Changeset 14303 for NEMO/trunk/doc/latex/NEMO/subfiles/chap_SBC.tex
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NEMO/trunk/doc/latex/NEMO/subfiles/chap_SBC.tex
r14257 r14303 15 15 \hline 16 16 {\em next} & {\em Simon M{\" u}ller} & {\em Update of \autoref{sec:SBC_TDE}; revision of \autoref{subsec:SBC_fwb}}\\[2mm] 17 {\em next} & {\em Pierre Mathiot} & {\em update of the ice shelf section (2019 developments)}\\[2mm] 17 18 {\em 4.0} & {\em ...} & {\em ...} \\ 18 19 {\em 3.6} & {\em ...} & {\em ...} \\ … … 72 73 (\np[=0..3]{nn_ice}{nn\_ice}), 73 74 \item the addition of river runoffs as surface freshwater fluxes or lateral inflow (\np[=.true.]{ln_rnf}{ln\_rnf}), 74 \item the addition of ice-shelf melting as lateral inflow (parameterisation) or75 as fluxes applied at the land-ice ocean interface (\np[=.true.]{ln_isf}{ln\_isf}),76 75 \item the addition of a freshwater flux adjustment in order to avoid a mean sea-level drift 77 76 (\np[=0..2]{nn_fwb}{nn\_fwb}), … … 97 96 One of these is modification by icebergs (see \autoref{sec:SBC_ICB_icebergs}), 98 97 which act as drifting sources of fresh water. 99 Another example of modification is that due to the ice shelf melting/freezing (see \autoref{sec:SBC_isf}),100 which provides additional sources of fresh water.101 98 102 99 %% ================================================================================================= … … 1181 1178 1182 1179 %% ================================================================================================= 1183 \section[Ice shelf melting (\textit{sbcisf.F90})]{Ice shelf melting (\protect\mdl{sbcisf})}1184 \label{sec: SBC_isf}1180 \section[Ice Shelf (ISF)]{Interaction with ice shelves (ISF)} 1181 \label{sec:isf} 1185 1182 1186 1183 \begin{listing} 1187 % \nlst{namsbc_isf}1188 \caption{\forcode{&nam sbc_isf}}1189 \label{lst:nam sbc_isf}1184 \nlst{namisf} 1185 \caption{\forcode{&namisf}} 1186 \label{lst:namisf} 1190 1187 \end{listing} 1191 1188 1192 The namelist variable in \nam{sbc}{sbc}, \np{nn_isf}{nn\_isf}, controls the ice shelf representation. 1193 Description and result of sensitivity test to \np{nn_isf}{nn\_isf} are presented in \citet{mathiot.jenkins.ea_GMD17}. 1194 The different options are illustrated in \autoref{fig:SBC_isf}. 1195 1189 The namelist variable in \nam{isf}{isf}, \np{ln_isf}{ln\_isf}, controls the ice shelf interactions: 1196 1190 \begin{description} 1197 \item [{\np[=1]{nn_isf}{nn\_isf}}]: The ice shelf cavity is represented (\np[=.true.]{ln_isfcav}{ln\_isfcav} needed). 1198 The fwf and heat flux are depending of the local water properties. 1199 1200 Two different bulk formulae are available: 1191 \item $\bullet$ representation of the ice shelf/ocean melting/freezing for opened cavity (cav, \np{ln_isfcav_mlt}{ln\_isfcav\_mlt}). 1192 \item $\bullet$ parametrisation of the ice shelf/ocean melting/freezing for closed cavities (par, \np{ln_isfpar_mlt}{ln\_isfpar\_mlt}). 1193 \item $\bullet$ coupling with an ice sheet model (\np{ln_isfcpl}{ln\_isfcpl}). 1194 \end{description} 1195 1196 \subsection{Ocean/Ice shelf fluxes in opened cavities} 1197 1198 \np{ln_isfcav_mlt}{ln\_isfcav\_mlt}\forcode{ = .true.} activates the ocean/ice shelf thermodynamics interactions at the ice shelf/ocean interface. 1199 If \np{ln_isfcav_mlt}\forcode{ = .false.}, thermodynamics interactions are desctivated but the ocean dynamics inside the cavity is still active. 1200 The logical flag \np{ln_isfcav}{ln\_isfcav} control whether or not the ice shelf cavities are closed. \np{ln_isfcav}{ln\_isfcav} is not defined in the namelist but in the domcfg.nc input file.\\ 1201 1202 3 options are available to represent to ice-shelf/ocean fluxes at the interface: 1203 \begin{description} 1204 \item[\np{cn_isfcav_mlt}\forcode{ = 'spe'}]: 1205 The fresh water flux is specified by a forcing fields \np{sn_isfcav_fwf}{sn\_isfcav\_fwf}. Convention of the input file is: positive toward the ocean (i.e. positive for melting and negative for freezing). 