Avinash Kumar

The Arctic Oscillation (AO) is a dominant mode of Northern Hemisphere atmospheric variability; however, its teleconnections with the Indian Ocean are not yet fully understood. This study provides a comprehensive assessment of how sea surface temperature (SST) variability across four Indian Ocean subregions—the Arabian Sea (AS), Bay of Bengal (BoB), Tropical Indian Ocean (TIO), and Southern Indian Ocean (SIO)—modulates the AO, using outputs from 35 CMIP6 models and observational datasets (ERA5, NOAA) for 1985–2014. The AO index, constructed via Empirical Orthogonal Function analysis of Northern Hemisphere sea level pressure anomalies, reveals a complex, regionally and seasonally dependent relationship with Indian Ocean SSTs. Notably, the SIO exhibits a robust and significant negative correlation with the AO during boreal winter (DJF; r = −0.53) and on an annual scale, indicating that positive AO phases are associated with cooling in the SIO, likely due to enhanced mid‐latitude westerlies that increase ocean mixing and upwelling of cooler subsurface water. In contrast, the AS and BoB show weaker, positive correlations, suggesting that AO‐driven atmospheric changes may enhance warm SST anomalies in these northern basins, possibly through alterations in monsoonal wind patterns and ocean–atmosphere heat exchanges. The influence of TIO is minimal, likely due to strong coupling with El Niño‐Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD). The CMIP6 multi‐model ensemble broadly captures the observed AO‐SST teleconnection patterns, but there is considerable inter‐model spread, reflecting differences in the representation of atmospheric teleconnections, ocean dynamics, and feedbacks. These findings highlight the critical importance of Indian Ocean SSTs—especially in the SIO—in shaping AO variability, and emphasise the need for improved representation of tropical‐extratropical interactions in climate models to enhance the accuracy of seasonal‐to‐decadal climate predictions and to better anticipate future changes in Northern Hemisphere climate dynamics under ongoing Indian Ocean warming.

Surface albedo (SAL), a critical factor in climate studies, significantly impacts the Earth's radiation budget and sea ice dynamics. The long‐term spatial and temporal variability of Antarctic SAL were derived from the third edition of the Cloud, Albedo, and Surface Radiation Dataset (CLARA‐A3). The analysis focused on spring and summer across five longitudinal sectors around Antarctica. The relationships of sea ice concentration (SIC) and SAL with climatic variables such as sea surface temperature (SST), 2 m air temperature (T2m), turbulent heat flux, and total cloud cover are explored in detail. The study examined SAL changes in two distinct timescales, pre‐2015 (1979–2015) and post‐2015 (2016–2021), to understand sea ice variations and trends in Antarctic climate change. The study revealed contrasting summer SAL trends, with a positive trend pre‐2015 and a decreasing trend post‐2016 across most of Antarctica, except the Amundsen‐Bellingshausen Sea, which showed an opposite trend. West Antarctica exhibited higher SAL compared to East Antarctica. SAL and SIC were significantly negatively correlated with SST, T2m, and turbulent heat flux across all sectors. Cross‐seasonal lead–lag analysis indicated that increased turbulent heat flux was followed by an increase in SAL after 1–5 months. Wind patterns showed that winds from higher to lower latitudes increased SIC and SAL, while winds from lower to higher latitudes reduced SIC. Post‐2015, notable wind direction reversals were observed in the Antarctic Peninsula during spring. Sectors with higher cloud cover absorbed more ocean heat, reducing turbulent heat flux and affecting SAL. Overall, post‐2015 observations highlighted major shifts in sea ice dynamics and SAL trends during both spring and summer seasons. The SIC decreased markedly across all sectors, with the Weddell Sea showing the most significant reduction. This study highlights regional and seasonal variations in SAL and its interactions with SIC and climatic factors, emphasising shifts in trends post‐2015.

Antarctic sea ice expansion and recession are asymmetric in nature, with regional and temporal variations. The decade-long overall increase in the Antarctic sea ice extent (SIE) until 2015 showed a decrease in recent years since satellite records were available. The present study focused on determining the atmospheric forcing and climate fluctuations responsible for the lowest SIE record in February 2022. Here, the lowest SIE record was assumed to result from the sea ice recession that began in September 2021. The SIE reached a record low of 2.16 × 10⁶km²in February 2022, which was 43% lower than the mean extent of the previous February months since the satellite era. However, the second-lowest SIE was recorded from November 2021 to January 2022. The Weddell Sea, Ross Sea, and Bellingshausen/Amundsen Seas (ABS) sectors experienced the maximum sea ice change on a regional scale. The record-low SIE occurred when the Amundsen Sea Low (ASL) pressure center was intensified, with the Southern Annular Mode (SAM) at its positive phase. Together, these two climate fluctuations played a role in modifying the pressure and wind patterns in Antarctica. The warm northerly winds largely contributed to decreased SIE. Further, the study investigated the Polar Cap Height (PCH), which demonstrates a strengthening of the stratospheric polar vortex and positive polarity of the SAM.

This study investigates the mechanism of seasonal sea ice variation and recent warming amplification. Seasonal temperature changes in the vertical structure reveal that the autumn and winter seasons are warming more than summer. The thermodynamic processes of sea-ice-air interactions via the heat flux component have been studied. The summer Arctic Sea ice has receded by half (∼52%), producing excessive heat. This sea ice loss plays a significant role in determining the heat exchange between the ocean and atmosphere in the following season. During a warm season, the ocean heats up due to incident solar radiation. As a result, delayed ice growth and atmospheric warming occur. Sea ice and heat flux feedbacks explain a large part of Arctic atmospheric warming. These abrupt changes are closely coupled to accelerated Arctic Sea ice loss and atmospheric warming, which are still uncertain.