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On Mertz and Ninnis Glaciers, East Antarctica

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On Mertz and Ninnis Glaciers, East Antarctica J ournal oJ GLaciology, VoL. 42, No . 142, 1996 On Mertz and Ninnis Glaciers, East Antarctica GERD WENDLER, KRlSTINA AHL:\fAs AND CRAIG S. LH\CLE Geophysical Institute, Unive rsity aJ Alaska- Fairbanks, Fairbanks, Alaska 99775-7320, U.S.A. ABSTRACT. Two large glacier tongues, which extend substa ntiall y across the coastline of King G eorge V Land in Eas t Antarctica, ha\'e been studied by remote sensing (sy nthetic aperture radar, JERS-I ). The to ngue of Mertz G lacier is in a state of advance, wh ile the Ninnis Glacier tongue is retreating. Some mo re speci fi c points are: The distin ctive surface structure a nd th e form of the glacier tongues indicates th a t they are Ooating. While th e tongue o f Ninnis G lacier has lost abo u t two-thirds of its a rea since 191 3, the M ertz Glacier tongue has ad vanced subs ta n tia ll y and has a bo u t doubled its areal ex tent over the sa me time p eriod. The annual movement of th e tong ue of ~Vl e rl Z G lacier was determined as about 1.2 km. This is close to th e value of the advance o f the tip of the tong ue since 1963, which was determined as 0.9 km year- I. INTRODUCTION the freq uency and in tensi ty of th e ka tabatic winds whi ch occ u r in th is area. H e gave a popular accoul1l in his book M ertz and Ninnis G laciers are located in Ki ng George V entitled The /taill e oJ the blizzard (M awson, 191 5). The Land, Eas t An tarctica (Fi g. 1). They are prominen t winds he experi enced - m ean annual speed of 19. 6 m s I features ; th e tongue of M ertz Gl acier, presently the la rger - are the stronges t found anywhere on pl a net Earth close of the two, ex tends a bou t 95 km into the ocean and has a n to sea le ve l. His da ta were doubted b ut more recent average width of a bo ut 40 km . This a rea of Antarctica obse rva ti o ns with au tom atic stations, which reco rd over was first explored by Sir Douglas ~1 awso n during his satellite , have co nfirmed hi s findin gs (Stearns a nd heroic trip between 19 11 and 19 14. M awson es tablished Wendler, 1988). his main cam p a t Cape Den iso n (67.02° S, 142.68° E ) in Cape D eniso n is located close to the South ~I agne ti c Commonwealth Bay. H e and hi s team were surprised by Pole a nd durin g the summer of 1912- 13 two trips were 1400 E 1450 E 150· E Fig. 1. Area map oJ King GeOlge V Land, East Antarctica. Downloaded from https://www.cambridge.org/core. 30 Sep 2021 at 01:01:56, subject to the Cambridge Core terms of use. 447 Joumal of Glaciology made towards the eas t. " The eastern coastal party" was resolution of 240 m. U nlike satellite im agery that is under the leadership of C. T. M agid an. H e and hi s two d epend ent on radiation of the \'isible or thermal IR companions went by foot from Cape Denison pulling a range in which the surface can be seen on ly in the absence heavy sled. They crossed the tongue of M ertz Glacier, of clouds, radar images are unaffected by weather and which was difficult because of many crevasses. At the darkness. SAR is therefore suitable for use in the polar point of their crossin g, which was relatively close to th e regions during winter and in regions characterized by coastline, they found a maximum eb'ation of 53 m. This hea"y cloud cover. altitude is in good agreem ent with later measurements. Velocity measurements were made using the ASF The Australian map (SQ55-56) of this area, which was Interactive Image Analysis System (IIAS) , which iss ued in 19 71 and based on data from 1961- 62, gave a provides network access to the Arctic Data Visualization maxim u m al ti tude of 49 m for the same general area. and Analysis L aboratory (ADV AL) and the Arctic After crossing l\IIertz Glacier, they co ntinued over the sea R egion Supercomputing Center (ARSC). Image-proces­ ice a nd crossed the tongue of Ninnis Glacier, where they sing software on the IIAS incl udes the Land Analysis determined a maximum elevation of 55 m. Then they System (LAS), International Imaging System's (IIS) we nt on further to explore the coastal region east of System 600 , PCI and Khoros. Ninnis Glacier and eventua ll y returned to Cape Deniso n. During their trip, they ran low on food and supplemented their supplies with penguins, whi ch are plentiful in this LONG-TERM CHANGES area; they reported them to taste quite good . The second party to the east, but a t a more inland ?