Stable isotope ratios (δ¹⁸O and δ²H) were analyzed at the stable isotope laboratory of the Faculty of Geography in the Lomonosov Moscow State University (headed by Prof. Yu. Vasil'chuk) using a Finnigan Delta‐V Plus mass spectrometer applying equilibration techniques. The values are presented in δ‐notation in per mil (‰) relative to the Vienna Standard Mean Ocean Water (VSMOW) expressed in per mil (‰). Analytical precision was ±0.1‰ for δ¹⁸O and±0.8‰ for δ²H. Oxygen isotope measurements of wedge ice sampled in 1987 were carried out in the isotope laboratory of the Institute of Geology of Estonia (headed by Prof. R. Vaikmäe) using a Finnigan Delta‐E mass spectrometer. Analytical precision was ±0.4‰.