1206 The latent heat fluxes is derived from the fresh water flux. 1207 The heat content flux is derived from the fwf flux assuming a temperature set to the freezing point in the top boundary layer (\np{rn_htbl}{rn\_htbl}) 1208 1209 \item[\np{cn_isfcav_mlt}\forcode{ = 'oasis'}]: 1210 The \forcode{'oasis'} is a prototype of what could be a method to spread precipitation on Antarctic ice sheet as ice shelf melt inside the cavity when a coupled model Atmosphere/Ocean is used. 1211 It has not been tested and therefore the model will stop if you try to use it. 1212 Actions will be undertake in 2020 to build a comprehensive interface to do so for Greenland, Antarctic and ice shelf (cav), ice shelf (par), icebergs, subglacial runoff and runoff. 1213 1214 \item[\np{cn_isfcav_mlt}\forcode{ = '2eq'}]: 1215 The heat flux and the fresh water flux (negative for melting) resulting from ice shelf melting/freezing are parameterized following \citet{Grosfeld1997}. 1216 This formulation is based on a balance between the vertical diffusive heat flux across the ocean top boundary layer (\autoref{eq:ISOMIP1}) 1217 and the latent heat due to melting/freezing (\autoref{eq:ISOMIP2}): 1218 1219 \begin{equation} 1220 \label{eq:ISOMIP1} 1221 \mathcal{Q}_h = \rho c_p \gamma (T_w - T_f) 1222 \end{equation} 1223 \begin{equation} 1224 \label{eq:ISOMIP2} 1225 q = \frac{-\mathcal{Q}_h}{L_f} 1226 \end{equation} 1227 1228 where $\mathcal{Q}_h$($W.m^{-2}$) is the heat flux,q($kg.s^{-1}m^{-2}$) the fresh-water flux, 1229 $L_f$ the specific latent heat, $T_w$ the temperature averaged over a boundary layer below the ice shelf (explained below), 1230 $T_f$ the freezing point using the pressure at the ice shelf base and the salinity of the water in the boundary layer, 1231 and $\gamma$ the thermal exchange coefficient. 1232 1233 \item[\np{cn_isfcav_mlt}\forcode{ = '3eq'}]: 1234 For realistic studies, the heat and freshwater fluxes are parameterized following \citep{Jenkins2001}. This formulation is based on three equations: 1235 a balance between the vertical diffusive heat flux across the boundary layer 1236 , the latent heat due to melting/freezing of ice and the vertical diffusive heat flux into the ice shelf (\autoref{eq:3eq1}); 1237 a balance between the vertical diffusive salt flux across the boundary layer and the salt source or sink represented by the melting/freezing (\autoref{eq:3eq2}); 1238 and a linear equation for the freezing temperature of sea water (\autoref{eq:3eq3}, detailed of the linearisation coefficient in \citet{AsayDavis2016}): 1239 1240 \begin{equation} 1241 \label{eq:3eq1} 1242 c_p \rho \gamma_T (T_w-T_b) = -L_f q - \rho_i c_{p,i} \kappa \frac{T_s - T_b}{h_{isf}} 1243 \end{equation} 1244 \begin{equation} 1245 \label{eq:3eq2} 1246 \rho \gamma_S (S_w - S_b) = (S_i - S_b)q 1247 \end{equation} 1248 \begin{equation} 1249 \label{eq:3eq3} 1250 T_b = \lambda_1 S_b + \lambda_2 +\lambda_3 z_{isf} 1251 \end{equation} 1252 1253 where $T_b$ is the temperature at the interface, $S_b$ the salinity at the interface, $\gamma_T$ and $\gamma_S$ the exchange coefficients for temperature and salt, respectively, 1254 $S_i$ the salinity of the ice (assumed to be 0), $h_{isf}$ the ice shelf thickness, $z_{isf}$ the ice shelf draft, $\rho_i$ the density of the iceshelf, 1255 $c_{p,i}$ the specific heat capacity of the ice, $\kappa$ the thermal diffusivity of the ice 1256 and $T_s$ the atmospheric surface temperature (at the ice/air interface, assumed to be -20C). 1257 The Liquidus slope ($\lambda_1$), the liquidus intercept ($\lambda_2$) and the Liquidus pressure coefficient ($\lambda_3$) 1258 for TEOS80 and TEOS10 are described in \citep{AsayDavis2016} and in \citep{Jourdain2017}. 1259 The linear system formed by \autoref{eq:3eq1}, \autoref{eq:3eq2} and the linearised equation for the freezing temperature of sea water (\autoref{eq:3eq3}) can be solved for $S_b$ or $T_b$. 