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Oxygen isotopes in bioarchaeology: Principles and applications, challenges and opportunities

The numerous lakes on the Tibetan Plateau (TP) play an important role in the regional hydrological cycle and water resources, but systematic observations of the lake water balance are scarce on the TP. Here we present a detailed study on the water cycle of Cona Lake, at the headwater of Nujiang-Salween River, based on three years (2011-2013) of observations of δ18O and δ2H, including samples from precipitation, upper lake water, and outlet surface water. Short-term atmospheric water vapor was also sampled for isotope analyses. The δ2H-δ18O relationship in lake water (δ2H = 6.67δ18O – 20.37) differed from that of local precipitation (δ2H = 8.29δ18O + 12.50) and the deuterium excess (d-excess) in the lake water (-7.5‰) was significantly lower than in local precipitation (10.7‰), indicating an evaporative isotope enrichment in lake water. The ratio of evaporation to inflow (E/I) of the lake water was calculated using both d-excess and δ18O. The E/I ratios of Cona lake ranged from 0.24 to 0.27 during the three years. Observations of atmospheric water vapor isotopic composition (δA) improved the accuracy in E/I ratio estimate over a simple precipitation equilibrium model, though a correction factor method provided nearly identical estimates of E/I ratio. The work demonstrates the feasibility of d-excess in the study of the water cycle for lakes in other regions of the world and provides recommendations on sampling strategies for accurate calculations of E/I ratio. This article is protected by copyright. All rights reserved.

Deuterium-excess determination of evaporation to inflow ratios of an alpine lake: Implications for water balance and modeling

Controls of precipitation δ 18 O on the northwestern Tibetan Plateau: A case study at Ngari station

\n Continued Africa-Eurasia convergence resulted in post–11 Ma surface uplift of the Central Anatolian Plateau (CAP) and the westward escape of the Anatolian microplate. Contemporaneously, a central Anatolian fluvio-lacustrine system developed that covered extensive parts of the rising CAP. Today, the semi-arid CAP interior—except for the Konya closed catchment—drains toward the Black Sea, the Mediterranean Sea, and the Persian Gulf. Lake connectivity and drainage patterns of the fluvio-lacustrine system in the evolving plateau region are, however, largely unknown.\n Here, we present sedimentological and stable isotopic (δ13C and δ18O) data (N = 665) from 13 well-dated lake sections covering the former fluvio-lacustrine depocenters of the southern CAP. Persistently (>1 m.y.) stable paleoenvironmental and hydrological conditions suggest that a low-relief environment characterized the southern CAP during plateau uplift. Throughout the late Miocene, various open and closed lakes of the southern CAP drained into closed, terminal lakes within the plateau interior. Sedimentation east of the Tuz Gölü fault ceased during the early Pliocene (ca. 5.3–3.6 Ma), when the eastern CAP became connected to marine base level as a result of river incision shortly after the switch from regional compression to extension. A final phase of lacustrine carbonate sedimentation characterizes most sampled basins, yet occurred asynchronously over the extent of the CAP. Therefore, the final episode of lacustrine sedimentation is unlikely to have been the result of a climatic event, consistent with the absence of a clear aridification trend in the lacustrine δ18O data. Rather, capping carbonates reflect the interplay of surface uplift and transition from inward- to outward-drained plateau regions and concomitant lake reorganization during the formation of the CAP and its margins.

Paleoenvironmental conditions and drainage evolution of the central Anatolian lake system (Turkey) during late Miocene to Pliocene surface uplift

Stable isotopes of O and H in water are meaningful indicators of hydrological and ecological patterns and processes. The Global Network of Isotopes in Precipitation (GNIP) and the Global Network of Isotopes in Rivers (GNIR) are the two most important global databases of isotopes in precipitation and rivers. While the data of GNIP is almost globally distributed, GNIR has an incomplete spatial coverage, which hinders the utilization of river isotopes to study global hydrological cycle. To fill this knowledge gap, this study supplements GNIR and provides a river isotope database with global-coverage by the meta-analysis method, i.e., collecting 17015 additional data points from 215 published articles. Based on the newly compiled database, we find that (1) the relationship between δ18O and δ2H in river waters exhibits an asymmetric imbricate feature, and bifurcation can be observed in Africa and North America, indicating the effect of evaporation on isotopes; (2) multiple regression analysis with geographical factors indicates that spatial patterns of river isotopes are quite different across regions; (3) multiple regression with geographical and meteorological factors can well predict the river isotopes, which provides regional regression models with r2 of 0.50 to 0.89, and the best predictors in different regions are different. This work presents a global map of river isotopes and establishes a benchmark for further research on isotopes in rivers.

Stable Isotope Composition of River Waters across the World

Water isotopes play an important role in the study of the alpine lake water budget and the hydrological cycle in the arid, far western Tibetan Plateau. These isotope records, derived from well-preserved sediments, are believed to reflect climatic and environmental changes. Using two years of δ18O and δD data from precipitation, river water, underground water, and lake water at the long alpine lake Bangong (LBG), together with local meteorological observations in the arid western Tibetan Plateau, this study reveals that the δ18O in the lake is over 10‰ more enriched than that in the local precipitation due to evaporation of the lake water. Spatial changes in both the lake water δ18O and d-excess (= δD - 8 * δ18O) are apparent, ranging from ∼-4.9‰ to +0.9‰ for δ18O, and -13.22‰ to -30.85‰ for d-excess, respectively, from east to west of the lakes. Simulation with the Craig-Gordon model shows that the isotopes in alpine inland lake water are controlled to a great extent by local relative humidity. U...

https://www.tandfonline.com/doi/pdf/10.1657/AAAR0015-028

Fengjing Liu

Papers

Lake Water Isotope Variation Linked with the In-Lake Water Cycle of the Alpine Bangong Co, Arid Western Tibetan Plateau