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1  \section{Forward sensitivity experiments}  \section{Forward sensitivity experiments}
2  \label{sec:forward}  \label{sec:forward}
3    
4  A second series of forward sensitivity experiments have been carried out on an  This section presents results from global and regional coupled ocean and sea
5  Arctic Ocean domain with open boundaries.  Once again the objective is to  ice simulations that exercise various capabilities of the MITgcm sea ice
6  compare the old B-grid LSR dynamic solver with the new C-grid LSR and EVP  model.  The first set of results is from a global, eddy-permitting, ocean and
7  solvers.  One additional experiment is carried out to illustrate the  sea ice configuration.  The second set of results is from a regional Arctic
8  differences between the two main options for sea ice thermodynamics in the MITgcm.  configuration, which is used to compare the B-grid and C-grid dynamic solvers
9    and various other capabilities of the MITgcm sea ice model.  
10    %
11    \ml{[do we really want to do this?:] The third set of
12    results is from a yet smaller regional domain, which is used to illustrate
13    treatment of sea ice open boundary condition in the MITgcm.}
14    
15    \subsection{Global Ocean and Sea Ice Simulation}
16    \label{sec:global}
17    
18    The global ocean and sea ice results presented below were carried out as part
19    of the Estimating the Circulation and Climate of the Ocean, Phase II (ECCO2)
20    project.  ECCO2 aims to produce increasingly accurate syntheses of all
21    available global-scale ocean and sea-ice data at resolutions that start to
22    resolve ocean eddies and other narrow current systems, which transport heat,
23    carbon, and other properties within the ocean \citep{menemenlis05}.  The
24    particular ECCO2 simulation discussed next is a baseline 28-year (1979-2006)
25    integration, labeled cube76, which has not yet been constrained by oceanic and
26    by sea ice data.  A cube-sphere grid projection is employed, which permits
27    relatively even grid spacing throughout the domain and which avoids polar
28    singularities \citep{adcroft04:_cubed_sphere}. Each face of the cube comprises
29    510 by 510 grid cells for a mean horizontal grid spacing of 18 km. There are
30    50 vertical levels ranging in thickness from 10 m near the surface to
31    approximately 450 m at a maximum model depth of 6150 m. Bathymetry is from the
32    National Geophysical Data Center (NGDC) 2-minute gridded global relief data
33    (ETOPO2) and the model employs the partial-cell formulation of
34    \citet{adcroft97:_shaved_cells}, which permits accurate representation of the
35    bathymetry. The model is integrated in a volume-conserving configuration using
36    a finite volume discretization with C-grid staggering of the prognostic
37    variables. In the ocean, the non-linear equation of state of \citet{jac95} is
38    used.
39    
40    The ocean model is coupled to the sea-ice model discussed in
41    \refsec{model} using the following specific options.  The
42    zero-heat-capacity thermodynamics formulation of \citet{hibler80} is
43    used to compute sea ice thickness and concentration.  Snow cover and
44    sea ice salinity are prognostic.  Open water, dry ice, wet ice, dry
45    snow, and wet snow albedo are, respectively, 0.15, 0.88, 0.79, 0.97,
46    and 0.83. Ice mechanics follow the viscous plastic rheology of
47    \citet{hibler79} and the ice momentum equation is solved numerically
48    using the C-grid implementation of the \citet{zhang97}'s LSOR dynamics
49    model discussed hereinabove.  The ice is coupled to the ocean using
50    the rescaled vertical coordinate system, z$^\ast$, of \citet{cam08},
51    that is, sea ice does not float above the ocean model but rather
52    deforms the ocean's model surface level.
