| 公告主旨 |
Understanding oxygen isotope records of climate change: Insights from a 5-year, daily resolved 18O precipitation record from Krabi, Thailand |
| 公告內容 |
Date: 2018/11/26 12:30-14:00
Speaker: Ludvig Löwemark – Associate Professor, Department of Geosciences, NTU
Abstract: Variations in oxygen isotopes in speleothems are often interpreted to reflect variations in the amount of precipitation controlled by changes in climate phenomena such as the monsoon or ENSO. However, this amount effect has recently been questioned, favoring other mechanisms such as moisture source（s）, rainout history, or the influence of local convection. A more than 5 years long daily resolved precipitation and 18O record from Thailand allows the relationship between precipitation patterns and rainwater 18O to be examined. Rainfall at the Krabi station was highly irregular with rain events ranging from 0.1 mm to nearly 150 mm per day. Rainwater 18O values vary from -17.50 to 8.24 ‰, with a long-term average close to -5 ‰. We demonstrate that while daily and amounted weighted seasonal 18O values show no correlation with rain amount, the amount weighted monthly values display a significant correlation with monthly rainfall. Statistical comparison to atmospheric parameters reveal a strong correlation to outgoing longwave radiation, suggesting that local convection rather than precipitation amount control variations in rainwater 18O in this region. Comparison to a short cave drip water record suggests that the atmospheric 18O signal is recorded with a muted amplitude in the drip water, and with a lag of one to two weeks.
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