commit b37ba93696cb3857fc24404fcafa64b64e20a830
parent bc7eb31fea566ab166c999d47a01c9e4f66720c0
Author: Anders Damsgaard <anders@adamsgaard.dk>
Date: Mon, 30 Sep 2019 16:23:16 +0200
Work on intro
Diffstat:
1 file changed, 12 insertions(+), 12 deletions(-)
diff --git a/continuum-granular-manuscript1.tex b/continuum-granular-manuscript1.tex
@@ -50,27 +50,27 @@ We show that past pulses in water pressure can transfer shear away from the ice-
\section{Introduction}%
\label{sec:introduction}
Subglacial sediment deformation is in many settings of primary importance to glacier flow \citep[e.g.][]{Boulton1974, Engelhardt1990, Fischer1994, Truffer2006}.
-The mechanical behavior of the sediment is long debated \citep[e.g.][]{Alley1986, Boulton1987, Kamb1991, Iverson1995, Hindmarsh1997, Hooke1997, Fowler2003, Iverson2010, Hart2011}.
+The mechanical behavior of the sediment is long debated \citep[e.g.][]{Alley1986, Boulton1987, Kamb1991, Iverson1995, Hindmarsh1997, Hooke1997, Fowler2003, Kavanaugh2006, Iverson2010, Hart2011}.
Early on, till was assumed to be viscous \citep{Boulton1987} which allowed the formulation of analytical solutions to the coupled ice-till problem \citep[e.g.][]{Walder1994, Hindmarsh1999, Fowler2000}.
+Viscous materials loose all strength if deformation rates approach zero, and strength is without an upper bound as rates increase.
Resultant glacier sliding laws are similar to hard-bed sliding laws without cavitation \citep[e.g.][]{Budd1979}.
+Traditional analytical and numerical modeling of till requires that stress and strain rate is linked, with linear to mildly non-linear rheologies being vastly simpler to solve.
-However, laboratory experiments on tills \citep[e.g.][]{Kamb1991, Iverson1998, Tulaczyk2000, Rathbun2008, Iverson2010, Iverson2015}
-and field observations \citep[e.g.][]{Iverson1995, Hooke1997, Tulaczyk2006}
-have concluded that till strength is nearly rate-independent, adhering to Mohr-Coulomb plasticity.
+However, laboratory experiments on tills \citep[e.g.][]{Kamb1991, Iverson1998, Tulaczyk2000, Rathbun2008, Iverson2010, Iverson2015} and field observations \citep[e.g.][]{Iverson1995, Hooke1997, Tulaczyk2006} have concluded that till strength is nearly independent of deformation rate, and behaves according to Mohr-Coulomb plasticity.
+Beneath the Mohr-Coulomb yield strength there can be slight creep with a highly-nonlinear rate dependence \citep[e.g.][]{Kamb1991, Damsgaard2016, Hart2019}.
+The presence of water can add a transient rate dependence due to volumetric adjustmend during early shear \citep[e.g.][]{Iverson1997, Moore2002, Damsgaard2015}, but the rate dependence is generally shortlived.
-\citet{Damsgaard2016} showed that creep before failure is rate dependent,
+Besides smaller scale laboratory and field investigations, the basal sliding problem is investigated by inverting observations of glacier-surface flow velocities to subglacial sliding physics.
+At Whillans Ice Plain the velocities vary three orders of magnitude during a tidal cycle, and are contributed by basal deformation \citep[e.g.][]{Bindschadler2003, Tulaczyk2006}.
+The inferred nonlinearity manifests itself in stress exponent values from 2 to over 10 \citep[e.g.][]{Tulaczyk2006, Gudmundsson2006, King2011, Gudmundsson2011, Walker2012, Rosier2014, Goldberg2014, Thompson2014, Rosier2015, Gillet-Chaulet2016, Minchew2016}.
+The degree of non-linearity may pose drastically different contributions to global mean sea-level rise in future scenarios \citep[e.g.][]{Parizek2013, Ritz2015}.
-\citet{Hart2011} argued that the rheology is dependent on water pressure.
-% remote-sensing inversion and modeling
-% Gudmundsson, Robel, Minchew, Winberry2011, Walker2013, Thompson2014, Rosier2015, Ritz2015, Bindschadler2003
-
-
-% Hart2017, Hart2019
% Damsgaard2013
-% Iverson2015
% Damsgaard2016
+% Kavanaugh
+
% Joughin2010
% Tsai, Schoof
