diff --git a/cime_config/config_grids.xml b/cime_config/config_grids.xml
index 7cdd7f0a0557..6315b4613e26 100755
--- a/cime_config/config_grids.xml
+++ b/cime_config/config_grids.xml
@@ -409,6 +409,16 @@
       <mask>IcoswISC30E3r5</mask>
     </model_grid>
 
+    <model_grid alias="T62_RRSwISC6to18E3r4" compset="(DATM|XATM|SATM)">
+      <grid name="atm">T62</grid>
+      <grid name="lnd">T62</grid>
+      <grid name="ocnice">RRSwISC6to18E3r4</grid>
+      <grid name="rof">rx1</grid>
+      <grid name="glc">null</grid>
+      <grid name="wav">null</grid>
+      <mask>RRSwISC6to18E3r4</mask>
+    </model_grid>
+
     <model_grid alias="TL319_oEC60to30v3" compset="(DATM|XATM|SATM)">
       <grid name="atm">TL319</grid>
       <grid name="lnd">TL319</grid>
@@ -529,6 +539,16 @@
       <mask>IcoswISC30E3r5</mask>
     </model_grid>
 
+    <model_grid alias="TL319_RRSwISC6to18E3r4" compset="(DATM|XATM|SATM)">
+      <grid name="atm">TL319</grid>
+      <grid name="lnd">TL319</grid>
+      <grid name="ocnice">RRSwISC6to18E3r4</grid>
+      <grid name="rof">JRA025</grid>
+      <grid name="glc">null</grid>
+      <grid name="wav">null</grid>
+      <mask>RRSwISC6to18E3r4</mask>
+    </model_grid>
+
     <model_grid alias="TL319_oRRS18to6v3" compset="(DATM|XATM|SATM)">
       <grid name="atm">TL319</grid>
       <grid name="lnd">TL319</grid>
@@ -1213,6 +1233,16 @@
       <mask>IcoswISC30E3r5</mask>
     </model_grid>
 
+    <model_grid alias="ne30pg2_RRSwISC6to18E3r4">
+      <grid name="atm">ne30np4.pg2</grid>
+      <grid name="lnd">ne30np4.pg2</grid>
+      <grid name="ocnice">RRSwISC6to18E3r4</grid>
+      <grid name="rof">r05</grid>
+      <grid name="glc">null</grid>
+      <grid name="wav">null</grid>
+      <mask>RRSwISC6to18E3r4</mask>
+    </model_grid>
+
     <model_grid alias="northamericax4v1_r0125_northamericax4v1" compset="(DOCN|XOCN|SOCN|AQP1)">
       <grid name="atm">ne0np4_northamericax4v1</grid>
       <grid name="lnd">r0125</grid>
@@ -1376,6 +1406,16 @@
       <mask>oRRS18to6v3</mask>
     </model_grid>
 
+    <model_grid alias="ne120pg2_r0125_RRSwISC6to18E3r4">
+      <grid name="atm">ne120np4.pg2</grid>
+      <grid name="lnd">r0125</grid>
+      <grid name="ocnice">RRSwISC6to18E3r4</grid>
+      <grid name="rof">r0125</grid>
+      <grid name="glc">null</grid>
+      <grid name="wav">null</grid>
+      <mask>RRSwISC6to18E3r4</mask>
+    </model_grid>
+
     <model_grid alias="ne60_ne60" compset="(DOCN|XOCN|SOCN|AQP1)">
       <grid name="atm">ne60np4</grid>
       <grid name="lnd">ne60np4</grid>
@@ -1466,6 +1506,26 @@
       <mask>IcoswISC30E3r5</mask>
     </model_grid>
 
+    <model_grid alias="ne120pg2_r05_RRSwISC6to18E3r4">
+      <grid name="atm">ne120np4.pg2</grid>
+      <grid name="lnd">r05</grid>
+      <grid name="ocnice">RRSwISC6to18E3r4</grid>
+      <grid name="rof">r05</grid>
+      <grid name="glc">null</grid>
+      <grid name="wav">null</grid>
+      <mask>RRSwISC6to18E3r4</mask>
+    </model_grid>
+
+    <model_grid alias="ne120pg2_r025_RRSwISC6to18E3r4">
+      <grid name="atm">ne120np4.pg2</grid>
+      <grid name="lnd">r025</grid>
+      <grid name="ocnice">RRSwISC6to18E3r4</grid>
+      <grid name="rof">r025</grid>
+      <grid name="glc">null</grid>
+      <grid name="wav">null</grid>
+      <mask>RRSwISC6to18E3r4</mask>
+    </model_grid>
+
     <model_grid alias="ne240_ne240" compset="(DOCN|XOCN|SOCN|AQP1)">
       <grid name="atm">ne240np4</grid>
       <grid name="lnd">ne240np4</grid>
@@ -2034,6 +2094,16 @@
       <mask>IcoswISC30E3r5</mask>
     </model_grid>
 
+    <model_grid alias="ne30pg2_r05_RRSwISC6to18E3r4">
+      <grid name="atm">ne30np4.pg2</grid>
+      <grid name="lnd">r05</grid>
+      <grid name="ocnice">RRSwISC6to18E3r4</grid>
+      <grid name="rof">r05</grid>
+      <grid name="glc">null</grid>
+      <grid name="wav">null</grid>
+      <mask>RRSwISC6to18E3r4</mask>
+    </model_grid>
+
     <model_grid alias="ne30pg2_r05_WC14to60E2r3">
       <grid name="atm">ne30np4.pg2</grid>
       <grid name="lnd">r05</grid>
@@ -2344,6 +2414,7 @@
       <file grid="atm|lnd" mask="SOwISC12to60E2r4">$DIN_LOC_ROOT/share/domains/domain.lnd.T62_SOwISC12to60E2r4.210119.nc</file>
       <file grid="atm|lnd" mask="ECwISC30to60E2r1">$DIN_LOC_ROOT/share/domains/domain.lnd.T62_ECwISC30to60E2r1.201007.nc</file>
       <file grid="atm|lnd" mask="IcoswISC30E3r5">$DIN_LOC_ROOT/share/domains/domain.lnd.T62_IcoswISC30E3r5.231121.nc</file>
+      <file grid="atm|lnd" mask="RRSwISC6to18E3r4">$DIN_LOC_ROOT/share/domains/domain.lnd.T62_RRSwISC6to18E3r4.240108.nc</file>
       <desc>T62 is Gaussian grid:</desc>
     </domain>
 
