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 Ni & ntilde;o-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.

In February 2023, the Antarctic Sea ice extent (SIE) reached a historic low of 1.7 million km2, which was 43 % lower than the monthly average extent recorded since 1979. This marked the second consecutive year of record lows, surpassing the minimum SIE from the previous year. Our study aims to understand the atmospheric and oceanic factors from September 2022 to August 2023 that contributed to these new lows. Throughout the study period, the monthly SIE consistently indicated lower extents compared to the long-term average. The Weddell Sea and Amundsen-Bellingshausen Sea (ABS) experienced the most decline in austral spring and summer, respectively, while the Ross Sea showed the minimum sea ice loss. The lower stratospheric cooling patterns observed during summer resulted in a reinforcement of the Southern Annular Mode (SAM), which caused intensification of the surface temperature inversion. This disturbance led to the Antarctic Polar Vortex shifting towards the Equator. The transition from the distinct triple La Nina event to the onset of a warm phase in 2023 resulted in the Amundsen Sea Low (ASL) deepening, which advected warm air into the region and push sea ice back towards the coast, reducing its extent particularly in the west of the Antarctic Peninsula region. Additionally, anomalies in the upper ocean (0-300 m) indicate subsurface ocean warming in most sectors.

ABSTRACT 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.

Background: Land surface temperature (LST) and vegetation play a very significant role in influencing soil moisture and its interaction with the crop. Crop Water Stress Index (CWSI) is one of the most applicable indices to measure the level of water stress to crops that can be quantified using satellite imagery. The upper Brahmaputra river valley of Assam is a rapidly growing region experiencing extensive urban expansion, which necessitates the assessment of changes in spatio-temporal LST and vegetation dynamics for sustainable land management. Methods: MODIS images were applied in this study to assess spatio-temporal LST, vegetation and Crop Water Stress (CWS). Normalized Difference Vegetation Index (NDVI) was adopted to assess the spatio-temporal vegetation dynamics. A correlation study was conducted to understand the relationship between LST, NDVI and CWSI. Result: It was observed that there was a strong negative correlation between LST and NDVI, whereas a strong positive correlation was found between LST and CWSI. Hotspot areas characterized by high temperature, low vegetation and high crop water stress were delineated in the ArcGIS platform. Between 2001 and 2021, all LST zones showed an increase in both maximum and minimum temperatures. Contour tilling, mulching and shade nets may effectively enhance soil moisture retention, fertility and microclimatic conditions in these hotspot areas.

Arctic Sea ice variability arises from both anthropogenic forcing and natural climate modes such as the El Ni & ntilde;o-Southern Oscillation (ENSO), North Atlantic Oscillation (NAO) and Arctic Oscillation (AO). While these modes are known to influence sea ice concentration (SIC) and thickness (SIT), their impacts on seasonal extremes remain less understood. In this study, the extreme SIC and SIT are investigated using ERA5 and CMEMS reanalysis products, applying a non-stationary generalised extreme value (GEV) framework with climate indices as covariates. Results indicate that winter and spring sea-ice variability is most pronounced in the Barents and Greenland Seas, where strong Atlantic inflows and dynamic atmospheric conditions make the marginal ice zone highly sensitive to even minor perturbations. Conversely, in the central and peripheral Arctic, variability maximises in summer and autumn, when melt processes, ice-albedo feedback and delayed freeze-up intensify interannual fluctuations. ENSO exerts notable seasonal effects: El Ni & ntilde;o events enhance extreme SIC in the Laptev Sea but reduce it in the East Siberian Sea during summer, while SIT extremes increase in the Canadian Arctic Archipelago (CAA) and decline in the East Siberian Sea across all seasons. NAO-related anomalies include stronger SIC and SIT extremes in the Beaufort Sea and CAA and reductions in the Chukchi Sea during autumn. AO effects include increased SIC in the Chukchi Sea during summer and autumn, but decreases in the Beaufort and CAA in summer; SIT extremes rise in the CAA during spring but fall in the Beaufort Sea in summer. Composite analysis further reveals that out-of-phase NAO-AO states intensify autumn sea ice extremes, whereas in-phase conditions exert weaker influences. These results emphasise the distinct and seasonally varying roles of climate modes in shaping Arctic Sea ice extremes, offering insights into future Arctic climate variability.

