Stable isotope ratios from tree rings are important proxies of past climate variations. We have analysed non-dated wood material from a larch (Larix sp.) recovered from glacial tills in the valley bottom of Grottedal, Kronprins Christian Land, North-East Greenland National Park (80.3°N, 21.5°W). The wood samples were radiocarbon dated using AMS 14C analysis at ETH Zürich. Results indicate that the samples are older than 48.5 ka and 49.7 ka BP. We analysed the δ13C, δ18O and δ2H isotope ratios of alpha-cellulose obtained from blocks of 10 annual rings for the Greenland sample and annual rings for the Iceland sample. Cellulose was extracted following the modified Jayme-Wise method (Boettger et al., 2007). The isotopes values were determined using conventional Isotope Ratio Mass Spectrometry (Isoprime 100) coupled to a pyrolysis unit (HEKAtech GmbH, Germany), which is similar to the previously used TC/EA (for technical details see (Leuenberger, 2007). This approach was extended to measurements of non-exchangeable hydrogen of alpha-cellulose using the on-line equilibration method (Filot et al., 2006; Loader et al., 2015). The results are reported in per mil (‰) relative to the Vienna Pee Dee Belemnite (VPDB) for carbon and to Vienna Standard Mean Ocean Water (VSMOW) for hydrogen and oxygen (Coplen, 1994).