1260 Afterward, the freshwater flux ($q$) and the heat flux ($\mathcal{Q}_h$) can be computed. 1261 1262 \end{description} 1263 1264 \begin{table}[h] 1265 \centering 1266 \caption{Description of the parameters hard coded into the ISF module} 1267 \label{tab:isf} 1268 \begin{tabular}{|l|l|l|l|} 1269 \hline 1270 Symbol & Description & Value & Unit \\ 1271 \hline 1272 $C_p$ & Ocean specific heat & 3992 & $J.kg^{-1}.K^{-1}$ \\ 1273 $L_f$ & Ice latent heat of fusion & $3.34 \times 10^5$ & $J.kg^{-1}$ \\ 1274 $C_{p,i}$ & Ice specific heat & 2000 & $J.kg^{-1}.K^{-1}$ \\ 1275 $\kappa$ & Heat diffusivity & $1.54 \times 10^{-6}$& $m^2.s^{-1}$ \\ 1276 $\rho_i$ & Ice density & 920 & $kg.m^3$ \\ 1277 \hline 1278 \end{tabular} 1279 \end{table} 1280 1281 Temperature and salinity used to compute the fluxes in \autoref{eq:ISOMIP1}, \autoref{eq:3eq1} and \autoref{eq:3eq2} are the average temperature in the top boundary layer \citep{losch_JGR08}. 1282 Its thickness is defined by \np{rn_htbl}{rn\_htbl}. 1283 The fluxes and friction velocity are computed using the mean temperature, salinity and velocity in the first \np{rn_htbl}{rn\_htbl} m. 1284 Then, the fluxes are spread over the same thickness (ie over one or several cells). 1285 If \np{rn_htbl}{rn\_htbl} is larger than top $e_{3}t$, there is no more direct feedback between the freezing point at the interface and the top cell temperature. 1286 This can lead to super-cool temperature in the top cell under melting condition. 1287 If \np{rn_htbl}{rn\_htbl} smaller than top $e_{3}t$, the top boundary layer thickness is set to the top cell thickness.\\ 1288 1289 Each melt formula (\np{cn_isfcav_mlt}\forcode{ = '3eq'} or \np{cn_isfcav_mlt}\forcode{ = '2eq'}) depends on an exchange coeficient ($\Gamma^{T,S}$) between the ocean and the ice. 1290 Below, the exchange coeficient $\Gamma^{T}$ and $\Gamma^{S}$ are respectively defined by \np{rn_gammat0}{rn\_gammat0} and \np{rn_gammas0}{rn\_gammas0}. 1291 There are 3 different ways to compute the exchange velocity: 1292 1293 \begin{description} 1294 \item[\np{cn_gammablk}\forcode{='spe'}]: 1295 The salt and heat exchange coefficients are constant and defined by: 1296 \[ 1297 \gamma^{T} = \Gamma^{T} 1298 \] 1299 \[ 1300 \gamma^{S} = \Gamma^{S} 1301 \] 1302 This is the recommended formulation for ISOMIP. 1303 1304 \item[\np{cn_gammablk}\forcode{='vel'}]: 1305 The salt and heat exchange coefficients are velocity dependent and defined as 1306 \[ 1307 \gamma^{T} = \Gamma^{T} \times u_{*} 1308 \] 1309 \[ 1310 \gamma^{S} = \Gamma^{S} \times u_{*} 1311 \] 1312 where $u_{*}$ is the friction velocity in the top boundary layer (ie first \np{rn_htbl}{rn\_htbl} meters). 1313 See \citet{jenkins.nicholls.ea_JPO10} for all the details on this formulation. It is the recommended formulation for realistic application and ISOMIP+/MISOMIP configuration. 1314 1315 \item[\np{cn_gammablk}\forcode{'vel\_stab'}]: 1316 The salt and heat exchange coefficients are velocity and stability dependent and defined as: 1317 \[ 1318 \gamma^{T,S} = \frac{u_{*}}{\Gamma_{Turb} + \Gamma^{T,S}_{Mole}} 1319 \] 1320 where $u_{*}$ is the friction velocity in the top boundary layer (ie first \np{rn_tbl}{rn\_htbl} meters), 1321 $\Gamma_{Turb}$ the contribution of the ocean stability and 1322 $\Gamma^{T,S}_{Mole}$ the contribution of the molecular diffusion. 1323 See \citet{holland.jenkins_JPO99} for all the details on this formulation. 1324 This formulation has not been extensively tested in NEMO (not recommended). 1325 \end{description} 1326 1327 \subsection{Ocean/Ice shelf fluxes in parametrised cavities} 1201 1328 1202 1329 \begin{description} 1203 \item [{\np[=1]{nn_isfblk}{nn\_isfblk}}]: The melt rate is based on a balance between the upward ocean heat flux and 1204 the latent heat flux at the ice shelf base. A complete description is available in \citet{hunter_trpt06}. 