©2010 Elsevier, Inc. 1 Chapter 11 Cuffey & Paterson

©2010 Elsevier, Inc. 1

Chapter 11Chapter 11

Cuffey & Paterson


FIGURE 11.1

The relation between increased flux and advance of a glacier terminus. Adapted from Nye (1960).


FIGURE 11.2

Schematic models for advance of a glacier following an increase of mass balance: (a) if thickness changes are negligible; (b) allowing for thickness changes.


FIGURE 11.3

Schematic models for: (a) the response of a glacier’s accumulation zone to an increase of mass balance; (b) the response of a glacier’s lower ablation zone to increased flux or decreased ablation.


FIGURE 11.4

Computed evolution of a discharge perturbation on a hypothetical mountain glacier (depicted in Figure 11.7). At time zero, a thin layer of uniform thickness was added to the entire glacier surface.


FIGURE 11.5

Instability of region of compressing flow. Adapted from Nye (1960).


FIGURE 11.6

Diffusion of a bulge.


FIGURE 11.7

Computed advance of a hypothetical glacier following a permanent increase of mass balance. Solid lines show the original, steady-state longitudinal profile. Broken lines show the profile after 20, 50, 100, and 300 years.


FIGURE 11.8

Observed thickness changes versus distance along three retreating glaciers, from multidecade measurements. Distancehas been normalized to the glacier length at the end of the observation period. Thickness changes have been normalized to the value at the terminus at the end of the observation period. From Schwitter and Raymond (1993).


FIGURE 11.9

Computed response of Berendon Glacier to a unit impulse. The specific balance perturbation was taken as 1myr−1 from t = 0 to t = 1 year and zero at other times. The increase in thickness is H1. The number on each curve is the fractional distance along-glacier, x/L, measured from the head. Adapted from Untersteiner and Nye (1968).


FIGURE 11.10

Changes of mean surface elevation of Mer de Glace, France, along four across-glacier profiles over a period of nine years. The broken line corresponds to a propagation velocity of 800 m yr−1. Adapted from Lliboutry (1958a).


FIGURE 11.11

Calculated profiles and flow of Nigardsbreen, Norway. (a) Change in profile from 1748 to 1988. Profile of 1748 is comparedto observed trimline. (b) Comparison of profiles during advance (year 1690) and retreat (year 1871), showing steeper and thicker front during advance. (c) Model ice velocities along the glacier in these years. Adapted from Oerlemans (1997) and Oerlemans (2001, pp. 90–91).


FIGURE 11.12

Predicted changes in thickness of East Antarctic Ice Sheet, along the flow line starting at Dome C, after a sudden rise in sea level 15 kyr ago. (a) Initial and present profiles. (b) – (f) Thickness changes over different intervals since the sea-level rise, showing how thinning propagates upstream. From Alley and Whillans (1984). Used with permission from the American Geophysical Union, Journal of Geophysical Research.


FIGURE 11.13

Predicted changes in thickness at Dome C as a function of time after sudden rise in sea level. (a) For sea-level rise only. (b) For sea-level rise combined with a 10% increase in accumulation rate and a surface warming of 7 °C. Adapted from Alley and Whillans (1984) by permission of the American Geophysical Union, Journal of Geophysical Research.


FIGURE 11.14

Response of ice sheets to gradual thinning of “soft” basal layer of ice-age ice. Thickness is that relative to an ice sheet consisting entirely of “hard” Holocene ice. Curve (a) represents Devon Island ice cap (H = 300 m,), curve (b) Dye 3 (H = 2037m, ˙), curve (c) Crête, Greenland (H = 3000m,). Adapted from Reeh (1985).


FIGURE 11.15

Time variations of measured surface velocity at two locations on the centerline of Columbia Glacier. The “downstream” location is 7 km downstream of the other location. Adapted from Meier et al. (1994) by permission of the American Geophysical Union, Journal of Geophysical Research.


FIGURE 11.16

Correspondence of Greenland Ice Sheet velocity with surface melt and lake drainage events. Top panel shows the variation of ice velocity at a site about 40 km from the margin of the Greenland Ice Sheet, measured by GPS (the measurement was continuous in the first period, weekly in the later two periods). Bottom panels show corresponding measured positive degree days, a proxy for meltwater generation, at a nearby site. The peak in velocity on Day 210 occurred when a nearby lake drained. Adapted from Joughin et al. (2008).


FIGURE 11.17

Schematic of a longitudinal section through the terminus region of a tidewater glacier.


FIGURE 11.18

Covariation of ice stream terminus position and ice velocity. Top curve shows the seasonal variations of the terminus position of Jakobshavn Ice Stream; larger values indicate advance of the floating terminus. Bottom curves show variations of ice velocity (measured with InSAR) at three locations; A is closest to the terminus (4 to 10 km from the terminus), C is farthest inland (about 25 km). Multiyear trends in velocity have been removed. Data courtesy of I. Joughin. Locations are close to those shown in Figure 3B of Joughin et al. (2008).


FIGURE 11.19

Schematic of the feedback processes operating in tidewater glaciers following an initial small retreat and thinning.


FIGURE 11.20

Longitudinal profiles of ice velocity along two glaciers before and after the collapse of the Larsen B Ice Shelf in early 2002. Ice flow is from left to right. Hektoria Glacier flowed into the part of the ice shelf that collapsed. Flask Glacier flowed into the surviving part of the ice shelf. Data courtesy of E. Rignot; analysis from Rignot et al. (2004). Data density is similar in all curves, but, for clarity, points are shown explicitly for only two cases.


FIGURE 11.21

Longitudinal profiles of surface and bed elevations on Pine Island Glacier (top), and the corresponding measured rates of thinning (bottom). The dashed line labelled “GL” indicates the grounding line position. Adapted from Shepherd et al. (2001).


FIGURE 11.22

Longitudinal profiles of velocity of Helheim Glacier, Greenland. Distances increase inland; terminus positions are shown at the upper left. Adapted from Howat et al. (2005). Used with permission from the American Geophysical Union, Howat, I.M., Joughin, I., Tulaczyk, S., and Gogineni, S., Rapid retreat and acceleration of Helheim Glacier, east Greenland (2005), Geophysical Research Letters, Fig. 3/pp. 3703–3712.

Documents

©2010 Elsevier, Inc. 1 Chapter 11 Cuffey & Paterson