Index: /issm/trunk-jpl/src/m/classes/mesh.py
===================================================================
--- /issm/trunk-jpl/src/m/classes/mesh.py	(revision 14005)
+++ /issm/trunk-jpl/src/m/classes/mesh.py	(revision 14006)
@@ -93,7 +93,7 @@
 		string="%s\n%s"%(string,fielddisplay(self,"elementonsurface","upper elements flags list"))
 		string="%s\n%s"%(string,fielddisplay(self,"uppervertex","upper vertex list (-1 for vertex on the upper surface)"))
-		string="%s\n%s"%(string,fielddisplay(self,"upperelements","upper element list (NaN for element on the upper layer)"))
+		string="%s\n%s"%(string,fielddisplay(self,"upperelements","upper element list (-1 for element on the upper layer)"))
 		string="%s\n%s"%(string,fielddisplay(self,"lowervertex","lower vertex list (-1 for vertex on the lower surface)"))
-		string="%s\n%s"%(string,fielddisplay(self,"lowerelements","lower element list (NaN for element on the lower layer)"))
+		string="%s\n%s"%(string,fielddisplay(self,"lowerelements","lower element list (-1 for element on the lower layer)"))
 		string="%s\n%s"%(string,fielddisplay(self,"vertexonboundary","vertices on the boundary of the domain flag list"))
 		string="%s\n%s"%(string,fielddisplay(self,"segments","edges on domain boundary (vertex1 vertex2 element)"))
Index: /issm/trunk-jpl/src/m/classes/model/model.py
===================================================================
--- /issm/trunk-jpl/src/m/classes/model/model.py	(revision 14005)
+++ /issm/trunk-jpl/src/m/classes/model/model.py	(revision 14006)
@@ -299,10 +299,10 @@
 
 			md2.mesh.upperelements=md1.mesh.upperelements[pos_elem]
-			pos=numpy.nonzero(numpy.logical_not(numpy.isnan(md2.mesh.upperelements)))[0]
-			md2.mesh.upperelements[pos]=Pelem[md2.mesh.upperelements[pos].astype(int)-1]
+			pos=numpy.nonzero(numpy.logical_not(md2.mesh.upperelements==-1))[0]
+			md2.mesh.upperelements[pos]=Pelem[md2.mesh.upperelements[pos]-1]
 
 			md2.mesh.lowerelements=md1.mesh.lowerelements[pos_elem]
-			pos=numpy.nonzero(numpy.logical_not(numpy.isnan(md2.mesh.lowerelements)))[0]
-			md2.mesh.lowerelements[pos]=Pelem[md2.mesh.lowerelements[pos].astype(int)-1]
+			pos=numpy.nonzero(numpy.logical_not(md2.mesh.lowerelements==-1))[0]
+			md2.mesh.lowerelements[pos]=Pelem[md2.mesh.lowerelements[pos]-1]
 
 		#Initial 2d mesh 
@@ -546,6 +546,6 @@
 
 		#same for lower and upper elements
-		mesh.lowerelements=float('NaN')*numpy.ones(number_el3d)
-		mesh.upperelements=float('NaN')*numpy.ones(number_el3d)
+		mesh.lowerelements=-1*numpy.ones(number_el3d,int)
+		mesh.upperelements=-1*numpy.ones(number_el3d,int)
 		mesh.lowerelements[md.mesh.numberofelements:]=numpy.arange(1,(numlayers-2)*md.mesh.numberofelements+1)
 		mesh.upperelements[:(numlayers-2)*md.mesh.numberofelements]=numpy.arange(md.mesh.numberofelements+1,(numlayers-1)*md.mesh.numberofelements+1)