1205 \item [{\np[=2]{nn_isfblk}{nn\_isfblk}}]: The melt rate and the heat flux are based on a 3 equations formulation 1206 (a heat flux budget at the ice base, a salt flux budget at the ice base and a linearised freezing point temperature equation). 1207 A complete description is available in \citet{jenkins_JGR91}. 1330 1331 \item[\np{cn_isfpar_mlt}\forcode{ = 'bg03'}]: 1332 The ice shelf cavities are not represented. 1333 The fwf and heat flux are computed using the \citet{beckmann.goosse_OM03} parameterisation of isf melting. 1334 The fluxes are distributed along the ice shelf edge between the depth of the average grounding line (GL) 1335 (\np{sn_isfpar_zmax}{sn\_isfpar\_zmax}) and the base of the ice shelf along the calving front 1336 (\np{sn_isfpar_zmin}{sn\_isfpar\_zmin}) as in (\np{cn_isfpar_mlt}\forcode{ = 'spe'}). 1337 The effective melting length (\np{sn_isfpar_Leff}{sn\_isfpar\_Leff}) is read from a file. 1338 This parametrisation has not been tested since a while and based on \citet{Favier2019}, 1339 this parametrisation should probably not be used. 1340 1341 \item[\np{cn_isfpar_mlt}\forcode{ = 'spe'}]: 1342 The ice shelf cavity is not represented. 1343 The fwf (\np{sn_isfpar_fwf}{sn\_isfpar\_fwf}) is prescribed and distributed along the ice shelf edge between 1344 the depth of the average grounding line (GL) (\np{sn_isfpar_zmax}{sn\_isfpar\_zmax}) and 1345 the base of the ice shelf along the calving front (\np{sn_isfpar_zmin}{sn\_isfpar\_min}). Convention of the input file is positive toward the ocean (i.e. positive for melting and negative for freezing). 1346 The heat flux ($Q_h$) is computed as $Q_h = fwf \times L_f$. 1347 1348 \item[\np{cn_isfpar_mlt}\forcode{ = 'oasis'}]: 1349 The \forcode{'oasis'} is a prototype of what could be a method to spread precipitation on Antarctic ice sheet as ice shelf melt inside the cavity when a coupled model Atmosphere/Ocean is used. 1350 It has not been tested and therefore the model will stop if you try to use it. 1351 Action will be undertake in 2020 to build a comprehensive interface to do so for Greenland, Antarctic and ice shelf (cav), ice shelf (par), icebergs, subglacial runoff and runoff. 1352 1208 1353 \end{description} 1209 1354 1210 Temperature and salinity used to compute the melt are the average temperature in the top boundary layer \citet{losch_JGR08}. 1211 Its thickness is defined by \np{rn_hisf_tbl}{rn\_hisf\_tbl}. 1212 The fluxes and friction velocity are computed using the mean temperature, salinity and velocity in the the first \np{rn_hisf_tbl}{rn\_hisf\_tbl} m. 1213 Then, the fluxes are spread over the same thickness (ie over one or several cells). 1214 If \np{rn_hisf_tbl}{rn\_hisf\_tbl} larger than top $e_{3}t$, there is no more feedback between the freezing point at the interface and the the top cell temperature. 1215 This can lead to super-cool temperature in the top cell under melting condition. 1216 If \np{rn_hisf_tbl}{rn\_hisf\_tbl} smaller than top $e_{3}t$, the top boundary layer thickness is set to the top cell thickness.\\ 1217 1218 Each melt bulk formula depends on a exchange coeficient ($\Gamma^{T,S}$) between the ocean and the ice. 1219 There are 3 different ways to compute the exchange coeficient: 1220 \begin{description} 1221 \item [{\np[=0]{nn_gammablk}{nn\_gammablk}}]: The salt and heat exchange coefficients are constant and defined by \np{rn_gammas0}{rn\_gammas0} and \np{rn_gammat0}{rn\_gammat0}. 1222 \begin{gather*} 1223 % \label{eq:SBC_isf_gamma_iso} 1224 \gamma^{T} = rn\_gammat0 \\ 1225 \gamma^{S} = rn\_gammas0 1226 \end{gather*} 1227 This is the recommended formulation for ISOMIP. 1228 \item [{\np[=1]{nn_gammablk}{nn\_gammablk}}]: The salt and heat exchange coefficients are velocity dependent and defined as 1229 \begin{gather*} 1230 \gamma^{T} = rn\_gammat0 \times u_{*} \\ 1231 \gamma^{S} = rn\_gammas0 \times u_{*} 1232 \end{gather*} 1233 where $u_{*}$ is the friction velocity in the top boundary layer (ie first \np{rn_hisf_tbl}{rn\_hisf\_tbl} meters). 