IRIAN JAYA, INDONESIA, and NEW ZEALAND

Types of Glaciers and Phenomena Observable
on Landsat Images
Glacier Advance and Recession
All of New Zealand's glaciers have generally been receding since the
beginning of the century (fig. 6), with fluctuating, but rising, end-of-
summer snowline elevations. During the "Late Neoglacial" cool period,
which persisted during the past 500 to 800 years, most New Zealand
glaciers reached three main maximums, climaxing in 1750, 1850, and
1890 (Wardle, 1973; Burrows, 1975; Burrows and Maunder, 1975; Bur­
rows and Russell, 1975; Salinger, 1976; Hessell, 1980, 1983; Salinger
and others, 1983). From 1890 there was a general slow recession of most
glaciers until the late 1920's, when a widespread rapid retreat com­
menced. This retreat is continuing, punctuated by only minor read-
vances in the more active glaciers (fig. 6). Associated with the retreat of
glacier termini, most glaciers have suffered a reduction in size and a rise
of snowline elevations. From 1971 to 1975, Ivory Glacier lost more than
30 m of thickness in the terminus area, less over other parts of the
glacier (fig. 7). The total volume of ice and snow lost during this period
for this glacier alone was 13.9 x 106 m3 , or an average annual loss of
3.5 x 106 m3 . During the same period the area of this glacier was re­
duced by 26 percent, from 0.80 km2 to 0.59 km2 . Where the larger
glaciers extend to low-gradient or ponded ice trunks at valley floor level,
recession is evident by a steady lowering of ice-surface levels, accom­
panied by little or no change in terminus position, or by the development
of a proglacial lake. These glaciers have glacier snouts that are normally
debris covered, and many have recently developed glacierkarst features.
The glacierkarst terrain on Tasman Glacier is well displayed on Landsat
3 RBV image 30324-21342, subscene A (fig. 11). Recently formed pro-
glacial lakes of Classen and Godley Glaciers also appear clearly near the
northern margin of this image. Figure 12 is an oblique aerial photograph
of Douglas Glacier's proglacial lake, which has developed during the past
20 years. The change in size of proglacial lakes is possibly the single best
indicator of glacier variations seen on satellite imagery.
In contrast to the slow response of glaciers with large low-gradient
trunks, large glaciers with steep trunks have been very reactive to small
mass-balance changes, and the long period of glacier recession during
the 20th century has been manifested in a series of small advances
superimposed upon a general recession, similar to waves on the seashore
at ebbing tide. Franz Josef and Fox Glaciers are of this type (figs. 13 and
14), but unfortunately no usable Landsat images of these glaciers exist.
Both glaciers lie in the corners of the available Landsat images and are
either poorly displayed or obscured by cloud cover.
H40 SATELLITE IMAGE ATLAS OF GLACIERS OF THE WORLD