Triple isotopic composition of oxygen in surface snow and water vapor at NEEM (Greenland)

TY - JOUR

T1 - Triple isotopic composition of oxygen in surface snow and water vapor at NEEM (Greenland)

AU - Landais, A.

AU - Steen-Larsen, Hans Christian

AU - Gullevic, M.

AU - Vinther, Bo Møllesøe

AU - Winkler, R.

PY - 2012/1/15

Y1 - 2012/1/15

N2 - The isotopic composition of water in polar ice cores is commonly used to reconstruct the climatic conditions both at the site of precipitation and at the site of oceanic source region. Theoretical studies have suggested that the variability of the parameter 17O excess resulting from the triple isotopic composition of oxygen in water should be driven by the relative humidity of the oceanic source region. Our new 17O excess measurements in surface water vapor and snow at the Greenland NEEM camp demonstrate the potential of 17O excess as a marker of source relative humidity. Using concomitant measurements of water vapor and precipitation, we first confirm the theoretical relationship between the fractionation coefficients at vapor-solid equilibrium α 17 eq_vap_sol and α 18 eq_vap_sol associated respectively with δ 17O and δ 18O: ln(α 17 eq_vap_sol)/ln(α 18 eq_vap_sol)=0.528. Our data reveal 17O excess seasonal variations in Greenland firn over the years 2003-2005. Their magnitude is of the order of 25ppm, with a minimum in July leading d-excess maximum level reached ~3months later. This is in agreement with our understanding of 17O excess and d-excess variations in polar regions with minima in 17O exces in phase with maxima in source relative humidity and maxima in d-excess largely influenced by source temperature increase. In a large northern Atlantic sector, relative humidity reaches its seasonal maximum in summer, earlier than the sea surface temperature maximum which takes place in fall.

AB - The isotopic composition of water in polar ice cores is commonly used to reconstruct the climatic conditions both at the site of precipitation and at the site of oceanic source region. Theoretical studies have suggested that the variability of the parameter 17O excess resulting from the triple isotopic composition of oxygen in water should be driven by the relative humidity of the oceanic source region. Our new 17O excess measurements in surface water vapor and snow at the Greenland NEEM camp demonstrate the potential of 17O excess as a marker of source relative humidity. Using concomitant measurements of water vapor and precipitation, we first confirm the theoretical relationship between the fractionation coefficients at vapor-solid equilibrium α 17 eq_vap_sol and α 18 eq_vap_sol associated respectively with δ 17O and δ 18O: ln(α 17 eq_vap_sol)/ln(α 18 eq_vap_sol)=0.528. Our data reveal 17O excess seasonal variations in Greenland firn over the years 2003-2005. Their magnitude is of the order of 25ppm, with a minimum in July leading d-excess maximum level reached ~3months later. This is in agreement with our understanding of 17O excess and d-excess variations in polar regions with minima in 17O exces in phase with maxima in source relative humidity and maxima in d-excess largely influenced by source temperature increase. In a large northern Atlantic sector, relative humidity reaches its seasonal maximum in summer, earlier than the sea surface temperature maximum which takes place in fall.

U2 - 10.1016/j.gca.2011.11.022

DO - 10.1016/j.gca.2011.11.022

M3 - Journal article

SN - 0016-7037

VL - 77

SP - 304

EP - 316

JO - Geochimica et Cosmochimica Acta

JF - Geochimica et Cosmochimica Acta

ER -