1234 See \citet{jenkins.nicholls.ea_JPO10} for all the details on this formulation. It is the recommended formulation for realistic application. 1235 \item [{\np[=2]{nn_gammablk}{nn\_gammablk}}]: The salt and heat exchange coefficients are velocity and stability dependent and defined as: 1236 \[ 1237 \gamma^{T,S} = \frac{u_{*}}{\Gamma_{Turb} + \Gamma^{T,S}_{Mole}} 1238 \] 1239 where $u_{*}$ is the friction velocity in the top boundary layer (ie first \np{rn_hisf_tbl}{rn\_hisf\_tbl} meters), 1240 $\Gamma_{Turb}$ the contribution of the ocean stability and 1241 $\Gamma^{T,S}_{Mole}$ the contribution of the molecular diffusion. 1242 See \citet{holland.jenkins_JPO99} for all the details on this formulation. 1243 This formulation has not been extensively tested in \NEMO\ (not recommended). 1244 \end{description} 1245 \item [{\np[=2]{nn_isf}{nn\_isf}}]: The ice shelf cavity is not represented. 1246 The fwf and heat flux are computed using the \citet{beckmann.goosse_OM03} parameterisation of isf melting. 1247 The fluxes are distributed along the ice shelf edge between the depth of the average grounding line (GL) 1248 (\np{sn_depmax_isf}{sn\_depmax\_isf}) and the base of the ice shelf along the calving front 1249 (\np{sn_depmin_isf}{sn\_depmin\_isf}) as in (\np[=3]{nn_isf}{nn\_isf}). 1250 The effective melting length (\np{sn_Leff_isf}{sn\_Leff\_isf}) is read from a file. 1251 \item [{\np[=3]{nn_isf}{nn\_isf}}]: The ice shelf cavity is not represented. 1252 The fwf (\np{sn_rnfisf}{sn\_rnfisf}) is prescribed and distributed along the ice shelf edge between 1253 the depth of the average grounding line (GL) (\np{sn_depmax_isf}{sn\_depmax\_isf}) and 1254 the base of the ice shelf along the calving front (\np{sn_depmin_isf}{sn\_depmin\_isf}). 1255 The heat flux ($Q_h$) is computed as $Q_h = fwf \times L_f$. 1256 \item [{\np[=4]{nn_isf}{nn\_isf}}]: The ice shelf cavity is opened (\np[=.true.]{ln_isfcav}{ln\_isfcav} needed). 1257 However, the fwf is not computed but specified from file \np{sn_fwfisf}{sn\_fwfisf}). 1258 The heat flux ($Q_h$) is computed as $Q_h = fwf \times L_f$. 1259 As in \np[=1]{nn_isf}{nn\_isf}, the fluxes are spread over the top boundary layer thickness (\np{rn_hisf_tbl}{rn\_hisf\_tbl}) 1260 \end{description} 1261 1262 $\bullet$ \np[=1]{nn_isf}{nn\_isf} and \np[=2]{nn_isf}{nn\_isf} compute a melt rate based on 1355 \np{cn_isfcav_mlt}\forcode{ = '2eq'}, \np{cn_isfcav_mlt}\forcode{ = '3eq'} and \np{cn_isfpar_mlt}\forcode{ = 'bg03'} compute a melt rate based on 1263 1356 the water mass properties, ocean velocities and depth. 1264 Th is flux is thus highly dependent of the model resolution (horizontal and vertical),1265 realism of the water masses onto the shelf ...\\1266 1267 $\bullet$ \np[=3]{nn_isf}{nn\_isf} and \np[=4]{nn_isf}{nn\_isf} read the melt rate from a file.1357 The resulting fluxes are thus highly dependent of the model resolution (horizontal and vertical) and 1358 realism of the water masses onto the shelf.\\ 1359 1360 \np{cn_isfcav_mlt}\forcode{ = 'spe'} and \np{cn_isfpar_mlt}\forcode{ = 'spe'} read the melt rate from a file. 1268 1361 You have total control of the fwf forcing. 1269 1362 This can be useful if the water masses on the shelf are not realistic or 1270 1363 the resolution (horizontal/vertical) are too coarse to have realistic melting or 1271 for studies where you need to control your heat and fw input.\\ 1272 1273 The ice shelf melt is implemented as a volume flux as for the runoff. 1274 The fw addition due to the ice shelf melting is, at each relevant depth level, added to 1275 the horizontal divergence (\textit{hdivn}) in the subroutine \rou{sbc\_isf\_div}, called from \mdl{divhor}. 1276 See \autoref{sec:SBC_rnf} for all the details about the divergence correction. 1364 for studies where you need to control your heat and fw input. 1365 However, if your forcing is not consistent with the dynamics below you can reach unrealistic low water temperature.\\ 1366 1367 The ice shelf fwf is implemented as a volume flux as for the runoff. 