The thickness of Lemon Creek Glacier, Alaska, as determined by gravity measurements

Thiel, Edward; LaChapelle, E.; Behrendt, John C.

doi:10.1029/tr038i005p00745

Cited by 19 publications

(25 citation statements)

References 4 publications

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“…As determined by geophysical means the greatest ice depth here exceeds 200 m at a position about 5 km up-glacier from the icefall ( Fig. 4) (Thiel et al 1957;Miller 1972).…”

Section: Introductionmentioning

confidence: 69%

Mass Balance Measurements on the Lemon Creek Glacier, Juneau Icefield, Alaska 1953-1998

Miller¹,

Pelto²

1999

Geografiska Annaler A

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Annual balance measurements on the Lemon Creek Glacier, Alaska conducted by the Juneau Icefield Research Program (JIRP) from 1953 through 1998 provide a continuous 46year record. This is one of the nine American glaciers selected in a global monitoring network during the International Geophysical year, 1957/58. These data have been acquired primarily by employing consistent ground methods, conducted on similar annual dates and calculated using comparable methodology. The results have been until now fairly precise, but of uncertain accuracy. An adjunct comparison of topographic surface maps of the glacier made in 1957 and 32 years later in 1989 provides a rough determination of glacier surface elevation changes which are clearly of less precision than the compilation of annual ground data. Airborne surface profiling in 1995, and global positioning system leveling transects in 1996-1998 update the record of surface elevation changes over the past decade. The mean glacier ice thickness reductions suggested by these methods from 1957-1989, from 1957-1995 and from 1957-1998 are -13.2 m, -16.4 m, and -21.7 m, respectively. It is of interest that the geodetic interpretations agree fairly well with the trend of sequential balances from ground-level stratigraphic measurements. To date, however, the infrequent mapping methods in this study have yielded specific balances averaging between 5 and 11% less than those resulting from our annual on-site glaciological monitoring. For future studies this can be an important factor. The ground data are, therefore, the ones in which we have most confidence. These show cumulative ice losses of -13.9 m (12.7 m water equivalent w.e.) from 1957-1989, of -19.0 m (-17.1 m w.e.) from 1957-1995, of -24.4 m (22 m w.e.) from 1957-1998, and -24.7 m (22.2 m w.e.) for the total cumulative loss over the full 46 years between 1953 and 1998. Although the balance trend has been increasingly negative it averages -0.48 m/a in w.e. or 0.52 m of ice loss per year.To refine the reliability of density determinations in this data set the effects of internal accumulation from refrozen meltwater producing diagenetic ice structures in the annual firnpack have been taken into account. An unusual dearth of such structures within the 1997/98 firnpack provided a unique opportunity to facilitate application of the probing technique over broad areas of the névé. This added to our ground truth and verified accuracy of the test-pit measurements used in these long-term mass balance computations.The glacier's continuing negative mass balance has fueled a terminal retreat of 800 m during the 1953-1998 period. The annual balance trend indicates that despite a higher mean elevation and a higher elevation terminus from thinning and retreat, mean annual balance has been strongly negative since 1977 (-0.78 m/a w.e.). Dramatically increased negative mass balances have occurred in the 1990s, with 1996 and 1997 being the only years on record with no retained accumulation since field observations were initiated in the glacier s...

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“…As determined by geophysical means the greatest ice depth here exceeds 200 m at a position about 5 km up-glacier from the icefall ( Fig. 4) (Thiel et al 1957;Miller 1972).…”

Section: Introductionmentioning

confidence: 69%

Mass Balance Measurements on the Lemon Creek Glacier, Juneau Icefield, Alaska 1953-1998

Miller¹,

Pelto²

1999

Geografiska Annaler A

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“…Detailed geological information is always lacking and because of this, estimates of the “regional” gravity field arising from bedrock density variations, are quite conjectural. These and other difficulties are acknowledged by authors engaged in ice thickness interpretation; Littlewood (1952), Bull and Hardy (1956), Thiel and others (1957), Russell and others (1960), Weber (1961) and Hyndman (Koerner and others, 1963, p. 71–72).…”

