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contains a distinct isotopic signature which depends on the respective temperature
during condensation (Dansgaard 1964 ). In theory it is possible to reconstruct the local
surface temperature from isotope ratios. However many other processes apart from
the condensation at site can in
uence the relative isotope concentration of precipi-
tation. Temperature variations at the source or even a change in the source area might
signi
fl
cantly change isotope concentrations (Jouzel et al. 1997 ). Circulation pathways
might undergo dynamic changes as well, which complicates the relationship between
temperature and isotope concentrations. The present day temperature-isotope rela-
tionship can be estimated, by measuring the isotope content in snow and
fitting it to
the observed temperatures at site (Dansgaard 1964 ; Jouzel et al. 1997 ). This rela-
tionship can then be used to reconstruct past temperature variations. To put this
reconstruction into perspective, it is necessary to establish a timeline for the ice core
s
isotope variations, which can be derived from annual layer counting in the upper part
of the ice core or via mass spectrometry of the deep part. Close to the bedrock it is
often impossible to decipher a meaningful chronology due to complicated
'
fl
ow pat-
terns of the ice which fold and heavily compress the local stratigraphy.
3D ice sheet modelling combined with tracer advection can provide a modeled
stratigraphy for Antarctica and Greenland, which can then be compared to the
available proxy data (Goelles et al. 2014 ; Lhomme et al. 2005 ; Clarke and Marshall
2002 ). We developed a passive tracer module for the 3D ISM RIMBAY (RIM-
TRACE) to reproduce the stratigraphy and isotope distribution of Greenland and
Antarctica. RIMTRACE is
ed model environments based on
the EISMINT geometry (Huybrechts and Payne 1996 ) and further validated against
the analytical Nye-Haefeli age-depth relation (Nye 1963 ; Haefeli 1963 ).
first tested on simpli
2 Methods
The 3D ISM RIMBAY forming the framework for the passive tracer advection
module is a
higher order ice sheet model based on the 3D ISM of
Pattyn ( 2003 ). The model includes all major features of the polar ice sheets [ice
shelves, nunataks, fast
multi physics
flowing glaciers, basal hydrology etc. (see Fig. 1 )]. Tracer
simulations are carried out on a regular grid with a variable resolution. In the
experiments discussed in this paper a resolution of 50 km is chosen. The ice sheet
was run with a combination of the shallow ice (SIA) and shallow shelf (SSA)
solution to the Navier-Stokes equation. The shallow ice approximation neglects all
stresses except for the vertical stress term. Ice
fl
flow is governed by the overburden
pressure of the ice and the surface and bedrock slope. Equation ( 1 ) highlights the
equation for the lateral velocity according to the SIA.
fl
r s Z
z
n
n 1
A ðh Þð s z Þ
n dz þ
u
ð z Þ¼
2
ðq g Þ
jrj
u b
ð
1
Þ
b
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