1368 The fwf addition due to the ice shelf melting is, at each relevant depth level, added to 1369 the horizontal divergence (\textit{hdivn}) in the subroutine \rou{isf\_hdiv}, called from \mdl{divhor}. 1370 See the runoff section \autoref{sec:SBC_rnf} for all the details about the divergence correction.\\ 1371 1372 Description and result of sensitivity tests to \np{ln_isfcav_mlt}{ln\_isfcav\_mlt} and \np{ln_isfpar_mlt}{ln\_isfpar\_mlt} are presented in \citet{mathiot.jenkins.ea_GMD17}. 1373 The different options are illustrated in \autoref{fig:ISF}. 1277 1374 1278 1375 \begin{figure}[!t] 1279 1376 \centering 1280 \includegraphics[width=0.66\textwidth]{SBC_isf }1377 \includegraphics[width=0.66\textwidth]{SBC_isf_v4.2} 1281 1378 \caption[Ice shelf location and fresh water flux definition]{ 1282 1379 Illustration of the location where the fwf is injected and 1283 whether or not the fwf is interacti f or not depending of \protect\np{nn_isf}{nn\_isf}.}1284 \label{fig: SBC_isf}1380 whether or not the fwf is interactive or not.} 1381 \label{fig:ISF} 1285 1382 \end{figure} 1286 1383 1287 %% ================================================================================================= 1288 \section{Ice sheet coupling} 1289 \label{sec:SBC_iscpl} 1290 1291 \begin{listing} 1292 % \nlst{namsbc_iscpl} 1293 \caption{\forcode{&namsbc_iscpl}} 1294 \label{lst:namsbc_iscpl} 1295 \end{listing} 1384 \subsection{Available outputs} 1385 The following outputs are availables via XIOS: 1386 \begin{description} 1387 \item[for parametrised cavities]: 1388 \begin{xmllines} 1389 <field id="isftfrz_par" long_name="freezing point temperature in the parametrization boundary layer" unit="degC" /> 1390 <field id="fwfisf_par" long_name="Ice shelf melt rate" unit="kg/m2/s" /> 1391 <field id="qoceisf_par" long_name="Ice shelf ocean heat flux" unit="W/m2" /> 1392 <field id="qlatisf_par" long_name="Ice shelf latent heat flux" unit="W/m2" /> 1393 <field id="qhcisf_par" long_name="Ice shelf heat content flux of injected water" unit="W/m2" /> 1394 <field id="fwfisf3d_par" long_name="Ice shelf melt rate" unit="kg/m2/s" grid_ref="grid_T_3D" /> 1395 <field id="qoceisf3d_par" long_name="Ice shelf ocean heat flux" unit="W/m2" grid_ref="grid_T_3D" /> 1396 <field id="qlatisf3d_par" long_name="Ice shelf latent heat flux" unit="W/m2" grid_ref="grid_T_3D" /> 1397 <field id="qhcisf3d_par" long_name="Ice shelf heat content flux of injected water" unit="W/m2" grid_ref="grid_T_3D" /> 1398 <field id="ttbl_par" long_name="temperature in the parametrisation boundary layer" unit="degC" /> 1399 <field id="isfthermald_par" long_name="thermal driving of ice shelf melting" unit="degC" /> 1400 \end{xmllines} 1401 \item[for open cavities]: 1402 \begin{xmllines} 1403 <field id="isftfrz_cav" long_name="freezing point temperature at ocean/isf interface" unit="degC" /> 1404 <field id="fwfisf_cav" long_name="Ice shelf melt rate" unit="kg/m2/s" /> 1405 <field id="qoceisf_cav" long_name="Ice shelf ocean heat flux" unit="W/m2" /> 1406 <field id="qlatisf_cav" long_name="Ice shelf latent heat flux" unit="W/m2" /> 1407 <field id="qhcisf_cav" long_name="Ice shelf heat content flux of injected water" unit="W/m2" /> 1408 <field id="fwfisf3d_cav" long_name="Ice shelf melt rate" unit="kg/m2/s" grid_ref="grid_T_3D" /> 1409 <field id="qoceisf3d_cav" long_name="Ice shelf ocean heat flux" unit="W/m2" grid_ref="grid_T_3D" /> 1410 <field id="qlatisf3d_cav" long_name="Ice shelf latent heat flux" unit="W/m2" grid_ref="grid_T_3D" /> 1411 <field id="qhcisf3d_cav" long_name="Ice shelf heat content flux of injected water" unit="W/m2" grid_ref="grid_T_3D" /> 1412 <field id="ttbl_cav" long_name="temperature in Losch tbl" unit="degC" /> 1413 <field id="isfthermald_cav" long_name="thermal driving of ice shelf melting" unit="degC" /> 1414 <field id="isfgammat" long_name="Ice shelf heat-transfert velocity" unit="m/s" /> 1415 <field id="isfgammas" long_name="Ice