@@ -2388,6 +2459,8 @@
       <file grid="ice|ocn" mask="ECwISC30to60E2r1">$DIN_LOC_ROOT/share/domains/domain.ocn.TL319_ECwISC30to60E2r1.201007.nc</file>
       <file grid="atm|lnd" mask="IcoswISC30E3r5">$DIN_LOC_ROOT/share/domains/domain.lnd.TL319_IcoswISC30E3r5.231121.nc</file>
       <file grid="ice|ocn" mask="IcoswISC30E3r5">$DIN_LOC_ROOT/share/domains/domain.ocn.TL319_IcoswISC30E3r5.231121.nc</file>
+      <file grid="atm|lnd" mask="RRSwISC6to18E3r4">$DIN_LOC_ROOT/share/domains/domain.lnd.TL319_RRSwISC6to18E3r4.240108.nc</file>
+      <file grid="ice|ocn" mask="RRSwISC6to18E3r4">$DIN_LOC_ROOT/share/domains/domain.ocn.TL319_RRSwISC6to18E3r4.240108.nc</file>
       <file grid="atm|lnd" mask="oRRS18to6v3">$DIN_LOC_ROOT/share/domains/domain.lnd.TL319_oRRS18to6v3.220124.nc</file>
       <file grid="ice|ocn" mask="oRRS18to6v3">$DIN_LOC_ROOT/share/domains/domain.ocn.TL319_oRRS18to6v3.220124.nc</file>
       <desc>TL319 is JRA lat/lon grid:</desc>
@@ -2497,6 +2570,8 @@
       <file grid="ice|ocn" mask="oRRS18to6v3">$DIN_LOC_ROOT/share/domains/domain.ocn.ne30pg2_oRRS18to6v3.211101.nc</file>
       <file grid="atm|lnd" mask="IcoswISC30E3r5">$DIN_LOC_ROOT/share/domains/domain.lnd.ne30pg2_IcoswISC30E3r5.231121.nc</file>
       <file grid="ice|ocn" mask="IcoswISC30E3r5">$DIN_LOC_ROOT/share/domains/domain.ocn.ne30pg2_IcoswISC30E3r5.231121.nc</file>
+      <file grid="atm|lnd" mask="RRSwISC6to18E3r4">$DIN_LOC_ROOT/share/domains/domain.lnd.ne30pg2_RRSwISC6to18E3r4.240108.nc</file>
+      <file grid="ice|ocn" mask="RRSwISC6to18E3r4">$DIN_LOC_ROOT/share/domains/domain.ocn.ne30pg2_RRSwISC6to18E3r4.240108.nc</file>
       <file grid="atm|lnd" mask="gx1v6">$DIN_LOC_ROOT/share/domains/domain.lnd.ne30pg2_gx1v6.190806.nc</file>
       <file grid="ice|ocn" mask="gx1v6">$DIN_LOC_ROOT/share/domains/domain.ocn.ne30pg2_gx1v6.190806.nc</file>
       <desc>ne30np4.pg2 is Spectral Elem 1-deg grid w/ 2x2 FV physics grid per element:</desc>
@@ -2568,6 +2643,8 @@
       <file grid="ice|ocn" mask="ICOS10">$DIN_LOC_ROOT/share/domains/domain.ocn.ne120pg2_ICOS10.230120.nc</file>
       <file grid="atm|lnd" mask="IcoswISC30E3r5">$DIN_LOC_ROOT/share/domains/domain.lnd.ne120pg2_IcoswISC30E3r5.231121.nc</file>
       <file grid="ice|ocn" mask="IcoswISC30E3r5">$DIN_LOC_ROOT/share/domains/domain.ocn.ne120pg2_IcoswISC30E3r5.231121.nc</file>
+      <file grid="atm|lnd" mask="RRSwISC6to18E3r4">$DIN_LOC_ROOT/share/domains/domain.lnd.ne120pg2_RRSwISC6to18E3r4.240108.nc</file>
+      <file grid="ice|ocn" mask="RRSwISC6to18E3r4">$DIN_LOC_ROOT/share/domains/domain.ocn.ne120pg2_RRSwISC6to18E3r4.240108.nc</file>
       <file grid="atm|lnd" mask="gx1v6">$DIN_LOC_ROOT/share/domains/domain.lnd.ne120pg2_gx1v6.190819.nc</file>
       <file grid="ice|ocn" mask="gx1v6">$DIN_LOC_ROOT/share/domains/domain.ocn.ne120pg2_gx1v6.190819.nc</file>
       <desc>ne120np4 is Spectral Elem 1/4-deg grid w/ 2x2 FV physics grid</desc>
@@ -2771,6 +2848,13 @@
       <desc>IcoswISC30E3r5 is a MPAS ocean grid generated with the jigsaw/compass process using a dual mesh that is a subdivided icosahedron, resulting in a nearly uniform resolution of 30 km. Additionally, it has ocean in ice-shelf cavities:</desc>
     </domain>
 
+    <domain name="RRSwISC6to18E3r4">
+      <nx>4085395</nx>
+      <ny>1</ny>
+      <file grid="ice|ocn">$DIN_LOC_ROOT/share/domains/domain.ocn.RRSwISC6to18E3r4.240108.nc</file>
+      <desc>RRSwISC6to18E3r4 is a MPAS ocean grid generated with the jigsaw/compass process using a mesh density function that is roughly proportional to the Rossby radius of deformation, with 18 km gridcells at low and 6 km gridcells at high latitudes. Additionally, it has ocean in ice-shelf cavities:</desc>
+    </domain>
+
     <!-- ROF (river) grids-->
 
     <domain name="r2">
@@ -2803,10 +2887,20 @@
       <file grid="lnd" mask="WC14to60E2r3">$DIN_LOC_ROOT/share/domains/domain.lnd.r05_WC14to60E2r3.200929.nc</file>
       <file grid="atm" mask="IcoswISC30E3r5">$DIN_LOC_ROOT/share/domains/domain.lnd.r05_IcoswISC30E3r5.231121.nc</file>
       <file grid="lnd" mask="IcoswISC30E3r5">$DIN_LOC_ROOT/share/domains/domain.lnd.r05_IcoswISC30E3r5.231121.nc</file>
+      <file grid="atm" mask="RRSwISC6to18E3r4">$DIN_LOC_ROOT/share/domains/domain.lnd.r05_RRSwISC6to18E3r4.240108.nc</file>
+      <file grid="lnd" mask="RRSwISC6to18E3r4">$DIN_LOC_ROOT/share/domains/domain.lnd.r05_RRSwISC6to18E3r4.240108.nc</file>
       <file grid="lnd" mask="gx1v6">$DIN_LOC_ROOT/share/domains/domain.lnd.r05_gx1v6.191014.nc</file>
       <desc>r05 is 1/2 degree river routing grid:</desc>
     </domain>
 
+    <domain name="r025">
+      <nx>1440</nx>
+      <ny>720</ny>
+      <file grid="atm" mask="RRSwISC6to18E3r4">$DIN_LOC_ROOT/share/domains/domain.lnd.r025_RRSwISC6to18E3r4.240212.nc</file>
+      <file grid="lnd" mask="RRSwISC6to18E3r4">$DIN_LOC_ROOT/share/domains/domain.lnd.r025_RRSwISC6to18E3r4.240212.nc</file>
+      <desc>r025 is 1/4 degree river routing grid:</desc>
+    </domain>
+
     <domain name="r01">
       <nx>3600</nx>
       <ny>1800</ny>
@@ -2829,6 +2923,8 @@
       <file grid="lnd" mask="gx1v6">$DIN_LOC_ROOT/share/domains/domain.lnd.r0125_gx1v6.191017.nc</file>
       <file grid="atm" mask="oARRM60to10">$DIN_LOC_ROOT/share/domains/domain.lnd.r0125_oARRM60to10.210630.nc</file>
       <file grid="lnd" mask="oARRM60to10">$DIN_LOC_ROOT/share/domains/domain.lnd.r0125_oARRM60to10.210630.nc</file>
+      <file grid="atm" mask="RRSwISC6to18E3r4">$DIN_LOC_ROOT/share/domains/domain.lnd.r0125_RRSwISC6to18E3r4.240108.nc</file>
+      <file grid="lnd" mask="RRSwISC6to18E3r4">$DIN_LOC_ROOT/share/domains/domain.lnd.r0125_RRSwISC6to18E3r4.240108.nc</file>
       <desc>r0125 is 1/8 degree river routing grid:</desc>
     </domain>
 
@@ -3265,6 +3361,14 @@
       <map name="OCN2ATM_SMAPNAME">cpl/gridmaps/IcoswISC30E3r5/map_IcoswISC30E3r5_to_ne30pg2_traave.20231121.nc</map>
     </gridmap>
 
