| 36 |
used. |
used. |
| 37 |
|
|
| 38 |
The ocean model is coupled to the sea-ice model discussed in |
The ocean model is coupled to the sea-ice model discussed in |
| 39 |
Section~\ref{sec:model} with the following specific options. The |
Section~\ref{sec:model} using the following specific options. The |
| 40 |
zero-heat-capacity thermodynamics formulation of \citet{hib80} is used to |
zero-heat-capacity thermodynamics formulation of \citet{hib80} is used to |
| 41 |
compute sea ice thickness and concentration. Snow cover and sea ice salinity |
compute sea ice thickness and concentration. Snow cover and sea ice salinity |
| 42 |
are prognostic. |
are prognostic. Open water, dry ice, wet ice, dry snow, and wet snow albedo |
| 43 |
|
are, respectively, 0.15, 0.88, 0.79, 0.97, and 0.83. Ice mechanics follow the |
| 44 |
Ice mechanics follow the viscous plastic rheology of |
viscous plastic rheology of \citet{hibler79} and the ice momentum equation is |
| 45 |
\citet{hibler79} and the ice momentum equation is solved numerically using the |
solved numerically using the C-grid implementation of the \citet{zhang97} LSR |
| 46 |
C-grid implementation of the \citet{zha97} LSR dyanmics model discussed |
dynamics model discussed hereinabove. The ice is coupled to the ocean using |
| 47 |
hereinabove. |
the rescaled vertical coordinate system, z$^\ast$, of |
| 48 |
|
\citet{cam08}, that is, sea ice does not float above the ocean model but |
| 49 |
Open water, dry |
rather deforms the ocean's model surface level. |
| 50 |
ice, wet ice, dry snow, and wet snow albedo are, respectively, 0.15, 0.85, |
|
| 51 |
0.76, 0.94, and 0.8. |
This particular ECCO2 simulation is initialized from temperature and salinity |
| 52 |
|
fields derived from the Polar science center Hydrographic Climatology (PHC) |
| 53 |
\subsection{Arctic Domain with Open Boundaries} |
3.0 \citep{ste01a}. Surface boundary conditions for the period January 1979 to |
| 54 |
\label{sec:arctic} |
July 2002 are derived from the European Centre for Medium-Range Weather |
| 55 |
|
Forecasts (ECMWF) 40 year re-analysis (ERA-40) \citep{upp05}. Surface |
| 56 |
|
boundary conditions after September 2002 are derived from the ECMWF |
| 57 |
|
operational analysis. There is a one month transition period, August 2002, |
| 58 |
|
during which the ERA-40 contribution decreases linearly from 1 to 0 and the |
| 59 |
|
ECMWF analysis contribution increases linearly from 0 to 1. Six-hourly |
| 60 |
|
surface winds, temperature, humidity, downward short- and long-wave |
| 61 |
|
radiations, and precipitation are converted to heat, freshwater, and wind |
| 62 |
|
stress fluxes using the \citet{large81,large82} bulk formulae. Shortwave |
| 63 |
|
radiation decays exponentially as per \citet{pau77}. Low frequency |
| 64 |
|
precipitation has been adjusted using the pentad (5-day) data from the Global |
| 65 |
|
Precipitation Climatology Project (GPCP) \citep{huf01}. The time-mean river |
| 66 |
|
run-off from \citet{lar01} is applied globally, except in the Arctic Ocean |
| 67 |
|
where monthly mean river runoff based on the Arctic Runoff Data Base (ARDB) |
| 68 |
|
and prepared by P. Winsor (personnal communication, 2007) is specificied. |
| 69 |
|
Additionally, there is a relaxation to the monthly-mean climatological sea |
| 70 |
|
surface salinity values from PHC 3.0, a relaxation time scale of 101 days. |
| 71 |
|
|
| 72 |
|
Vertical mixing follows \citet{lar94} but with meridionally and vertically |
| 73 |
|
varying background vertical diffusivity; at the surface, vertical diffusivity |
| 74 |
|
is $4.4\times 10^{-6}$~m$^2$~s$^{-1}$ at the Equator, $3.6\times |
| 75 |
|
10^{-6}$~m$^2$~s$^{-1}$ north of 70$^\circ$N, and $1.9\times |
| 76 |
|
10^{-5}$~m$^2$~s$^{-1}$ south of 30$^\circ$S and between 30$^\circ$N and |
| 77 |
|
60$^\circ$N , with sinusoidally varying values in between these latitudes; |
| 78 |
|
vertically, diffusivity increases to $1.1\times 10^{-4}$~m$^2$~s$^{-1}$ at a a |
| 79 |
|
depth of 6150 m as per \citet{bry79}. A high order monotonicity-preserving |
| 80 |
|
advection scheme \citep{dar04} is employed and there is no explicit horizontal |
| 81 |
|
diffusivity. Horizontal viscosity follows \citet{lei96} but modified to sense |
| 82 |
|
the divergent flow as per \citet{kem08}. |
| 83 |
|
|
| 84 |
\subsection{Arctic Domain with Open Boundaries} |
\subsection{Arctic Domain with Open Boundaries} |
| 85 |
\label{sec:arctic} |
\label{sec:arctic} |
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