Controls on Deuterium Excess across Asia

Bershaw, John

doi:10.3390/geosciences8070257

Cited by 89 publications

(51 citation statements)

References 47 publications

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“…The background digital elevation map (DEM) is from the Shuttle Radar Topography Mission (SRTM). consistent with altitudinal transects elsewhere (Froehlich et al, 2008;Kong et al, 2013;Bershaw, 2018). However, both d-excess and 17 O-excess increase with elevation more than the modeling of subcloud evaporation predicts, raising the possibility that upper tropospheric and/or stratospheric water vapor is influencing the isotopic composition of meteoric water in the mountains (e.g.…”

Section: Introductionmentioning

confidence: 57%

“…Estimated d-excess values of precipitation at the cloud base (unaffected by subcloud evaporation) are shown as open symbols in Fig. 6, suggesting that the majority of d-excess changes with elevation can be explained by subcloud evaporation, consistent with the windward side of ranges elsewhere (Bershaw, 2018). Generally, subcloud evaporation decreases with elevation as the average surface air temperature decreases and relative humidity of the unsaturated air column increases.…”

Section: Subcloud Evaporationmentioning

confidence: 79%

“…A positive relationship between d-excess and elevation along the windward side of mountain ranges has been observed globally and is interpreted, in part, as a decrease in subcloud evaporation of raindrops as elevation increases (Froehlich et al, 2008;Kong et al, 2013;Bershaw, 2018). Relatively low temperatures of condensation at high elevations also cause an increase in d-excess of precipitation ($0.3&/À1 C) based on empirically derived fractionation experiments (Majoube, 1971).…”

Section: Subcloud Evaporationmentioning

confidence: 86%

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Deuterium excess and <sup>17</sup>O-excess variability in meteoric water across the Pacific Northwest, USA

Bershaw¹,

Hansen²,

Schauer

2020

Tellus B: Chemical and Physical Meteorology

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High-precision triple oxygen isotope analysis of water has given rise to a novel second-order parameter, 17 O-excess (often denoted as D 17 O), which describes the deviation from a reference relationship between d 18 O and d 17 O. This tracer, like deuterium excess (d-excess), is affected by kinetic fractionation (diffusion) during phase changes within the hydrologic cycle. However, unlike d-excess, 17 O-excess is present in paleowater proxy minerals and is not thought to vary significantly with temperature. This makes it a promising tool in paleoclimate research, particularly in relatively arid continental regions where traditional approaches have produced equivocal results. We present new d 18 O, d 17 O, and d 2 H data from stream waters along two east-west transects in the Pacific Northwest to explore the sensitivity of 17 O-excess to topography, climate, and moisture source. We find that discrepancies in d-excess and 17 O-excess between the Olympic Mountains and Coast Range are consistent with distinct moisture source meteorology, inferred from air-mass back trajectory analysis. We suggest that vapor d-excess is affected by relative humidity and temperature at its oceanic source, whereas 17 O-excess vapor is controlled by relative humidity at its oceanic source. Like dexcess, 17 O-excess is significantly affected by evaporation in the rain shadow of the Cascade Mountains, supporting its utility as an aridity indicator in paleoclimate studies where d 2 H data are unavailable. We use a raindrop evaporation model and local meteorology to investigate the effects of subcloud evaporation on dexcess and 17 O-excess along altitudinal transects. We find that subcloud evaporation explains much, but not all of observed increases in d-excess with elevation and a minor amount of 17 O-excess variation in the Olympic Mountains and Coast Range of Oregon. KEY POINTS 1. 17 O-excess correlates spatially with relative humidity across the Pacific Northwest, supporting its use as an aridity indicator in paleoclimate studies. 2. Discrepancies in d-excess and 17 O-excess between the Olympic Mountains and Oregon Coast Range suggest that their moisture source is different. 3. Subcloud evaporation explains most of observed increases in d-excess with elevation, and a minor amount of 17 O-excess variation in the Olympic Mountains and Oregon Coast Range.