+    <gridmap atm_grid="ne30np4.pg2" ocn_grid="RRSwISC6to18E3r4">
+      <map name="ATM2OCN_FMAPNAME">cpl/gridmaps/ne30pg2/map_ne30pg2_to_RRSwISC6to18E3r4_traave.20240108.nc</map>
+      <map name="ATM2OCN_VMAPNAME">cpl/gridmaps/ne30pg2/map_ne30pg2_to_RRSwISC6to18E3r4_trbilin.20240108.nc</map>
+      <map name="ATM2OCN_SMAPNAME">cpl/gridmaps/ne30pg2/map_ne30pg2_to_RRSwISC6to18E3r4-nomask_trbilin.20240108.nc</map>
+      <map name="OCN2ATM_FMAPNAME">cpl/gridmaps/RRSwISC6to18E3r4/map_RRSwISC6to18E3r4_to_ne30pg2_traave.20240108.nc</map>
+      <map name="OCN2ATM_SMAPNAME">cpl/gridmaps/RRSwISC6to18E3r4/map_RRSwISC6to18E3r4_to_ne30pg2_traave.20240108.nc</map>
+    </gridmap>
+
     <gridmap atm_grid="ne30np4.pg3" ocn_grid="oEC60to30v3">
       <map name="ATM2OCN_FMAPNAME">cpl/gridmaps/ne30pg3/map_ne30pg3_to_oEC60to30v3_mono.200331.nc</map>
       <map name="ATM2OCN_VMAPNAME">cpl/gridmaps/ne30pg3/map_ne30pg3_to_oEC60to30v3_bilin.200331.nc</map>
@@ -3438,6 +3542,13 @@
       <map name="ATM2ROF_SMAPNAME">cpl/gridmaps/ne120pg2/map_ne120pg2_to_r0125_mono.200707.nc</map>
     </gridmap>
 
+    <gridmap atm_grid="ne120np4.pg2" lnd_grid="r025">
+      <map name="ATM2LND_FMAPNAME">cpl/gridmaps/ne120pg2/map_ne120pg2_to_r025_traave.20240212.nc</map>
+      <map name="ATM2LND_SMAPNAME">cpl/gridmaps/ne120pg2/map_ne120pg2_to_r025_traave.20240212.nc</map>
+      <map name="LND2ATM_FMAPNAME">cpl/gridmaps/ne120pg2/map_r025_to_ne120pg2_traave.20240212.nc</map>
+      <map name="LND2ATM_SMAPNAME">cpl/gridmaps/ne120pg2/map_r025_to_ne120pg2_traave.20240212.nc</map>
+    </gridmap>
+
     <gridmap atm_grid="ne120np4" ocn_grid="oRRS18to6v3">
       <map name="ATM2OCN_FMAPNAME">cpl/gridmaps/ne120np4/map_ne120np4_to_oRRS18to6v3_mono.20200702.nc</map>
       <map name="ATM2OCN_VMAPNAME">cpl/gridmaps/ne120np4/map_ne120np4_to_oRRS18to6v3_mono.20200702.nc</map>
@@ -3486,6 +3597,14 @@
       <map name="OCN2ATM_SMAPNAME">cpl/gridmaps/IcoswISC30E3r5/map_IcoswISC30E3r5_to_ne120pg2_traave.20231121.nc</map>
     </gridmap>
 
+    <gridmap atm_grid="ne120np4.pg2" ocn_grid="RRSwISC6to18E3r4">
+      <map name="ATM2OCN_FMAPNAME">cpl/gridmaps/ne120pg2/map_ne120pg2_to_RRSwISC6to18E3r4_traave.20240108.nc</map>
+      <map name="ATM2OCN_VMAPNAME">cpl/gridmaps/ne120pg2/map_ne120pg2_to_RRSwISC6to18E3r4_trbilin.20240108.nc</map>
+      <map name="ATM2OCN_SMAPNAME">cpl/gridmaps/ne120pg2/map_ne120pg2_to_RRSwISC6to18E3r4-nomask_trbilin.20240108.nc</map>
+      <map name="OCN2ATM_FMAPNAME">cpl/gridmaps/RRSwISC6to18E3r4/map_RRSwISC6to18E3r4_to_ne120pg2_traave.20240108.nc</map>
+      <map name="OCN2ATM_SMAPNAME">cpl/gridmaps/RRSwISC6to18E3r4/map_RRSwISC6to18E3r4_to_ne120pg2_traave.20240108.nc</map>
+    </gridmap>
+
     <gridmap atm_grid="ne120np4.pg2" lnd_grid="r05">
       <map name="ATM2LND_FMAPNAME">cpl/gridmaps/ne120pg2/map_ne120pg2_to_r05_mono.200331.nc</map>
       <map name="ATM2LND_SMAPNAME">cpl/gridmaps/ne120pg2/map_ne120pg2_to_r05_bilin.200331.nc</map>
@@ -3498,6 +3617,11 @@
       <map name="ATM2ROF_SMAPNAME">cpl/gridmaps/ne120pg2/map_ne120pg2_to_r05_bilin.200331.nc</map>
     </gridmap>
 
+    <gridmap atm_grid="ne120np4.pg2" rof_grid="r025">
+      <map name="ATM2ROF_FMAPNAME">cpl/gridmaps/ne120pg2/map_ne120pg2_to_r025_traave.20240212.nc</map>
+      <map name="ATM2ROF_SMAPNAME">cpl/gridmaps/ne120pg2/map_ne120pg2_to_r025_trbilin.20240212.nc</map>
+    </gridmap>
+
     <gridmap atm_grid="ne240np4" ocn_grid="gx1v6">
       <map name="ATM2OCN_FMAPNAME">cpl/gridmaps/ne240np4/map_ne240np4_to_gx1v6_aave_110428.nc</map>
       <map name="ATM2OCN_SMAPNAME">cpl/gridmaps/ne240np4/map_ne240np4_to_gx1v6_aave_110428.nc</map>
@@ -3984,6 +4108,14 @@
       <map name="OCN2ATM_SMAPNAME">cpl/gridmaps/IcoswISC30E3r5/map_IcoswISC30E3r5_to_T62_traave.20231121.nc</map>
     </gridmap>
 
+    <gridmap atm_grid="T62" ocn_grid="RRSwISC6to18E3r4">
+      <map name="ATM2OCN_FMAPNAME">cpl/gridmaps/T62/map_T62_to_RRSwISC6to18E3r4_traave.20240108.nc</map>
+      <map name="ATM2OCN_SMAPNAME">cpl/gridmaps/T62/map_T62_to_RRSwISC6to18E3r4-nomask_trbilin.20240108.nc</map>
+      <map name="ATM2OCN_VMAPNAME">cpl/gridmaps/T62/map_T62_to_RRSwISC6to18E3r4_esmfpatch.20240108.nc</map>
+      <map name="OCN2ATM_FMAPNAME">cpl/gridmaps/RRSwISC6to18E3r4/map_RRSwISC6to18E3r4_to_T62_traave.20240108.nc</map>
+      <map name="OCN2ATM_SMAPNAME">cpl/gridmaps/RRSwISC6to18E3r4/map_RRSwISC6to18E3r4_to_T62_traave.20240108.nc</map>
+    </gridmap>
+
     <gridmap atm_grid="TL319" ocn_grid="oEC60to30v3">
       <map name="ATM2OCN_FMAPNAME">cpl/gridmaps/TL319/map_TL319_to_oEC60to30v3_aave.181203.nc</map>
       <map name="ATM2OCN_SMAPNAME">cpl/gridmaps/TL319/map_TL319_to_oEC60to30v3_bilin.181203.nc</map>
@@ -4080,6 +4212,14 @@
       <map name="OCN2ATM_SMAPNAME">cpl/gridmaps/IcoswISC30E3r5/map_IcoswISC30E3r5_to_TL319_traave.20231121.nc</map>
     </gridmap>
 
