102 References Jarvik, E. A. V. 1961: Devonian vertebrates. In Raaseh,G. O. (edit.) Geologyof the Arctic 1, 197-204. TorontoU.P. Alexander-Marraek, P. D. & Friend, P. E 1976: Devonian Jarvlk, E. A. V.1972: Middle and Upper Devonian Porolepi­ sediments of East Greenland. III: The eastern sequenee, formes from East Greenland with special reference to Glyp­ Vilddal Supergroup and part of the Kap Kolthoff Super- tolepis groehla~dica n.sp, and a discussion on the.structure of group.Meddr Grønland 206(3), 122 pp. ' the head in the Porolepiformes. Meddr Grønland 187(2),307 Bendix-Almgreen, S. E. 1976:' Palaeovertebrate faunas of pp. Greenland. In Eseher, A. & Watt, W. S. (edit.) Geology of Jarvik, E. A. V. 1980: Basic structure and evolution of ver- Greenland, 536-573. Copenhagen: Geol. Surv. Greenland. tebrates 1, 575 pp. London: Aeadeinic Press.' ' Birkelund, T. & Pereh-Nielsen, K. 1976: Late Palaeozoie ­ Jarvik, E. A. V. 1985: Devonian osteolepiform fishes from Mesozoic evolution ofcentral East Greenland. In Escher, A. East Greenland. Meddr Grønland Geosd. 13; 52 pp. & Watt, W. S. (edit.) Geology of Greenland, 304-339. Co­ Lehman, J.-P. 1959: Les dipneustes du Devonien superieurdu ,penhagen: Geo!. Surv. Greenland. Groenland. Meddr Grønland 160(4),58 pI'.", Bjerring, H. C. 1985: Faets and thoughts on piscine phylogeny. Mayne, W. 1942: Stratigraphie 'und Faziesverhiiltnisse der In Foreman, R. E., Gorbman, A. & Olsson, R. (edit.) Oberpermischen Ablagerungen Ostgr6enlands (Olim 'Ober­ Evolutionary biology of primitivefishes. NATO Adv. Stud. karbon-Unterperm') zwisehen Woll.as~oJl:F6r1and und den Inst. Ser. A, life sci. 103,31-57. New York: Plenum Press. , Kejser Josephs . MeddrGrø~land 115(1,), 128 pp. Biitler, H. 1954: Die stratigraphisehe Gliederung der Mittelde~ Nicholson, J. & Friend, P. E 1976: Devon'iansediments of East vonisehen Serien im Gebiete von Kap Franklin an Kejser Greenland. V:The central sequence,Kåp Graah Group and Grøn~; Franz Joseph Fjord in Zentral-Ostgronland. Meddr Mount Celsius Supergroup. MeddrGrønland i06(5), 118 pp. land 116(7), 126 pp. Nielsen' E. 1935: Thi: Permian~nd EotriMsic'vertebrate-bear­ Claek, J. A. in press: New Tetrapod material from the Upper . 'iog b~ds at Godthaab Gulf (East Gr~enlå-ndy. Meddr Grøn- Devonian of East Greenland. Palaeontology. land 98(1), 111 pp. . Friend, P. F.,Alexander-Marraek, P. D., Nicholsen, J. & Peel; J. S. & Yochelson, E. L. 1984:Permian Toxeomorpho­ Yeats,' A. K. 1976a: Devonian sediments of East Greenland. rida from Greenland: an appraisal of the molluscan class I: Introduetion, c1assificationof sequences, petrographie Xenoconchia. Lethaia 17, 211-221. , notes. Meddr Grønland 206(1), 56 pp. Stensi6, E. A. 1931: 'UpperDevonian vertebrates from East Friend, P. 'E, Alexander-Marrack, P. D., Nicholson, J. & Greenland eolleeted by the Danish Greeriland expeditions in, Yeats, A. K. 1976b: Devonian sediments of East Greenland. , 1929 ånd 1930. Meddr Grønland 86(1), 212 pp. II: Sedimentary structures and fossils. Meddr Grønland 206 Stensi6,E. A. 1936:0n the Plaeode~mi ofthe Upper Devo­ (2),91 pp, nian of East Greenland. Supplement to part I. Meddr Grøn­ Friend, P. E, Alexander-Marrack, P. D., Allen, K. C., Niehol­ land 97(2), 52 pp. son, J. & Yeats, A. K. 1983: Devonian sediments of East Warren; J. W. & Wakefield,N: A~ 1972: Trackwilys of tetra­ Greenland. VI: Review of results. Meddr Grønland 206(6), pod vertebrates from theUpper Devonian of Victoria, Aus­ 96 pp. tralia. Nature, Lond. 238, 469-470. Jarvik, E. A. V. 1952: On the fish-like tail in the ichthyostegid Yeats, A. K. & Friend, P. F. 1978: Devonian sediments of East stegoeephalians, with description of a new stegocephalian Greenland. IV: The western sequence, Kap Kolthoff Super­ and a new erossopterygian from the upper Devonian of East , group ofthe western areas. Meddr Grønland 206(4),112 pp. Greenland. Meddr Grønland 114(12), 90 pp.

