A 70-yr record of oxygen-18 variability in an ice core from the Tanggula Mountains, central Tibetan Plateau

Climate of the Past 01/2010; DOI: 10.5194/cp-6-219-2010
Source: DOAJ

ABSTRACT A 33 m ice core was retrieved from the Tanggula Mts, central Tibetan Plateau at 5743 m a.s.l. in August 2005. Annual average δ18O values were determined for the upper 17 m depth (14.6 m w.eq.), representing the time series since the mid-1930s. Data are compared to previous results of an ice core from Mt. Geladaindong, 100 km to the northwest, for the period 1935–2003. During the time 1935–1960, δ18O values differed by 2–3‰ between the two ice cores, with generally lower ratios preserved in the Tanggula 2005 core. Differences in interannual variability and overall average ratios between the two study locations highlight the spatially variable climate controls on ice core isotope ratios within the boundary of monsoon- and westerly-impacted regions of the central Tibetan Plateau. Average annual net accumulation was 261 mm w.eq. for the period 1935–2004. The overall average δ18O value was −13.2‰ and exhibited a statistically significant increase from the 1935–1969 average (−13.7‰) to the 1970–2004 average (−12.6‰). Despite the observed increase in isotope ratios, isotopic temperature dependence was not evident, based on comparison with long-term data from meteorological stations to the north and southwest of the study location. Lack of correlation between average δ18O values and temperature is likely due to monsoon influence, which results in relatively greater isotopic depletion of moisture during the warm season. Evidence of monsoon impacts on precipitation in the central Tibetan Plateau has been previously documented, and statistically significant negative correlation (r=−0.37, p18O values and North India monsoon rainfall was observed for the period 1935–2004. Although the δ18O data agree well with the monsoon rainfall amount, no significant correlation was observed between the core accumulation and the monsoon rainfall amount. Previous model and observational results suggest monsoon impact on δ18O in precipitation may extend beyond the immediate extent of heavy monsoon rainfall, reaching the central Tibetan Plateau. These results provide evidence that the δ18O variability at this study location may be sensitive to southern monsoon intensity.

  • [Show abstract] [Hide abstract]
    ABSTRACT: [1] The stable oxygen isotope ratio (δ18O) in precipitation is an integrated tracer of atmospheric processes worldwide. Since the 1990s, an intensive effort has been dedicated to studying precipitation isotopic composition at more than 20 stations in the Tibetan Plateau (TP) located at the convergence of air masses between the westerlies and Indian monsoon. In this paper, we establish a database of precipitation δ18O and use different models to evaluate the climatic controls of precipitation δ18O over the TP. The spatial and temporal patterns of precipitation δ18O and their relationships with temperature and precipitation reveal three distinct domains, respectively associated with the influence of the westerlies (northern TP), Indian monsoon (southern TP), and transition in between. Precipitation δ18O in the monsoon domain experiences an abrupt decrease in May and most depletion in August, attributable to the shifting moisture origin between Bay of Bengal (BOB) and southern Indian Ocean. High-resolution atmospheric models capture the spatial and temporal patterns of precipitation δ18O and their relationships with moisture transport from the westerlies and Indian monsoon. Only in the westerlies domain are atmospheric models able to represent the relationships between climate and precipitation δ18O. More significant temperature effect exists when either the westerlies or Indian monsoon is the sole dominant atmospheric process. The observed and simulated altitude-δ18O relationships strongly depend on the season and the domain (Indian monsoon or westerlies). Our results have crucial implications for the interpretation of paleoclimate records and for the application of atmospheric simulations to quantifying paleoclimate and paleo-elevation changes.
    Reviews of Geophysics. 11/2013;
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The climate significance of oxygen isotopes from the central Tibetan Plateau (cTP) ice cores is a debated issue because of large scale atmospheric circulation. A high-resolution δ18O record was recovered from the Xiao Dongkemadi (XD) ice core, which expanded the spatial coverage of δ18O data in this region. Annual average δ18O correlated significantly with nearby MJJAS air temperatures, suggesting the δ18O can be used as a proxy to reconstruct regional climate change. The reconstructed temperature anomaly is related to the regional and global warming trends, and the greater warming amplitude since 1970s is related to the elevation dependency of the warming signal. The close relationship of the warming to variations in glacier mass balances and discharge reveal that recent warming has led to obvious glacier shrinkage and runoff increase. Correlation analysis suggests that monsoon and westerly moisture substantially influence the cTP ice core records, along with an increase in their level of contribution to the XD core accumulation in recent decades, and confirms a teleconnection of regional climate of the cTP ice cores with climate parameters in the Indian and North Atlantic Oceans.
    Journal of Asian Earth Sciences. 02/2015; 98.
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Paleoaltimetry based on stable isotopes (δ18O and δ2H) of paleowater from the central and northern Tibetan Plateau is challenged by the lack of a clear relationship between isotopic composition and elevation north of the Himalaya. In order to determine the environmental factor(s) responsible for temporal changes in isotopic composition revealed in the geologic record, an understanding of the modern controls on isotope evolution in the continental interior is necessary. Here, we present new δ18O and deuterium excess (d excess) data from modern surface water along a roughly south-north transect on the eastern part of the Himalaya and Tibetan Plateau. Results corroborate an inverse relationship betweenδ18O and elevation in the Himalaya. Northward across the plateau, there is a positive trend in meteoric water δ18O that is linear (˜1.5‰ per degree latitude) and robust (R2 = 0.94). A positive trend northward is also observed in d excess of surface water from large rivers. We show that Rayleigh distillation modified by surface water recycling can account for the observed spatial distribution of both δ18O and d excessacross the plateau. HYSPLIT modeling of air parcel back trajectories suggests that air mass mixing varies from east to west across the plateau. However, isotopic trends along the plateau's eastern margin are consistent with roughly parallel transects to the west, suggesting that a local process like moisture recycling exerts control over the isotopic evolution across the entire plateau, regardless of origin of air masses. Assuming the northern Tibetan Plateau was equally far from an oceanic source during late Eocene-Miocene time, paleoelevations of the Hoh Xil Basin are recalculated to account for recycling, increasing elevation estimates by 1100-2700 m.
    Journal of Geophysical Research Atmospheres 01/2012; 117(D2):2110-. · 3.44 Impact Factor

Full-text (2 Sources)

Available from
May 29, 2014