+    <gridmap atm_grid="TL319" ocn_grid="RRSwISC6to18E3r4">
+      <map name="ATM2OCN_FMAPNAME">cpl/gridmaps/TL319/map_TL319_to_RRSwISC6to18E3r4_traave.20240108.nc</map>
+      <map name="ATM2OCN_SMAPNAME">cpl/gridmaps/TL319/map_TL319_to_RRSwISC6to18E3r4-nomask_trbilin.20240108.nc</map>
+      <map name="ATM2OCN_VMAPNAME">cpl/gridmaps/TL319/map_TL319_to_RRSwISC6to18E3r4_esmfpatch.20240108.nc</map>
+      <map name="OCN2ATM_FMAPNAME">cpl/gridmaps/RRSwISC6to18E3r4/map_RRSwISC6to18E3r4_to_TL319_traave.20240108.nc</map>
+      <map name="OCN2ATM_SMAPNAME">cpl/gridmaps/RRSwISC6to18E3r4/map_RRSwISC6to18E3r4_to_TL319_traave.20240108.nc</map>
+    </gridmap>
+
     <gridmap atm_grid="TL319" ocn_grid="oRRS18to6v3">
       <map name="ATM2OCN_FMAPNAME">cpl/gridmaps/TL319/map_TL319_to_oRRS18to6v3_aave.220124.nc</map>
       <map name="ATM2OCN_SMAPNAME">cpl/gridmaps/TL319/map_TL319_to_oRRS18to6v3_bilin.220124.nc</map>
@@ -4540,6 +4680,11 @@
       <map name="ROF2OCN_LIQ_RMAPNAME">cpl/cpl6/map_rx1_to_IcoswISC30E3r5_cstmnn.r150e300.20231121.nc</map>
     </gridmap>
 
+    <gridmap ocn_grid="RRSwISC6to18E3r4" rof_grid="rx1">
+      <map name="ROF2OCN_ICE_RMAPNAME">cpl/cpl6/map_rx1_to_RRSwISC6to18E3r4_cstmnn.r50e100.20240108.nc</map>
+      <map name="ROF2OCN_LIQ_RMAPNAME">cpl/cpl6/map_rx1_to_RRSwISC6to18E3r4_cstmnn.r50e100.20240108.nc</map>
+    </gridmap>
+
     <gridmap ocn_grid="oEC60to30v3" rof_grid="JRA025">
       <map name="ROF2OCN_ICE_RMAPNAME">cpl/cpl6/map_JRA025_to_oEC60to30v3_smoothed.r150e300.181204.nc</map>
       <map name="ROF2OCN_LIQ_RMAPNAME">cpl/cpl6/map_JRA025_to_oEC60to30v3_smoothed.r150e300.181204.nc</map>
@@ -4600,6 +4745,11 @@
       <map name="ROF2OCN_LIQ_RMAPNAME">cpl/cpl6/map_JRA025_to_IcoswISC30E3r5_cstmnn.r150e300.20231121.nc</map>
     </gridmap>
 
+    <gridmap ocn_grid="RRSwISC6to18E3r4" rof_grid="JRA025">
+      <map name="ROF2OCN_ICE_RMAPNAME">cpl/cpl6/map_JRA025_to_RRSwISC6to18E3r4_cstmnn.r50e100.20240108.nc</map>
+      <map name="ROF2OCN_LIQ_RMAPNAME">cpl/cpl6/map_JRA025_to_RRSwISC6to18E3r4_cstmnn.r50e100.20240108.nc</map>
+    </gridmap>
+
     <gridmap ocn_grid="oRRS18to6v3" rof_grid="JRA025">
       <map name="ROF2OCN_ICE_RMAPNAME">cpl/cpl6/map_JRA025_to_oRRS18to6v3_smoothed.r50e100.220124.nc</map>
       <map name="ROF2OCN_LIQ_RMAPNAME">cpl/cpl6/map_JRA025_to_oRRS18to6v3_smoothed.r50e100.220124.nc</map>
@@ -4685,6 +4835,16 @@
       <map name="ROF2OCN_LIQ_RMAPNAME">cpl/cpl6/map_r05_to_IcoswISC30E3r5_cstmnn.r150e300.20231121.nc</map>
     </gridmap>
 
+    <gridmap ocn_grid="RRSwISC6to18E3r4" rof_grid="r05">
+      <map name="ROF2OCN_ICE_RMAPNAME">cpl/cpl6/map_r05_to_RRSwISC6to18E3r4_cstmnn.r50e100.20240108.nc</map>
+      <map name="ROF2OCN_LIQ_RMAPNAME">cpl/cpl6/map_r05_to_RRSwISC6to18E3r4_cstmnn.r50e100.20240108.nc</map>
+    </gridmap>
+
+    <gridmap ocn_grid="RRSwISC6to18E3r4" rof_grid="r025">
+      <map name="ROF2OCN_ICE_RMAPNAME">cpl/cpl6/map_r025_to_RRSwISC6to18E3r4_cstmnn.r50e100.20240319.nc</map>
+      <map name="ROF2OCN_LIQ_RMAPNAME">cpl/cpl6/map_r025_to_RRSwISC6to18E3r4_cstmnn.r50e100.20240319.nc</map>
+    </gridmap>
+
     <gridmap ocn_grid="WC14to60E2r3" rof_grid="r0125">
       <map name="ROF2OCN_ICE_RMAPNAME">cpl/cpl6/map_r0125_to_WC14to60E2r3_smoothed.r150e300.200929.nc</map>
       <map name="ROF2OCN_LIQ_RMAPNAME">cpl/cpl6/map_r0125_to_WC14to60E2r3_smoothed.r150e300.200929.nc</map>
@@ -4735,6 +4895,11 @@
       <map name="ROF2OCN_LIQ_RMAPNAME">cpl/cpl6/map_r0125_to_oRRS18to6v3_smoothed.r50e100.170111.nc</map>
     </gridmap>
 
+    <gridmap ocn_grid="RRSwISC6to18E3r4" rof_grid="r0125">
+      <map name="ROF2OCN_ICE_RMAPNAME">cpl/cpl6/map_r0125_to_RRSwISC6to18E3r4_cstmnn.r50e100.20240108.nc</map>
+      <map name="ROF2OCN_LIQ_RMAPNAME">cpl/cpl6/map_r0125_to_RRSwISC6to18E3r4_cstmnn.r50e100.20240108.nc</map>
+    </gridmap>
+
     <gridmap ocn_grid="oRRS15to5" rof_grid="r0125">
       <map name="ROF2OCN_ICE_RMAPNAME">cpl/cpl6/map_r0125_to_oRRS15to5_nn.160720.nc</map>
       <map name="ROF2OCN_LIQ_RMAPNAME">cpl/cpl6/map_r0125_to_oRRS15to5_nn.160720.nc</map>
diff --git a/components/elm/bld/namelist_files/namelist_definition.xml b/components/elm/bld/namelist_files/namelist_definition.xml
index 1353f8b84b64..9dca4e6bcf58 100644
--- a/components/elm/bld/namelist_files/namelist_definition.xml
+++ b/components/elm/bld/namelist_files/namelist_definition.xml
@@ -1404,7 +1404,7 @@ Representative concentration pathway for future scenarios [radiative forcing at
 
 <entry id="mask" type="char*20" category="default_settings"
        group="default_settings"
-       valid_values="USGS,gx3v7,gx1v6,navy,test,tx0.1v2,tx1v1,T62,TL319,cruncep,oEC60to30v3,oEC60to30v3wLI,ECwISC30to60E1r2,EC30to60E2r2,WC14to60E2r3,WCAtl12to45E2r4,SOwISC12to60E2r4,ECwISC30to60E2r1,oRRS18to6,oRRS18to6v3,oRRS15to5,oARRM60to10,oARRM60to6,ARRM10to60E2r1,oQU480,oQU240,oQU240wLI,oQU120,oRRS30to10v3,oRRS30to10v3wLI,360x720cru,NLDASww3a,NLDAS,tx0.1v2,ICOS10,IcoswISC30E3r5">
+       valid_values="USGS,gx3v7,gx1v6,navy,test,tx0.1v2,tx1v1,T62,TL319,cruncep,oEC60to30v3,oEC60to30v3wLI,ECwISC30to60E1r2,EC30to60E2r2,WC14to60E2r3,WCAtl12to45E2r4,SOwISC12to60E2r4,ECwISC30to60E2r1,oRRS18to6,oRRS18to6v3,oRRS15to5,oARRM60to10,oARRM60to6,ARRM10to60E2r1,oQU480,oQU240,oQU240wLI,oQU120,oRRS30to10v3,oRRS30to10v3wLI,360x720cru,NLDASww3a,NLDAS,tx0.1v2,ICOS10,IcoswISC30E3r5,RRSwISC6to18E3r4">
 Land mask description
 </entry>
 
