Mechanisms associated with the rapid decline in sea ice cover around a stranded ship in the Lazarev Sea, Antarctica

In the satellite data era starting from 1979, the extent of Antarctic sea ice increased moderately for the first 37 years. However, the extent decreased to record low levels from 2016 to 2020, with the drop being greatest in the Weddell and Lazarev Seas of the Southern Ocean. An important question for the scientific fraternity and policymakers is to understand what ocean-atmospheric processes triggered such a rapid decline in sea ice. We employ in-situ, satellite, and atmospheric reanalysis data to examine the causative mechanism of anomalous sea ice variability in the Lazarev Sea at a time of ice growth in the annual cycle (March-April 2019), when a cargo ship was stuck in extensive ice cover and freed following the unusual decline in sea ice. High-resolution Sentinel-1 synthetic aperture radar captured a distinct view of the ship location and track within extensive ice cover of fast sea ice, dense pack ice, and icebergs in the Lazarev Sea on 27 March 2019. Subsequently, the sea ice cover declined and reached the fourth lowest extent in the entire satellite record during April 2019 which was 25.6% lower than the long-term mean value of 2.65 × 10⁶ km². We show that the anomalous sea ice variability was due to the occurrence of eastward-moving polar cyclones, including a quasi-stationary explosive development that impacted sea ice through extreme changes in ocean-atmospheric conditions. The cyclone-induced dynamic (poleward propagation of ocean waves and ice motion) and thermodynamic (heat and moisture plumes from midlatitudes, ocean mixed layer warming) processes coupled with high tides provided a conducive environment for an exceptional decline in sea ice over the region of ship movement.

Decadal changes in global phytoplankton compositions influenced by biogeochemical variables

The global environmental changes owing to natural and anthropogenic influences are challenging the structure and functioning of the ocean ecosystem. The complex processes interacting within the physical, chemical, and biological environment at different spatio-temporal scales and their impact on the ocean ecosystem processes are yet to be investigated. A long term trend on phytoplankton biomass in terms of Chlorophyll-a concentration (Chl-a), phytoplankton compositions and the processes that control the variability is required for understanding the ocean ecosystem. This study investigated decadal trends (2002-2015) of phytoplankton composition and biogeochemical parameters over the Global Ocean (GO), Southern Ocean (SO), and the Arctic Ocean (AO) using ocean color remote sensing and assimilated data from the National Aeronautics and Space Administration (NASA) Ocean biogeochemical model. The results revealed the dominance of larger cell phytoplankton mainly diatoms throughout the SO and AO; however, the coccolithophores dominate in the remaining part of the GO. Analysis of nutrients showed that nitrate is not a limiting factor for the variability of phytoplankton biomass in the SO and AO. The low nitrate concentration influenced in the rest of the GO. The photosynthetically available radiation (PAR) limiting the phytoplankton biomass and composition in the SO and AO. Although the SO is known as the high nutrient low chlorophyll (HNLC) region of the GO, the low iron concentration along with the PAR co-limits the growth of phytoplankton biomass. Trend analysis showed that an increase in Chl-a and diatoms in the SO and AO. In contrast, it declined significantly in the other regions of the GO, in response to the consistent increase in sea surface temperature. The results indicated that, shifting of phytoplankton community from regional to global scale have a greater implication for climate change and marine ecosystem.

Mechanism of sea-ice expansion in the Indian Ocean sector of Antarctica: Insights from satellite observation and model reanalysis

In the backdrop of global warming, Antarctic sea-ice variability showed an overall expansion with the regional heterogeneity of increasing and decreasing patterns. Analysis of satellite derived sea-ice extent, during 1979 to 2015, in the Indian Ocean sector of Antarctica (IOA) revealed expansion of 2.4±1.2% decade-1. We find strengthening of westerly wind during the austral summer (between 50°S to 62°S) facilitated northward advection of a cool and fresh layer. Also, the strong westerly wind cools the upper ocean due to net heat loss from the ocean surface. The combined effect of northward advection of cold fresh layer and net heat loss from the surface, favours sea-ice expansion in the subsequent seasons, in the IOA region, north of 62°S. However, sea-ice retreat was observed near the Kerguelen Plateau, due to upper ocean warming, and hence a non-annular pattern of sea-ice extent in the IOA was observed.

