Fuchs, G.

Gerdau, H.

Henning, K.

Klapdor, N.

Kohnen, H.

Möller, D.

Reinwarth, O.

Suhrmeyer, L.

English

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Polarforschung 51 (1): 17-19, 1981Survey and Mapping of the lee Front along theAntaretie Coast between 8 0 Wand 62 0 WBy G. Fuchs, H. Gerdau, K. Henning, N. Klapdor, H. Kohnen, D. Möller, O. Reinwarthand L. Suhrrneyer"Summary: During the site survey expedition to the Filchner lee Shelf the position of the iee front was mapped continuously between 25°Wand the Antarctic Peninsula at 62°W using satellite positioning techniques. The height of the ice front was measured by the aid of opticalmethods and altirnetry. Since the first iee front survey in 1957, which was carried out with classical nautical methods, the iee front of theFilchner/Ronne system seerns to have advanced by 10 km to 25 km. This result , wh ich has also been obtained from other West Antarctic ieeshelves, has to be substanmtiated by Future measurements.Zusammenfassung: Während der Standorderkundungsexpedition zum Filchner-Ronne-Schelfeis 1979/80 wurde der Verlauf der Schelfeis-kante entlang der antarktischen Küste von etwa 25 °W bis zur Antarktischen Halbinsel bei 62°W mit Hilfe eines Satellitennavigationsgeräteskartiert. Die Höhe der Barriere wurde vermessen. Seit der Eisfrontaufnahme 1957 - allerdings mit klassischen nautischen Mitteln - scheintdas Filchner-Ronne-Schelfeis um 10 km bis 25 km vorgestoßen zu sein. Dieses Ergebnis, das auch bei anderen Schelfeisen der Westantarktisbeobachtet wurde, ist an hand zukünftiger Messungen zu überprüfen und zu erhärten.The German Antarctic Expedition 1979/80 (site survey Filchner/Ronne Ice Shelf) left Buenos Aires on 18December 1979 on board the Norwegian research icebreaker POLARSIRKEL heading first for South Ge-orgia. From South Georgia the vessel passed the South Sandwich lslands and sailed through theeastern Weddell Sea between 24°W and 12°W towards the continent. The route of the expedition isshown in Fig. I. Due to the excellent pack ice conditions POLARSIRKEL arrived at Cape Norvegia(71 ° 17' S, 12° 23' W) on 31 December 1979. Some scientific projects had already been carried out on theway south which are outlined elsewhere in this volume.Fig. 1: The route of the German AntarcticExpedition 1979/80.Abb. 1: Route der deutschen Standorterkun-dungsexpedition 1979/80.* Dipl.-Ing. Gcrd Fuchs. Dorsch Consult, Elsenheimerstr. 63, 0-8000 München 21Dipl.-Ing. Horst Gerdau und Prof. Dr, Dietrich Möller, Institut für Vermessungskunde der Technischen Universität, Pockelstr. 4, 0-3300Braunschweig.Ing. Klaus Herming und Kpt . Lothar Suhrmcyer, Deutsche Offshore Gesellschaft, An den Landungsbrücken, Brückenhaus , 0-2000 Harn-burg 4Or. Norbert Klapdor , Am Maashof 39,0-4100 Duisburg 31Dr. Hcinz Kohnen, Institut für Geophysik der Universität, Corrcnsstr. 24, 0-4400 Münster (Westf.)Dip!. Met. O. Rcinwarth, Kommission für Glaziologie der Bayerischen Akademie der Wissenschaften, Marstallplatz 8, 0~8000 Mün-chen 2217hand, this region was of secondary interest for the goal of the expedition, the ship proceeded straight tothe British station HaIley (71 0 1T S, 12 023' W). The height of the barrier was, nevertheless, estimated byoptical methods wherever possible, yielding me an heigths of 30 to 45 m over this section wh ich could beconfirmed on the way back.From HaIley westward POLARSIRKEL foIlowed the continental fringe elose to the coast line. The posi-tion of the ice front and the height of the barrier were surveyed continuously. The ice front was mappedby using the ship's one-channel doppler satellite-positioning instrument (type: Nautikon) together withthe ship's radar and gyro-cornpass. The height of the barrier was estimated by optical methods (sextant)and sporadicaIly by altimetry using the helicopter. The latter method was applied when the ice front wastoo far for the optical measurements. Tab. 1 and Fig. 2 contain the results.Surveyed area with satellite-controlled positions25° 15' W - 27° 36' w74° 39' 5 - 76° 06' 528° 26' W - 36° 12' W76°08'5 -77°41'536°48' W -41°24' W77° 45' 5 - 77° 34' 542 ° 09' W - 48 ° 59' W77° 39' 5 - 77° W' 550° W - 55 ° 57' W77°5 -75°53'556023' W - 61 ° 18' W75°53'5 -74°50'5Mean heightof the barrier20 rn-45 rn10 rn-25 rn(35 rn-40 rn)40 rn7 rn-15 rn20 rn-30 rnRemarksContinuous vertical c1iff with single inlets; Brunt lce Shelf;No distinct barrier; the co ast is formed in this section by heavilycrevassed gIaciers;Filchner Ice Shelf; continuous shallow