53    
54    This particular ECCO2 simulation is initialized from temperature and salinity
55    fields derived from the Polar science center Hydrographic Climatology (PHC)
56    3.0 \citep{ste01a}. Surface boundary conditions for the period January 1979 to
57    July 2002 are derived from the European Centre for Medium-Range Weather
58    Forecasts (ECMWF) 40 year re-analysis (ERA-40) \citep{upp05}.  Surface
59    boundary conditions after September 2002 are derived from the ECMWF
60    operational analysis.  There is a one month transition period, August 2002,
61    during which the ERA-40 contribution decreases linearly from 1 to 0 and the
62    ECMWF analysis contribution increases linearly from 0 to 1.  Six-hourly
63    surface winds, temperature, humidity, downward short- and long-wave
64    radiations, and precipitation are converted to heat, freshwater, and wind
65    stress fluxes using the \citet{large81,large82} bulk formulae.  Shortwave
66    radiation decays exponentially as per \citet{pau77}.  Low frequency
67    precipitation has been adjusted using the pentad (5-day) data from the Global
68    Precipitation Climatology Project \citep[GPCP][]{huf01}.  The time-mean river
69    run-off from \citet{lar01} is applied globally, except in the Arctic Ocean
70    where monthly mean river runoff based on the Arctic Runoff Data Base (ARDB)
71    and prepared by P. Winsor (personnal communication, 2007) is specificied.
72    Additionally, there is a relaxation to the monthly-mean climatological sea
73    surface salinity values from PHC 3.0, a relaxation time scale of 101 days.
74    
75    Vertical mixing follows \citet{lar94} but with meridionally and vertically
76    varying background vertical diffusivity; at the surface, vertical diffusivity
77    is $4.4\times 10^{-6}$~m$^2$~s$^{-1}$ at the Equator, $3.6\times
78    10^{-6}$~m$^2$~s$^{-1}$ north of 70$^\circ$N, and $1.9\times
79    10^{-5}$~m$^2$~s$^{-1}$ south of 30$^\circ$S and between 30$^\circ$N and
80    60$^\circ$N , with sinusoidally varying values in between these latitudes;
81    vertically, diffusivity increases to $1.1\times 10^{-4}$~m$^2$~s$^{-1}$ at a a
82    depth of 6150 m as per \citet{bry79}.  A high order monotonicity-preserving
83    advection scheme \citep{dar04} is employed and there is no explicit horizontal
84    diffusivity.  Horizontal viscosity follows \citet{lei96} but modified to sense
85    the divergent flow as per \citet{kem08}.
86    
87    \ml{[Dimitris, here you need to either provide figures, so that I can
88      write text, or you can provide both figures and text. I guess, one
89      figure, showing the northern and southern hemisphere in summer and
90      winter is fine (four panels), as we are showing so many figures in
91      the next section.]}
92    
93    
94  \subsection{Arctic Domain with Open Boundaries}  \subsection{Arctic Domain with Open Boundaries}
95  \label{sec:arctic}  \label{sec:arctic}
96    
97  The Arctic domain of integration is illustrated in Fig.~\ref{fig:arctic1}.  It  A series of forward sensitivity experiments have been carried out on
98  is carved out from, and obtains open boundary conditions from, the  an Arctic Ocean domain with open boundaries.  The objective is to
99  global cubed-sphere configuration of the Estimating the Circulation  compare the old B-grid LSR dynamic solver with the new C-grid LSR and
100  and Climate of the Ocean, Phase II (ECCO2) project  EVP solvers.  Additional experiments are is carried out to illustrate
101  \citet{menemenlis05}.  The domain size is 420 by 384 grid boxes  the differences between different ice advection schemes, ocean-ice
102  horizontally with mean horizontal grid spacing of 18 km.  stress formulations and the two main options for sea ice
103    thermodynamics in the MITgcm.
104    
105    The Arctic domain of integration is illustrated in
106    \reffig{arctic_topog}.  It is carved out from, and obtains open
107    boundary conditions from, the global cubed-sphere configuration
108    described above.  The horizontal domain size is 420 by 384 grid boxes.
