Sir,

A glaciological expedition from the Institute of Geography, U.S.S.R. Academy of Sciences, renewed investigations on the Franz Josef Land archipelago glaciation, after a 30 year break. A new field camp was established at the westernmost island of Franz Josef Land — Alexandra Land, 12 km south of the Nagurskaya meteorological station and 5 km north of Loonney (Lunar) ice cap. Preliminary investigations of the glacier were carried out in April-May 1990 with the purpose of choosing a location for deep drilling, as planned for subsequent years.

Loonney ice cap has an area of 658 km² and comprises three connected ice-cap summits consolidated as a ridge 40 km long (Reference Grosval'dGrosval’d and others, 1973). The expedition studied only the northern summit. Barometric levelling carried out with the help of a microbarometer M-lll (accuracy of pressure determination 0.001 mbar) showed that the uppermost point on the northern part of the glacier was 375ma.s.l. (Fig. 1). The glacier edge at the summit field-camp profile was situated at an elevation of 31 m.

Fig. 1. Surface-elevation profile of the northern slope of the Loonney ice cap and stratigraphy of firn layers from a core near the deep-hole site (A): 1; snow 2–4, ice layers with a thicknesses less than lern, 1cm and more than 1 cm, respectively.

1 km north of the summit, at an elevation of 362 m, a hole was drilled to a depth of 53.6 m for temperature measurements (Fig. 2). During drilling, the bottom 5–10 m of the hole was filled with a water-glycerine-alcohol mixture which was pumped out each evening. During the drilling, and 1 and 3d after drilling terminated, temperatures were measured with a digital read-out platinum thermometer. The temperature profile showed a negative temperature gradient similar to that observed on several nearby glaciers — Vestfonna, Austfonna, Jackson and Acadcmii Nauk (Reference Grosval'dGrosval’d and others, 1973; Reference KotlyakovKotlyakov, 1985; Reference Zagorodnov and ArkhipovZagorodnov and Arkhipov, 1989; Reference Zagorodnov, Sin’kevich and ArkhipovZagorodnov and others, 1990). The temperature gradient measured 0.6°C at a depth of 20–53.6 m. The temperature of the lower margin of the active layer (10 m) was −2.0°C; in a dry hole located 5 m from the deep one, it was −2.1°C at 8.7 m depth.

Firn-layer stratigraphy was studied in cores from three holes, two of which were drilled 4–5 m from the deep hole and the third 1.5 km to the north, in the down-slope direction. In all the cores, the firn included ice layers with a thickness up to 50 cm. The change from firn to solid ice occurred at a depth of 6–6.5 m (see fig. 1a). Indirect evidence, a sudden loss of drilling fluid, suggests that permeable firn layers can exist to a depth of 12–14 m.

Fig. 2. Temperature distribution in the Loonney ice cap.

Based on the stratigraphie and 10 m temperature data, we speculate that all the investigated cores were formed in a firn-ice zone (lower percolation) similar to that observed at Austfonna (Reference ArkhipovArkhipov and others, 1987; Reference Sin'kevichSin'kevich, in press). This zone is characterized (i) by melt water and liquid-precipitation percolation through the entire layer thickness, and (ii) by active ice-layer formation both within the firn and at the upper margin of the solid ice. The results of our investigations showed that, if one of the ice layers is more than 1 m thick and has negative temperature, it can be accepted as the upper margin of the solid (waterproof) ice (Reference Sin'kevichSin’kevich, in press). It is worthwhile noting that almost the same stratigraphy and temperature regime were observed on Jackson ice cap, Franz Josef Land, in 1958–60 (Reference Grosval'dGrosval’d and others, 1973).

Because of the lack of time, the boundaries of the firn basin could not be determined. However, at the summit field camp, the following information was obtained: (i) 6 km from the glacier edge, at an elevation of 330 m, the snow—firn thickness was 6 m, almost similar to that observed at the deep-hole site; (ii) 2.5–4.5 km from the glacier edge, at an elevation of 230–300 m, we observed a firn layer 10–30 cm thick. This rapid decrease in thickness of the firn layer over a distance of 1.5 km and between 300 and 330 m is similar to that observed at Svea-Kongsvcgen glacier (Reference Korolev, Sin’kevich and TarusovKorolev and others, 1988) and Austfonna (Reference Sin'kevichSin'kevich, in press). The firn line of 1989 can be established at a height of 220–230 m.

The rapid decrease in thickness of the firn layer evidently occurs because of the increased summer melting accompanied by a decrease in precipitation down-slope. The latter cicumstance is corroborated by the snow-thickness data measured down-slope from the summit field camp on 20–25 May; snow thickness measured 11–120 cm at the summit, decreased to 95–115 cm at 230–300 m elevation, and to 70–95 cm near the glacier edge. The mean snow density was 400 kg m⁻³. Thus, the winter accumulation in 1990 on the Loonney ice cap equalled 0.4–0.5 m water equivalent within the firn basin. This value is close to the accumulation measured at the same location in 1961 (Reference MarkinMarkin, 1964) but is more than twice as large as that measured in 1962 (Reference GovorukhaGovoruha, 1964).

From data presented here, we have concluded that contemporary accumulation, firn stratigraphy and 10 m temperatures are very similar to those obtained earlier on the opposite shore of the Barents Sea — on the Vestfonna and Austfonna ice caps of Nordaustlandet, Svalbard. The deep-hole temperature profile from Vestfonna (Reference KotlyakovKotlyakov, 1985) paralleled the Alexandra Land profile (the latter is colder) to a tenth of a degree. Future deep drilling, involving detailed core investigations and new data on the englacial temperature distribution should enable us to determine whether there is also a similar history of development on the Loonney ice cap.

Sergey A. Sin’bkevich

Pavel A. Korolev

Konstantin E. Smirnov

Institute of Geography, U.S.S.R. Academy of Sciences, Moscow 109017, U.S.S.R. 5 October 1990, revised 27 December 1990