The D/H isotope ratio is used to attribute boundary layer humidity changes to the set of contributing fluxes for a case following a snowstorm in which a snow pack of about 10 cm vanished. Profiles of H<sub>2</sub>O and CO<sub>2</sub> mixing ratio, D/H isotope ratio, and several thermodynamic properties were measured from the surface to 300 m every 15 min during four winter days near Boulder, Colorado. Coeval analysis of the D/H ratios and CO<sub>2</sub> concentrations find these two variables to be complementary with the former being sensitive to daytime surface fluxes and the latter particularly indicative of nocturnal surface sources. Together they capture evidence for strong vertical mixing during the day, weaker mixing by turbulent bursts and low level jets within the nocturnal stable boundary layer during the night, and frost formation in the morning. The profiles are generally not well described with a gradient mixing line analysis because D/H ratios of the end members (i.e., surface fluxes and the free troposphere) evolve throughout the day which leads to large uncertainties in the estimate of the D/H ratio of surface water flux. A mass balance model is constructed for the snow pack, and constrained with observations to provide an optimal estimate of the partitioning of the surface water flux into contributions from sublimation, evaporation of melt water in the snow and evaporation from ponds. Results show that while vapor measurements are important in constraining surface fluxes, measurements of the source reservoirs (soil water, snow pack and standing liquid) offer stronger constraint on the surface water balance. Measurements of surface water are therefore essential in developing observational programs that seek to use isotopic data for flux attribution
The U.S. contribution to the International Trans‐Antarctic Scientific Expedition (ITASE) program obtained several ice cores from the West Antarctic Ice Sheet. Because of proximity to the Pacific Ocean, the West Antarctic ice cores are expected to have an El Niño–Southern Oscillation (ENSO) signature. The ITASE 2001‐5 core δ18O isotope was selected for detailed analysis here because its location, high annual accumulation, and record length make it an ideal candidate for capturing the effects of regional circulation anomalies in the isotopic composition. The 2001‐5 core is compared to two other cores, the 2001‐2 and 2001‐3 cores, which are further west and therefore capture some spatial variability of the regional circulation on various time scales. Analysis shows that several phenomena, including ENSO, leave a signature in the ice cores. Evidence suggests that ENSO signals in the ice cores are significantly modulated by low‐frequency variability. Correlation with the Southern Annular Mode (SAM), global temperature, Pacific Decadal Oscillation, and ENSO shows that temperature and ENSO generally appear to have the strongest influence on the 2001‐5 isotope signal while there is no clearly dominant single influence in the other cores. Results suggest that the teleconnection between ENSO and the 2001‐5 core is quite dependent on the state of the SAM. Specifically, when the Southern Oscillation Index (SOI) and SAM are in phase, there is an ENSO related pressure anomaly west of the Antarctic Peninsula, in the vicinity of the ice cores studied. This extends previous findings to span the entire 20th century.
The D/H isotope ratio is used to attribute boundary layer humidity changes to the set of contributing fluxes for a case following a snowstorm in which a snow pack of about 10 cm vanished. Profiles of H<sub>2</sub>O and CO<sub>2</sub> mixing ratio, D/H isotope ratio, and several thermodynamic properties were measured from the surface to 300 m every 15 min during four winter days near Boulder, Colorado. Coeval analysis of the D/H ratios and CO<sub>2</sub> concentrations find these two variables to be complementary with the former being sensitive to daytime surface fluxes and the latter particularly indicative of nocturnal surface sources. Together they capture evidence for strong vertical mixing during the day, weaker mixing by turbulent bursts and low level jets within the nocturnal stable boundary layer during the night, and frost formation in the morning. The profiles are generally not well described with a gradient mixing line analysis because D/H ratios of the end members (i.e., surface fluxes and the free troposphere) evolve throughout the day which leads to large uncertainties in the estimate of the D/H ratio of surface water flux. A mass balance model is constructed for the snow pack, and constrained with observations to provide an optimal estimate of the partitioning of the surface water flux into contributions from sublimation, evaporation of melt water in the snow and evaporation from ponds. Results show that while vapor measurements are important in constraining surface fluxes, measurements of the source reservoirs (soil water, snow pack and standing liquid) offer stronger constraint on the surface water balance. Measurements of surface water are therefore essential in developing observational programs that seek to use isotopic data for flux attribution
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.