Black Rapids Glacier, a surge-type glacier in the Alaska Range, most recently surged in 1936–37 and is currently in its quiescent phase. Mass balance, ice velocity and thickness change have been measured at three to ten sites from 1972 to 1994. The annual speed has undergone cyclical fluctuations of as much as 45% about the mean speed. Ice thickness and surface slope did not change enough to cause the speed fluctuations through changes in ice deformation, which indicates that they are being drinven by changes in basal motion. The behavior of Black Rapids Glacier during this quiescent phase is significantly different from that of Variegated Glacier, another well-studied surge-type glacier in Alaska. The present medial-moraine configuration of Black Rapids Glacier indicates that a surge could occur at any time. However, ice velocity data indicate that the next surge may not be imminent. We belive that there is little chance that the next surge will cross and dam the Delta River.

Estimates of internal accumulation for five Alaskan glaciers in different climates suggests that internal accumulation occurs in glaciers throughout Alaska. A method of estimating the quantity of internal accumulation is based on the annual minimum temperature ?Γ the snow-firn interface. The consistency of the estimates suggests that valid approximations of internal accumulation can be made over large areas. The estimates have not been confirmed by measurements of mass change, but are believed to be accurate within 10 percent. Point balance quantities of internal accumulation range from 0.65 m a-1, which is 64% of the annual accumulation on McCall Glacier, to 0.12 m a-1, 7% of the annual accumulation on Wolverine Glacier. The amount of internal accumulation decreases rapidly from north to south in Alaska; however it should be expected worldwide where sub-freezing, porous firn is invaded by water.Internal accumulation occurs in temperate glaciers in strongly maritime climates as well as glaciers in cold continental climates where it delays the onset of runoff, accelerates the process of converting snow into glacier ice, and explains the occurrence of temperate glaciers in permafrost areas.

Hubbard Glacier, the largest tide-water glacier in North America, has advanced since it was first mapped in 1895 by moving a protective submarine moraine into the entrance of Russell Fiord. In May 1986, a weak surge of the Valerie tributary of Hubbard Glacier caused the glacier to block the fiord entrance, converting the body of water into a large glacier-dammed lake. This lake filled to a height of 25.5 m and stored 5.4 km3 of water before it burst out on 8 October 1986, producing a peak flow of 105 000 m3 s−1 averaged for 1 h.Hubbard Glacier is expected to continue advancing because its accumulation area ratio (AAR) is 0.95, which is unusually large. Such an advance would undoubtedly block Russell Fiord again. If this happens, it is predicted that the lake will fill to a height of 39 m over a period of 1.1–1.5 years and then overflow into the Situk River near Yakutat. This, in turn, would increase the average flow of that small stream from ils present rate of between 10 and 15 ms−1 to an estimated annual average discharge of 230 m s−1. Such an increase in flow would be expected to flood and erode forest lands, fish habitats, subsistence fishing camps, archaeological sites, and roads. At the same time, the increased water depth in Russell Fiord could be expected to increase the calving rate of Hubbard Glacier, potentially threatening the stability of its calving terminus.

ABSTRACT. M ass-ba la n ce quantities at spec ific points on a glacier as d e fin ed in [IHD] ( 1970) relate either to a nnua l maxim a or minim a in ice m ass a t th a t point (the stratigraphic system), or to va lues at the beginn ing and end of a h ydro logic yea r (the annual or fixed-date .rystem ). M os t quantiti es meas ured in th e fi eld relate to summer surfa ces, whi ch correspond to the annua l minima at th e m easurement points. vVh en stratigraph ic system point va lu es a re integ rated over a wh ole gla cier, th e resu lt may be m ea ningl ess because annua l maxim a a nd minima and summ er su rfaces may fo rm at d ifferent tim es a t d ifferent places.The co mb ined system utilizes several kinds of data to d eri ve mea ningful area-a ve rage results tha t ca n be directl y rel a ted to other h ydrologic and m eteorologic info rmatio n. M ea surem ents to summer surfaces a t certa in specifi c times, including the beginning a nd end of a hydrologic year, a re a dd ed togethe r w ith proper recognition of the typ es of m a teria l in vol ved: old firn a nd ice, snow a nd superimposed ice of th e year under study. new firn form ed during tha t year , a nd late snow d eposited towa rd th e end of th e year. Other " ba la nce increm ent" te rms rela te va lues a t the b eginning a nd end of a h ydro logic yea r to corresponding a rea-average ba lan ce minim a . As a resu lt, two types of "net ba lan ce" and man y o th er terms a rc g ive n precise m eaning for a gl acier as a whole. Th e sch em e is sufficiently versa til e to be u sed on a n y g la cier, a lthough th e terms relating to summer surfaces are not d efin ed on a gl acier in which a blatio n or accumulatio n is contin uous throughout a yea r. R ESUME. V ne methode pour combiner les metltodes stratigraphiques et allllllelles d'estimation des bilans glaciaires :line contribution a la Decennie Hy drologique i ntematiollalc. L es b il a ns m a ti ere en d es po ints representatifs sur un gl ac ier , tel s que defin is p a r le d ocument [ IHD] ( 1970) sont eta blis soit a p a rtir d es maxim a e t minim a a nnu els en ce point (m ethode stratigraphique), so it a partir d es va leurs a u d e but e t a la fin d e l'a nn ee h ydrologique (me th ode a nnuell e ou a date fix e) . L a plupart d es va leurs m esurees sur le terrain se ra pportent a d es surfaces d 'ete qui correspond ent a ux minima a nnucl s a ux points d e mes ure. Lorsqu e les va leurs po nctu ell es d e la m ethod e stra tigraphique so nt integrees sur tout un glacier , le r esultat peut c tre d e pourvu de signifi catio n pa rce q u e les minim a e t m axim a a nnuels et les surfaces d 'e te p eu vent se former a diff<' rentes epoques d a ns les differents endroits.La m e th od e combin ee utilise plusieurs sOl'tes d e d onnees pour o btenir d es r esulta ts signifi ca tifs en m oyenn e p a r unite d e surface qui p euvent etre direc tem en t comparces a ux a utres informa tions hydrologiques e t m eteorologiques . Des m esures d e surfaces d 'e te a certaines epoques d e t...

This report presents 23 years (1970 to 1992) of observations of Black Rapids Glacier, Alaska. Black Rapids Glacier is a surge-type glacier which most recently surged in 1936-37 and is currently in its quiescent phase. This glacier is of special interest because it is a potential hazard to the trans-Alaska oil pipeline. Ten sites on the glacier were monitored from 1972 to 1987, and three sites were monitored from 1988 to 1992. The measurement program presented here includes observations of surface mass balance, ice velocity, and surface altitude made twice each year. Additional one-time data include observations of ice thickness, previously unreported observations of the 1936-37 surge, establishment of the geodetic control monuments, and a new map of Black Rapids Glacier.