into three main parts. Firstly, examining the climatology of the sea ice extent in the Indian Ocean sector and Indian summer monsoon rainfall, both seasonal and monthly. Secondly, examines the relationship between the sea ice extent in the Indian Ocean sector and Indian summer monsoon rainfall variability under the influence of the Mascarene High. Thirdly, offers the mechanism connecting the sea ice extent in the Indian Ocean sector and Indian summer monsoon rainfall regarding atmospheric circulation features and compares it with several CMIP5 models. The long term monthly average of the sea ice extent in the Indian Ocean sector for 35 years shows that the maximum amount of sea ice extent produced is in October while the minimum amount is in February. The highest seasonal month of the sea ice extent during September-October- November (SON), and the lowest was in December-January-February (DJF). Furthermore, the northeastern region of India receives the highest mean annual rainfall during the summer monsoon season, whereas the northwestern region of India receives the lowest mean annual rainfall. The correlation analysis revealed that the April-May- June (AMJ) sea ice extent in the Indian Ocean sector significantly positively correlated with the Indian summer monsoon rainfall, particularly over the Peninsular India region from 1979 to 2013 (r = 0.44, p < 0.05). This connection is indicated by the correspondence of the high ice phase (HIP) and low ice phase (LIP) years to the strengthening and weakening of the Mascarene High, resulting in the increase and decrease of Indian summer monsoon rainfall. The empirical orthogonal function (EOF) and correlation analysis show that the first and third modes of principal component (PC1 and PC3) of AMJ sea ice extent in the Indian Ocean sector during are significantly correlated with the second mode of principal component (PC2) of Indian summer monsoon rainfall. The reanalysis data revealed that the changes in the sea ice extent excite meridional wave train responses along the Indian Ocean for both principal component modes. Positive (negative) sea ice extent anomalies based on first and third EOFs (EOF1 and EOF3), contribute to the strengthening (weakening) of the Polar, Ferrel, and Hadley cells, inducing stronger (weaker) convective activity over the Indian latitudes. The stronger (weaker) convective activity over the Indian region leads to more (less) rainfall over the region during high (low) ice phase years. Furthermore, a stronger (weaker) polar jet during the high (low) ice phase is also noted. The AMJ sea ice extent simulated by the NorESM1-M model was significantly positively correlated with Indian summer monsoon rainfall, whereas the IPSL-CM54-LR model showed a negative correlation. Both models were able to captured certain atmospheric teleconnection features found in the reanalysis.

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