Glaciological research in Antarctica

land (GGU) was observer on behalf of the Danish Polar Center in and preparation of a common Nordic research effort in Antarctica. The Nordic Antarctic Research Programme (NARP) involves Norway, Sweden and Finland, which are all Antarctic Treaty Consultative Partners, whereas Denmark is an observer. A natural continuation of this work was Danish participation in the Antarctic research, and a GGU glaciologist took part in the Norwegian Antarctic Research Expedition (NARE) 1992/93 arranged by the Norwegian Polar Research Institute. The expedition started from Cape Town in South Africa, 8 December 1992 and ended at the same place on 9 March 1993. The Danish glaciological work in Antarctica took the form of stable isotope studies on blue ice areas near the Norwegian research station Troll in Dronning Maud Land, East Antarctica (Thomsen & Hagen, in press). In addition, the GGU glaciologist took part in two Norwegian glaciological programmes, concerning the mass balance and dynamics of Jutulstraumen ice stream in Dronning Maud Land (Hagen & Melvold, in press) and studies of iceocean interaction under the Filchner-Ronne ice shelf, West Antarctica (Orheim et al., in press). The GGU participation was financed by the Norwegian Polar Research Institute, Norwegian Research Council and Danish Natural Science Research Council.


Stable isotope studies at blue ice areas
Oxygen-18 isotope (0 18 0) studies from deep ice-cores have demonstrated that the large ice sheets of Antarctica and Greenland are rich sources of information about climate many thousands of years back in time (e.g. Dansgaard et al., 1982;Lorius et al., 1985;Jouzel et al., 1987;Lorius et al., 1989). Comparisons of <> 18 0 records from deep icecores and records measured on surface ice from the ablation zone of the Greenland ice sheet show that old ice found at depth in the central regions of the ice sheet can also be retrieved at the surface of the ice sheet margins. Here ice of different ages is found in a sequence with the oldest ice nearest to the ice edge. (Clausen & Stauffer, · 1988;0erter&Reeh, 1993;Reehetal., 1987Reehetal., , 1991.0ne of these ice margin records reveals that palaeoclimatic Rapp. Grfln/ands geol. Unders. 160, 83--86 ( 1994i

Glaciological research in Antarctica
Henrik H(/Jjmark Thomsen and Jon Ove Hagen data spanning back c. 150 000 years can be retrieved from surface ice at ice margin locations (Reeh et al., 1991). Furthermore, stable isotope studies from the Greenland ice sheet margin in the Thule area, North-West Greenland, show that the isotopic signature of the ice, in terms of mean value as well as variability, is characteristic for the site of formation of the ice and for its thermal and phase change history since the time of formation (Reeh et al., 1990). At many locations in Antarctica blue ice is exposed at the surface. These blue ice areas have a negative mass balance and are therefore ablation zones, which implies ice flow with a net upward emergence velocity (Orheim & Lucchitta, 1990). The blue ice areas therefore have a potential for palaeoclimatic studies, as old ice might emerge to the ice surface at these locations. 0 18 0 values of scattered ice samples from blue ice areas in the Transantarctic Mountains indicate that data on the ice source areas and palaeoclimate can be retrieved from the surface ice (Faure, 1990;Grootes, 1990) in the same way as from the ablation zone of the Greenland ice sheet.
The objectives of the current study were to investigate the stable isotope signature of the Antarctic blue ice areas, to assess the source area of the emerging ice, and to evaluate the potential of these areas as source areas for palaeo-environmental studies. Surface ice samples, to be analysed for 0 18 0, have been collected from two blue ice areas around Jutulsessen, Dronning Maud Land, East Antarctica.