The burden of diabetes and impaired glucose tolerance in India using the WHO 1999 criteria: prevalence of diabetes in India study (PODIS)

This random multistage cross-sectional population survey was undertaken to determine the prevalence of diabetes mellitus (DM) and impaired glucose tolerance (IGT) in subjects aged 25 years and above in India. The study was carried out in 77 centers (40 urban and 37 rural). 18363 (9008 males and 9355 females) subjects were studied. 10617 (5379 males and 5238 females) were from urban areas and 7746 (3629 males and 4117 females) from rural areas. Blood samples were taken after a fast of 10-12 h and 2 h after 75 g of oral glucose. Subjects were categorized as having IGT or DM using the World Health Organisation (WHO) (1999) criteria. The standardized prevalence rate for DM in the total Indian, urban and rural populations was 4.3, 5.9 and 2.7%, respectively. The corresponding IGT rates in the three populations was 5.2, 6.3 and 3.7%, respectively. The urban prevalence of DM and IGT was significantly greater than in the rural population (P < 0.001 in both instances). The prevalence of DM was significantly, more than that of IGT (P < 0.001) within both the rural and urban populations. Type 2 diabetes is a major health problem is India.

Comparing the ADA 1997 and the WHO 1999 criteria: Prevalence of Diabetes in India Study

This random multistage cross-sectional population survey was undertaken to determine the prevalence of type 2 diabetes mellitus (DM) in subjects aged 25 years and above in India. The study was carried out in 77 centres (42 urban and 35 rural) to reflect the size and heterogeneity of the Indian population. 18,363 (9008 male and 9355 female) subjects were studied. 10,617 (5379 males and 5238 females) were from urban areas and 7746 (3629 males and 4117 females) from rural areas. Blood samples were taken after a fast of 10-12 and 2 h after 75 g of oral glucose. Subjects were categorized as having impaired fasting glycemia (IFG) or DM using the 1997 ADA or having impaired glucose tolerance (IGT) or DM using the 1999 WHO criteria. The age- and gender-standardized prevalence rate for DM using the ADA criteria was 3.6% whilst that using the WHO criteria was 4.3% (P < 0.001). The respective standardized prevalence of DM, using the two criteria was, 4.7 and 5.6%, respectively (P < 0.001) in the urban Indian population and 2.0 and 2.7% (P < 0.02) in the rural Indian population. Using the WHO criteria, 581 subjects were newly diagnosed whilst the ADA criteria newly diagnosed 437 subjects. The respective numbers for the urban population were 425 and 323, and for the rural population were 146 and 114, respectively. The ADA criteria could diagnose 75.2, 76.0 and 73.0% of the subjects who had DM as per the WHO criteria. Of 739 Indian subjects who had IFG, 106 (14.3%) were diagnosed as having DM by the WHO criteria whilst 505 (68.3%) had values compatible with a diagnosis of IGT. Of the 536 urban subjects with IFG, 74 (13.8%) had DM and 350 (65.3%) had IGT using the WHO criteria. Of the 302 rural subjects with IFG, 32 (15.8%) had DM and 155 (76.3%) had IGT using the WHO criteria. 505 (49.9%) of 1012 Indian subjects with IGT as per the WHO criteria had IFG. 350 (47.7%) of 733 urban subjects and 155 (55.5%) of 279 rural subjects with IGT had values compatible with IFG as per the ADA criteria. Type 2 diabetes is a major health problem is India. The use of the ADA criteria would underestimate the prevalence of DM by not diagnosing subjects showing a poor response to a glucose challenge. This along with the discrepancies between subjects showing IGF or IGT could be a challenge to any prevention program.

The burden of diabetes and impaired fasting glucose in India using the ADA 1997 criteria: prevalence of diabetes in India study (PODIS)

This random multistage cross sectional population survey was undertaken to determine the prevalence of diabetes mellitus (DM) and impaired fasting glycemia/glucose (IFG) in subjects aged 25 years and above in India. The study was carried out in 108 centers (49 urban and 59 rural) to reflect the size and heterogeneity of the Indian population. 41,270 (20,534 males and 20,736 females) subjects were studied. 21,516 (10,865 males and 10,651 females) were from urban areas and 19,754 (9669 males and 10,085 females) from rural areas. Blood samples were taken after a fast of 10-12h and the subjects were categorized as having IFG or DM using the 1997 American Diabetes Association criteria. The age and gender standardized prevalence rate for DM and IFG in the total Indian population was 3.3 and 3.6% respectively (P < 0.001). The standardized prevalence of DM and IFG in urban areas was significantly higher than that for the rural population (urban DM prevalence 4.6% versus rural DM prevalence 1.9%, P < 0.001; urban IFG prevalence 4.8% versus rural IFG prevalence 2.5%, P < 0.001). There was no statistically significant difference in the prevalence between DM (4.6%) and IFG (4.8%) in the urban population. The rural prevalence of IFG (2.5%) was significantly (P <0.001) more than the rural prevalence of DM (1.9%). Type 2 diabetes is a major health problem is India.