TY - JOUR AU - Risi Camille, Landais Amaelle PY - 2010// TI - Understanding the 17O excess glacial-interglacial variations in Vostok precipitation T2 - J. Geophys. Res. JO - J. Geophys. Res. SP - D10112 - VL - 115 IS - D10 PB - AGU KW - 17 O excess KW - ice core isotopic composition KW - surface relative humidity KW - 4932 Paleoceanography: Ice cores KW - 0454 Biogeosciences: Isotopic composition and chemistry KW - 0365 Atmospheric Composition and Structure: Troposphere: composition and chemistry KW - 1655 Global Change: Water cycles KW - 3344 Atmospheric Processes: Paleoclimatology KW - N2 - Combined measurements of δ18O, δ17O, and δD in ice cores, leading to d excess and 17O excess, are expected to provide new constraints on the water cycle and past climates. We explore different processes, both in the source regions and during the poleward transport, that could explain the 17O excess increase by 20 per meg observed from the Last Glacial Maximum (LGM) to Early Holocene (EH) at the Vostok station. Using a single-column model over tropical and subtropical oceans, we show that the relative humidity at the surface is the main factor controlling 17O excess in source regions. Then, using a Rayleigh-type model, we show that the 17O excess signal from the source region is preserved in the polar snowfall, contrary to d excess. Evaporative recharge over mid and high latitudes and δ18O seasonality in polar regions can also affect the Vostok 17O excess but cannot account for most of the 20 per meg deglacial increase from LGM to EH. On the other hand, a decrease of the relative humidity at the surface (rhs) by 8 to 22% would explain the observed change in 17O excess. Such a change would not necessarily be incompatible with a nearly unchanged boundary layer relative humidity, if the surface thermodynamic disequilibrium decreased by 4C. Such a change in rhs would affect source and polar temperatures reconstructions from δ18O and d excess measurements, strengthening the interest of 17O excess measurements to better constrain such changes. SN - 0148-0227 UR - http://dx.doi.org/10.1029/2008JD011535 N1 - exported from refbase (http://publi.ipev.fr/polar_references/show.php?record=201), last updated on Wed, 03 Jul 2024 20:26:32 +0200 ID - RisiCamille2010 ER -