Yalalt Nyamgerel

Polar snow and its accumulation preserve valuable information derived from the atmosphere on past climate and environmental changes in high resolution, particularly in coastal sites. A 2.5-m snow-pit was excavated from the coastal ice rise (Moore Dome) near Amundsen Sea region in February 2012. This study evaluated the isotopic and chemical compositions in the snow-pit and compared them with meteorological variables. Based on the seasonal peaks of the MSA and nssSO42– together with 18O, D, and d-excess, the snow-pit record was corresponded to accumulation during austral winter 2011 to summer 2011/2012. The annual mean accumulation rate was assumed thus to be as large as or even higher than 1.03 m w.e. yr–1 at this site. A relatively warm winter temperature in 2011 was traceable in the variations of 18O, D, and d-excess. This study emphasizes the importance of the high snow accumulation observed at this site in providing valuable information on sub-annual variations in climate and environmental changes through the study of longer ice cores.

The triple oxygen isotopes (¹⁶O, ¹⁷O, and ¹⁸O) are very useful in hydrological and climatological studies because of their sensitivity to environmental conditions. This review presents an overview of the published literature on the potential applications of ¹⁷O in hydrological studies. Dual-inlet isotope ratio mass spectrometry and laser absorption spectroscopy have been used to measure ¹⁷O, which provides information on atmospheric conditions at the moisture source and isotopic fractionations during transport and deposition processes. The variations of δ¹⁷O from the developed global meteoric water line, with a slope of 0.528, indicate the importance of regional or local effects on the ¹⁷O distribution. In polar regions, factors such as the supersaturation effect, intrusion of stratospheric vapor, post-depositional processes (local moisture recycling through sublimation), regional circulation patterns, sea ice concentration and local meteorological conditions determine the distribution of ¹⁷O-excess. Numerous studies have used these isotopes to detect the changes in the moisture source, mixing of different water vapor, evaporative loss in dry regions, re-evaporation of rain drops during warm precipitation and convective storms in low and mid-latitude waters. Owing to the large variation of the spatial scale of hydrological processes with their extent (i.e., whether the processes are local or regional), more studies based on isotopic composition of surface and subsurface water, convective precipitation, and water vapor, are required. In particular, in situ measurements are important for accurate simulations of atmospheric hydrological cycles by isotope-enabled general circulation models.

Seasonal variations of the isotopic and chemical compositions of snowpits can provide useful tools for dating the age of the snowpit and examining the sources of aerosol. Based on the seasonal layers with D and 18O maxima and minima, it was determined that the snowpit, conducted in the vicinity of the Jang Bogo Station in Antarctica, contained snow deposited over a three-year period (2008–2010). Distinct seasonal variations of stable water isotopes were observed, with a slope of 8.2 from the linear isotopic relationship between oxygen and hydrogen, which indicates that the snow accumulated during three years without a significant post-depositional process. The positive correlations (r > 0.85) between Na+ and other ions in the winter period and the positive relationship the concentrations of the methanesulphonic acid (MSA) and non-sea salt sulfate (nssSO42–) in the warm period (r = 0.6, spring to summer) indicate the significant contributions of an oceanic source to the snowpit. Based on principal component analysis, the isotopic and chemical variables were classified into species representing input of sea-salt aerosol and suggesting potential seasonal markers. This study will support further investigations using ice cores in this region.