109    \begin{figure*}
110    \includegraphics*[width=0.44\linewidth,viewport=139 210 496 606,clip]{\fpath/topography}
111    %\includegraphics*[width=0.44\linewidth,viewport=0 0 496 606,clip]{\fpath/topography}
112    \includegraphics*[width=0.46\linewidth]{\fpath/archipelago}
113    \caption{Left: Bathymetry and domain boudaries of Arctic
114      Domain; the dashed line marks the boundaries of the inset on the
115      right hand side. The letters in the inset label sections in the
116      Canadian Archipelago, where ice transport is evaluated:
117      A: Nares Strait; %
118      B: \ml{Meighen Island}; %
119      C: Prince Gustaf Adolf Sea; %
120      D: \ml{Brock Island}; %
121      E: McClure Strait; %
122      F: Amundsen Gulf; %
123      G: Lancaster Sound; %
124      H: Barrow Strait \ml{W.}; %
125      I: Barrow Strait \ml{E.}; %
126      J: Barrow Strait \ml{N.}. %
127      \label{fig:arctic_topog}}
128    \end{figure*}
129    
130    The main dynamic difference from cube sphere is that it does not use
131    rescaled vertical coordinates (z$^\ast$) and the surface boundary
132    conditions for freshwater input are different, because those features
133    are not supported by the open boundary code.
134    
135    Open water, dry ice, wet ice, dry snow, and wet snow albedo are,
136    respectively, 0.15, 0.85, 0.76, 0.94, and 0.8.
137    
138    The model is integrated from January, 1992 to March \ml{[???]}, 2000,
139    with three different dynamical solvers and two different boundary
140    conditions:
141    \begin{description}
142    \item[B-LSR-ns:] the original LSOR solver of \citet{zhang97} on an
143      Arakawa B-grid, implying no-slip lateral boundary conditions
144      ($\vek{u}=0$ exactly);
145    \item[C-LSR-ns:] the LSOR solver discretized on a C-grid with no-slip lateral
146      boundary conditions (implemented via ghost-points);
147    \item[C-LSR-fs:] the LSOR solver on a C-grid with free-slip lateral boundary
148      conditions;
149    \item[C-EVP-ns:] the EVP solver of \citet{hunke01} on a C-grid with
150      no-slip lateral boundary conditions;
151    \item[C-EVP-fs:] the EVP solver on a C-grid with free-slip lateral
152      boundary conditions;
153    \item[C-LSR-ns adv33:] C-LSR-ns with a third-order flux limited
154      direct-space-time advection scheme \citep{hundsdorfer94};
155    \item[C-LSR-ns TEM:] C-LSR-ns with a truncated
156      ellispe method (TEM) rheology \citep{hibler97};
157    \item[C-LSR-ns HB87:] C-LSR-ns with ocean-ice stress coupling according
158      to \citet{hibler87};
159    \item[C-EVP-ns damp:] C-EVP-ns with additional damping to reduce small
160      scale noise \citep{hunke01}.
161    \end{description}
162    Both LSOR and EVP solvers solve the same viscous-plastic rheology, so
163    that differences between runs B-LSR-ns, C-LSR-ns, and C-EVP-ns can be
164    interpreted as pure model error. Lateral boundary conditions on a
165    coarse grid (compared to the roughness of the true coast line) are
166    unclear, so that comparing the no-slip solutions to the free-slip
167    solutions gives another measure of uncertainty in sea ice
168    modeling. The remaining experiments explore further
169    sensitivities of the system to different physics (change in rheology,
170    advection and diffusion properties and stress coupling) and numerics
171    (numerical method to damp noise in the EVP solutions).
172    
173    A principle difficulty in comparing the solutions obtained with
174    different variants of the dynamics solver lies in the non-linear
175    feedback of the ice dynamics and thermodynamics. Already after a few
176    months the solutions have diverged so far from each other that
177    comparing velocities only makes sense within the first 3~months of the
178    integration while the ice distribution is still close to the initial
179    conditions. At the end of the integration, the differences between the
180    model solutions can be interpreted as cumulated model uncertainties.
181    
182    \reffig{iceveloc} shows ice velocities averaged over Janunary,
183    February, and March (JFM) of 1992 for the C-LSR-ns solution; also
184    shown are the differences between B-grid and C-grid, LSR and EVP, and
185    no-slip and free-slip solution. The velocity field of the C-LSR-ns
186    solution (\reffig{iceveloc}a) roughly resembles the drift velocities
187    of some of the AOMIP (Arctic Ocean Model Intercomparison Project)
188    models in an cyclonic circulation regime (CCR) \citep[their
189    Figure\,6]{martin07} with a Beaufort Gyre and a transpolar drift
190    shifted eastwards towards Alaska.
