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Vertical profiles of salinity, and isotopic abundance ratios of hydrogen (δ2H) and oxygen (δ18O) of 18 landfast ice cores, collected along the northeast coast of James Bay in March 2019, and one ice core collected in Belcher Islands, were used to obtain the winter timeseries of the spatiotemporal evolution of the under-ice plume of La Grande River (LGR), the dominant river in the area. Variability in the isotopic composition and salinity of the ice cores indicated changes to the water source composition at the ice–water interface when the ice layers formed. The increased presence of river water beneath the ice during January–March was marked by more negative isotopic ratios in the lower portion of the ice as river discharge was increased for hydroelectric production. River water was the source of ∼43% of the ice in our ice core samples (n = 320) with the interquartile range from 16% to 71%. The river water fractions incorporated into the ice indicate that LGR under-ice plume extended more than 75 km north and at least 30 km south of the river mouth for ∼3 months. These findings correspond well with more challenging to obtain hydrographic observations. End-of-winter ice core sampling and analysis for isotopic abundance has potential as a tool to monitor dispersal of LGR discharge into the ice-covered coastal environment.

Indian summer monsoon (ISM) rainfall is contributed by two moisture sources; Arabian Sea (AS) and Bay of Bengal (BoB). While monsoonal rainfall in eastern and central India is dominantly contributed by the vapor derived from BoB, the source of rainfall in western India is mostly from AS vapor. Meteorological conditions in these regions also differ. In contrast to the BoB component of monsoon in central India, temporal variations in the AS sourced rainfall from western India are poorly constrained due to lack of paleohydrological records. Towards this, pedogenic carbonates were collected from two chronologically constrained cliff sections in the Gujarat alluvial plain, western India. Oxygen isotopic ratio of carbonate (δ 18 O carbonate ) was used to reconstruct variation in AS derived rainfall and its influence on vegetation and fluvial systems in western India for the last 75 ka. A negative correlation between the δ 18 O value of modern rainwater and its amount (known as amount-effect) in the study site is used as a framework for interpreting variations in δ 18 O carbonate values. The amount-effect based monsoon reconstruction showed that two distinct dry phases at 75 ka to 60 ka and 30 ka to 10 ka were punctuated by a wet phase from 60 ka to 30 ka. These hydroclimatic variations in western India during the late Quaternary were responsible for the changes in regional fluvial architecture. Comparison with published records showed that fluctuations in the AS sourced rainfall were more pronounced compared to BoB component. Carbon isotopic ratio (δ 13 C) of carbonate and co-existing organic matter were used to reconstruct vegetation composition. Significant and strong positive correlation between δ 18 O carbonate and δ 13 C carbonate values indicated that rainfall amount controlled the relative abundance of C 3 -C 4 plants in western India during the late Quaternary period. Furthermore, C 3 plants were more abundant in western India for the last 75 ka relative to central India. [ABSTRACT FROM AUTHOR]

The variation of the δ18O in precipitation and the relationship with precipitation amount at Kyangjin Base House and Yala Glacier Camp in Langtang Valley, Nepal Himalayas were analyzed. The variations of the δ18O with precipitation had great scatter, and the correlations between the δ18O and precipitation changed with time on the synoptic scale. On the seasonal scale, there was marked amount effect at Kyangjin Base House. However, the δ18O-precipitation gradient was smaller than that on the synoptic scale. Because of the maintenance of the basic equilibrium between stable isotopic compositions in atmospheric vapor and precipitation, the evaporation enrichment was light during the rainy season. Therefore, the variation of stable isotopic compositions in precipitation was independent on the sampling intervals. Simulations show that the rainfall in Langtang Valley was not the outcome of the initial condensation of ocean vapor that originated from low latitudes. The stable isotopic compositions in precipitation were greatly depleted due to the strong rainout of the vapor from oceans as the vapor was raised over the Himalayas. [ABSTRACT FROM AUTHOR]