Water stable isotopes (δ<sup>2</sup>H and δ<sup>18</sup>O) in the Peninsula of Yucatan, Mexico

Abstract. The hydrogen and oxygen isotopic composition of water is a very important tool to estimate water balance, groundwater recharge, and evaporation. Water isotopes have been used to increase our understanding of the distribution and amounts of renewable and non-renewable groundwater. Isotopic data from precipitation and groundwater is available in much of Mexico but there is little information from the Peninsula of Yucatan, an area heavily relying in groundwater in which current estimates of groundwater availability are uncertain. In this paper, we compiled published and unpublished δ2H and δ18O data in meteoric (waters derived from precipitation), ground- and pore-waters, to obtain a regional meteoric water line (RMWL) expressed by the equation δ2H = 8.1846 δ18O + 10.289. The data suggest that precipitation originates in convective systems, low-pressure events, moisture from frontal events, and from re-condensed moisture. The evaporation lines from groundwater suggest mixing of water with different isotopic composition, but also provide clues to recent meteoric water rapid recharge, likely from rain events of great intensity. We present a groundwater isoscape of the Peninsula of Yucatan and finally address the lack of conciliation between hydrogeology and groundwater management.

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Stable water isotopes in the MITgcm (checkpoint 64w)

10.5194/gmd-2017-7 ◽

2017 ◽

Author(s):

Rike Völpel ◽

André Paul ◽

Annegret Krandick ◽

Stefan Mulitza ◽

Michael Schulz

Keyword(s):

Isotopic Composition ◽

Observational Data ◽

General Circulation Model ◽

General Circulation ◽

Circulation Model ◽

Deep Ocean ◽

Oxygen Isotopic Composition ◽

Water Isotopes ◽

Stable Water Isotopes ◽

Oxygen Isotopic

Abstract. We present the first results of the implementation of stable water isotopes in the ocean general circulation model MITgcm. The model is forced with the isotopic content of precipitation and water vapor from an atmospheric general circulation model (NCAR IsoCAM), while the fractionation during evaporation is treated explicitly in the MITgcm. Results of the equilibrium simulation under pre-industrial conditions are compared to observational data and paleoclimate records (the oxygen isotopic composition of planktic foraminiferal calcite). The broad patterns and magnitude of the stable water isotopes in annual mean seawater are well captured in the model, both at the sea surface as well as in the deep ocean. However, the surface water in the Arctic Ocean is not depleted enough, due to the absence of highly depleted precipitation and snow fall and slightly enriched river runoff. This shortcoming is also recognizable in the isotopic composition of the seawater-salinity relationship in mid-latitudes. Deep ocean characteristics of the vertical water mass distribution in the Atlantic Ocean closely resemble observational data. Apart from the systematic offset of the modeled oxygen isotopic composition of planktic foraminiferal calcite towards lower values, the comparison with proxy data shows a good agreement. We summarize that the offset is mainly caused by gametogenic calcification and a matter of choice of the applied paleotemperature equation. Overall, the newly developed stable water isotope package opens wide prospects for long-term simulations in a paleoclimatic context.

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Changes of Ionic and Oxygen Isotopic Composition of the Snowpack at the Glacier Austre Okstindbreen, Norway, 1995

Hydrology Research ◽

10.2166/nh.1998.0001 ◽

1998 ◽

Vol 29 (1) ◽

pp. 1-20 ◽

Cited By ~ 20

Author(s):

Peter Raben ◽

Wilfred H. Theakstone

Keyword(s):

Isotopic Composition ◽

Sea Level ◽

Oxygen Isotopes ◽

Oxygen Isotopic Composition ◽

Isotopic Ratios ◽

Vertical Variations ◽

Oxygen Isotopic ◽

The Difference ◽

Liquid Precipitation ◽

Different Altitudes

Marked vertical variations of ions and oxygen isotopes were present in the snowpack at the glacier Austre Okstindbreen during the pre-melting phase in 1995 at sites between 825 m and 1,470 m above sea level. As the first meltwater percolated from the top of the pack, ions were moved to a greater depth, but the isotopic composition remained relatively unchanged. Ions continued to move downwards through the pack during the melting phase, even when there was little surface melting and no addition of liquid precipitation. The at-a-depth correlation between ionic concentrations and isotopic ratios, strong in the pre-melting phase, weakened during melting. In August, concentrations of Na+ and Mg2+ ions in the residual pack were low and vertical variations were slight; 18O enrichment had occurred. The difference of the time at which melting of the snowpack starts at different altitudes influences the input of ions and isotopes to the underlying glacier.

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δ2Hn-alkane and δ18Osugar biomarker proxies from leaves and topsoils of the Bale Mountains, Ethiopia, and implications for paleoclimate reconstructions

Biogeochemistry ◽

10.1007/s10533-021-00773-z ◽

2021 ◽

Author(s):

Bruk Lemma ◽

Lucas Bittner ◽

Bruno Glaser ◽

Seifu Kebede ◽

Sileshi Nemomissa ◽

...

Keyword(s):

Isotopic Composition ◽

Leaf Growth ◽

Thermal Conversion ◽

Oxygen Isotopic Composition ◽

Leaf Water ◽

Isotope Ratio Mass Spectrometer ◽

Oxygen Isotopic ◽

Calibration Study ◽

Microclimatic Conditions ◽

Paleoclimate Reconstructions

AbstractThe hydrogen isotopic composition of leaf wax–derived n-alkane (δ2Hn-alkane) and oxygen isotopic composition of hemicellulose–derived sugar (δ18Osugar) biomarkers are valuable proxies for paleoclimate reconstructions. Here, we present a calibration study along the Bale Mountains in Ethiopia to evaluate how accurately and precisely the isotopic composition of precipitation is imprinted in these biomarkers. n-Alkanes and sugars were extracted from the leaf and topsoil samples and compound–specific δ2Hn-alkane and δ18Osugar values were measured using a gas chromatograph–thermal conversion–isotope ratio mass spectrometer (GC–TC–IRMS). The weighted mean δ2Hn-alkane and δ18Osugar values range from − 186 to − 89‰ and from + 27 to + 46‰, respectively. Degradation and root inputs did not appear to alter the isotopic composition of the biomarkers in the soil samples analyzed. Yet, the δ2Hn-alkane values show a statistically significant species dependence and δ18Osugar yielded the same species–dependent trends. The reconstructed leaf water of Erica arborea and Erica trimera is 2H– and 18O–enriched by + 55 ± 5 and + 9 ± 1‰, respectively, compared to precipitation. By contrast, Festuca abyssinica reveals the most negative δ2Hn-alkane and least positive δ18Osugar values. This can be attributed to “signal–dampening” caused by basal grass leaf growth. The intermediate values for Alchemilla haumannii and Helichrysum splendidum can be likely explained with plant physiological differences or microclimatic conditions affecting relative humidity (RH) and thus RH–dependent leaf water isotope enrichment. While the actual RH values range from 69 to 82% (x̄ = 80 ± 3.4%), the reconstructed RH values based on a recently suggested coupled δ2Hn-alkane –δ18Osugar (paleo–) hygrometer approach yielded a mean of 78 ± 21%. Our findings corroborate (i) that vegetation changes, particularly in terms of grass versus non–grassy vegetation, need to be considered in paleoclimate studies based on δ2Hn-alkane and δ18Osugar records and (ii) that the coupled δ2Hn-alkane –δ18Osugar (paleo–) hygrometer approach holds great potential for deriving additional paleoclimatic information compared to single isotope approaches.

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