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World Glacier Inventory — Inventaire mondial des Glaciers (Proceedings of the Riederalp Workshop, September 1978; Actes de l'Atelier de Riederalp, septembre 1978): IAHS-AISH Publ. no. 126, 1980. A preliminary inventory of Alaskan glaciers A. Post and M. F. Meier Abstract. The total area of glaciers in the twelve main mountain systems of Alaska is estimated to be 74 700 km 2 . A total of 1001 glaciers (723 km 2 ) were measured in a glacier inventory of the Brooks Range. Un inventaire préliminaire des glaciers de l'Alaska Résumé. La superficie totale des glaciers des douze principaux systèmes montagneux de l'Alaska est estimée à 74 700 km 2 . Dans le cadre d'un inventaire des glaciers du Brooks Range, on a mesuré un nombre total de 1001 glaciers (723 km 2 ). AN APPROXIMATE ASSESSMENT OF TOTAL GLACIER AREA The area of glaciers in individual mountain massifs was measured by correcting the glacier outlines on 1:250 000 scale maps using recent aerial photographs, drawing closed curves so that the glacier area outside the curve roughly equalled the non-glacial area within the curve, then integrating the area using a planimeter. This method could not be used for the Seward Peninsula or the Kilbuk-Wood River Mountains because of inadequate maps and photographs; a more complete inventory was performed for the Brooks Range. The results were summed for the twelve main mountain systems in Alaska (Table 1); the total area is about 74 700 km 2 . TABLE 1. North West Southwest Interior South-central Southeast Approximate area of glaciers in Alaska [km 2 ] Brooks Range Seward Peninsula Kilbuk-Wood River Mtns Aleutian Islands Alaska Peninsula Alaska Range Talkeetna Mtns WrangeE Mtns Kenai Mtns Chugach Mtns St Elias Mtns Coast Mtns Total 723 ~3 ~230 960 1250 13 900 800 8 300 4 600 21600 11800 10 500 74 700 km 2 Areas of glacier ice within drainage basins can also be measured, but subjective interpretation of ice divide locations is involved. A complete, glacier-by-glacier inventory in some regions will be very difficult, but not just because of the large numbers of glaciers. Some glaciers span political boundaries or drainage basin divides. Most of the larger glaciers are bounded in part by obscure or constantly changing ice divides, making objective assessment difficult. A particularly extreme example is Bering Glacier: it is in and between two countries (USA, Canada), two major drainages 45 46 A. Post and M. F. Meier (Pacific, Chitina-Copper), and two major mountain ranges, (Chugach and St Elias Mountains). Furthermore, the main glacier drainage system has at least five differently named component areas (Stellar, Bering, Columbus, Quintino Sella Glaciers and Bagley Ice Field), and estimates of its total area range from 1740 to 6200 km 2 depending on how the 'Bering Glacier' is defined (Table 2). TABLE 2. What is the area of Bering Glacier? [km2 ] 'Bering Glacier' part of piedmont lobe Piedmont lobe (mostly ablation area) Ice drainage to piedmont lobe 'Bering Glacier' and 'Bagley Ice Field' system Frequently published value * Includes 490 km 2 in Canada. Total area is only approximate location of ice divides is very uncertain. f Preferred value. 1740 2800 5000*f 6200* 5800* as the INVENTORY OF THE GLACIERS OF THE BROOKS RANGE A glacier-by-glacier inventory of the Brooks Range was performed using preliminary copies of topographic maps of 1:63 350 scale, with glacier margins checked or reinterpreted by comparison with aerial photographs. In this study, 1001 glaciers were identified and measured, and additional small ones may have been missed. The exposed ice area is 647 km2 and a total area (exposed plus moraine-covered ice) is 723 km 2 . Individual glaciers range in area from 0.03 km 2 to 16.8 km 2 , with a mean area of 7.23 km 2 . The amount of glacierized area increases from west to east and from north to south, as does the altitude of the mountain peaks. Northward facing basins are more heavily glacierized than the basins facing south. The altitude of the glaciers ranges from 919 m (base of the lowest) to 2108 m (top of the highest); the mean altitude weighted by area of all glaciers is 1797 m. DISCUSSION Vivian: We have the same problems on a smaller scale in the western Alps as Meier has shown us. For example, in the Mont Blanc area, ice drains into the River Po (Italy) and into the Arve and Rhône (France). There is also a problem in delineation of the different glaciers flowing out of the same ice caps. These are indeed great problems of glacier inventory. Meier: Yes, I agree. Miiller: Would you please indicate what techniques you intend to use for those glacierized areas where the standard glacier inventory cannot be completed for lack of funds. Meier: First, we are measuring a number of parameters for well known or important glaciers (location, area, maximum and minimum and, sometimes, median altitude, equilibrium line altitude, classification and snout activity, etc.) In Alaska this is less than 50 glaciers. Second, we are measuring the total glacier area in major mountain ranges, A preliminary inventory of Alaskan glaciers 47 individual massifs, etc. In some cases, we are dividing these into major drainage basins also but this is sometimes difficult because the location of the ice divides is not always certain. Third, we intend to measure in detail all glaciers in selected small areas in order to obtain information on lengths, altitudes, etc. by a sampling technique. Finally, as time and circumstances permit, we will make more complete inventories such as those for the North Cascades, Sierra Nevada and Brooks Range. Williams: Why don't you use a polar planimeter for a more accurate measurement of glacier areas from topographic maps? Is it a question of personnel and resources or time? Meier: We did use a planimeter in some cases, in other cases we counted dots. In either case, we simplified the glacier outline to speed up the area measurement. We could have measured the areas more accurately but this would not be consistent with the approximate nature of the basic data.