Due to low snow accumulation rates,
annual layer counting is not a viable option for dating the VLG ice core. The upper 4 m of the core were dated through correlation with a 4 m-deep snow pit record from the same site.
The snow pit data were sampled with 1 cm resolution and dated using annual layer counting of seasonal fluctuations of sodium with a precision of ±1 yr for the 36 yr
record (Bertler et al., 2004a,b).
Average annual accumulation over this time period is 0.033±0.013 mw.e. a−1.
The tritium measurements were used to identify major peaks caused by nuclear testing
between 1957 and 1966 as well as seasonal tritium variations.
The dating error of the tritium measurements is b0.3 yrs (Patterson
et al., 2005).