FJL has the highest index of glaciation of all Arctic lands:
nearly 85% of the land surface is covered by glaciers and the ice
shore stretches 2,650 kilometers which is 59.4% of the total
coastline (Atlas of the Arctic 1985). The mean ice thickness is
estimated as 180 meters. The relief is dominated by typical
plateaus with heights ranging from 30 to 500 meters, which are
generally covered by glaciers. The glacial topography of
numerous ice sheets and domes is mostly homogeneous. This is
probably the reason why the locations and values of the
maximum heights in FJL are still uncertain. According to the
present cartographic knowledge the maximum heights of the
archipelago reach 620 m on Wiener Neustadt Island and 606 m
in Wilczek Land, Wullerstorf Mountains, but several
publications (Grosswald 1973, Barr 1995) give, however
without explanation, the highest point as 670 m above sea level
in Wilczek Land. There is no agreement on the distribution of
depths in straits of the archipelago, either. For instance, the
depths in the deepest FIL straits are known to reach 557 m in
British Channel, 580 m in Rhodes Channel and 608 m in Backs
Channel. Nevertheless, it should be noted that several
cartographic sources give a depth of 800 m for the British
Channel near Elizabeth Island.
In contrast to any continental area, the standard level, or datum
plane, to which all heights or depths are compared in FJL is the
mean level of the Barents Sea. The northern Barents Sea level is
being recorded since 1957 by tide gauge observations at the
Krenkel station, Hayes Island, in the central part of the
archipelago. Elevations of the benchmarks NN 1-4 located close
to the station above the adopted datum were established in 1956
and 1971 and corrected in 1978. No strong tidal effects are to be _
observed in FJL. The height of tides in FJL can reach 0.5-0.6 m
and even more under heavy winds, but systematic observations
show that changes in annual and monthly mean sea level usually
do not exceed 20 to 30 cm (Fig 1).
All the components of the topography in FJL are presently
undergoing significant changes caused by glacial flow, calving
and active marine abrasion of ice shores as well as other coastal
processes and recent tectonic movements in the archipelago.
Due to difficult access and logistical problems, there are but a
few substantial studies of topographic changes in FJL; their
terrestrial and temporal coverage is poor thus usually rendering
impossible any systematic topological investigation at a
regional scale. FJL's terra firma is close to the margin of the
Barents Sea continental shelf stretching along the presently
active mid-oceanic Hackel spreading ridge system which might
strongly affect current geophysical processes in the archipelago.
However, neither its geodynamics nor its environmental impact
on FJL are completely known or fully understood at present.
A number of indirect studies have been made that attempt to
interpret current geodynamics in FJL by means of
geomorphological methods, e.g. by comparing the heights of
marine terraces with the radiocarbon ages of the organic rests
(bones, timbers, molluscan fauna) sampled on the surface of
those terraces (Grosswald 1973, Matishov 1993). These studies
led to the conclusion that the earth's crust in that area had been
subjected to geologically recent uplifts, although the terrace
spectra, even of adjacent islands, sometimes were beyond
correlation (Lubinsky, personal communication 1995). The
hypothesis seemed to be in good correspondence with the
"Walbeinhebungstheorie" originating from finds of whale bones
on marine terraces of Spitsbergen, and with the theory of
glacioisostatic movements in Fennoscandia Although
470
explorations were performed on several islands in western
(Alexandra Land) and central (Bell, Hayes, Hooker islands,
etc.) parts of FJL, this hypothesis was later on simply
extrapolated to the whole archipelago and even into the present
time. The sequential character of movements was never proved,
but, nevertheless, the "averaged rates" were published and it
was stated that "the archipelago of Franz Josef Land is now
rising by an average rate of 2.5-3 mm per year" (Naslund 1994,
Glazowskiy 1992; cited from Barr 1995). However, many
uncertainties still persist in this theory, and the new Russian
map (1993) showing contemporary vertical movements of the
earth's crust at 1:5,000,000 scale represents FJL as a "white
spot" indicating the lack of appropriate data.
A.
95
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76 78 80 ^82 84 86 88 90 9495 year
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observation
| mSLOGMT WSL6GMT 0SL:12GMT CERTUM
Figure 1. Barents Sea level observed at the Krenkel station,
Franz Josef Land: multi-year (MMSL) and annual mean se
level (A); monthly mean sea level observed in 1994/95 at 6
GMT, 12 GMT and averaged (B); averaged sea level during
1-24 July, 1995 (C); current sea level observed on the dates of
field observations (D).
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B4. Vienna 1996
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