diff --git a/components/mpas-ocean/bld/namelist_files/namelist_defaults_mpaso.xml b/components/mpas-ocean/bld/namelist_files/namelist_defaults_mpaso.xml
index 4069eb144cff..9d68c22440d9 100644
--- a/components/mpas-ocean/bld/namelist_files/namelist_defaults_mpaso.xml
+++ b/components/mpas-ocean/bld/namelist_files/namelist_defaults_mpaso.xml
@@ -49,6 +49,7 @@
 <config_dt ocn_grid="SOwISC12to60E2r4">'00:10:00'</config_dt>
 <config_dt ocn_grid="ECwISC30to60E2r1">'00:30:00'</config_dt>
 <config_dt ocn_grid="IcoswISC30E3r5">'00:30:00'</config_dt>
+<config_dt ocn_grid="RRSwISC6to18E3r4">'00:05:00'</config_dt>
 <config_time_integrator>'split_explicit_ab2'</config_time_integrator>
 <config_number_of_time_levels>2</config_number_of_time_levels>
 
@@ -73,6 +74,7 @@
 <config_hmix_scaleWithMesh ocn_grid="SOwISC12to60E2r4">.true.</config_hmix_scaleWithMesh>
 <config_hmix_scaleWithMesh ocn_grid="ECwISC30to60E2r1">.true.</config_hmix_scaleWithMesh>
 <config_hmix_scaleWithMesh ocn_grid="IcoswISC30E3r5">.true.</config_hmix_scaleWithMesh>
+<config_hmix_scaleWithMesh ocn_grid="RRSwISC6to18E3r4">.true.</config_hmix_scaleWithMesh>
 <config_maxMeshDensity>-1.0</config_maxMeshDensity>
 <config_hmix_use_ref_cell_width>.false.</config_hmix_use_ref_cell_width>
 <config_hmix_ref_cell_width>30.0e3</config_hmix_ref_cell_width>
@@ -124,6 +126,7 @@
 <config_mom_del4 ocn_grid="SOwISC12to60E2r4">1.18e10</config_mom_del4>
 <config_mom_del4 ocn_grid="ECwISC30to60E2r1">1.2e11</config_mom_del4>
 <config_mom_del4 ocn_grid="IcoswISC30E3r5">1.2e11</config_mom_del4>
+<config_mom_del4 ocn_grid="RRSwISC6to18E3r4">3.2e09</config_mom_del4>
 <config_mom_del4_div_factor>1.0</config_mom_del4_div_factor>
 <config_use_tracer_del4>.false.</config_use_tracer_del4>
 <config_tracer_del4>0.0</config_tracer_del4>
@@ -140,6 +143,7 @@
 <config_use_Redi ocn_grid="oRRS30to10v3wLI">.false.</config_use_Redi>
 <config_use_Redi ocn_grid="oRRS18to6v3">.false.</config_use_Redi>
 <config_use_Redi ocn_grid="oRRS15to5">.false.</config_use_Redi>
+<config_use_Redi ocn_grid="RRSwISC6to18E3r4">.false.</config_use_Redi>
 <config_Redi_closure>'constant'</config_Redi_closure>
 <config_Redi_constant_kappa>400.0</config_Redi_constant_kappa>
 <config_Redi_constant_kappa ocn_forcing="datm_forced_restoring">400.0</config_Redi_constant_kappa>
@@ -174,6 +178,7 @@
 <config_use_GM ocn_grid="oRRS30to10v3wLI">.false.</config_use_GM>
 <config_use_GM ocn_grid="oRRS18to6v3">.false.</config_use_GM>
 <config_use_GM ocn_grid="oRRS15to5">.false.</config_use_GM>
+<config_use_GM ocn_grid="RRSwISC6to18E3r4">.false.</config_use_GM>
 <config_GM_closure>'EdenGreatbatch'</config_GM_closure>
 <config_GM_closure ocn_grid="EC30to60E2r2">'constant'</config_GM_closure>
 <config_GM_closure ocn_grid="WC14to60E2r3">'constant'</config_GM_closure>
@@ -347,6 +352,7 @@
 <config_land_ice_flux_mode ocn_grid="SOwISC12to60E2r4">'pressure_only'</config_land_ice_flux_mode>
 <config_land_ice_flux_mode ocn_grid="ECwISC30to60E2r1">'pressure_only'</config_land_ice_flux_mode>
 <config_land_ice_flux_mode ocn_grid="IcoswISC30E3r5">'pressure_only'</config_land_ice_flux_mode>
+<config_land_ice_flux_mode ocn_grid="RRSwISC6to18E3r4">'pressure_only'</config_land_ice_flux_mode>
 <config_land_ice_flux_formulation>'Jenkins'</config_land_ice_flux_formulation>
 <config_land_ice_flux_useHollandJenkinsAdvDiff>.false.</config_land_ice_flux_useHollandJenkinsAdvDiff>
 <config_land_ice_flux_attenuation_coefficient>10.0</config_land_ice_flux_attenuation_coefficient>
@@ -360,6 +366,7 @@
 <config_land_ice_flux_explicit_topDragCoeff ocn_grid="SOwISC12to60E2r4">4.48e-3</config_land_ice_flux_explicit_topDragCoeff>
 <config_land_ice_flux_explicit_topDragCoeff ocn_grid="ECwISC30to60E2r1">4.48e-3</config_land_ice_flux_explicit_topDragCoeff>
 <config_land_ice_flux_explicit_topDragCoeff ocn_grid="IcoswISC30E3r5">4.48e-3</config_land_ice_flux_explicit_topDragCoeff>
+<config_land_ice_flux_explicit_topDragCoeff ocn_grid="RRSwISC6to18E3r4">4.48e-3</config_land_ice_flux_explicit_topDragCoeff>
 <config_land_ice_flux_ISOMIP_gammaT>1e-4</config_land_ice_flux_ISOMIP_gammaT>
 <config_land_ice_flux_rms_tidal_velocity>5e-2</config_land_ice_flux_rms_tidal_velocity>
 <config_land_ice_flux_jenkins_heat_transfer_coefficient>0.011</config_land_ice_flux_jenkins_heat_transfer_coefficient>
@@ -368,12 +375,14 @@
 <config_land_ice_flux_jenkins_heat_transfer_coefficient ocn_grid="SOwISC12to60E2r4">0.00295</config_land_ice_flux_jenkins_heat_transfer_coefficient>
 <config_land_ice_flux_jenkins_heat_transfer_coefficient ocn_grid="ECwISC30to60E2r1">0.00295</config_land_ice_flux_jenkins_heat_transfer_coefficient>
 <config_land_ice_flux_jenkins_heat_transfer_coefficient ocn_grid="IcoswISC30E3r5">0.00295</config_land_ice_flux_jenkins_heat_transfer_coefficient>
+<config_land_ice_flux_jenkins_heat_transfer_coefficient ocn_grid="RRSwISC6to18E3r4">0.00295</config_land_ice_flux_jenkins_heat_transfer_coefficient>
 <config_land_ice_flux_jenkins_salt_transfer_coefficient>3.1e-4</config_land_ice_flux_jenkins_salt_transfer_coefficient>
 <config_land_ice_flux_jenkins_salt_transfer_coefficient ocn_grid="oEC60to30v3wLI">8.42e-5</config_land_ice_flux_jenkins_salt_transfer_coefficient>
 <config_land_ice_flux_jenkins_salt_transfer_coefficient ocn_grid="ECwISC30to60E1r2">8.42e-5</config_land_ice_flux_jenkins_salt_transfer_coefficient>
 <config_land_ice_flux_jenkins_salt_transfer_coefficient ocn_grid="SOwISC12to60E2r4">8.42e-5</config_land_ice_flux_jenkins_salt_transfer_coefficient>
 <config_land_ice_flux_jenkins_salt_transfer_coefficient ocn_grid="ECwISC30to60E2r1">8.42e-5</config_land_ice_flux_jenkins_salt_transfer_coefficient>
 <config_land_ice_flux_jenkins_salt_transfer_coefficient ocn_grid="IcoswISC30E3r5">8.42e-5</config_land_ice_flux_jenkins_salt_transfer_coefficient>
+<config_land_ice_flux_jenkins_salt_transfer_coefficient ocn_grid="RRSwISC6to18E3r4">8.42e-5</config_land_ice_flux_jenkins_salt_transfer_coefficient>
 