shelf salt-transfert velocity" unit="m/s" /> 1416 <field id="stbl" long_name="salinity in the Losh tbl" unit="1e-3" /> 1417 <field id="utbl" long_name="zonal current in the Losh tbl at T point" unit="m/s" /> 1418 <field id="vtbl" long_name="merid current in the Losh tbl at T point" unit="m/s" /> 1419 <field id="isfustar" long_name="ustar at T point used in ice shelf melting" unit="m/s" /> 1420 <field id="qconisf" long_name="Conductive heat flux through the ice shelf" unit="W/m2" /> 1421 \end{xmllines} 1422 \end{description} 1423 1424 %% ================================================================================================= 1425 \subsection{Ice sheet coupling} 1426 \label{subsec:ISF_iscpl} 1296 1427 1297 1428 Ice sheet/ocean coupling is done through file exchange at the restart step. 1298 At each restart step :1299 1300 \begin{ enumerate}1301 \item the ice sheet model send a new bathymetry and ice shelf draft netcdf file.1302 \item a new domcfg.nc file is built using the DOMAINcfg tools.1303 \item \NEMO\run for a specific period and output the average melt rate over the period.1304 \item the ice sheet model run using the melt rate outputed in step 4.1305 \item go back to 1.1306 \end{ enumerate}1307 1308 If \np [=.true.]{ln_iscpl}{ln\_iscpl}, the isf draft is assume to be different at each restart step with1429 At each restart step, the procedure is this one: 1430 1431 \begin{description} 1432 \item[Step 1]: the ice sheet model send a new bathymetry and ice shelf draft netcdf file. 1433 \item[Step 2]: a new domcfg.nc file is built using the DOMAINcfg tools. 1434 \item[Step 3]: NEMO run for a specific period and output the average melt rate over the period. 1435 \item[Step 4]: the ice sheet model run using the melt rate outputed in step 3. 1436 \item[Step 5]: go back to 1. 1437 \end{description} 1438 1439 If \np{ln_iscpl}\forcode{ = .true.}, the isf draft is assume to be different at each restart step with 1309 1440 potentially some new wet/dry cells due to the ice sheet dynamics/thermodynamics. 1310 The wetting and drying scheme applied on the restart is very simple and described below for the 6 different possible cases:1441 The wetting and drying scheme, applied on the restart, is very simple. The 6 different possible cases for the tracer and ssh are: 1311 1442 1312 1443 \begin{description} 1313 \item [Thin a cell down]: T/S/ssh are unchanged and U/V in the top cell are corrected to keep the barotropic transport (bt) constant 1314 ($bt_b=bt_n$). 1315 \item [Enlarge a cell]: See case "Thin a cell down" 1316 \item [Dry a cell]: mask, T/S, U/V and ssh are set to 0. 1317 Furthermore, U/V into the water column are modified to satisfy ($bt_b=bt_n$). 1318 \item [Wet a cell]: mask is set to 1, T/S is extrapolated from neighbours, $ssh_n = ssh_b$ and U/V set to 0. 1319 If no neighbours, T/S is extrapolated from old top cell value. 1320 If no neighbours along i,j and k (both previous test failed), T/S/U/V/ssh and mask are set to 0. 1321 \item [Dry a column]: mask, T/S, U/V are set to 0 everywhere in the column and ssh set to 0. 1322 \item [Wet a column]: set mask to 1, T/S is extrapolated from neighbours, ssh is extrapolated from neighbours and U/V set to 0. 1323 If no neighbour, T/S/U/V and mask set to 0. 1444 \item[Thin a cell]: 1445 T/S/ssh are unchanged. 1446 1447 \item[Enlarge a cell]: 1448 See case "Thin a cell down" 1449 1450 \item[Dry a cell]: 1451 Mask, T/S, U/V and ssh are set to 0. 1452 1453 \item[Wet a cell]: 1454 Mask is set to 1, T/S is extrapolated from neighbours, $ssh_n = ssh_b$. 1455 If no neighbours, T/S is extrapolated from old top cell value. 1456 If no neighbours along i,j and k (both previous tests failed), T/S/ssh and mask are set to 0. 1457 1458 \item[Dry a column]: 1459 mask, T/S and ssh are set to 0. 1460 1461 \item[Wet a column]: 1462 set mask to 1, T/S/ssh are extrapolated from neighbours. 1463 If no neighbour, T/S/ssh and mask set to 0. 