% stirs two density layers when grad. Ri is unstable
	Tm=mean(T(i:i+1));T(i:i+1)=Tm*ones(2,1);
	Sm=mean(S(i:i+1));S(i:i+1)=Sm*ones(2,1); 
	Sigm=mean(Sig(i:i+1)); Sig(i:i+1)=Sigm*ones(2,1);
	UVm=mean(UV(i:i+1,:)); 
		UV(i:i+1,1)=UVm(1)*ones(2,1);
		UV(i:i+1,2)=UVm(2)*ones(2,1);