Seasonal Deuterium Excess in a Tien Shan Ice Core: Influence of Moisture Transport and Recycling in Central Asia
Abstract
Stable water isotope (δ18O, δD) data from a high elevation (5100 masl) ice core recovered from the Tien Shan Mountains, Kyrgyzstan, display a seasonal cycle in deuterium excess (d = δD - 8*δ18O) related to changes in the regional hydrologic cycle during 1994-2000. While there is a strong correlation (r2 = 0.98) between δ18O and δD in the ice core samples, the regression slope (6.9) and mean d value (23.0) are significantly different than the global meteoric water line slope of 8 and global d value of 10. The resulting time-series ice core d profile contains distinct winter maxima and summer minima, with a yearly d amplitude of ~15-20 \permil. Local-scale processes (i.e., sublimation, partial summer melting, snow formation temperature) that may affect d values preserved in the ice core are not consistent with the observed seasonal variability. Rather, we suggest that regional-scale hydrological conditions, including seasonal changes in moisture source, transport, and recycling in the Caspian/Aral Sea region, are responsible for the observed d variability. Examination of data from the Global Network of Isotopes in Precipitation (GNIP) indicates similar seasonal changes in southwestern Central Asian (Afghanistan and Tajikistan), likely related to moisture supply from the Mediterranean Sea during summer. The two years with the highest d values in the ice core record are 1997 and 1998, suggesting a possible link to ENSO ocean/atmosphere variability. The isotope data presented here provide a basis for interpreting centennial-scale ice core d records currently being developed from the region, and highlight the complexity of time-series isotope records from mid-latitude ice cores.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2002
- Bibcode:
- 2002AGUFMPP52A0325K
- Keywords:
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- 1610 Atmosphere (0315;
- 0325);
- 1620 Climate dynamics (3309);
- 1655 Water cycles (1836);
- 1827 Glaciology (1863);
- 1863 Snow and ice (1827)