Theory of glacier variations; reply to Dr. Nye’s letter

The Editor,

Journal of Glaciology

Sir,

In his letter Dr. Nye (1965) asked for examples of flow against the direction of the surface slope over a distance substantially greater than the ice thickness.

I observed areas with backward slope on many Arctic glaciers and in the 80 km. wide belt along the margin of the Antarctic Ice Sheet for a distance of more than 2,000 km. For instance, at long. 93° 26.5’ E., 55 km. in from the coast there is a centre of a wide depression of the surface of the Antarctic Ice Sheet with the bottom more than 150 m. below the northern edge of the depression. The ice thickness in the centre, measured by seismic shooting on 23 December1957, was 840 m. The backward slope up to 2–3° was observed for a distance of almost 5 km. So the stress of more than pgh sin α ≃ 3.4 bars is transferred there at a distance of not less than 5h from a higher area of at least the same length.

In the same letter Dr. Nye gave the function a ₀(x) for his “ideal glacier” that corresponds in his opinion to realistic function h ₀(x) But this latter function has the break point

with dh ₀/dx increasing by C(4L ²−1). Between

and

where,

, the thickness increasing by about

of the one at the point x = 0, and then it diminishes rapidly down to zero at x = L. I believe that glaciers of such a shape cannot exist.

I did not find Dr. Nye’s other replies met my points satisfactorily for reasons explained in my letter that is being published in Materialy Glyatsiologicheskikh Issledovaniy. Khronika. Obsuzhdeniya [Materials of Glaciological Studies. News. Discussions], No. 12, 1966.