 <!-- advection -->
 <config_vert_advection_method>'flux-form'</config_vert_advection_method>
@@ -397,6 +406,7 @@
 <config_implicit_top_drag_coeff ocn_grid="SOwISC12to60E2r4">4.48e-3</config_implicit_top_drag_coeff>
 <config_implicit_top_drag_coeff ocn_grid="ECwISC30to60E2r1">4.48e-3</config_implicit_top_drag_coeff>
 <config_implicit_top_drag_coeff ocn_grid="IcoswISC30E3r5">4.48e-3</config_implicit_top_drag_coeff>
+<config_implicit_top_drag_coeff ocn_grid="RRSwISC6to18E3r4">4.48e-3</config_implicit_top_drag_coeff>
 <config_loglaw_bottom_roughness>1.0e-3</config_loglaw_bottom_roughness>
 <config_loglaw_layer_depth_max>10.0</config_loglaw_layer_depth_max>
 <config_loglaw_bottom_drag_min>2.5e-3</config_loglaw_bottom_drag_min>
@@ -475,6 +485,7 @@
 <config_btr_dt ocn_grid="SOwISC12to60E2r4">'0000_00:00:15'</config_btr_dt>
 <config_btr_dt ocn_grid="ECwISC30to60E2r1">'0000_00:01:15'</config_btr_dt>
 <config_btr_dt ocn_grid="IcoswISC30E3r5">'0000_00:01:00'</config_btr_dt>
+<config_btr_dt ocn_grid="RRSwISC6to18E3r4">'0000_00:00:10'</config_btr_dt>
 <config_n_btr_cor_iter>2</config_n_btr_cor_iter>
 <config_vel_correction>.true.</config_vel_correction>
 <config_btr_subcycle_loop_factor>2</config_btr_subcycle_loop_factor>
@@ -516,6 +527,7 @@
 <config_check_ssh_consistency ocn_grid="SOwISC12to60E2r4">.false.</config_check_ssh_consistency>
 <config_check_ssh_consistency ocn_grid="ECwISC30to60E2r1">.false.</config_check_ssh_consistency>
 <config_check_ssh_consistency ocn_grid="IcoswISC30E3r5">.false.</config_check_ssh_consistency>
+<config_check_ssh_consistency ocn_grid="RRSwISC6to18E3r4">.false.</config_check_ssh_consistency>
 <config_filter_btr_mode>.false.</config_filter_btr_mode>
 <config_prescribe_velocity>.false.</config_prescribe_velocity>
 <config_prescribe_thickness>.false.</config_prescribe_thickness>
@@ -1033,6 +1045,7 @@
 <config_AM_mocStreamfunction_enable ocn_grid="SOwISC12to60E2r4">.true.</config_AM_mocStreamfunction_enable>
 <config_AM_mocStreamfunction_enable ocn_grid="ECwISC30to60E2r1">.true.</config_AM_mocStreamfunction_enable>
 <config_AM_mocStreamfunction_enable ocn_grid="IcoswISC30E3r5">.true.</config_AM_mocStreamfunction_enable>
+<config_AM_mocStreamfunction_enable ocn_grid="RRSwISC6to18E3r4">.true.</config_AM_mocStreamfunction_enable>
 <config_AM_mocStreamfunction_compute_interval>'0000-00-00_01:00:00'</config_AM_mocStreamfunction_compute_interval>
 <config_AM_mocStreamfunction_output_stream>'mocStreamfunctionOutput'</config_AM_mocStreamfunction_output_stream>
 <config_AM_mocStreamfunction_compute_on_startup>.true.</config_AM_mocStreamfunction_compute_on_startup>
@@ -1115,16 +1128,19 @@
 <config_AM_conservationCheck_enable ocn_grid="SOwISC12to60E2r4">.true.</config_AM_conservationCheck_enable>
 <config_AM_conservationCheck_enable ocn_grid="ECwISC30to60E2r1">.true.</config_AM_conservationCheck_enable>
 <config_AM_conservationCheck_enable ocn_grid="IcoswISC30E3r5">.true.</config_AM_conservationCheck_enable>
+<config_AM_conservationCheck_enable ocn_grid="RRSwISC6to18E3r4">.true.</config_AM_conservationCheck_enable>
 <config_AM_conservationCheck_compute_interval>'dt'</config_AM_conservationCheck_compute_interval>
 <config_AM_conservationCheck_output_stream>'conservationCheckOutput'</config_AM_conservationCheck_output_stream>
 <config_AM_conservationCheck_compute_on_startup>.false.</config_AM_conservationCheck_compute_on_startup>
 <config_AM_conservationCheck_compute_on_startup ocn_grid="SOwISC12to60E2r4">.true.</config_AM_conservationCheck_compute_on_startup>
 <config_AM_conservationCheck_compute_on_startup ocn_grid="ECwISC30to60E2r1">.true.</config_AM_conservationCheck_compute_on_startup>
 <config_AM_conservationCheck_compute_on_startup ocn_grid="IcoswISC30E3r5">.true.</config_AM_conservationCheck_compute_on_startup>
+<config_AM_conservationCheck_compute_on_startup ocn_grid="RRSwISC6to18E3r4">.true.</config_AM_conservationCheck_compute_on_startup>
 <config_AM_conservationCheck_write_on_startup>.false.</config_AM_conservationCheck_write_on_startup>
 <config_AM_conservationCheck_write_on_startup ocn_grid="SOwISC12to60E2r4">.true.</config_AM_conservationCheck_write_on_startup>
 <config_AM_conservationCheck_write_on_startup ocn_grid="ECwISC30to60E2r1">.true.</config_AM_conservationCheck_write_on_startup>
 <config_AM_conservationCheck_write_on_startup ocn_grid="IcoswISC30E3r5">.true.</config_AM_conservationCheck_write_on_startup>
+<config_AM_conservationCheck_write_on_startup ocn_grid="RRSwISC6to18E3r4">.true.</config_AM_conservationCheck_write_on_startup>
 <config_AM_conservationCheck_write_to_logfile>.true.</config_AM_conservationCheck_write_to_logfile>
 <config_AM_conservationCheck_restart_stream>'conservationCheckRestart'</config_AM_conservationCheck_restart_stream>
 
diff --git a/components/mpas-ocean/cime_config/buildnml b/components/mpas-ocean/cime_config/buildnml
index a363c27883a3..3bd2d15c461a 100755
--- a/components/mpas-ocean/cime_config/buildnml
+++ b/components/mpas-ocean/cime_config/buildnml
@@ -296,6 +296,20 @@ def buildnml(case, caseroot, compname):
         if ocn_ismf == 'data':
             data_ismf_file = 'prescribed_ismf_adusumilli2020.IcoswISC30E3r5.20231120.nc'
 
