Strain heating and the energy of metamorphism

2011 ◽  
Keyword(s):  
Strain Heating

scholarly journals Thermodynamics of a fast-moving Greenlandic outlet glacier revealed by fiber-optic distributed temperature sensing

2021 ◽  
Vol 7 (20) ◽  
pp. eabe7136
Author(s):  
Robert Law ◽  
Poul Christoffersen ◽  
Bryn Hubbard ◽  
Samuel H. Doyle ◽  
Thomas R. Chudley ◽  
...  
Keyword(s):  
Fiber Optic ◽  
Basal Layer ◽  
Temperature Sensing ◽  
Distributed Temperature Sensing ◽  
Catchment Scale ◽  
Outlet Glacier ◽  
Coarse Spatial Resolution ◽  
High Vertical Resolution ◽  
Fast Motion ◽  
Strain Heating

Measurements of ice temperature provide crucial constraints on ice viscosity and the thermodynamic processes occurring within a glacier. However, such measurements are presently limited by a small number of relatively coarse-spatial-resolution borehole records, especially for ice sheets. Here, we advance our understanding of glacier thermodynamics with an exceptionally high-vertical-resolution (~0.65 m), distributed-fiber-optic temperature-sensing profile from a 1043-m borehole drilled to the base of Sermeq Kujalleq (Store Glacier), Greenland. We report substantial but isolated strain heating within interglacial-phase ice at 208 to 242 m depth together with strongly heterogeneous ice deformation in glacial-phase ice below 889 m. We also observe a high-strain interface between glacial- and interglacial-phase ice and a 73-m-thick temperate basal layer, interpreted as locally formed and important for the glacier’s fast motion. These findings demonstrate notable spatial heterogeneity, both vertically and at the catchment scale, in the conditions facilitating the fast motion of marine-terminating glaciers in Greenland.

Strain heating in process zones; implications for metamorphism and partial melting in the lithosphere

2014 ◽  
Vol 394 ◽  
pp. 216-228 ◽  
Author(s):  
Maud H. Devès ◽  
Stephen R. Tait ◽  
Geoffrey C.P. King ◽  
Raphaël Grandin
Keyword(s):  
Partial Melting ◽  
Strain Heating

A heat-flow reconnaissance of southeastern Alaska

1985 ◽  
Vol 22 (3) ◽  
pp. 416-421 ◽  
Author(s):  
J. H. Sass ◽  
L. A. Lawver ◽  
R. J. Munroe
Keyword(s):  
Heat Flow ◽  
Plate Boundary ◽  
Thermal Spring ◽  
High Heat ◽  
Transform Fault ◽  
High Heat Flow ◽  
Queen Charlotte Islands ◽  
Late Tertiary ◽  
The Mean ◽  
Strain Heating

Heat flow was measured at nine sites in crystalline and sedimentary rocks of southeastern Alaska. Seven of the sites, located between 115 and 155 km landward of the Queen Charlotte – Fairweather transform fault, have an average heat flow of 59 ± 6 mW m−2. This value is significantly higher than the mean of 42 mW m−2 in the coastal provinces between Cape Mendocino and the Queen Charlotte Islands, to the south, and is lower than the mean of 72 ± 2 mW m−2 for 81 values within 100 km of the San Andreas transform fault, even farther south. This intermediate value suggests the absence of significant heat sinks associated with Cenozoic subduction and of heat sources related to either late Cenozoic tectono-magmatic events or significant shear-strain heating. At Warm Springs Bay, 75 km from the plate boundary, an anomalously high heat flow of 150 mW m−2 can most plausibly be ascribed to the thermal spring activity from which its name is derived. At Quartz Hill, 240 km landward of the plate boundary, a value of 115 mW m−2 might indicate a transition to a province of high heat flow resulting from late Tertiary and Quaternary extension and volcanism.

scholarly journals Thermal Response of a Small Ice Cap to Climatic Forcing

1990 ◽  
Vol 36 (122) ◽  
pp. 49-56 ◽  
Author(s):  
Brian Hanson
Keyword(s):  
Response Times ◽  
Thermal Response ◽  
Warming Trend ◽  
Temperature Fields ◽  
Ice Cap ◽  
Dimensional Finite Element ◽  
Order Of Magnitude ◽  
Sensitivity Studies ◽  
Strain Heating ◽  
Flow Plane

AbstractTwo-dimensional finite-element calculations of velocity and temperature fields have been applied to the energy balance of a cross-section of Barnes Ice Cap, Baffin Island, Canada. The flow plane currently is cooling near the ice divide and warming near the margin. Long-term simulations show a net warming trend followed by a cooling trend with a steady-state average temperature similar to the present. Sensitivity studies on an idealized version of the flow plane show that the overall temperature responds less than surface-temperature forcing, because a negative feedback in temperature advection is substantially larger than a positive feed-back in strain heating. The response times of the flow plane by itself are somewhat faster but of the same magnitude as response times that would be estimated from one-dimensional modeling. When bedrock-temperature calculations are included, response times increase an order of magnitude, but these do not substantially affect the short-term response.

