ABSTRACT. Oxygen-isotope a nd chl ori nity d eterminations, as wel l as petrographic observations, indicate that the basement ice of the Ward Hunt I ce Shelf is largely composed of a unique brackish ice, w hi ch interdigitates with sea ice. Some iced firn occurs near the top of the basement ice, below an unconformi ty.Stratifica tion in brackish a nd sea ice represents ann ua l increments to the bottom o f the ice shelf. The c-axis vertical ori enta tio n and small-angle g rain-bounda r y relations in brackish ice a re explained by nucleation and fl oa ting of ice d endrites from the undercooled brackish water zone to the bottom of th e ice shelf, where they attach themselves sub-pa ra ll el to the plane of the undersurface.I ce isla nd T-3 did not come from a break-up of the main pa rt of the "~Yard Hunt I ce Shelf but probably origin a ted in a nearby a rea to the west. RESUME.
Analysis of glaciologial data indicates that grounding of the Ward Hunt Ice Shelf and its conversion into an ice rise was primarily the result of local thickening of a floating ice shelf and the availability of a very gently sloping sea floor on which the ice shelf came to rest. Application of heat conduction theory to a series of thermal profiles through the Ward Hunt Ice Shelf, and the Ward Hunt, Camp Creek and Cape Discovery ice rises shows that present heat flow in this area of northern Ellesmere Island is more than twice normal, and that the outer and intermediate parts of the Ward Hunt ice rise grounded 250–350 years ago, during a cycle of climatic deterioration. Development and localization of ice rises along northern Ellesmere Island are strongly influenced by topography, and all ice rises we have studied seem to have formed within the past 1 600 years, possibly with major growth in the interval from 1 000 to 150 years ago.
ABSTRACT. Analysis of glaciological data indicates that grounding o f th e Ward Hunt Ice Shelf a nd its conve rsion into a n ice rise was primarily the result of local thicken ing of a floating ice shelf a nd the availability of a very gently sloping sea floor on which the ice shelf cam e to rest. Application of heat cond uc tion theory to a series of thermal profiles through the Ward Hunt I ce Shelf, a nd the '''la rd Hunt, Ca mp Creek and Cape Discovery ice rises sh ows that present heat flow in this area of north ern Ell esmere Isla nd is m ore than twice norma l, and th a t the outer and intermediate parts of the ' <\lard Hunt ice rise grounded years a go, during a cycle of climatic deterioration. D evelopment and locali zat io n of ice rises a long northern Ell esm ere I sland a re strongl y influenced by topogra ph y, and all ice ri ses we ha ve studi ed seem LO have fonn ed within th e past 1 600 yea rs, possibl y with m ajor growth in the interva l from 1 000 10 150 years ago.R ESUME. gegenwartige W a rmefluss in diesem Gebiet cl es norclwes tIi chen Ellesm e re Isla nd m ehr als doppelt so sta rk ist wie norma l und dass die a usseren unci mittl eren Teile d er ' <\la rd Hunt Eiskuppel vor 250-350 J a hren wah rend ein er Pe riod e der Klima ve rsc hlechterung a uf Grund gerieten. Die Eiskuppel entl a ng dem norclwestli che n Ellesmere Isla nd sind in ihrer Entstehung und L age stark durch di e Topographic beeinflusst; a ll e untersucht cn Eiskuppel schein en sich in d en letzte n 1 600 J a hren gebildet zu haben, moglicherweise mit einer H a uptwachstumsperiode in d er Zeit zwischen 1 000 und 150 J a hre n vor der Gegenwart. I NTROD UCTlO 1The Ward Hunt I ce Shelf of northern Ell esmere Island (Fig. I) is a 500 km 2 sheet of Roating ice, 43 m in average thi ckn ess . Its uniqu e topograph y is marked by a success ion of east-west ridges and troughs, 230 a nd 55 m respectively in average width, and several kilometers in average length. DUl-ing the m elt season th e troughs become m elt-water lakes, with water d epths Ructuating between 3 and 1.5 m. Massive ca lving in 1962 has resulted in the loss of approximately half the original ice-sh elf area (Hattersley-Smith, 1963) . Radio echo so unding (Evans and oth ers, 1969) suggests that thi cknesses of the ice shelf m ay vary between 20 and 85 m, which is a more ex treme Ructuation than that detected by seismic 43
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