Chemical and isotopic profiles from snow pits and shallow firn cores on Campbell Glacier, northern Victoria Land, Antarctica

Abstract

The chemical (Na+, K+, Mg2+, Ca2+, CH3SO3 − (MSA), Cl− , NO3 − , SO4 2-) and isotopic (δl8O) composition of snow and firn samples from Campbell Glacier, northern Victoria Land, Antarctica, was studied to evaluate the accumulation rate of snow and to investigate the chemical contribution from some emission sources (marine biogenic activity, sea and crust). During the 1994-95 Italian Antarctic Expedition, snow and firn were collected from snow pits and from cores obtained from drilling at three sites (A: 74°41'S, 164°30' E; B: 74°15' S, 164° '04' E; C: 73°45' S, 163°20' E), located ai 50 m (on the floating glacier tongue), 800 m and 1580 m a.s.l., respectively. The mean concentration of sea salt decreased with increasing distance from the coast and with altitude. Generally, the Na+/K+ and Na+/Ca2+ ratios were much lower than the bulk sea-water ratios at sites B and C. The MSA showed mean concentrations (0.27 and 0.17 ¿teq 1 at sites B and C, respectively) consistent with data obtained from other Antarctic sites. The mean concentrations of NO3 ranged from 2.1 μeq 1−1 (site A) to 0.97 μeq1 1 (site C).The mean nss (non-sea-salt) SO4 2-/SO4 2- ratio was -0.055,0.54 and 0.42 at sites A, B and C, respectively. Moreover, the relationship between a2+, nssCa2+, SO4 2- and nssSO4 was quite different at sites B and C. in order to expla in the relationships between the elements and compounds studied at these sites, chemical fractionation and/or reactions inside air masses and différent origin of the air masses at the two sites should be considered. A comparison of the isotopic and chemical profiles was carried out in order to provide a more reliable chronological scale. The chemical and δ18O seasonal variations recorded along the firn cores from the upper site of Campbell Glacier seem to be fairly homogeneous. This made it possible to identify many annual cycles (14-18 years for the 7 m firn core). Using the measured density values, the accumulation rale was also calculated for lower and upper Campbell Glacier. It did not appear to differ between the two sites (150-170 kg m −2a−1 at site B and 140-180 kg m−2a−1at site C) and is in keeping with rates calculated previously for the same area.