S.E.B.-A.• J.A.C.. H.O.• Geologisk Museum. University Museum of Zoology, Grønlands Geologiske Undersøgelse. øs/er Voldgade 5-7. Downing 'Stree/, øs/er Voldgade 10, DK-1350 Copenhagen K, Cambridge CB2 3EJ, . DK-1350 Copenhagen K, Denmark. e ,U. K: Denmark.

Glacier velocities from aerial photographs in Noith and North~East Greenland .. ; ; ,A. K. Higgins

General descriptions of the of North and descriptions, however, provide little in the way of quim­ North-East Greenland have been givenby Koch (1928), titative data on ' velocities, although Davies & Krinsley canc1uded that a large number af glaciers and Davies & Krinsley (1962) and Weidick (1975). These,

Rapp, Grønlands geol. Unders. 140, 102-105 (1988) 103

56' 44' 20' 8' 250 km

1. Petermann Gletscher 11. Nioghalvfjerdsfjorden 2. Steensby Gletscher 12. Zachariæ Isstrøm 3. Ryder Gletscher D. Dijmphna Sund 4. C.H. Ostenfeld Gletscher F. Freuche~ Land 5. Jungersen Gletscher H: Hendrik ø 6. Hans Tavsen Iskappe HF. Hagen Fjord 7. Hunt Fjord ice shelt J. jtikelbugten 8. Academy Gletscher . N. NordenskitildFjord : ~ ", 9. Hagen Bræ . V. Victoria Fjord 10. Flade Isblink

, ':.

smal! ice caps in North Greenland exhibited stable con­ Washington Land and Hal! Lari~L" At.leastth~northern ditions, with a significant number showing evidence of 40 km ofthe glacier is afloat; a~dmatching ol surface recent retreat. Comparisons of vertical aerial photo­ features on aerial photographs from 1959 and 1978 dem­ graphs taken in 1959-63, 1971 and 1978 permit mea­ onstrate that the central.part ofthe glacier has moved l T surements ef glacier velocity to be made on floating ice km in 19 years, an average velocity of 895 m/year. tongues which have preserved a distinctive surface pat­ . The position of the, glacier te~ininus is reported to tern of meandering streams and . These show have had a fairly stable positionslnce 1876 (Koch, 1928; . the largest glaciers draining the Inland Ice in North and Davies & Krinsley, 1962), which indieates that large North-East .Greenland to have average velocities rang­ icebergs must regularly calve from the front arid escape ing from 300 to 900 mlyear. into Robeson Channel, where there is often open water This study of vertical aerial phot6graphs has also in the summer. demonstrated that for floating glacier tongues the posi­ tion of the is not areliable indicator of Steensby Gletscher (fig. 1: no. 2) drains intothe head of advance or retreat. In the of North Greenland Sankt George Fjord, betWeen Warming 'LaridandNye- . semi-permanent sea ice often maintains the integrity of boe Land. Itis 62.km long; and about 3.5 km wide at the advancing floating glacier fronts for periods of ten to front where it characteristicallybreaks up into several twenty years (Koch, 1928; Weidick, 1975); the break-up floating lobes separated by aggregates of small icebergs of the floating tongue in rare summers when the sea ice (Ahnert, 1963). Aerial photographs from 1963, 1971 melts completely may give the impression of a sudden and 1978 demonstratea velocity .of 430mfyear. Ah­ retreat, but this 'retreat' is unrelated to changes in the nert's estimate of an,annual advance of 5A to 8.7 km mass balance. was based on an incorrect assumption. The semi-perma­ nentsea ice has maintained the advancingfront of Petennann Gletscher (fig. 1: no. 1) isJlO km long and 15 Steensby Gletscher as an jntaet mass,and no large km wide at its front, and occupies a deep deft between icebergs drifted away from the frontbetween 1953 and 1978. 104 RyderGleischer.(fig.:I: no. 3) is more than 80 kmlong measured velocity determined from 1963 and1978 verti­ and drains northwards between Wulff Land and Perinin cal aerialphotographs is 350 mlyear. Land;' where it is8km.wide.Characteristic surfaee features on tliefrontal floating segment of· the. glaCier Hans Tavsen Iskappe (fig. 1: no. 6)'is an independent ice .demonstrate a movement olup to 8 km between.1963 cap about 70 km' across. Three small outlet glaciers and 1978,an average velocityof about 535 mlyear. draining into the fjord tothe west have measured veloc: Lauge Koch's observations in 1917 showedthe float­ ities 'of 40-70 mlyear, and a larger.glacierdraining' ingglacier otongue to extend il considerabledistance northwards 100 mlyear. A drilling operation was carried farther·north. than at present,into the'fjord between out on Hans Tavsen Iskappe durin~ the1975 Greenland Hendrik ø and Wulff Land (Koch, 1928). Davies & lce Sheet Prograrnme (Langwaye( al., 1985)~ Krinsley (1962) note that' this tongue had broken up prior to '1947, and that the positionof the glacier front Hunt Fjord ic~ shelj(fig.i: no. 7). Small ice shelves withdrew a further 5 km from 1947. to 1956. Between occurjn northe'm Peary Land, one of which completely .1971 and 1978 the front has advanced without drift of fills Hunt Fjord; a smaller ice sheifpartially blocks the significant icebergs away from the front. sound west o~ Hunt Fjord. These are the only ice Break-up and dispersal of tlie floating glaciertongue' shelves in NorthGreenland whichbear comparison with cldrly takes place only in rare summers when the sea the better known ice shelves'fringing northern Ellesm~ ice melts completely. Oblique aerial photographs from ere Island (Jeffries, 1987). Like them they appear to be 1953 show a collection oflarge icebergs off the front of very ancient features and exhiblt a comparable surface Ryder Gletscher, which in an ice-free summer prior to pattem of undulatlng ridgesand water-filled hollows. 1963 had drifted 15 to 45 km northwards to positions . However, the North Greenland ice shelves are ,clearly between Hendrik ø and WulffLand. These tabular fed by the' alpine glaciers in north Peary Land, and ic~bergs oCcupied virtuaIly unchanged positions o~ 1963 while they generally show little:.signof rnovement be- , and 1978 aerial photographs and in 1985 (personal ob­ tween1963 and 1978 aerial photographs; a glacier feed- . servations), showing the sea' ice had not melted com­ ing aportion'of the we!;t frqnt of Hunt Fjord ice shelf is pletely for ilt least 22 years. moving forward at 23 mlyear.

