Open AccessUnderstanding the 17 O excess glacial‐interglacial variations in Vostok precipitation
Author(s) -
Risi Camille,
Landais Amaelle,
Bony Sandrine,
Jouzel Jean,
MassonDelmotte Valérie,
Vimeux Françoise
Publication year - 2010
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2008jd011535
Subject(s) - relative humidity , interglacial , climatology , geology , last glacial maximum , atmospheric sciences , glacial period , ice core , humidity , precipitation , geomorphology , thermodynamics , meteorology , physics
Combined measurements of δ 18 O, δ 17 O, and δ D in ice cores, leading to d excess and 17 O 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 17 O 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 17 O excess in source regions. Then, using a Rayleigh‐type model, we show that the 17 O excess signal from the source region is preserved in the polar snowfall, contrary to d excess. Evaporative recharge over mid and high latitudes and δ 18 O seasonality in polar regions can also affect the Vostok 17 O 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 (rh s ) by 8 to 22% would explain the observed change in 17 O excess. Such a change would not necessarily be incompatible with a nearly unchanged boundary layer relative humidity, if the surface thermodynamic disequilibrium decreased by 4°C. Such a change in rh s would affect source and polar temperatures reconstructions from δ 18 O and d excess measurements, strengthening the interest of 17 O excess measurements to better constrain such changes.