1324 1464 \end{description} 1465 1466 The method described above will strongly affect the barotropic transport under an ice shelf when the geometry change. 1467 In order to keep the model stable, an adjustment of the dynamics at the initialisation after the coupling step is needed. 1468 The idea behind this is to keep $\pd[\eta]{t}$ as it should be without change in geometry at the initialisation. 1469 This will prevent any strong velocity due to large pressure gradient. 1470 To do so, we correct the horizontal divergence before $\pd[\eta]{t}$ is computed in the first time step.\\ 1325 1471 1326 1472 Furthermore, as the before and now fields are not compatible (modification of the geometry), … … 1329 1475 The horizontal extrapolation to fill new cell with realistic value is called \np{nn_drown}{nn\_drown} times. 1330 1476 It means that if the grounding line retreat by more than \np{nn_drown}{nn\_drown} cells between 2 coupling steps, 1331 the code will be unable to fill all the new wet cells properly .1477 the code will be unable to fill all the new wet cells properly and the model is likely to blow up at the initialisation. 1332 1478 The default number is set up for the MISOMIP idealised experiments. 1333 1479 This coupling procedure is able to take into account grounding line and calving front migration. 1334 However, it is a non-conservative proc esse.1480 However, it is a non-conservative proccess. 1335 1481 This could lead to a trend in heat/salt content and volume.\\ 1336 1482 1337 1483 In order to remove the trend and keep the conservation level as close to 0 as possible, 1338 a simple conservation scheme is available with \np[=.true.]{ln_hsb}{ln\_hsb}. 1339 The heat/salt/vol. gain/loss is diagnosed, as well as the location. 1340 A correction increment is computed and apply each time step during the next \np{rn_fiscpl}{rn\_fiscpl} time steps. 1341 For safety, it is advised to set \np{rn_fiscpl}{rn\_fiscpl} equal to the coupling period (smallest increment possible). 1342 The corrective increment is apply into the cell itself (if it is a wet cell), the neigbouring cells or the closest wet cell (if the cell is now dry). 1484 a simple conservation scheme is available with \np{ln_isfcpl_cons}\forcode{ = .true.}. 1485 The heat/salt/vol. gain/loss are diagnosed, as well as the location. 1486 A correction increment is computed and applied each time step during the model run. 1487 The corrective increment are applied into the cells itself (if it is a wet cell), the neigbouring cells or the closest wet cell (if the cell is now dry). 1343 1488 1344 1489 %% ================================================================================================= … … 1388 1533 which are assumed to propagate with their larger parent and thus delay fluxing into the ocean. 1389 1534 Melt water (and other variables on the configuration grid) are written into the main \NEMO\ model output files. 1535 1536 By default, iceberg thermodynamic and dynamic are computed using ocean surface variable (sst, ssu, ssv) and the icebergs are not sensible to the bathymetry (only to land) whatever the iceberg draft. 1537 \citet{Merino_OM2016} developed an option to use vertical profiles of ocean currents and temperature instead (\np{ln_M2016}{ln\_M2016}). 1538 Full details on the sensitivity to this parameter in done in \citet{Merino_OM2016}. 1539 If \np{ln_M2016}{ln\_M2016} activated, \np{ln_icb_grd}{ln\_icb\_grd} activate (or not) an option to prevent thick icebergs to move across shallow bank (ie shallower than the iceberg draft). 1540 This option need to be used with care as it could required to either change the distribution to prevent generation of icebergs with draft larger than the bathymetry 1541 or to build a variable \forcode{maxclass} to prevent NEMO filling the icebergs classes too thick for the local bathymetry. 1390 1542 1391 1543 Extensive diagnostics can be produced.
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