The Jutulsessen area
The Jutulsessen mountain complex (72°S, 2°40'E) is part of the large nunatak area running approximately parallel to and about 200 km inland from the ice shelf margin at the Antarctic coast (Fig. 1 ). The nunatak area forms a kind of barrier for the ice draining from the Antarctic plateau to the south at elevations over 3000 m a.s.l. Ice from the plateau drains to the lower part of the ice sheet near the coast through several glacier streams between the nunataks (Fig. 1).
A large blue ice area is developed in S::etet, the central part of Jutulsessen, and extends to the west along the west- ern pa rt of Cirjotlia whe re the Norwegian research station Tro l I is located (Fig. I ). The surface s lope of the blue ice areas indicates that the ice fl ows east towards Tro ll and south towards S x tet. Evidence of th e p resent ice fl ow to the bl ue ice areas is given by the general ice surface topography an d ice llow struc ru res fr om sa tell ite image maps (Norsk Pohl rins ti tutt, 199 1 a , b, 1992). Th is indicates Lh at the blue ice exposed near Troll is ice drain ing throu g h Fj e l Ii mellom , p an ly de ri ved fro m th e p la teau d rain ing throu gh G luvrek le nbree n o r Bak hallet and partly from a local accumu la tio n area ctl Terningskarvet (F ig . I) . The same origin is likely fo r the b lue ice ex posed at S~tet, but there is a chance of fi nding ice here flowing from th e plateau through Sveabrcc n, or from a local accumu lation area at N ups kam me n (Fig . I) .

Ice sampl ing programme and preli minary results
A tota l or abmtt 650 ice an d sn ow samples were collected from the bl ue ice area around Troll at Grjotlia and at S::etet ( Fig . I ) to be analysed for 6 1 "0. The samp les were take n fro m the ice su rface a long pro l"i les beginning a t the ice margi 1 L a nd or ie ntated parall el to the esti mated ice flow directio n. Where. now patches were present at the surface. samp les were al ·o taken from the . now. At seve ra l pl aces along the profiles diffuse dttst bands cou ld be observed . as has been described from blue ice areas elsewhere in An ta rctica (Koeb crl, 1990: Ca sicly et al., 1992. The du. L bands rire traceab le f"or many hund reds o f me tres perpendicu lar to the ice rl ow di rection. Fu rthermore, numerous froze n 111el twater ho les (cryoconite holes) eac h containing small stones or gravel mate ria l were observed o n the The deep frozen world of Antarct ica. Vertical ice wall near the Norwegian researc h stat ion Troll in Dronn ing Ma ud Land. , 1\ntarctica.
Photo: Henrik l !0j111ark Th o msen/The Norwegia n Antarctic Resemch Expedit ion 1992/93. surface . Surface struc tures observed a lo ng the profile lin es were described and photographed to enabl e them to be corre lated with th e 0 10 record.
The initi a l results a rc c urrently being assess ed . lt is a lready clear that a one kiloml'. trc lo ng p ro file w ith a sample spacing of 4 m j ust south o f Tro l I station ( Fig. l ) shows a marked sys tema tic 8 18 0 va ri ation from the ice margin ups tream along th e profile . 8 10 values be tween -43%, ancl -45o/c~ are typical for th e o utermost part of the profile ne ar the ice marg in , incre as ing to va lues b tween -34%0 and -36%" one kilometre fu rthe r u pstream. Between these e x treme values , three marked oscill ation s occur with 8 18 0 changes fr o m 6%0 to l 2%c A t thi · preliminary stage of the work it is too early to draw concl usions. but the variations desc ribed ind ica te lh t: possi bil ity of ex tracting information o n h oth ice source areas and palaeoclimatc.
Ack1101v/edgeme111s. Th is pape r i, puhl ic,11i o11 No . 130 of the Norwe g ian /\ ntarct ic Re search Exped iti o ns. ( 1992/93 ). T he stud y is su pported by the Norweg_ian Po la r Research Jnstitutc, the Norwegian Resemc h Council a nd the Danish Natural Sc ience Research Co un ci l. 0yvind A. Hpyda l and Kj etil Me l void frn rn 1he Nor wegian Polar Researc h lnstitute and Jan-Gunn ar Winthe r from the Norwe gia n I lydrotechn ical Laboratory (NHL) are tha nk ed for he lp with collection of samples . I lenri k Clausen J"rorn th e De partmen t of Ge ophys ics. :--Jiels Bo hr in stitute fo r 1\ strono1 11y. Physics and Geo phys ics al lhe University o l"Copc nhagen is thanked fo r analysi, o f" the sa 111p lcs .