Funded by the German Science Foundation (DFG), the Project of the Remote Sensing Department of the Institute of Geography of the University of Goettingen, Germany, has studied the surface changes of several Glaciers in South-Central Alaska, mainly in the Knik Glacier Area, 90km east-north-east of Anchorage. Aerial surveys utilizing an innovative new method with a handheld survey camera in conjunction with small, slow flying light aircraft, were conducted by the first author, the project scientist and also pilot/camera operator. Ground truth field work was mainly achieved by the use of bush flying and landing techniques to gain access to the wilderness area without roads or tracks, or funding to use commercial helicopters. DGPS, optical and Laser rangefinders have been used in traditional ways to measure the distance between the glacier terminus and the established GCP network. The technical emphasis of the project was on the use of existing technology in an affordable way, at the same time countering the persistent adverse weather conditions of high mountain terrain in a maritime climate regime with a new aerial survey method for localized targets. Apart from off the shelf products, the purpose-built photogrammetry software “Polarphox” was used to facilitate automated surface measurements in the convergent images.

The project was able to measure and document the very recent retreat of the calving fronts of the Knik Glacier, the Colony Glacier and the Whiteout Glacier. Previous movements and local advances within those glacier fronts have been recorded by the project, since its early beginnings in 1998. The observations in the area have been supplemented by public data of the Austin Post collection’s aerial photography of 1964 etc. Other sources of aerial and terrestrial photography have been used to gain an overview of the status of the area’s glaciers in the timeframe between 1964 and 1998. The general findings are that no significant advance of the Knik-, Colony- and Lake George Glacier existed during the study period and that a more or less constant thinning and retreat of those glaciers since 1964 can be seen as a fact. The Whiteout Glacier appears as a surging glacier, as determined by geomorphological methods during the study period. No historical data, other than 1964 USGS aerial photography and the resulting 1:36360 scale maps, of this glacier could be found. Due to this its status between 1964 and 1998 remains unknown. The terminus position of 1998 lay 730m up-valley compared to 1998. Since 98 it has further retreated and left its proglacial lake behind. Although this individual is a surging glacier in retreat, this type of change (the disappearance of a floating terminus) is seen as common among Alaska’s glaciers of this type. Extensive reconnaissance flights in Alaska’s mountain ranges have been undertaken for comparison of recent day glacier status and older USGS data. With that, concurring with findings of others, a more or less continued retreat of the glaciers since the little ice age appears to be continued, certainly when comparing 1964 data with recent imagery. Absolutely no significant change was detected regarding the status of the small high cirque glaciers of the immediate study area itself during the period of 1998-2007. On glaciers of this type where 1964 data was found, no significant change could be observed since those pictures have been taken. The main loss in ice mass within the project timeframe and study area occurred due to the disintegration by calving of large areas of floating glacier terminus/tongues, which previously have covered significant areas of proglacial lakes and moraine dammed lakes. This phenomenon mainly occurred in 2005-07, but it also coincides with the mass-wasting of floating bodies of glacier tongues of other glaciers in Alaska outside the immediate study area. All glaciers where this was observed are of the large valley glacier type, with tongues in proglacial lakes. Tidal Glaciers have not been taken into account purposefully, because of the inherent mechanism of their calving. Summarizing, the retreat of the Knik Glacier largely began in the early 1990s, with intensified calving and thus enlargement of the proglacial lakes. There was little change between 1964-67 and 1992. By recent measurements and comparison with an aerial picture of 1992, the terminus of the 80km long Knik Glacier has retreated 1.9km within the proglacial lake.