Index: /issm/trunk-jpl/src/c/classes/FemModel.cpp
===================================================================
--- /issm/trunk-jpl/src/c/classes/FemModel.cpp	(revision 16446)
+++ /issm/trunk-jpl/src/c/classes/FemModel.cpp	(revision 16447)
@@ -369,31 +369,38 @@
 int  FemModel::UpdateVertexPositionsx(void){ /*{{{*/
 
-	Vector<IssmDouble> *vz        = NULL;
-	IssmDouble         *thickness = NULL;
-	IssmDouble         *bed       = NULL;
+	IssmDouble         *surface = NULL;
+	IssmDouble         *bed     = NULL;
 
 	/*get vertex vectors for bed and thickness: */
-	GetVectorFromInputsx(&thickness,this, ThicknessEnum,VertexEnum);
-	GetVectorFromInputsx(&bed      ,this, BedEnum,      VertexEnum);
+	GetVectorFromInputsx(&surface  ,this, SurfaceEnum,VertexEnum);
+	GetVectorFromInputsx(&bed      ,this, BedEnum,    VertexEnum);
 
 	/*Allocate vector*/
-	vz=new Vector<IssmDouble>(vertices->NumberOfVertices());
+	Vector<IssmDouble> *vx=new Vector<IssmDouble>(vertices->NumberOfVertices());
+	Vector<IssmDouble> *vy=new Vector<IssmDouble>(vertices->NumberOfVertices());
+	Vector<IssmDouble> *vz=new Vector<IssmDouble>(vertices->NumberOfVertices());
 
 	/*Update verices new geometry: */
 	for(int i=0;i<vertices->Size();i++){
 		Vertex* vertex=(Vertex*)vertices->GetObjectByOffset(i);
-		vertex->UpdatePosition(vz,parameters,thickness,bed);
+		vertex->UpdatePosition(vx,vy,vz,parameters,surface,bed);
 	}
 
 	/*Assemble mesh velocity*/
+	vx->Assemble();
+	vy->Assemble();
 	vz->Assemble();
 
 	/*Update element inputs*/
+	InputUpdateFromVectorx(this,vx,VxMeshEnum,VertexPIdEnum);
+	InputUpdateFromVectorx(this,vy,VyMeshEnum,VertexPIdEnum);
 	InputUpdateFromVectorx(this,vz,VzMeshEnum,VertexPIdEnum);
 
 	/*Free ressources:*/
+	delete vx;
+	delete vy;
 	delete vz;
 	xDelete<IssmDouble>(bed);
-	xDelete<IssmDouble>(thickness);
+	xDelete<IssmDouble>(surface);
 	return 1;
 }
Index: /issm/trunk-jpl/src/c/classes/Vertex.cpp
===================================================================
--- /issm/trunk-jpl/src/c/classes/Vertex.cpp	(revision 16446)
+++ /issm/trunk-jpl/src/c/classes/Vertex.cpp	(revision 16447)
@@ -32,7 +32,17 @@
 	this->y            = iomodel->Data(MeshYEnum)[i];
 	this->z            = iomodel->Data(MeshZEnum)[i];
+	this->meshtype     = iomodel->meshtype;
 
 	_assert_(iomodel->Data(BedEnum) && iomodel->Data(ThicknessEnum) && iomodel->numbernodetoelementconnectivity);
-	this->sigma        = (iomodel->Data(MeshZEnum)[i]-iomodel->Data(BedEnum)[i])/(iomodel->Data(ThicknessEnum)[i]);
+	switch(iomodel->meshtype){
+		case Mesh3DEnum:
+		case Mesh2DhorizontalEnum:
+			this->sigma = (iomodel->Data(MeshZEnum)[i]-iomodel->Data(BedEnum)[i])/(iomodel->Data(ThicknessEnum)[i]);
+			break;
+		case Mesh2DverticalEnum:
+			this->sigma = (iomodel->Data(MeshYEnum)[i]-iomodel->Data(BedEnum)[i])/(iomodel->Data(ThicknessEnum)[i]);
+			break;
+	}
+
 	this->connectivity = iomodel->numbernodetoelementconnectivity[i];
 
@@ -112,8 +122,9 @@
 /*}}}*/
 /*FUNCTION Vertex::UpdatePosition {{{*/
-void  Vertex::UpdatePosition(Vector<IssmDouble>* vz,Parameters* parameters,IssmDouble* thickness,IssmDouble* bed){
-
-	IssmDouble oldz,newz;
-	IssmDouble dt,velz;
+void  Vertex::UpdatePosition(Vector<IssmDouble>* vx,Vector<IssmDouble>* vy,Vector<IssmDouble>* vz,Parameters* parameters,IssmDouble* surface,IssmDouble* bed){
+
+	IssmDouble oldy,newy,vely;
+	IssmDouble oldz,newz,velz;
+	IssmDouble dt;
 
 	/*Get time stepping*/
@@ -121,11 +132,18 @@
 
 	/*sigma remains constant. z=bed+sigma*thickness*/
-	oldz = this->z;
-	newz = bed[this->pid]+sigma*thickness[this->pid];
-	velz = (newz-oldz)/dt;
-	this->z = newz;
-
-	/*put vz in vector*/
-	vz->SetValue(this->pid,velz,INS_VAL);
+	if(this->meshtype==Mesh2DverticalEnum){
+		oldy = this->y;
+		newy = bed[this->pid]+sigma*(surface[this->pid] - bed[this->pid]);
+		vely = (newy-oldy)/dt;
+		this->y = newy;
+		vy->SetValue(this->pid,vely,INS_VAL);
+	}
+	else{
+		oldz = this->z;
+		newz = bed[this->pid]+sigma*(surface[this->pid] - bed[this->pid]);
+		velz = (newz-oldz)/dt;
+		this->z = newz;
+		vz->SetValue(this->pid,velz,INS_VAL);
+	}
 }
 /*}}}*/
Index: /issm/trunk-jpl/src/c/classes/Vertex.h
===================================================================
--- /issm/trunk-jpl/src/c/classes/Vertex.h	(revision 16446)
+++ /issm/trunk-jpl/src/c/classes/Vertex.h	(revision 16447)
@@ -21,4 +21,5 @@
 	public: 
 		bool       clone;
+		int        meshtype;
 		int        id;           // random index
 		int        sid;          // "serial" id (rank of this vertex if the dataset was on 1 cpu)
@@ -49,5 +50,5 @@
 		IssmDouble GetY(void); 
 		IssmDouble GetZ(void); 
-		void       UpdatePosition(Vector<IssmDouble>* vz,Parameters* parameters,IssmDouble* thickness,IssmDouble* bed);
+		void       UpdatePosition(Vector<IssmDouble>* vx,Vector<IssmDouble>* vy,Vector<IssmDouble>* vz,Parameters* parameters,IssmDouble* thickness,IssmDouble* bed);
 		void       DistributePids(int* ppidcount);
 		void       OffsetPids(int pidcount);