Section: Interpretation Of the Gravity Datamentioning

confidence: 99%

A Gravity Survey of the Melville Island Ice Caps

Spector¹

1966

J. Glaciol.

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ABSTRACT. A gravity survey was made in June o f 1963 of four ice caps on western M e lv ille Island, Ca nadia n A rct ic Archipelago. I ce thicknesses were interpreted from Bou g u e r anomalies at 138 stations. Th e regional g ravity fi eld of the area has a simple form and is associaled with a uniform bedrock geology. Because of this, the inte rpretation of th e g rav ity d ata was g rea tly simplifi ed in compa rison with th e more usual glaciologica l problem. It was found that greatest ice thi ckn esses ranged from 30 to 50 m., fillin g hidden valleys or d epressions under th e main ice-cap bod y. I ce-cap vo lumes ranged from 0·2 to 1·0 km .l. REsUME. L eve gravimitrique des ca/olles de_glace de l'!le de M e/ville. Un leve g ravimetrique a ete effectue en juin 1963 des quatre calottes d e g lace de I'I le de Melvill e ouest, Archipe l A rc tiqu e Canadien . L 'e pa isse ur de la g lace a e te d ed uite des a nomalies d e Bouguer en 138 stations. Le champ d e gravite regional d e la zo ne e tudiee a un e form e simple et il es t assoc ie it la geo log ie uniforme du socle roc he ux. Ainsi , l' inte rpre tation d es m esures gravimetriques a ete g rand e m e nt simplifiee e n compa ra ison d es probl emes glacio log iqu es courants. II a ete trouve que la plus grande epa isseur de glace se tena it entre 30 e t 50 m , rem plissant d es vallees et d epressions cachees so us I'e nsembl e de la ca lolte d e g lace. L es volumes d es calottes de glace sont compris entre 0,2 et 1,0 km l .ZUSAMMENFASS NG . SchweremessllIIOen azif den Eiska/J/Jen von M elville Island. I m J uni 1963 wu rde n Schwerem essunge n a uf vie r Eiskappen im westli chen Melv ill e I sla nd , Ka nadi sche r Arktis-Archipel, durchgeflihrt. Dic Eisdicke wurde a us Boug uer-An oma li en a n 138 Statio nen abgeleite t. D as reg iona le Schwe rkra ftfeld hat e infache F orm , herrlihrcnd vom g le ichfiirmigen geo log ischen Aufbau des U nl ergrundes. D esha lb vereinfachte si ch im V ergleich ZlI dem so nst vorli egenden g laz io logischen Pro b le m di e Interpretatio n d er Schwerkraftwerte we itge he nd . Als griisste E isdic ken wurd en W erte zw ischen 30 und 50 m gefunden ; sie treten auf liber T a lern oder V erti efun gen, di e si ch unter d er H a uptm asse der Eiskappe n verberge n. Das Vo lumen d er Eiskappen li eg t zwisehen 0 , 2 und 1, 0 km l . THE GRAVITY S URVEYTh e general loca tion of the ice caps is shown in Figure I ; they are d esignated as "North ", " W est", "Eas t" and "South " ice cap according to th eir rela tive positions. Approximately ellipti cal in shape, the ice caps lie on the dissected plateau which is th e prin cipal topographic form of west Melvill e Isla nd. Th e ice caps range in a rea fr om 15 to 55 km.' and li e at an average eleva tion of 550 m.The objectives of the gravity survey, performed inJune 1963, w er e to find the gen eral form of the ice bodies and to determine the locations of greatest ice thickn ess, su itable for a future bore hol e for glacio logical a nd h ea t-flow studi es . Th e survey was...

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“…The adopted ice thicknesses at the glaciological stations are given in Table III and * For the calculation of the anomalies given by the models, the m e thod of Hubbert ( 1948) was used. This method has been used by Thiel and others ( 1957) on a glacier in Alaska. The programming of this method has been carried out by Talwani and others (1959) for an IBM 650 computer and by Chevalier ( 1963) for the CAB 500 computer used for this study.…”

Section: Gravity Measurementsmentioning

confidence: 99%

Ice-Flow and Thickness Measurements in the Sør-Rondane, Dronning Maud Land, Antarctica

Autenboer¹,

Blaiklock²

1966

J. Glaciol.

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Velocity and ice-thickness profiles were measured un the western glaciers of the Sør-Rondane during the Expéditions Antarctiques Belges of 1959 and 1960 Some of the stations were re-occupied for velocity measurements during the Expédition Antarctique Belgo-Néerlandaise, Campagne d’Été 1964–65.The profiles, with stations at 1 mile. (1.6 km.) intervals, were generally east-west and at right-angles to the direction of flow of the plateau outlet glaciers. The movement was measured by resection of each station from the main triangulation points over periods ranging from 256 to 1,501 days. Double ties with a Worden geodetic-type gravity meter were measured between the stations. An additional gravity station was occupied on rock at each end of the profile. The ice thickness and the subglacial topography are calculated from the gravity profiles. Combined with the surface velocity, they allow an estimate of the discharge of the glacier. The results indicate a close relationship between the glacier flow and the supply from the Antarctic Ice Sheet, as demonstrated by a study of the aerial photographs.

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The thickness of Lemon Creek Glacier, Alaska, as determined by gravity measurements

Cited by 19 publications

References 4 publications

Mass Balance Measurements on the Lemon Creek Glacier, Juneau Icefield, Alaska 1953-1998

Mass Balance Measurements on the Lemon Creek Glacier, Juneau Icefield, Alaska 1953-1998

A Gravity Survey of the Melville Island Ice Caps

Ice-Flow and Thickness Measurements in the Sør-Rondane, Dronning Maud Land, Antarctica

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