Deuterium excess

Jouzel, J., Merlivat, L., and Lorius, C. (1982). Deuterium excess in an East Antarctic ice core suggests higher relative humidity at the oceanic surface during the last glacial maximum. Nature 299, 688-691. 

Neither the numerieal eoefficient 8 nor the eonstant 10, also ealled the deuterium excess d, are eonstant in nature. Both may vary depending on the eonditions of evaporation, vapor transport and preeipitation and, as a result, offer insight into eli-matie proeesses. The deuterium exeess d is a valuable tool to derive information on relative humidities. 

Later, Dansgaard (1964) introduced the concept of deuterium excess , d defined as c = 5D -8 5 0. Neither the numerical coefficient, 8, nor the deuterium excess, d, are really constant, both depend on local climatic processes. The long-term arithmetic mean for all analyzed stations of the IAEA network (Rozanski et al. 1993) is ... 

Table 3.1 Variations in the numerical constant and the deuterium excess for selected stations of the IAEA global network (Rozanski et al, 1993)...

As is well known the isotopic composition of water is controlled by two mass-dependent processes (1) the equilibrium fractionation that is caused by the different vapor pressures of H2 0 and H2 0 and (2) the kinetic fractionation that is caused by the different diffusivities of H2 0 and H2 0 during transport in air. Angert et al. (2004) have demonstrated that for kinetic water transport in air, the slope in a 5 0-5 0 diagram is 0.511, whereas it is 0.526 for equilibrium effects. Similar values have been given by Luz and Barkan (2007). is thus a unique tracer, which is, in contrast to the deuterium excess, temperature-independent and which may give additional information on humidity relations. 

This equation describes the linear distribution of data points on a plot of 8D versus 8lsO that is commonly referred to as the global meteoric-water line (GMWL). The zero intercept for this line, defined as the deuterium excess... 

Talma AS, Netterberg F (1983) Stable isotope abundances in calcretes. In Residual Deposits Surface Related Weathering Processes and Materials. Wilson, RCL (ed) Oxford Blackwell Scientific Publ., p 221-233 Tian L, Masson-Delmotte V, Stievenard M, Tao T, Jouzel J (2001) Tibetan Plateau summer monsoon northward extent revealed by measurements of water stable isotopes. J Geophys Res 106 28,081-28,088 Tian L, Yao T, White JWC, Yu W, Wang N (2005) Westerly moisture transport to the middle of Himalayas revealed from the high deuterium excess. Chinese Sci Bull 50 1026-130 Uba CE, Heubeck C, Hulka C (2006) Evolution of the late Cenozoic Chaco foreland basin, southern Bolivia. Basin Res 18 145-170... 

Figure 7 also shows the influence of sea surface temperature, on 5p. Merlivat and Jouzel (1979), Johnsen et al. (1989), and Petit et al. (1991) show that source conditions (temperature and humidity) also influence the relative amounts of HDO and H2 0 in the parcel and thus the deuterium excess in precipitation. The model reproduces deuterium-excess values observed in Greenland (Johnsen et al., 1989) and in Antarctica, where d becomes higher than 15%o in central regions (Petit et al., 1991 Dahe et al, 1994). These results as well as those concerning the isotope-temperature relationship were further confirmed by Ciais and Jouzel (1994), who introduced mixed clouds into the Rayleigh-type model, thereby allowing supercooled liquid droplets and ice crystals to coexist between-15 °C... 

Either 6D or profiles can be indifferently used as a climatic record. Different choices have been made by various teams. The climate reconstruction is based on the interpretation of the 6D profile for Vostok, Dome B, old Dome C and EPICA Dome C, and on for all the other cores. Interestingly, measuring both isotopes on the same core brings additional information about the changes affecting the oceanic sources of Antarctic precipitation through the deuterium-excess parameter. Most of the ice core projects now include measurements of both isotopes. Based on the Vostok core results, we illustrate in Section 4.08.8 how this co-isotopic approach can be used. 

Figure 11 Vostok temperature changes from present-day values back to 420 kyr BP, estimated either AT s(spat) (in red) by the conventional approach based on the 6D profile alone (Petit et al., 1999) accounting correctly for the oceanic correction (see text), or A7 s(inv) (in green) from the inverse method based on the use of deuterium excess to account for moisture source changes (source Vimeux et al, 2002).

There are two complementary ways to assess the influence of the origin of a precipitation on its isotopic content. First, the combined measurement of both 5D and 5 0 enables the calculation of a second-order isotopic parameter, the deuterium excess (d=5D —86 0) which (see Section 4.08.4.1) depends on the temperature and relative humidity of the evaporative source (and, to a lesser degree, on the wind speed). In turn, this parameter contains information about conditions prevailing in these source regions and it has been applied, as of early 2000s, only for Antarctic sites (Culfey and Vimeux, 2001 Stenni et al., 2001 Vimeux et al, 2002), to correct the conventional approach for source temperature... 

Armengaud A., Koster R., Jouzel J., and Ciais P. (1998) Deuterium excess in Greenland snow analysis with simple and complex models. J. Geophys. Res. 103, 8653-8947. 

Cuffey K. M. and Vimeux F. (2001) Covariation of carbon dioxide and temperature from the Vostok ice core after deuterium-excess correction. Nature 421, 523-527. 

Fisher D. A. (1991) Remarks on the deuterium excess in precipitation in cold regions. Tellus 43B, 401 -407. 

Vimeux F., Cufifey K., and Jouzel J. (2002) New insights into southern hemisphere temperature changes from Vostok ice cores using deuterium excess correction. Earth. Planet. Sci. Lett. 203, 829-843. 

This equation, known as the global meteoric waterline (GMWL), is based on precipitation data from locations around the globe. The slope and intercept of the local meteoric waterline (LMWL) for rain from a specific catchment or basin can be different from the GMWL. The deuterium excess (d excess, or d) parameter has been defined to describe these different meteoric waterlines (MWLs), such that... 

A partial correction can be made for this source-temperature influence on 5 O and 5D of precipitation by using a derived quantity called the deuterium excess, d, of that precipitation although this procedure needs further verification. A plot of precipitation 5D versus produces a meteoric water line with a slope of about 8 (Craig 1961). Adopting the slope of 8 exactly, the 5 0 and 5D of any sample define a line with an intercept called the deuterium excess, d (Dansgaard 1964). This varies spatially and temporally in response to both equilibrium and kinetic effects during evaporation, which... 

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