Even though the word glaciology truly stands for the study of ice in all its phases and conditions, sadly the subject of glaciology generally implies the study of glaciers. Popular dictionaries even define glaciology as “the study of the distribution, character, and effects of glaciers” (Simpson and Weiner 1989). This definition has certainly been expanded over the years to include large ice masses, such as ice sheets and ice shelves. Glaciological sciences are becoming increasingly important in the twenty‐first century with current international attention on climate change (popularized as “global warming”) and environment impacts due to increasing pollution of air and water bodies. Melting of glaciers, ice sheets, and ice shelves with concomitant rising of sea level, surface temperature of the oceans, and decrease in the extent of sea ice covers are some of the issues of importance. As such, the studies related to the physics of glaciers and ice are receiving a renewed interest. Accordingly, Paterson (1994) revised his original 1969 book (second edition in 1981) completely, “in order to keep pace with the extensive developments since the second edition was published.” No doubt, Paterson (1994) performed a formidable task, saying, “The vast expansion of the literature in recent years is making it increasingly difficult for one person to write a comprehensive account of the physics of glaciers.” The dictionary definition of “glaciology” has, however, remained unchanged; the physics and mechanics of ice has remained within the framework related to slow movements of large ice masses of glacial origin. The compaction of porous snow to nonpermeable ice and the long‐term flow of the mass in terms of secondary and tertiary stages of dislocation/diffusion creep over the range of stresses important in normal glacier flow (50–200 kPa or 5 × 10−6E to 2 × 10−5E, where E is the Young's modulus of ice) remained the focus (Paterson 1994).
Glaciologists devoted to understanding the long‐term response of glaciers or ice sheets and their environmental impacts, such as sea level rise, have had no requirements for understanding strength‐related mechanical properties of ice. However, ice–structure interactions (including off‐shore structures), bearing capacity of floating ice covers or winter roads used for transportation, building materials and roads subjected to freezing and thawing, permafrost‐related issues, etc. are some of the many ice engineering problems. In all of these types of ice engineering problems, knowledge of transient (primary) creep of ice and micromechanics of deformation, nucleation, and kinetics of cracking is essential. Naturally, ice engineers looked toward glaciological literature for their inputs. However, glaciologists were influenced by ideas developed for long‐term flow of glaciers on the basis of steady‐state flow. They concentrated their efforts toward the use of “mcr,”
Realizing the ice engineering issues, the senior author looked at materials science interconnected to very short‐term (early transient) creep of polycrystalline metals and alloys when he started his career in physics and mechanics of ice in 1975. He noticed that since the pioneering work of da Costa Andrade (1910) on steel, materials scientists paid only a “passing interest” in transient or the decreasing primary creep regime. Efforts were concentrated mainly on secondary, steady‐state, or strictly speaking minimum creep rate (Norton 1929; Nadai 1938; Glen 1955; Garofalo 1965; Odqvist 1974; Gittus 1975; Evans and Wilshire 1985; Cadek 1988; Nabarro and de Villiers 1995; Kassner 2015, etc.). However, creep failures either by fracture or necking depend on stress and temperature. Ruptures tend to occur near the end of the primary creep approaching the secondary stage and most certainly during the accelerating or tertiary regimes. Similar to the primary creep, historically, little attention has been paid to tertiary stages until recently. Yet, innumerable studies have been performed in characterizing the secondary creep or strictly speaking minimum creep rate, of various materials. To reduce effort and time, most studies are being performed at relatively high stresses to attain well‐defined minimum creep rates in reasonable lengths of time.
The European Creep Collaborative Committee (ECCC), an industry‐led group representing 16 member nations formed in 1992, has joined forces with key experts in Japan, North America, and around the world to coordinate data generation, collation, and assessment activities to provide the optimum basis for creep‐rupture strength values. On behalf of the Working Group 1 of the ECCC, Holdsworth et al. (2005) have tabulated a wide range of mathematical expressions based essentially on a few classical representations of primary, secondary, and tertiary creep, as well as creep strain equations adopted in assessment intercomparisons. None of the reviewed models seem to have addressed the effect of grain size on transient, secondary, or tertiary creep. The text misses the related and rather advanced stage of activities in high‐temperature physics and mechanics of polycrystalline ice, including nucleation and multiplication of grain‐facet‐sized intergranular cracks and crack‐enhanced creep and failure, carried out since the late 1970s. These concepts and their extension to complex aerospace alloys are presented in Chapters 5–9.
It should be recognized that ice engineering is part of a new engineering frontier – the frontier of engineering physics of high‐temperature material science and application. Like any other high‐temperature material, ice also exhibits certain unavoidable complexities. “Delayed elastic” response, the essential element of the EDEV theory presented in this book, is strictly a high‐temperature phenomenon (Sinha 1979). Time‐dependent elastic or “delayed elastic” or “anelastic” (not a preferred term according to British Standard Institution 1975) behavior is a high‐temperature material response and it is demonstrated herein that this response leads to the explanations of complex and wide‐ranging issues for materials science and engineering applications, including geophysics of post‐glacial rebound (Chapter 10) and plate tectonics (Chapter 11).
1.3.2 Ice: An Analog to Understand High‐Temperature Properties of Solids
Taking a multidisciplinary approach using research in various fields enables an integrated cross‐disciplinary viewpoint that removes barriers of understanding across and within different fields.
Think of an ice cube floating at the top in a glass of drinking water in your hand. That ice cube may contain hundreds of crystals and the water is the liquid state of ice. Similarly, a floating ice cover in rivers, lakes, and oceans is a solid plate floating on its own melt. The bottom surface of an ice cover is always at its melting point, T m, and temperatures at the upper surfaces are not far from T m. The complexities that we see happening in ice sheets in “short observable times” (seconds, minutes, or few hours) occur under our feet over millennia or millions of years. As mentioned earlier, the correspondence between geophysical aspects of tectonics and “floating ice sheets” is striking as an analog model material. Wind driven snow cover on a floating ice sheet is like the lithosphere on ice that is not unlike the asthenosphere above the water, equivalent to the lower part of the mantle. An ice sheet bends, creeps, and cracks when a load is placed on it (as described in detail in Chapter