\IIawson's team was th e first group to map the King course, was "the far eastern party" under the leadership George V Land coas t, using measurements obtained of M awson. His two compa nions were Dr X. l\IIertz and between 1911 a nd 1914. The general outline of the Lieut. B. E. S. Ninnis. They crossed Mertz G lacier further tongues of Mertz and Ninnis Glaciers is included in his inland a nd also reported very crevassed a reas. After map (Mawson, 19 15, p. 240 ). The Australians published having crossed Ninnis G lacier, in an area about 150 km to maps on a scale of I : I 000000 of this area in 197 1 (SR55- the east, Ninnis and his dog team met th eir deaths in a 56) and in 1974 (SQ55-56) (Australia 1971, 1974) based large crevasse. This was even more tragic as his sled on observations carried ou t in 1961 and 1962. In 1993, carried most of the food supply, whi ch they were unable SAR imagery of this area was acquired by JERS-l. to retrieve. The trip home was a race against starvation; Figure 2 shows the outlines of the glacier tongues from all Mertz perished and Mawson himself barely survi\·ed . three sou rces. Table I shows the areas of the glac ier lvIawson named these two glaciers a ft er hi s fallen tongues sea ward of the coastline. com rades . In the case of Mertz Glacier, the size of the tongue has increased substa ntially during this century. Tt has more th an doubled its size, from a bout 3830km2 in 1913 to SA TELLITE IMAGES about 8100 km2 at present. During the earli er p a rt of this century, the glacier tongue m ostly broadened but, sin ce The Alaska SAR Fac ility (ASF), which is operated under 1962, the glacier tongue has advanced abou t 26 km or contract with NASA by the Geophysical Institute, about 0.9 km. year I . University of Alaska- Fairbanks, is the only satellite sy nthetic aperture radar (SAR) receiving station in th e United States. Data from the first and second European Remote Sensing Satellites (ERS-I and ERS-2) and from the J apanese SAR satellite UERS-I ) are received and processed here. ERS-I and 2 do not have on-board tape recorders, so SAR image d ata mu st be d own-linked in real time to a receiving antenna that is "visi ble" to the 67 S~-----'~~----rT--~~--.~.,----~•• ~-------- ~ satellites; that is, th e satelli tes ca n acq uire data only within the station masks of the receiving anten nas. JERS- l has a n on-board tape record er and can therefore acquire SAR data worldwide, which are then down­ linked when the satellite is within a station mas k. Our area of interest was not within the sta tion mask of any ground station for ERS- I and 2, alth ough it is now within ~ S~--------------r-------~+L--~~~~----~ the station mask of the recently operational ~vI cMu rd o antenna . (Also, a receiving station is now under King George V Land construction at Hobart, Tasmania.) The SAR data employed in this study were acquired ove r E ast Antarctica by JERS-I ; the data were su bseq uen tly down-linked and processed at ASF. The SAR on board JERS- I is L-band (1.27 GHz; wavelength = 0.235 m ) 144' E 146' E 148 0 E and has a swath width of 75 km , a pixel spacing of 12.5 m in full resolution a nd a resolution of 30 m. Low­ Fig . 2. The positions of the N/ertz and Ainnis Glacier reso lu tion im ages have a pixel spacing of 100111 and a tongues in 1912- J3, 1962 and 1993. Downloaded448 from https://www.cambridge.org/core. 30 Sep 2021 at 01:01:56, subject to the Cambridge Core terms of use. Wendler and others : On NJert;;. and JVinnis Glaciers, East Antarctica Table 1. Areas of Mert;;. and Ni1lnis Glacier tongues in dumping it over the cres t on to the proglacial sid e in the 1913, 1962 and 1993 style of a bulldozer . This process can graduall y ad,·ance the terminus out over the length of a rela ti,·ely d eep fjord on a tim e-scale of the order of 1000 years (Meier a nd P ost, 1913 1962 1993 198 7); i.
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