C. H. Ostenfeld Gletscher (fig. 1: no. 4). In May 1917 Acaderny Gletscher (fig. 1: no. 8). Eatly observationsof Lauge Koch encountered inthe outer part of Victoria the 10 km ',wide glacier at the head of Independence Fjord what he initially took tobe glacier ice from the Fjordiitdicate a floating frontal portion of hummocky , . floating,tongue of C. H.Ostenfeld Gletscher, butlater . ice and densely packed icebergs, extending about 12 km · concluded it mightbe old sea ice (Koch, 1928).,His first into the fjord (Peary, 1898; Freuchen, 1915;' Koch, impression. was correct, and as shown by Davies & 1928). This floating portion ofAcademy Gletscher had Krinsley (1962) the inner 75' km of Victoria Fjord is dispersed by 1956(Davies & Krinsley, 1962), and aerial tightly packed by large and small icebergs derived from. photographs from 1962 and 1978 show no ind~cation of' theglaciers at.the head of the fjord. The position ofthe . re-establishment: It is inferred that since the 1950sthe iceberg front is currently much the same as in 1917.. fjord ice hasmelted sufficiently frequently that floating Six largeglaciers merge at the head ofVictoria Fjord, segments of theglacierdisintegrate and disperse before, of which the mostimportant is C. H. Ostenfeld they canform substantial ice tongues. No velocitymea-" Gletscher; it is up to 7 km wide and has a more or less surements arepossibie on aerlal photographs bf. the' tonnected floating segmentprojecting for 25 km into .'. present crevassed frontal portiori.. .' Victoria .Fjord~ Velocity measurements .made Oll' tlie' '...... basis of aerial photographs from 1963, 1971·and 1978 . Hagen Bræ (fig. l: no. 9), at the'h~ad ofHa'ge~Fjord~ is · range from 750 to 815 mlyear. 1\\'0 glaciers west of C. .·75 km long andabout 10 km wide in its central part. H. Ostenfeld Gletscher are inactive, whereasthe three Towards the front the glacier'widens, and while the · glaciersto thi:: easihavevelocitiesof 400-550mlyear. .southem part is. partially dammed by two islands ·and breaks up, the northern part of the front con'tinues into JungersenGleischer(fig. 1: no. 5). This is not a large . the fjord as a floating segment 6 km wide and up to 18 · glacier filling Nordenskiold Fjord as depicted by Koch km long. Davies & Krinsiey (1962)describe the floating. (1928), but as shown onmodem maps it is a relatively glacier tongue as stagnant with a surface of interlacing small glacier 2.5 kmwidc: draining from the Inland lce streams and large interconnecting ponds in parallel .south ofFreuchen Land into the head of the fjord. The troughs. Aerial photographs from 1960 and 1978 show 105 ' that Acådemy Gletscher wlth itsfloatingfront is moving scribed by Koch & Wegener (1911) as 'Dasschwini­ outwards at 540 m1year. Large tabular icebergs up to 5 mende Indlan<,leisder Jokelbugt';andwas classified by km'by 2 km in size, whichformed the front ofthe glacier Koch (1928) as 'confluenHce!; The floating glacierice tongue in 1960, had broken free and drifted up to 45 km cover a region 100 km from north to south and·amaxi­ towards the,outerpart of Hagen Fjord by 1978. mum of 50 km from east to west. Zachariæ Isstrøm has a minimum width of 20 km, and Flade Isblink (fig. l:'no. 10). Northern Kronprins Chris­ the central active stream has a velocity estimated from tian Land supportsa large' independent , Flade, 1963 and 1978verticalaeIial photographs to be at least