+    elif ocn_grid == 'RRSwISC6to18E3r4':
+        decomp_date = '20240105'
+        decomp_prefix = 'partitions/mpas-o.graph.info.'
+        restoring_file = 'sss.PHC2_monthlyClimatology.RRSwISC6to18E3r4.20240105.nc'
+        analysis_mask_file = 'RRSwISC6to18E3r4_mocBasinsAndTransects20210623.nc'
+        ic_date = '20240105'
+        ic_prefix = 'mpaso.RRSwISC6to18E3r4'
+        if ocn_ic_mode == 'spunup':
+             ic_date = '20240110'
+             ic_prefix = 'mpaso.RRSwISC6to18E3r4.rstFromG-chrysalis'
+        if ocn_ismf == 'data':
+            data_ismf_file = 'prescribed_ismf_paolo2023.RRSwISC6to18E3r4.20240227.nc'
+
+
     #--------------------------------------------------------------------
     # Set OCN_FORCING = datm_forced_restoring if restoring file is available
     #--------------------------------------------------------------------
@@ -422,7 +436,7 @@ def buildnml(case, caseroot, compname):
             lines.append('')
             lines.append('<immutable_stream name="mesh"')
             lines.append('                  type="none"')
-            if ocn_grid.startswith("oRRS1"):
+            if ocn_grid.startswith("oRRS1") or ocn_grid.startswith("RRSwISC6"):
                 lines.append('                  io_type="pnetcdf,cdf5"')
             else:
                 lines.append('                  io_type="{}"'.format(ocn_pio_typename))
@@ -431,7 +445,7 @@ def buildnml(case, caseroot, compname):
             lines.append('/>')
             lines.append('<immutable_stream name="input"')
             lines.append('                  type="input"')
-            if ocn_grid.startswith("oRRS1"):
+            if ocn_grid.startswith("oRRS1") or ocn_grid.startswith("RRSwISC6"):
                 lines.append('                  io_type="pnetcdf,cdf5"')
             else:
                 lines.append('                  io_type="{}"'.format(ocn_pio_typename))
@@ -452,7 +466,7 @@ def buildnml(case, caseroot, compname):
             lines.append('-->')
             lines.append('<immutable_stream name="restart"')
             lines.append('                  type="input;output"')
-            if ocn_grid.startswith("oRRS1"):
+            if ocn_grid.startswith("oRRS1") or ocn_grid.startswith("RRSwISC6"):
                 lines.append('                  io_type="pnetcdf,cdf5"')
             else:
                 lines.append('                  io_type="{}"'.format(ocn_pio_typename))
@@ -471,7 +485,7 @@ def buildnml(case, caseroot, compname):
             lines.append('')
             lines.append('<stream name="output"')
             lines.append('        type="output"')
-            if ocn_grid.startswith("oRRS1"):
+            if ocn_grid.startswith("oRRS1") or ocn_grid.startswith("RRSwISC6"):
                 lines.append('        io_type="pnetcdf,cdf5"')
             else:
                 lines.append('        io_type="{}"'.format(ocn_pio_typename))
@@ -755,7 +769,7 @@ def buildnml(case, caseroot, compname):
             lines.append('<stream name="eddyProductVariablesOutput"')
             lines.append('        type="output"')
             lines.append('        precision="single"')
-            if ocn_grid.startswith("oRRS1"):
+            if ocn_grid.startswith("oRRS1") or ocn_grid.startswith("RRSwISC6"):
                 lines.append('        io_type="pnetcdf,cdf5"')
             else:
                 lines.append('        io_type="{}"'.format(ocn_pio_typename))
@@ -1135,7 +1149,7 @@ def buildnml(case, caseroot, compname):
             lines.append('<stream name="timeSeriesStatsMonthlyOutput"')
             lines.append('        type="output"')
             lines.append('        precision="single"')
-            if ocn_grid.startswith("oRRS1"):
+            if ocn_grid.startswith("oRRS1") or ocn_grid.startswith("RRSwISC6"):
                 lines.append('        io_type="pnetcdf,cdf5"')
             else:
                 lines.append('        io_type="{}"'.format(ocn_pio_typename))
@@ -1181,7 +1195,7 @@ def buildnml(case, caseroot, compname):
             lines.append('    <var name="atmosphericPressure"/>')
             lines.append('    <var name="normalMLEvelocity"/>')
             lines.append('    <var name="vertMLEBolusVelocityTop"/>')
-            if not ocn_grid.startswith("oRRS1"):
+            if not (ocn_grid.startswith("oRRS1") or ocn_grid.startswith("RRSwISC6")):
                 lines.append('    <var name="normalGMBolusVelocity"/>')
                 lines.append('    <var name="vertGMBolusVelocityTop"/>')
                 lines.append('    <var name="cGMphaseSpeed"/>')
@@ -1362,7 +1376,7 @@ def buildnml(case, caseroot, compname):
             lines.append('<stream name="timeSeriesStatsMonthlyMaxOutput"')
             lines.append('        type="output"')
             lines.append('        precision="single"')
-            if ocn_grid.startswith("oRRS1"):
+            if ocn_grid.startswith("oRRS1") or ocn_grid.startswith("RRSwISC6"):
                 lines.append('        io_type="pnetcdf,cdf5"')
             else:
                 lines.append('        io_type="{}"'.format(ocn_pio_typename))
@@ -1424,7 +1438,7 @@ def buildnml(case, caseroot, compname):
             lines.append('<stream name="timeSeriesStatsMonthlyMinOutput"')
             lines.append('        type="output"')
             lines.append('        precision="single"')
-            if ocn_grid.startswith("oRRS1"):
+            if ocn_grid.startswith("oRRS1") or ocn_grid.startswith("RRSwISC6"):
                 lines.append('        io_type="pnetcdf,cdf5"')
             else:
                 lines.append('        io_type="{}"'.format(ocn_pio_typename))
@@ -1527,7 +1541,7 @@ def buildnml(case, caseroot, compname):
             lines.append('')
             lines.append('<stream name="timeSeriesStatsMonthlyRestart"')
             lines.append('        type="input;output"')
-            if ocn_grid.startswith("oRRS1"):
+            if ocn_grid.startswith("oRRS1") or ocn_grid.startswith("RRSwISC6"):
                 lines.append('        io_type="pnetcdf,cdf5"')
             else:
                 lines.append('        io_type="{}"'.format(ocn_pio_typename))
@@ -1543,7 +1557,7 @@ def buildnml(case, caseroot, compname):
             lines.append('')
             lines.append('<stream name="timeSeriesStatsMonthlyMaxRestart"')
             lines.append('        type="input;output"')
-            if ocn_grid.startswith("oRRS1"):
+            if ocn_grid.startswith("oRRS1") or ocn_grid.startswith("RRSwISC6"):
                 lines.append('        io_type="pnetcdf,cdf5"')
             else:
                 lines.append('        io_type="{}"'.format(ocn_pio_typename))
@@ -1559,7 +1573,7 @@ def buildnml(case, caseroot, compname):
             lines.append('')
             lines.append('<stream name="timeSeriesStatsMonthlyMinRestart"')
             lines.append('        type="input;output"')
-            if ocn_grid.startswith("oRRS1"):
+            if ocn_grid.startswith("oRRS1") or ocn_grid.startswith("RRSwISC6"):
                 lines.append('        io_type="pnetcdf,cdf5"')
             else:
                 lines.append('        io_type="{}"'.format(ocn_pio_typename))
diff --git a/components/mpas-seaice/bld/namelist_files/namelist_defaults_mpassi.xml b/components/mpas-seaice/bld/namelist_files/namelist_defaults_mpassi.xml
index 1414ffc777de..c7e32a857231 100644
--- a/components/mpas-seaice/bld/namelist_files/namelist_defaults_mpassi.xml
+++ b/components/mpas-seaice/bld/namelist_files/namelist_defaults_mpassi.xml
@@ -25,6 +25,7 @@
 <config_dt ice_grid="SOwISC12to60E2r4">1800.0</config_dt>
 <config_dt ice_grid="ECwISC30to60E2r1">1800.0</config_dt>
 <config_dt ice_grid="IcoswISC30E3r5">1800.0</config_dt>
+<config_dt ice_grid="RRSwISC6to18E3r4">900.0</config_dt>
 <config_calendar_type>'noleap'</config_calendar_type>
 <config_start_time>'2000-01-01_00:00:00'</config_start_time>
 <config_stop_time>'none'</config_stop_time>
@@ -80,6 +81,7 @@
 <config_initial_latitude_north ice_grid="ARRM10to60E2r1">75.0</config_initial_latitude_north>
 <config_initial_latitude_north ice_grid="oRRS30to10v3wLI">85.0</config_initial_latitude_north>
 <config_initial_latitude_north ice_grid="oRRS18to6v3">85.0</config_initial_latitude_north>
+<config_initial_latitude_north ice_grid="RRSwISC6to18E3r4">85.0</config_initial_latitude_north>
 <config_initial_latitude_south>-60.0</config_initial_latitude_south>
 <config_initial_latitude_south ice_grid="oEC60to30v3wLI">-75.0</config_initial_latitude_south>
 <config_initial_latitude_south ice_grid="ECwISC30to60E1r2">-75.0</config_initial_latitude_south>
@@ -90,6 +92,7 @@
 <config_initial_latitude_south ice_grid="ARRM10to60E2r1">-85.0</config_initial_latitude_south>
 <config_initial_latitude_south ice_grid="oRRS30to10v3wLI">-85.0</config_initial_latitude_south>
 <config_initial_latitude_south ice_grid="oRRS18to6v3">-85.0</config_initial_latitude_south>
+<config_initial_latitude_south ice_grid="RRSwISC6to18E3r4">-85.0</config_initial_latitude_south>
 <config_initial_velocity_type>'uniform'</config_initial_velocity_type>
 <config_initial_uvelocity>0.0</config_initial_uvelocity>
 <config_initial_vvelocity>0.0</config_initial_vvelocity>
@@ -148,6 +151,7 @@
 <config_dynamics_subcycle_number ice_grid="SOwISC12to60E2r4">1</config_dynamics_subcycle_number>
 <config_dynamics_subcycle_number ice_grid="ECwISC30to60E2r1">1</config_dynamics_subcycle_number>
 <config_dynamics_subcycle_number ice_grid="IcoswISC30E3r5">1</config_dynamics_subcycle_number>
+<config_dynamics_subcycle_number ice_grid="RRSwISC6to18E3r4">2</config_dynamics_subcycle_number>
 <config_rotate_cartesian_grid>true</config_rotate_cartesian_grid>
 <config_include_metric_terms>true</config_include_metric_terms>
 <config_elastic_subcycle_number>120</config_elastic_subcycle_number>
diff --git a/components/mpas-seaice/cime_config/buildnml b/components/mpas-seaice/cime_config/buildnml
index 92e5eaf0d004..5c0dfb67ece5 100755
--- a/components/mpas-seaice/cime_config/buildnml
+++ b/components/mpas-seaice/cime_config/buildnml
@@ -263,6 +263,16 @@ def buildnml(case, caseroot, compname):
             grid_date = '20231121'
             grid_prefix = 'mpassi.IcoswISC30E3r5.rstFromG-chrysalis'
 