191    
192    The difference beween runs C-LSR-ns and B-LSR-ns (\reffig{iceveloc}b)
193    is most pronounced along the coastlines, where the discretization
194    differs most between B and C-grids: On a B-grid the tangential
195    velocity lies on the boundary (and is thus zero through the no-slip
196    boundary conditions), whereas on the C-grid it is half a cell width
197    away from the boundary, thus allowing more flow. The B-LSR-ns solution
198    has less ice drift through the Fram Strait and especially the along
199    Greenland's east coast; also, the flow through Baffin Bay and Davis
200    Strait into the Labrador Sea is reduced with respect the C-LSR-ns
201    solution.  \ml{[Do we expect this? Say something about that]}
202    %
203    Compared to the differences between B and C-grid solutions,the
204    C-LSR-fs ice drift field differs much less from the C-LSR-ns solution
205    (\reffig{iceveloc}c).  As expected the differences are largest along
206    coastlines: because of the free-slip boundary conditions, flow is
207    faster in the C-LSR-fs solution, for example, along the east coast
208    of Greenland, the north coast of Alaska, and the east Coast of Baffin
209    Island.
210    \begin{figure}[htbp]
211      \centering
212      \subfigure[{\footnotesize C-LSR-ns}]
213    %  {\includegraphics[width=0.44\textwidth]{\fpath/JFMuv_lsr_noslip}}
214      {\includegraphics[width=0.44\textwidth]{\fpath/JFMuv_C-LSR-ns}}
215      \subfigure[{\footnotesize B-LSR-ns $-$ C-LSR-ns}]
216    %  {\includegraphics[width=0.44\textwidth]{\fpath/JFMuv_bgrid-lsr_noslip}}\\
217      {\includegraphics[width=0.44\textwidth]{\fpath/JFMuv_B-LSR-ns-C-LSR-ns}}\\
218      \subfigure[{\footnotesize C-LSR-fs $-$ C-LSR-ns}]
219    %  {\includegraphics[width=0.44\textwidth]{\fpath/JFMuv_lsr_slip-lsr_noslip}}
220      {\includegraphics[width=0.44\textwidth]{\fpath/JFMuv_C-LSR-fs-C-LSR-ns}}
221      \subfigure[{\footnotesize C-EVP-ns $-$ C-LSR-ns}]
222    %  {\includegraphics[width=0.44\textwidth]{\fpath/JFMuv_evp_noslip-lsr_noslip}}
223      {\includegraphics[width=0.44\textwidth]{\fpath/JFMuv_C-EVP-ns-C-LSR-ns}}
224      \caption{(a) Ice drift velocity of the C-LSR-ns solution averaged
225        over the first 3 months of integration [cm/s]; (b)-(d) difference
226        between B-LSR-ns, C-LSR-fs, C-EVP-ns, and C-LSR-ns solutions
227        [cm/s]; color indicates speed (or differences of speed), vectors
228        indicate direction only.}
229      \label{fig:iceveloc}
230    \end{figure}
231    
232    The C-EVP-ns solution is very different from the C-LSR-ns solution
233    (\reffig{iceveloc}d). The EVP-approximation of the VP-dynamics allows
234    for increased drift by over 2\,cm/s in the Beaufort Gyre and the
235    transarctic drift. \ml{Also the Beaufort Gyre is moved towards Alaska
236      in the C-EVP-ns solution. [Really?]} In general, drift velocities are
237    biased towards higher values in the EVP solutions as can be seen from
238    a histogram of the differences in \reffig{drifthist}.