Mapping the water surface is a significant aspect of identifying the extension or shrinkage of any water body. It is a beneficial technique for a region, experiencing gradual river shifting, erosion, or frequent flood events. Climate change often causes excessive rainfall or drought conditions in a riverine region, significantly impacting water over-spilling or shrinkage and sedimentation of a river. The spatio-temporal study of delineation and mapping of water surface area helps to determine the pattern of change of a water body, analyze the trend of shifting of a river course, and estimate the change in the proportion of water surface area. All these kinds of assessments are helpful in analyzing the inundated area of a flood prone region. This study aims to delineate water bodies of Lakhimpur district of Assam using Geographic Information System (GIS) and remote sensing over a temporal scale of twenty years from 2001 to 2021. Normalized Difference Vegetation Index (NDVI) and Normalized Difference Water Index (NDWI) are used in this study to map and estimate the changes and extension of water bodies of the region. It is observed that there is an increase of 16.75% in water bodies in the district from 2001 to 2021

Understanding the relationship between Arctic Sea Ice Concentration (SIC) and Indian Summer Monsoon Rainfall (ISMR) is crucial for analysing regional climate change. Present study investigates this connection using satellite observations and simulations from Coupled Model Intercomparison Project Phase 5 (CMIP5) and CMIP6 coupled climate models, focusing on external forcing from 1979 to 2021. Rotated Empirical Orthogonal Function (REOF) analysis identified the dominant mode (PC1) of ISMR, explaining 31.7% of the variance with significant regional variability. Singular Value Decomposition (SVD) analysis revealed a maximum covariance of 41.1% during spring between Arctic SIC observations and ISMR. Leading SVD correlations for the multi-model ensemble mean (MMEM) simulations of spring Arctic SIC were 30.6% (CMIP5) and 42.8% (CMIP6). Our results demonstrate a significant correlation between ISMR PC1 and observed Arctic spring SIC (r = -0.25, p < 0.10), particularly in the Central Arctic (r = 0.51, p < 0.01) and the Barents-Kara Sea (r = -0.39, p < 0.01). During the High Sea Ice Years (HSYs) in the Central Arctic, distinct pressure pattern centres developed extending from western Europe to the western Pacific Ocean and were linked to the circumglobal teleconnection (CGT) influence circulation. Anomalous highs over western central Asia and a strengthened easterly jet enhance rainfall in northwestern and peninsular India. Conversely, weakened jets and high-pressure systems during Low Sea Ice Years (LSYs) hinder the monsoon. This highlights the influence of upper atmospheric Rossby waves on circulation patterns. Similarly, during LSYs in the Barents-Kara Sea, the North Atlantic-Eurasia teleconnection wave train pattern and ridge formation over northwestern Europe affect the Indian monsoon's onset. North European geopotential height anomalies contribute to formation of these ridges and troughs, impacting wind patterns and thermodynamic instability, ultimately influencing rainfall distribution. This comprehensive study underscores the far-reaching impacts of seasonal Arctic changes on the ISMR, emphasising the critical role of climate teleconnections between Arctic SIC and the Indian monsoon. Our results suggest an improved understanding of regional Arctic SIC dynamics is vital for accurate ISMR predictions using future climate models.