+    elif ice_grid == 'RRSwISC6to18E3r4':
+        decomp_date = '20240105'
+        decomp_prefix = 'partitions/mpas-seaice.graph.info.'
+        grid_date = '20240105'
+        grid_prefix = 'mpassi.RRSwISC6to18E3r4'
+        data_iceberg_file = 'Iceberg_Climatology_Merino.RRSwISC6to18E3r4.20240105.nc'
+        if ice_ic_mode == 'spunup':
+            grid_date = '20240110'
+            grid_prefix = 'mpassi.RRSwISC6to18E3r4.rstFromG-chrysalis'
+
     elif ice_grid == 'ICOS10':
         grid_date = '211015'
         grid_prefix = 'seaice.ICOS10'
@@ -396,7 +406,7 @@ def buildnml(case, caseroot, compname):
             lines.append('<streams>')
             lines.append('<immutable_stream name="mesh"')
             lines.append('                  type="none"')
-            if ice_grid.startswith("oRRS1"):
+            if ice_grid.startswith("oRRS1") or ice_grid.startswith("RRSwISC6"):
                 lines.append('                  io_type="pnetcdf,cdf5"')
             else:
                 lines.append('                  io_type="{}"'.format(ice_pio_typename))
@@ -405,7 +415,7 @@ def buildnml(case, caseroot, compname):
             lines.append('')
             lines.append('<immutable_stream name="input"')
             lines.append('                  type="input"')
-            if ice_grid.startswith("oRRS1"):
+            if ice_grid.startswith("oRRS1") or ice_grid.startswith("RRSwISC6"):
                 lines.append('                  io_type="pnetcdf,cdf5"')
             else:
                 lines.append('                  io_type="{}"'.format(ice_pio_typename))
@@ -427,7 +437,7 @@ def buildnml(case, caseroot, compname):
             lines.append('')
             lines.append('<immutable_stream name="restart"')
             lines.append('                  type="input;output"')
-            if ice_grid.startswith("oRRS1"):
+            if ice_grid.startswith("oRRS1") or ice_grid.startswith("RRSwISC6"):
                 lines.append('                  io_type="pnetcdf,cdf5"')
             else:
                 lines.append('                  io_type="{}"'.format(ice_pio_typename))
@@ -443,7 +453,7 @@ def buildnml(case, caseroot, compname):
             if ice_ic_mode == 'spunup':
                 lines.append('<immutable_stream name="restart_ic"')
                 lines.append('                  type="input"')
-                if ice_grid.startswith("oRRS1"):
+                if ice_grid.startswith("oRRS1") or ice_grid.startswith("RRSwISC6"):
                     lines.append('                  io_type="pnetcdf,cdf5"')
                 else:
                     lines.append('                  io_type="{}"'.format(ice_pio_typename))
diff --git a/driver-mct/cime_config/config_component_e3sm.xml b/driver-mct/cime_config/config_component_e3sm.xml
index dd7a5ddb6c15..25dd58fd48c6 100755
--- a/driver-mct/cime_config/config_component_e3sm.xml
+++ b/driver-mct/cime_config/config_component_e3sm.xml
@@ -232,6 +232,7 @@
       <value compset="_SOCN"                     >CESM1_MOD</value>
       <value compset="_MPASO"                    >CESM1_MOD</value>
       <value compset="_MPASSI.*_MPASO"           >RASM_OPTION1</value>
+      <value compset="_MPASSI.*_MPASO" grid="oi%RRSwISC6to18E3r4">RASM_OPTION2</value>
     </values>
     <group>run_coupling</group>
     <file>env_run.xml</file>
@@ -374,6 +375,7 @@
       <value compset="_DATM.*_SLND.*MPAS" grid="oi%oRRS30to10v3">96</value>
       <value compset="_DATM.*_SLND.*MPAS" grid="oi%oRRS18to6v3">96</value>
       <value compset="_DATM.*_SLND.*MPAS" grid="oi%oRRS15to5">96</value>
+      <value compset="_DATM.*_SLND.*MPAS" grid="oi%RRSwISC6to18E3r4">96</value>
       <value compset="_DATM.*_SLND.*MPAS" grid="oi%oARRM60to10">96</value>
       <value compset="_DATM.*_SLND.*MPAS" grid="oi%oARRM60to6">96</value>
       <value compset="_EAM.*_ELM.*MPASO">48</value>
@@ -488,6 +490,7 @@
       <value compset="_MPASO" grid="oi%WC14to60E2r3">48</value>
       <value compset="_MPASO" grid="oi%oRRS30to10v3">48</value>
       <value compset="_MPASO" grid="oi%oRRS18to6v3">48</value>
+      <value compset="_MPASO" grid="oi%RRSwISC6to18E3r4">96</value>
       <value compset="_MPASO" grid="oi%oRRS15to5">96</value>
       <value compset="_MPASO" grid="oi%oARRM60to10">48</value>
       <value compset="_MPASO" grid="oi%oARRM60to6">48</value>