Isblink. It is more than 100 km long and tip to 75 kJn 470 m1year. The northern part of the floating glacier ice wide but has orilya,'few outlet glaciers which reach the .is a single intact mass whose outward expansion is hin­ sea, the most important being that east of Station Nord dered by large andsmall islands. Between the islands , where' a floating glacier up to 25 km broad extends ,narrow tonguesof.shelf ice up to 15 km Iong move northwards into the sea for up to ,15 km. The eastern out\yards at 220-280 mlyear. The southern area of float­ lobe ofthis floating glacier moves at 175 in annuaIly and ing glacier ice ftllingJokelbugten comprises tightly the western lobe at 360 m annuaIly. There was no signif­ packed, broken, tabular icebergs. Movement ofindivid­ icant loss from the advaricing front between 1961 and' ual icebergs varies from 66 m to 600 m1year averaged 1978, although extensive open water .leads were ad­ over 15 years, the rate of movement being clearly re­ jacent to the front on the 1978 aerial photographs. lated to the damming effect ofislands, and large ice­ bergs trapped between islands. Nioghalvfjerdsfjorden (fig. 1: no. 11). The interiorof Nioghalvfjerdsfjorden is filled by an extensive floating ,gIacier tongue, of which a northern branch projects into References Dijmphna Sund west of Hovgaard ø. The main glacier is 60 km l~ng and, 18 km wide at its narrowest point; It Ahnert, F. 1963: The terminal disintegration of ,Steensby, widens eastwards arid the outer 30 km segment is afloat. Gletscher, North GreenJand. J. Glaciol. 4,537-545. regime~ A prominent system of undulating ridges andhollows; Davies, W. E. & Krinsley, D. B, 1962:The recent of· first ~escribed by'Koch & Wegener (1911), is developed the ice cap margin in' North Greenland. Publs int. Ass: Scient. Hydrol. 58, 119-~30., on the surface of the floating glacier. Freuchen, P. 1915: General observations as to natural candi­ The velocity of parts of the main glacier have beeri tions in thI': country traversed by,' the, expedition. Meddr measuredfrom 1962 and 1978 aerial photographs at Grønland 51(9), 361-369.' ,. 310-330 m1year. The main floatingfront of the glacier i_n Jeffries; M. O: 1987: The growth, structuie aIid disintegraticlIi Nioghalvfjerdsfjorden abuts against a series of small of Arctic ice shelves.PolarBec. 23, 631-649. islands. On the riorthside of the' fjord movements of Koch, J. P. & Wegener, A. 1911: Die gIaciologischen Beobach­ only 35~0 m1year have been measured, whereas on the, tungen'der Danmark-Expeditionen: Meddr Grønland 46(1), south side of the fjord tongues ofice projecting between 1-77. . islands move seawards at rates of up to 160 mlyear. The Koch, L. 1928: Contributions to ,the' of North branch of th!': glacier moving north into Dijmphna Sund Greenland.Meddr Grønland 65(2), 181-464. has anaverage velocity o.f 210-230 mlyear. ' Langway, C. C., Jr., Oeschger, H. & Dansgaard, W. 1985: The Greenland Program in perspective. Monogr. Arner. geophys. Un: 33, 1~., .'. (fig~ Zachariæ Isstrøm!Jokelbugten 1: no. 12). The Peary, R. A. 1898: Northward over the 'Great læ', 521 & 625 . largest area of floating glacier ice in Greenland isthat pp. New York: F. A. Stokes. tilling Jokelbugten, which emanates from Zachariæ Iss­ Weidick, A.1975: A review of Quatemaryinvestigations in trøm~ This area of ice-covered sea wasinitially de- Greenland. lnst. Polat Stud. Rep. 55, 161 pp.