Antarctica, the southernmost continent on Earth, is a harsh and remote place with an extreme climate. Despite its challenges, the continent has become a significant site for scientific research, particularly in the fields of earth sciences, glaciology, environmental science, atmospheric sciences, meteorology, palaeoclimatology, and biology. As a signatory to the Antarctic Treaty, India has actively pursued scientific research on the continent since 1981. The Indian Antarctic Program has conducted research, provided logistical support, and monitored environmental activities in Antarctica for over four decades. Science is a currency in Antarctica, and international collaboration is the route to progress. This article explores India's efforts, particularly those of the Ministry of Earth Sciences, Government of India, and the National Centre for Polar and Ocean Research, in fostering international collaboration in Antarctica.

The study assessed the extent of the Getz Ice Shelf over a 19-year period using satellite data and divided it into three sectors. The average of rates (AOR), end point rate (EPR), and linear regression (LR) methods were employed to estimate the rate of change, with the LR method showing the strongest correlation. The analysis revealed a shrinkage rate of 42 m/year during February from 2003 to 2019. Over the last 17 years, recession was observed in 60% of transects, while progradation occurred in 40%. The recent decline in Getz ice shelf extent is closely linked to the record low sea ice extent in the Amundsen Sea sector. Predictions for 2024 and 2029 indicated progradation in Sector I and recession in Sectors II and III, as determined by LR analysis. The root mean square error values of transects in Sectors II and III showed good correlation with past positions and satellite-based observations of ice shelves. To validate the predicted ice shelf extent cross-verified with the satellite and predicted data from 2020 to 2022. These findings highlight the complex interactions between climatic forcings, such as wind speed, sea surface temperature (SST), and the Southern Annular Mode (SAM). Positive SAM and increased zonal winds can contribute to warm water upwelling near the Antarctic coast, impacting ice shelf extent. The relationship between ice mass loss and SST provides valuable insights into the dynamic processes of melting and progradation in the Getz Ice Shelf during February. Ocean warming plays a significant role in increased basal melting and changes in sea ice mass. The study emphasizes the significant impact of ocean-atmospheric factors on Antarctic ice shelf dynamics and highlights the necessity for ongoing satellite observations and enhanced comprehension of these processes to accurately predict future changes in Antarctic ice shelves.

The Ronne ice shelf (RIS) dynamics and mass balance play key role to decipher changes in the global climate scenario. The spatio-temporal changes in ice shelf extent of the RIS were studied by dividing the study area into three sectors (I, II, II) and further into a number of transects at 5 km uniform intervals using multi-dated Moderate Resolution Imaging Spectro-radiometer (MODIS) satellite data (2004–2019) of the austral summer months (January–March). The average of rates (AOR), end point rate (EPR), and linear regression (LR) methods were used to estimate the rate of change in RIS extent. Based on the analysis, Sector II shows prominent changes, hence further detailed study has been carried out in this sector. The study reveals that the RIS extent has been prograded at the rate of 11 km/year to 26 km/year in 2019 with maximum increase of 26 km at TR63. Based on all the three methods, ice shelf extent shows a progradation in almost all transects. The RIS bounded by Lassiter coast (LC) and Berkner Island (BI) recorded advancement in the ice shelf extents which is the feedback of morphological features like ice rise, small inlets along the ice shelf. The present study demonstrates that the combined use of satellite imagery and statistical techniques can be useful in quantifying ice shelf morphological variability.

Sea ice variability patterns are highly influenced by several large-scale ocean-atmospheric oscillations. We analysed both statistical and wavelet coherence methods to examine sea ice's interannual and interdecadal variability. During the past 42-year, the total Southern Ocean sea ice extent (SIE) has expanded, while the Amundsen-Bellingshausen Sea SIE has decreased. A wavelet coherence analysis (WCA) of El Niño Southern Oscillation (ENSO) and the SIE in various sectors revealed an out-of-phase correlation between the Indian Ocean and the Ross Sea. There are significant out-of-phase correlations between sea ice variability and Indian Ocean Dipole (IOD) on an interannual scale. A consistent phase relationship was seen between SIE and Southern Annular Mode (SAM) over the past decade, with in-phase relationships advancing to out-of-phase relationships. The Interdecadal Pacific Oscillation (IPO) shifted from positive to negative after the 1990s. In recent years, SAM has had a stronger impact on sea ice variability than ENSO.

