- Timestamp:
- 2015-12-04T17:56:07+01:00 (8 years ago)
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branches/2015/dev_MetOffice_merge_2015/DOC/TexFiles/Chapters/Chap_SBC.tex
r5120 r6006 996 996 at each relevant depth level, added to the horizontal divergence (\textit{hdivn}) in the subroutine \rou{sbc\_isf\_div} 997 997 (called from \mdl{divcur}). 998 999 \section{ Ice sheet coupling} 1000 \label{SBC_iscpl} 1001 %------------------------------------------namsbc_iscpl---------------------------------------------------- 1002 \namdisplay{namsbc_iscpl} 1003 %-------------------------------------------------------------------------------------------------------- 1004 Ice sheet/ocean coupling is done through file exchange at the restart step. NEMO, at each restart step, 1005 read the bathymetry and ice shelf draft variable in a netcdf file. 1006 If \np{ln\_iscpl = ~true}, the isf draft is assume to be different at each restart step 1007 with potentially some new wet/dry cells due to the ice sheet dynamics/thermodynamics. 1008 The wetting and drying scheme applied on the restart is very simple and described below for the 6 different cases: 1009 \begin{description} 1010 \item[Thin a cell down:] 1011 T/S/ssh are unchanged and U/V in the top cell are corrected to keep the barotropic transport (bt) constant ($bt_b=bt_n$). 1012 \item[Enlarge a cell:] 1013 See case "Thin a cell down" 1014 \item[Dry a cell:] 1015 mask, T/S, U/V and ssh are set to 0. Furthermore, U/V into the water column are modified to satisfy ($bt_b=bt_n$). 1016 \item[Wet a cell:] 1017 mask is set to 1, T/S is extrapolated from neighbours, $ssh_n = ssh_b$ and U/V set to 0. If no neighbours along i,j and k, T/S/U/V and mask are set to 0. 1018 \item[Dry a column:] 1019 mask, T/S, U/V are set to 0 everywhere in the column and ssh set to 0. 1020 \item[Wet a column:] 1021 set mask to 1, T/S is extrapolated from neighbours, ssh is extrapolated from neighbours and U/V set to 0. If no neighbour, T/S/U/V and mask set to 0. 1022 \end{description} 1023 The extrapolation is call \np{nn\_drown} times. It means that if the grounding line retreat by more than \np{nn\_drown} cells between 2 coupling steps, 1024 the code will be unable to fill all the new wet cells properly. The default number is set up for the MISOMIP idealised experiments.\\ 1025 This coupling procedure is able to take into account grounding line and calving front migration. However, it is a non-conservative processe. 1026 This could lead to a trend in heat/salt content and volume. In order to remove the trend and keep the conservation level as close to 0 as possible, 1027 a simple conservation scheme is available with \np{ln\_hsb = ~true}. The heat/salt/vol. gain/loss is diagnose, as well as the location. 1028 Based on what is done on sbcrnf to prescribed a source of heat/salt/vol., the heat/salt/vol. gain/loss is removed/added, 1029 over a period of \np{rn\_fiscpl} time step, into the system. 1030 So after \np{rn\_fiscpl} time step, all the heat/salt/vol. gain/loss due to extrapolation process is canceled.\\ 1031 1032 As the before and now fields are not compatible (modification of the geometry), the restart time step is prescribed to be an euler time step instead of a leap frog and $fields_b = fields_n$. 998 1033 % 999 1034 % ================================================================
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