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Section: Introductionmentioning

confidence: 57%

Section: Subcloud Evaporationmentioning

confidence: 79%

Section: Subcloud Evaporationmentioning

confidence: 86%

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Deuterium excess and <sup>17</sup>O-excess variability in meteoric water across the Pacific Northwest, USA

Bershaw¹,

Hansen²,

Schauer

2020

Tellus B: Chemical and Physical Meteorology

Self Cite

View full text Add to dashboard Cite

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“…Similarly, d-excess increases with elevation (h > 80%), ranging from near +10‰ (0-1,000 m asl) to >15‰ in high relief windward ranges, whereas d-excess < 10‰ is often reported in leeward regions due to strong sub-cloud evaporation (Bershaw, 2018) (see Supplementary Figure S1B). This effect is amplified in areas with rugged topography.…”

Section: Rainfall Generation: Local Regional and Global Features Trmentioning

confidence: 96%

Tracing Water Sources and Fluxes in a Dynamic Tropical Environment: From Observations to Modeling

et al. 2020

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Tropical regions cover approximately 36% of the Earth's landmass. These regions are home to 40% of the world's population, which is projected to increase to over 50% by 2030 under a remarkable climate variability scenario often exacerbated by El Niño Southern Oscillation (ENSO) and other climate teleconnections. In the tropics, ecohydrological conditions are typically under the influence of complex land-oceanatmosphere interactions that produce a dynamic cycling of mass and energy reflected in a clear partition of water fluxes. Here, we present a review of 7 years of a concerted and continuous water stable isotope monitoring across Costa Rica, including key insights learned, main methodological advances and limitations (both in experimental designs and data analysis), potential data gaps, and future research opportunities with a humid tropical perspective. The uniqueness of the geographic location of Costa Rica within the mountainous Central America Isthmus, receiving moisture inputs from the Caribbean Sea (windward) and the Pacific Ocean (complex leeward topography), and experiencing strong ENSO events, poses a clear advantage for the use of isotopic variations to underpin key drivers in ecohydrological responses. In a sequential approach, isotopic variations are analyzed from moisture transport, rainfall generation, and groundwater/surface connectivity to Bayesian and rainfall-runoff modeling. The overarching goal of this review is to provide a robust humid tropical example with a progressive escalation from common water isotope observations to more complex modeling outputs and applications to enhance water resource management in the tropics.

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“…The higher the evaporation degree, the larger the d value is; after a raindrop is condensed, the stronger the re-evaporative fractionation under the cloud, the smaller the d value is. The d value is not only affected by temperature, relative humidity as well as wind speed at the locations where the water vapor sourced but also by the fractionation due to re-evaporation of raindrops as they leave the cloud (below cloud evaporation) [10,11]. In the Mediterranean area, d values are generally higher in autumn-winter precipitation than those in spring-summer precipitation, which can be attributed to the influence of Mediterranean air masses [12,13].…”

Section: Introductionmentioning

confidence: 97%

Deuterium Excess in Precipitation Reveals Water Vapor Source in the Monsoon Margin Sites in Northwest China

Chen

Zhang

Argiriou

et al. 2020

Water

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The deuterium excess (d) in precipitation, determined by the stable hydrogen and oxygen isotopes (δ2H and δ18O), is a widely applied parameter in tracing the water vapor source. Based on the multiple-year observations of stable water isotopes in precipitation at four stations in the Lanzhou city, Northwest China, we analyzed the variations in deuterium excess in precipitation at the Asian monsoon margin region. The mean value of deuterium excess at the study region is 11.0‰ in the dry season and 8.0‰ in the wet season. The d value in precipitation negatively correlates with air temperature and vapor pressure. The low d value during the wet season reflects the monsoon moisture transported from long distances. During the dry season, the continental air masses correspond to the higher d value in precipitation. The moisture regimes based on reanalysis data are generally consistent with the findings using a stable isotopic approach, and the monsoon moisture is highlighted in summer precipitation at these monsoon margin sites.

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Controls on Deuterium Excess across Asia

Cited by 89 publications

References 47 publications

Deuterium excess and <sup>17</sup>O-excess variability in meteoric water across the Pacific Northwest, USA

Deuterium excess and <sup>17</sup>O-excess variability in meteoric water across the Pacific Northwest, USA

Tracing Water Sources and Fluxes in a Dynamic Tropical Environment: From Observations to Modeling

Deuterium Excess in Precipitation Reveals Water Vapor Source in the Monsoon Margin Sites in Northwest China

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