239    \begin{figure}[htbp]
240      \centering
241      \includegraphics[width=\textwidth]{\fpath/drifthist_C-EVP-ns-C-LSR-ns}
242      \caption{Histogram of drift velocity differences for C-LSR-ns and
243        C-EVP-ns solution [cm/s].}
244      \label{fig:drifthist}
245    \end{figure}
246    
247    \reffig{icethick}a shows the effective thickness (volume per unit
248    area) of the C-LSR-ns solution, averaged over January, February, March
249    of year 2000. By this time of the integration, the differences in the
250    ice drift velocities have led to the evolution of very different ice
251    thickness distributions, which are shown in \reffig{icethick}b--d, and
252    area distributions (not shown).  \ml{Compared to other solutions, for
253      example, AOMIP the ice thickness distribution blablabal}
254    \begin{figure}[htbp]
255      \centering
256      \subfigure[{\footnotesize C-LSR-ns}]
257      {\includegraphics[width=0.44\textwidth]{\fpath/JFMheff2000_lsr_noslip}}
258      \subfigure[{\footnotesize B-LSR-ns $-$ C-LSR-ns}]
259      {\includegraphics[width=0.44\textwidth]{\fpath/JFMheff2000_bgrid-lsr_noslip}}\\
260      \subfigure[{\footnotesize C-LSR-fs $-$ C-LSR-ns}]
261      {\includegraphics[width=0.44\textwidth]{\fpath/JFMheff2000_lsr_slip-lsr_noslip}}
262      \subfigure[{\footnotesize C-EVP-ns $-$ C-LSR-ns}]
263      {\includegraphics[width=0.44\textwidth]{\fpath/JFMheff2000_evp_noslip-lsr_noslip}}
264      \caption{(a) Effective thickness (volume per unit area) of the
265        C-LSR-ns solution, averaged over the months Janurary through March
266        2000 [m]; (b)-(d) difference between B-LSR-ns, C-LSR-fs, C-EVP-ns,
267        and C-LSR-ns solutions [cm/s].}
268      \label{fig:icethick}
269    \end{figure}
270    %
271    The generally weaker ice drift velocities in the B-LSR-ns solution,
272    when compared to the C-LSR-ns solution, in particular through the
273    narrow passages in the Canadian Archipelago, lead to a larger build-up
274    of ice north of Greenland and the Archipelago by 2\,m effective
275    thickness and more in the B-grid solution (\reffig{icethick}b). But
276    the ice volume in not larger everywhere: further west, there are
277    patches of smaller ice volume in the B-grid solution, most likely
278    because the Beaufort Gyre is weaker and hence not as effective in
279    transporting ice westwards. There are also dipoles of ice volume
280    differences with more ice on the upstream side of island groups and
281    less ice in their lee, such as Franz-Josef-Land and \ml{IDONTKNOW},
282    because ice tends to flow along coasts less easily in the B-LSR-ns
283    solution.
284    
285    Imposing a free-slip boundary condition in C-LSR-fs leads to a much
286    smaller differences to C-LSR-ns than the transition from the B-grid to
287    the C-grid (\reffig{icethick}c), but in the Canadian Archipelago it
288    still reduces the effective ice thickness by up to 2\,m where the ice
289    is thick and the straits are narrow. Dipoles of ice thickness
290    differences can also be observed around islands, because the free-slip
291    solution allows more flow around islands than the no-slip solution.
292    Everywhere else the ice volume is affected only slightly by the
293    different boundary condition.
294    %
295    The C-EVP-ns solution has generally stronger drift velocities than the
296    C-LSR-ns solution. Consequently, more ice can be moved from the eastern
297    part of the Arctic, where ice volumes are smaller, to the western
298    Arctic where ice piles up along the coast (\reffig{icethick}d). Within
299    the Canadian Archipelago, more drift leads to faster ice export and
300    reduced effective ice thickness.
301    
302    The difference in ice volume and ice drift velocities between the
303    different experiments has consequences for the ice transport out of
304    the Arctic. Although by far the most exported ice drifts through the
305    Fram Strait (approximately $2300\pm610\text{\,km$^3$\,y$^{-1}$}$), a
306    considerable amount (order $160\text{\,km$^3$\,y$^{-1}$}$) ice is
307    exported through the Canadian Archipelago \citep[and references
308    therein]{serreze06}.  \reffig{archipelago} shows a time series of
309    \ml{[maybe smooth to different time scales:] daily averaged, smoothed
310      with monthly running means,} ice transports through various straits
311    in the Canadian Archipelago and the Fram Strait for the different
312    model solutions. The export through Fram Strait agrees with the
313    observations in all model solutions (annual averages range from $2112$
314    to $2425\text{\,km$^3$\,y$^{-1}$}$), while the export through
315    Lancaster Sound is lower (annual averages are $66$ to
316    $256\text{\,km$^3$\,y$^{-1}$}$) than observed
317    \citep[???][]{lancaster}.  Generally, the C-EVP solutions have highest
318    maximum (export out of the Artic) and minimum (import into the Artic)
319    fluxes as the drift velocities are largest in this solution.  In the
320    extreme, both B- and C-grid LSOR solvers have practically no ice
321    transport through the Nares Strait, which is only a few grid points
322    wide, while the C-EVP solutions allow up to
323    $600\text{\,km$^3$\,y$^{-1}$}$ in summer. As as consequence, the
324    import into the Candian Archipelago is overestimated in all EVP
325    solutions (range: $539$ to $773\text{\,km$^3$\,y$^{-1}$}$), while the
326    C-LSR solutions get the order of magnitude right (range: $132$ to
327    $165\text{\,km$^3$\,y$^{-1}$}$); the B-LSR-ns solution grossly
328    underestimates the ice transport with $77\text{\,km$^3$\,y$^{-1}$}$.