Climate variability is thought to have an impact on the Ronne Ice Shelf (RIS), one of the largest ice shelf in Antarctica, located at the mouth of the Weddell Sea. However, investigations evaluating the impact of climate variability on the geometry (front edge) of this ice body have not yet been done. This study examines a spatialtemporal shift in the front edge of the Ronne Ice Shelf during the years 2004-2019 using an integrated approach based on remote sensing and climate data. The Moderate Resolution Imaging Spectro-radiometer (MODIS) satellite images have been used to study the changes in the ice shelf along transects drawn at a constant interval of 5 km throughout the 16-year period over the second half of the austral summer months (February to March). The study reveals that there has been net progradation of -20 km in the front edge of the ice shelf in the sector 2 between 2004 and 2019. This progradation in the ice shelf may be attributed to draining of upper ice streams to the RIS and the decrease in temperature. Thus, the present study establishes how a combination of the use of satellite imagery and statistics can effectively be used to comprehend and quantify changes in the variability of the front edge of the ice shelf.

Antarctic sea ice variability is primarily associated with ocean-atmospheric forcing driven by anomalous conditions over the tropical regions of the Pacific and Indian Oceans. The ice-ocean-atmosphere dynamics in the Indian Ocean Sector (IOS) of Antarctica have been studied using monthly satellite and reanalysis observations over four decades (1979-2019). In this study, we revealed that the annual sea ice extent (SIE) in the IOS increases at a rate of 0.7 +/- 0.9% decade(-1), with a maximum increase in austral summer (5.9 +/- 3.7% decade(-1)). The wavelet approach was used to determine the variability in IOS sea ice caused by the El Nino/Southern Oscillation (ENSO) and southern annular mode (SAM). The SIE has a significant association with both indices during the summer and autumn. In comparison to ENSO, the sea ice variability associated with SAM is typically seasonal in nature and lacks distinct patterns. The wavelet coherence analysis revealed a relatively weak relationship between ENSO and SAM but a highly significant coherence between climatic indices and SIE. We observed that sea ice in the IOS is influenced significantly by climatic oscillations during their negative SAM/El Nino or positive SAM/La Nina phases. Furthermore, the study demonstrated a substantial impact of climatic disturbances in determining the sea ice variability in the IOS.

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 × 10 6 km 2 in 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.

Global overturning circulation plays a vital role in atmospheric CO2 and climate variability during glacial-interglacial (G-I) cycles; however, the exact mechanism remains elusive due to inadequate knowledge on past deep water circulation in the global ocean. Since no deep water is formed in the northern Indian Ocean, it ventilates from the south and acts only as a host for deep water circulation. Absence of any active deep water formation makes the northern Indian Ocean an ideal location to assess the extent of southern source waters and its role on past CO2 variability during the G-I climate cycles. This study provides the first record of deep water circulation in the Arabian Sea, the northwestern Indian Ocean, during the past 136 ka based on authigenic Nd isotope record (epsilon(Nd)). The Arabian Sea epsilon(Nd) record shows large variability ranging from -8.8 to -6.5 with more radiogenic values during the glacial stages (MIS 2 & 6) and less radiogenic values during the interglacial stages (MIS 1 & 5) indicating changes in water mass sources. The observation of more radiogenic epsilon(Nd) values similar to the glacial Antarctic Bottom Water (AABW) indicates enhanced flow of AABW (95-100%) and substantial reduction and/or almost complete retreat of North Atlantic Deep Water (NADW, 0-5%) during the glacials, whereas less radiogenic values indicate enhanced flow of NADW (similar to 20-40%) during the interglacials. The Arabian Sea e N d record followed exactly similar pattern to that of the equatorial Indian Ocean (EIO). However, amplitude of their variations differed significantly during the interglacials (MIS 1 & 5); the Arabian Sea epsilon(Nd) values were more radiogenic than the EIO. This suggests that during the interglacials, the Arabian Sea received more fraction of AABW through the western pathway, whereas the EIO received more fraction of NADW through the central pathway. This highlights differences in deep water exports from the Southern Ocean to the Arabian Sea and the EIO during the interglacials whereas export of similar water masses and its uniform distribution up to the northern Indian Ocean during the glacials. Our findings of significant G-I changes in AABW and NADW exports to the Indian Ocean and intra-basinal differences in their distribution have important implications for regional biogeochemical processes, paleo-redox conditions in the water column, carbon sink (organic and inorganic) and atmospheric CO2 variability during the G-I climate transitions. (C) 2021 Elsevier Ltd. All rights reserved.