Creep strain-heating due to folding

1986 ◽  
Vol 43 (1) ◽  
pp. 56-66 ◽  
Author(s):  
K.T. Wan ◽  
F.A. Cozzarelli ◽  
D. Hodge
Keyword(s):  
Creep Strain ◽  
Strain Heating

scholarly journals Sliding versus till deformation in the fast motion of an ice stream over a viscous till

2000 ◽  
Vol 46 (155) ◽  
pp. 633-640 ◽  
Author(s):  
Throstur Thorsteinsson ◽  
Charles F. Raymond
Keyword(s):  
Viscous Fluid ◽  
Incompressible Viscous Fluid ◽  
Ice Streams ◽  
Short Scale ◽  
Fluid Behavior ◽  
Fast Motion ◽  
Strain Heating ◽  
Fast Flow ◽  
Basal Melting ◽  
Scale Roughness

AbstractThe partitioning between till deformation and sliding in the fast flow of ice streams with active basal melting is examined assuming no adhesion of the till to the ice base and incompressible viscous fluid behavior for the till. For deforming-till thickness of 10 m or less the predicted contribution to basal motion by sliding is larger than shearing in the till unless there is short-scale roughness with wavelengths less than order 0.1 m on the ice sole. At such short scales strain heating within the till and focused melting on the ice sole would quickly eliminate the roughness. Thus, fast flow over a till bed would be expected to be mostly by sliding over the subglacial till. More realistic continuum behavior of the till including non-linear and compressible deformation strengthens the conclusion. If sliding is not dominant, then there must be adhesion of the till to the ice base, some mechanism that continuously generates short-scale roughness on the ice–till interface, or very weak internal slip boundaries within the till.

scholarly journals Melting and freezing beneath the Ross ice streams, Antarctica

2004 ◽  
Vol 50 (168) ◽  
pp. 96-108 ◽  
Author(s):  
Ian Joughin ◽  
Slawek Tulaczyk ◽  
Douglas R. MacAyeal ◽  
Hermann Engelhardt
Keyword(s):  
Steady Flow ◽  
Temperature Model ◽  
West Antarctica ◽  
Ice Streams ◽  
Horizontal Advection ◽  
Ice Stream ◽  
Whillans Ice Stream ◽  
Shear Heating ◽  
Strain Heating ◽  
Inland Ice

AbstractWe have estimated temperature gradients and melt rates at the bottom of the ice streams in West Antarctica. Measured velocities were used to include the effects of horizontal advection and strain heating in the temperature model and to determine shear heating at the bed. Our modeled temperatures agree well with measured temperatures from boreholes in regions of steady flow. We find that ice-stream tributaries and the inland ice account for about 87% of the total melt generated beneath the Ross ice streams and their catchments. Our estimates indicate that the ice plains of Whillans Ice Stream and Ice Stream C (even when active) have large areas subject to basal freezing, confirming earlier estimates that import of water from upstream is necessary to sustain motion. The relatively low melt rates on Whillans Ice Stream are consistent with observations of deceleration over the last few decades and suggest a shutdown may take place in the future, possibly within this century. While there are pockets of basal freezing beneath Ice Streams D and E, there are larger areas of basal melt that produce enough melt to more than offset the freezing, which is consistent with inferences of relatively steady flow for these ice streams over the last millennium.

The thermal regime of the descending lithosphere: the effect of varying angle and rate of subduction

1978 ◽  
Vol 15 (4) ◽  
pp. 626-641 ◽  
Author(s):  
L. J. Sydora ◽  
F. W. Jones ◽  
R. St. J. Lambert
Keyword(s):  
Thermal Regime ◽  
Numerical Approach ◽  
High Heat ◽  
Dominant Factor ◽  
Heat Sources ◽  
High Heat Flow ◽  
The Earth ◽  
Gravity Fields ◽  
Subducting Plate ◽  
Strain Heating

The local temperature and gravity fields associated with a subducting plate are investigated using a finite-difference numerical approach. A model that simulates the downgoing slab is used to study various dip angles, different rates of subduction, heat sources and the effect of rising material from the upper surface of the slab. The model assumes a simple descent mechanism that is discussed in terms of the associated earthquake field. The amount of shear-strain heating along the upper surface of the slab is a crucial factor in determining the thermal regime. When melting occurs, rising material from the top of the slab produces high heat flow values at the surface of the Earth on the continental side of the oceanic trench. Also, the results indicate that rising melt will mask the gravity effect of the cold sinking slab at low subduction velocities, and it is the presence of rising melt that is the dominant factor that influences the surface heat flux and gravity field.

scholarly journals The role of the margins in the dynamics of an active ice stream

1994 ◽  
Vol 40 (136) ◽  
pp. 527-538 ◽  
Author(s):  
K. A. Echelmeyer ◽  
W. D. Harrison ◽  
C. Larsen ◽  
J. E. Mitchell
Keyword(s):  
Numerical Models ◽  
Force Balance ◽  
Shear Stresses ◽  
List Type ◽  
Ice Stream ◽  
Strain Heating ◽  
Ice Stream B ◽  
Basal Shear ◽  
Marginal Zones

AbstractA transverse profile of velocity was measured across Ice Stream B, West Antarctica, in order to determine the role of the margins in the force balance of an active ice stream. The profile extended from near the ice-stream center line, through a marginal shear zone and on to the slow-moving ice sheet. The velocity profile exhibits a high degree of shear deformation within a marginal zone, where intense, chaotic crevassing occurs. Detailed analysis of the profile, using analytical and numerical models of ice flow, leads to the following conclusions regarding the roles of the bed and the margins in ice-stream dynamics:(i)The overall resistive drag on the ice stream is partitioned nearly equally between the margins and the bed and, thus, both are important in the force balance of the ice stream.(ii)The ice within the chaotic zone must be about 10 times softer than the ice in the central part of the ice stream.(iii)The average basal shear stress is 0.06 × 105Pa. This implies that the entire bed cannot be blanketed by the weak, deformable till observed by Engelhardt and others (1990) near the center of the ice stream — there must be regions of increased basal drag.(iv)High strain rates and shear stresses in the marginal zones indicate that strain heating in the margins may be significant.While the exact quantitative values leading to these conclusions are somewhat model and location-dependent, the overall conclusions are robust. As such, they are likely to have importance for ice-stream dynamics in general.

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