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

Climate of the Past (Impact Factor: 3.38). 04/2010; 6(2). DOI: 10.5194/cp-6-219-2010
Source: DOAJ


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.

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Available from: Baiqing Xu, Dec 18, 2013
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    • "While northern TP δ 18 O is mostly controlled by temperature-driven distillation, as in mid and high latitudes, the situation is more complex in the monsoon sector of the southern TP (Yao et al. 2013). A number of studies have attributed recent increasing trends in south TP ice core δ 18 O to regional warming (Thompson et al. 2000; Yao et al. 2006a; Zhao et al. 2012), while process-based studies have stressed the importance of changes in precipitation amount and Indian monsoon intensity (Vuille et al. 2005; Kaspari et al. 2007; Joswiak et al. 2010). Some authors have also stressed that spatial patterns are related to changes in air mass trajectories and moisture sources (Tian et al. 2003; Johnson and Ingram 2004; Breitenbach et al. 2010). "
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    ABSTRACT: Ice cores from the Tibetan Plateau provide high-resolution records of changes in the snow and ice isotopic composition. In the monsoon sector of southern Tibetan Plateau, their climatic interpretation has been controversial. Here, we present a new high-resolution δ18O record obtained from 2206 measurements performed at 2-3 cm depth resolution along a 55.1 m depth ice core retrieved from the Noijinkansang glacier (NK, 5950 m a.s.l.) that spans the period from 1864 to 2006 AD. The data are characterized by high δ18O values in the nineteenth century, 1910s and 1960s, followed by a drop in the late 1970s and a recent increasing trend. The comparison with regional meteorological data and with a simulation performed with the LMDZiso general circulation model leads to the attribution of the abrupt shift in the late 1970s predominantly to changes in regional atmospheric circulation, together with the impact of atmospheric temperature change. Correlation analyses suggest that the large-scale modes of variability (PDO and ENSO, i.e. Pacific Decadal Oscillation and El Nino-Southern Oscillation) play important roles in modulating NK δ18O changes. The NK δ18O minimum at the end of the 1970s coincides with a PDO phase shift, an inflexion point of the zonal index (representing the overall intensity of the surface westerly anomalies over middle latitudes) as well as ENSO, implying interdecadal modulation of the influence of the PDO/ENSO on the Indian monsoon on southern TP precipitation δ18O. While convective activity above North India controls the intra-seasonal variability of precipitation δ18O in southern TP, other processes associated with changes in large-scale atmospheric circulation act at the inter-annual scale.
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    • "for comparison to those from the GLDD (Kang et al., 2007) and TGL (Joswiak et al., 2010) cores. The XD core d 18 O shows a relatively large span of 10‰ from À17.93‰ at 11.30 m depth to À8.38‰ at 0.27 m depth, and its median and mean values are À13.73‰ and À13.57‰, respectively. "
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