Law Dome d18O data 2100BP to 1996 as 4-year averages

Ages older than 700BP estimated from flow-model constrained by layer-thickness data (similar to Morgan et al., J. Glaciol, 43(143), 3-10, 1997). Estimated error at 2ky BP on the order of a few decades. Ages younger than 700BP from layer counting.

Estimated error +/-1 year at 700BP scaling to absolute (zero error) from 193-0BP. d18O values in per mille. Approximate accuracy of individual measurements 0.1 per mille, but each datum presented here is an integration of between 4 and 40 individual measurements, dependent upon age and sampling scheme. For conversion to temperature, values of ~0.2-0.3 per mille/degree C are deduced from short-term comparisons.

Longer term comparison of seasonal amplitude (van Ommen and Morgan, JGR, 102(D8), 1997) indicates conversion coefficient of 0.44 per mille/degree C. Spatially derived conversion coefficients are on the order of 0.6-0.7 pe r mille/degree C, but are unlikely to be appropriate. Note on annual phasing: A year for the purposes of averaging of the resolved-annual cycles, is by convention marked by the isotope maximum. Thus, calendar year 1994, for example, starts with the isotope peak in the Austral summer of 1993/1994 and concludes at the 1994/1995 peak.

Studies show that on the average, the isotope peak occurs around January 10 (van Ommen and Morgan, JGR, 102(D8), 9351-9357, 1997). This work was completed as part of ASAC/AAS project 757.