329  \begin{figure}  \begin{figure}
330  %\centerline{{\includegraphics*[width=0.44\linewidth]{\fpath/arctic1.eps}}}  %\centerline{{\includegraphics*[width=0.6\linewidth]{\fpath/Jan1992xport}}}
331  \caption{Bathymetry of Arctic Domain.\label{fig:arctic1}}  \centerline{{\includegraphics*[width=0.6\linewidth]{\fpath/ice_export}}}
332    \caption{Transport through Canadian Archipelago for different solver
333      flavors. The letters refer to the labels of the sections in
334      \reffig{arctic_topog}; positive values are flux out of the Arctic;
335      legend abbreviations are explained in \reftab{experiments}.
336    \label{fig:archipelago}}
337  \end{figure}  \end{figure}
338    
339  There are 50 vertical levels ranging in thickness from 10 m near the surface  \ml{[Transport to narrow straits, area?, more runs, TEM, advection
340  to approximately 450 m at a maximum model depth of 6150 m. Bathymetry is from    schemes, Winton TD, discussion about differences in terms of model
341  the National Geophysical Data Center (NGDC) 2-minute gridded global relief    error? that's tricky as it means refering to Tremblay, thus our ice
342  data (ETOPO2) and the model employs the partial-cell formulation of    models are all erroneous!]}
343  \citet{adcroft97:_shaved_cells}, which permits accurate representation of the bathymetry. The  
344  model is integrated in a volume-conserving configuration using a finite volume  In summary, we find that different dynamical solvers can yield very
345  discretization with C-grid staggering of the prognostic variables. In the  different solutions. In contrast, the differences between free-slip
346  ocean, the non-linear equation of state of \citet{jackett95}.  The ocean model is  and no-slip solutions \emph{with the same solver} are considerably
347  coupled to a sea-ice model described hereinabove.    smaller (the difference for the EVP solver is not shown, but similar
348    to that for the LSOR solver). Albeit smaller, the differences between
349  This particular ECCO2 simulation is initialized from rest using the  free and no-slip solutions in ice drift can lead to large differences
350  January temperature and salinity distribution from the World Ocean  in ice volume over the integration time. At first, this observation
351  Atlas 2001 (WOA01) [Conkright et al., 2002] and it is integrated for  seems counterintuitive, as we expect that the solution
352  32 years prior to the 1996--2001 period discussed in the study. Surface  \emph{technique} should not affect the \emph{solution} to a higher
353  boundary conditions are from the National Centers for Environmental  degree than actually modifying the equations. A more detailed study on
354  Prediction and the National Center for Atmospheric Research  these differences is beyond the scope of this paper, but at this point
355  (NCEP/NCAR) atmospheric reanalysis [Kistler et al., 2001]. Six-hourly  we may speculate, that the large difference between B-grid, C-grid,
356  surface winds, temperature, humidity, downward short- and long-wave  LSOR, and EVP solutions stem from incomplete convergence of the
357  radiations, and precipitation are converted to heat, freshwater, and  solvers due to linearization and due to different methods of
358  wind stress fluxes using the \citet{large81, large82} bulk formulae.  linearization \citep[and Bruno Tremblay, personal
359  Shortwave radiation decays exponentially as per Paulson and Simpson  communication]{hunke01}: if the convergence of the non-linear momentum
360  [1977]. Additionally the time-mean river run-off from Large and Nurser  equations is not complete for all linearized solvers, then one can
361  [2001] is applied and there is a relaxation to the monthly-mean  imagine that each solver stops at a different point in velocity-space
362  climatological sea surface salinity values from WOA01 with a  thus leading to different solutions for the ice drift velocities. If
363  relaxation time scale of 3 months. Vertical mixing follows  this were true, this tantalizing circumstance had a dramatic impact on
364  \citet{large94} with background vertical diffusivity of  sea-ice modeling in general, and we would need to improve the solution
365  $1.5\times10^{-5}\text{\,m$^{2}$\,s$^{-1}$}$ and viscosity of  technique of dynamic sea ice model, most likely at a very high
366  $10^{-3}\text{\,m$^{2}$\,s$^{-1}$}$. A third order, direct-space-time  compuational cost (Bruno Tremblay, personal communication).