The polar regions are a critical component of the global climate system, with changes taking place at high latitudes having global implications. Anthropogenic activity is affecting both the Arctic and Antarctic, but the two polar regions are responding in very different ways, which complicated the separation of the anthropogenic signal from natural variability. The contributed articles in this issue describe polar scientific studies from various national and international research organizations. The studies are largely confined to understanding the ocean-atmospheric sciences, paleoclimatic conditions and biogeochemical processes in the polar and surrounding ocean realms. This special issue on "Polar Studies - Window to the changing Earth" presents high-quality and topical scientific research concerned with both polar regions. It is an initiative to commemorate the four decades of India's activities in polar research and its international scientific collaborations. In addition, it coincides with the completion of 75 years of India's Independence being celebrated as "Azadi Ka Amrit Mahotsav (Elixir of Freedom Festival)" and the holding of the first SCAR Open Science Conference in India, August 2022.

The distribution of diatom taxa was studied in the Enderby Basin, East Antarctica during the austral summer of 2010. In this study, the influence of freshwater at east of the 55°E was observed due to the melting of sea-ice, resulting in stratified (shallow Mixed Layer Depth (MLD)) and low saline conditions. This decrease in sea-surface salinity was associated with an increase in pCO2 and decrease in total diatom abundance. Corethron criophilum was recognized as the most abundant diatom (absolute abundance up to 30 × 104 cells L−1; 35% contribution to total diatom taxa) and its elevated abundances recorded at west of the 55°E. Reduced C. criophilum and increased abundances of Fragilariopsis curta and Thalassiothrix antarctica were documented at east of the 55oE. This study shows that despite shallow MLD and macronutrient availability, the diatom abundance at east of 55oE was low. We suspect that, the factors such as micronutrient unavailability, freshening of the upper water column, transportation by water masses, and photoinhibition possibly affect the production of diatoms at east of the 55oE. The elevated abundance of diatoms to the west of the 55°E resulted in low pCO2 levels and high meso-zooplankton abundance. This study suggests the need of long term monitoring of phytoplankton community structure and factors influencing their production in the East Antarctic region. This is essential to better understand the projected effects of physico-chemical conditions (especially pCO2 and temperature) on Southern Ocean phytoplankton and thus biological carbon pump.

The soil temperature within the Arctic coasts within the continuous permafrost is not widely measured; the temporal and spatial resolutions of the measured temperature observations are relatively high. In this study, we examined the methods to interpolate, hindcast and forecast temperature measurements within the active layer and shallow permafrost when the temperature measurements at the surface or near the surface are available. The temperature variations along the year are periodic, and hence attempts are made to express the seasonal variations with a combination of periodic function (Fourier components); which are used as boundary conditions to reach the analytical solutions. The temperature measurements from surface to about 10 metre of depths at the Baydaratskaya Bay, Kara Sea are available. We adopted a data-driven model based on simplified analytical closed-form solution derived from the boundary conditions. The parameters of the solution are calibrated from the field measurements and validated with field observations. The model then can be used to hindcast and forecast temperature at any points within the soil.