engleski

Glaciochemical investigations on the subterranean ice deposit of Vukušić Ice Cave, Velebit Mountain, Croatia

Vukušić Ice Cave (Vukušić sniježnica, 44.8N, 14.98E 1490 m asl) is located near the Zavižan Peak in the north part of Velebit Mountain, Croatia. Thickness of its ice deposit is estimated to be more than 10 m. We investigated the perennial ice accumulations to evaluate the potential of the preserved glaciochemical signal for paleoclimatological reconstruction(s). Two drill cores (2.4 m and 26 cm long) were extracted from the ice deposit on 28.10.2008. The upper 2 m long segment of the 2.4 m long ice core was partitioned into 36 sections. Tritium activity of the deepest 40 cm long section of the 2.4 m ice core and of the total section of the 26 cm ice core of the deposit were analysed using electrolytic enrichment. The results from the lower and upper samples are 1.8±0.5 TU and 9.9±0.6 TU, respectively. The tritium activity of the upper sample agrees with the mean tritium activity of the local (sub)recent precipitation. The tritium activity of the lower sample proves contribution of “modern” (post-1953) precipitation. It means that the ice accumulated from precipitation fallen around 1950-55, or the section is significantly older but “modern” water percolated and contaminated the deeper layers. Four outcropping wood macro-remnant (branch, trunk) were sampled from the overhanging ice wall and one was penetrated by the driller at 1.4 m below the actual ice surface. The deepest accessed sample (~4.2 m below the surface) was dated by radiocarbon method. Derived conventional date is 197±50 BP yr, calibrated age ranges are 1640-1690 (17.7%), 1730-1810 (39%) 1920-1960 (11.5%). Stable isotopic data (18O and D) of the 36 cave ice samples range from 11.97‰ to 8.02‰ and from 82‰ to 53.1‰ (vs. VSMOW), respectively. The isotopic range values and the derived isotopic waterline of cave ice agree reasonably well with the corresponding data of the local meteoric water line of precipitation (Zavižan 44.82N, 14.98E, 1594 m asl.) collected over the period September 2000 – December 2003. Concentrations of 45 elements were analysed using a double-focusing inductively coupled plasma sector-field mass spectrometer and 41 chemical species presented results above the detection limit at least in one sample out of the 36 analysed samples. Elevated concentrations were generally found in the uppermost sample which included the surface mud cover and in the sample above the intercalated wood where higher mud content was also observed. Fluctuations of concentrations along the profile are to be discussed for a few elements.

Ice cave; stable isotopes; tritium; Velebit

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