367  advection scheme with flux limiter is employed \citep{hundsdorfer94}  
368  and there is no explicit horizontal diffusivity. Horizontal viscosity  
 follows \citet{lei96} but  
 modified to sense the divergent flow as per Fox-Kemper and Menemenlis  
 [in press].  Shortwave radiation decays exponentially as per Paulson  
 and Simpson [1977].  Additionally, the time-mean runoff of Large and  
 Nurser [2001] is applied near the coastline and, where there is open  
 water, there is a relaxation to monthly-mean WOA01 sea surface  
 salinity with a time constant of 45 days.  
   
 Open water, dry  
 ice, wet ice, dry snow, and wet snow albedo are, respectively, 0.15, 0.85,  
 0.76, 0.94, and 0.8.  
369    
370  \begin{itemize}  \begin{itemize}
371  \item Configuration  \item Configuration
# Line 82  ice, wet ice, dry snow, and wet snow alb Line 385  ice, wet ice, dry snow, and wet snow alb
385  \end{itemize}  \end{itemize}
386    
387  \begin{itemize}  \begin{itemize}
388  \item B-grid LSR no-slip  \item B-grid LSR no-slip: B-LSR-ns
389  \item C-grid LSR no-slip  \item C-grid LSR no-slip: C-LSR-ns
390  \item C-grid LSR slip  \item C-grid LSR slip:    C-LSR-fs
391  \item C-grid EVP no-slip  \item C-grid EVP no-slip: C-EVP-ns
392  \item C-grid EVP slip  \item C-grid EVP slip:    C-EVP-fs
393  \item C-grid LSR + TEM (truncated ellipse method, no tensile stress, new flag)  \item C-grid LSR + TEM (truncated ellipse method, no tensile stress,
394  \item C-grid LSR no-slip + Winton    new flag): C-LSR-ns+TEM
395    \item C-grid LSR with different advection scheme: 33 vs 77, vs. default?
396    \item C-grid LSR no-slip + Winton:
397  \item  speed-performance-accuracy (small)  \item  speed-performance-accuracy (small)
398    ice transport through Canadian Archipelago differences    ice transport through Canadian Archipelago differences
399    thickness distribution differences    thickness distribution differences
# Line 104  We anticipate small differences between Line 409  We anticipate small differences between
409  \item VP vs.\ EVP: speed performance, accuracy?  \item VP vs.\ EVP: speed performance, accuracy?
410  \item ocean stress: different water mass properties beneath the ice  \item ocean stress: different water mass properties beneath the ice
411  \end{itemize}  \end{itemize}
412    
413    %\begin{figure}
414    %\centerline{{\includegraphics*[width=0.6\linewidth]{\fpath/JFM1992uvice}}}
415    %\caption{Surface sea ice velocity for different solver flavors.
416    %\label{fig:iceveloc}}
417    %\end{figure}
418    
419    %\begin{figure}
420    %\centerline{{\includegraphics*[width=0.6\linewidth]{\fpath/JFM2000heff}}}
421    %\caption{Sea ice thickness for different solver flavors.
422    %\label{fig:icethick}}
423    %\end{figure}
424    
425    %%% Local Variables:
426    %%% mode: latex
427    %%% TeX-master: "ceaice"
428    %%% End:
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