barrier; slightly increasingfrom 10 m to 20 m at 40° 54' W (area Druzhnaya);Gould Bay, Berkner Island; Gould Bay was covered with fast iceand optical height determinations were only sporadically possible; the va-lues in brackets result from helicopter survey (altimeter);Ronne lee Shelf; flat and even barrier;Ronne Ice Shelf to Antarctic Peninsula; the height of thc barrierincreases suddenly at a sm all inlet at about 56 0 W to 30 mTab. I: Mean heights of the ice barriet between Halley and the Antarctic Peninsula determined optically from board the ship and partly byhelicopter altirnetry. The coordtnates wcre measured by Doppler satellite-positioning and give thc range within which the height determina-tions were carried out.Tab. I: Mittlere Höhen der Schelfeiskante zwischen Halley und der Antarktischen Halbinsel. Die Höhen wurden mit einem Sextanten vonBord des Schiffes sowie teilweise mittels des Helikopterhöhenmessers gewonnen. Die Positionen wurden mit einem Satellitennavigationsge-rät bestimmt; sie geben den Bereich an, in dem die Höhenmessungen durchgeführt wurden.The pack ice conditions of the 79/80 season were extrernely favourable as shown in the previous chapter ,The ship could, therefore, proceed unrestrained to the Antarctic Peninsula (most western position: 72 042' S, 61 019' W), wh ich was reached on 5 January 1980.The position of the ice front is plot ted in Fig. 2. There is a gap in the data between 75 050' S, 27 020' Wand Vahsel Bay. In this region aIl the coast is fringed by heavily crevassed glaciers which do not exibit anydistinct front line or barrier. We were consequently not able to map this part of the coast line with ourmethod.There is a distinct and very interesting difference in the positions of the ice front of the Filchner /RonneIce Shelf between 1957 and 1979/80. The accuracy of our measurements is about ± l' in latitude, equiva-lent to ± 1 nM (nautical mile). It cannot be assumed that the ice front of 1957 was obtained with a similarprecision because modern navigation and positioning techniques like those used by our expedition werenot yet available at that time. Thus, an advance of the ice front of 10 to 25 km between 1957 and 1980, ascan be deduced from the two different shore lines, has to be regarded with caution. However, extrapola-ting at 50 0 W the difference between ice movement at the front (1070 m/a; MÖLLER & GERDAU, 1981)and annual break-off (approximately 100 m/a; KOHNEN & HAG, 1981) over the past 23 years yields anadvance of about 20 to 23 km. These numbers rnatch fairly weIl the apparent advance of the Ronne IceShelf in this area obtained from the two ice front positions. The differences between the two shore linesare considerably smaIler in front of Berkner Island where the movement of the grounded ice is much slo-wer which is another hint of a real advance. ZAKHAROV & KOTLYAKOV (1980) have argued on the18--------+ -------~'r-----------------_:+73·-----f~--------cf_,L+---~75·Fucr-ner lceShelfFig. 2: Position of the ice front in 1957 and 1980 and expedition reute 1979/80.Abb. 2: Die Lage der Schelfeiskante 1957 und 1980 sowie die Operationen der POLARSIRKEL vor dem Schelfeis.basis of satellite observations that the ice shelves fringing the Weddell Sea generally advance and that theadvance is balanced by major calving activities every few decades.Since advance and retreat of the ice front are of basic importance for mass balance and ice dynamic con-siderations, an accurate survey of the ice front will be one of our prime interests during the forthcomingyears.The cruise of POLARS1RKEL in the Weddell Sea is also plotted in Fig. 2 giving the accurate positions,dates and tracks of the biological and oceanographic observations.ReferencesK 0 h n e n, H. & P. Hag (1981): Radio echo sounding investigations on the Filchner/Ronne lee Shelf 1979/80. - Polarforschung51 (I): 55-60M Ö I I e r, D. & H. Ger d a u (1981): Geodetic surveying on the Filchner/Ronne lce Shelf and in the Atka Bay 1979/80. - Polarfor-schung 51 (I): 43-53Z a k h a r 0 v, V. S. & V. M. Kot I yak 0 v (1980): New data on the dynamics of ice shelves in the Weddell Sea. - Akad. Sei. USSR,Seetion of Glaciology of the Soviet Geophysical Committee and Institute of Geography, Data of Glaciological Studies, Publ. 39:181-18519

Survey and Mapping of the Ice Front along the Antarctic Coast between 8° W and 62° W

Survey and Mapping of the Ice Front along the Antarctic Coast between 8° W and 62° W

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