function [OceanNodes,LakeNodes,GLgeo,GLnodes,GLele,OceanElements]=LakeOrOcean(CtrlVar,MUA,GF,GLgeo,GLnodes,GLele)

[OceanNodes,LakeNodes,GLgeo,GLnodes,GLele]=LakeOrOcean(CtrlVar,MUA,GF,GLgeo,GLnodes,GLele)

Only CtrlVar and MUA are required input variables:

Example:

load PIG-TWG-RestartFile.mat ; CtrlVar=CtrlVarInRestartFile;
CtrlVar.doplots=1 ;  CtrlVar.PlotOceanLakeNodes=1;
[OceanNodes,LakeNodes,GLgeo,GLnodes,GLele]=LakeOrOcean(CtrlVar,MUA,F.GF) ;

Tries to determine which floating nodes are part of the ocean and which belong to subglacial lakes.

Uses GLgeometry to determine the longest grounding line and assumes that this grounding line represents the ocean boundary. Then determines if nodal point at floating level are inside or outside of this boundary.

May not always work, and anyhow I am not sure if one can always objectively decide what is an ocean and what a lake.

This approach will fail in some circumstances. If, for example, parts of an ice-rise go afloat and the resulting subglacial lake does not make a connection to the surronding ocean, then this lake will not be identified as a lake but classified as a part of the ocean...

Just use this m-file as a starting point towards defining lake/ocean nodes.

Note: GLgeo calculated is slighly different from the usual way of doing this because here the grounding line needs to be closed.

Returns a logical indexing (this was changed from indexing vectors on 20 Dec, 2018)

Note: An alternative starting point might be:

IEle=EleFlooding(CtrlVar,MUA,NodeSeed,EleSubset);

Also consider using: LakeOrOcean3.m , which uses an alternative approach for the problem.

Currently, Úa users are split into LakeOrOcean.m and the LakeOrOcean3.m camps. The LakeOrOcean3.m approach is to consider lake being a lake if it is enclosed by grounded ice. The LakeOrOcean.m approach is to identify the longest grounding line and consider any floating areas upstream of that grounding line to be lakes and all other floating areas a part of the ocean. Both of these approached can fail. However, arguably the LakeOcean3.m definition of a lake is more likely to be generally accepted by members of a typical university geography department.

OceanNodes=[];
LakeNodes=[];
OceanElements=[];


if nargin<4 || isempty(GLgeo) || isempty(GLnodes) || isempty(GLele)
    [GLgeo,GLnodes,GLele]=GLgeometry(MUA.connectivity,MUA.coordinates,GF,CtrlVar);
end

if ~isfield(GF,'NodesDownstreamOfGroundingLines')
    [GF,GLgeo,GLnodes,GLele]=IceSheetIceShelves(CtrlVar,MUA,GF,GLgeo,GLnodes,GLele);
end

I=find(GF.NodesDownstreamOfGroundingLines);


if ~isempty(I)


    GFtemp=GF; GFtemp.node(MUA.Boundary.Nodes)=0;  % I need to `close' the grounding line, so I set all boundary nodes to floating status
    GLgeoMod=GLgeometry(MUA.connectivity,MUA.coordinates,GFtemp,CtrlVar);
    [xGL1,yGL1] = ArrangeGroundingLinePos(CtrlVar,GLgeoMod,1);

    x=MUA.coordinates(:,1); y=MUA.coordinates(:,2);
    %  IN = inpolygon(x(I),y(I),xGL,yGL);  % for some reason this standard matlab routine is much slower than inpoly
    [IN,ON] = inpoly([x(I) y(I)],[xGL1 yGL1],[],1);

    % There is a bit of a question here what to do with nodes that are
    % directly on the grounding line. I've here decided to consider them part of
    % the ocean.
    Ind=~IN  | ON ; % ocean nodes are not within grounding line, but can be on it


    OceanNodes=I(Ind);
    LakeNodes=I(~Ind);

    II=false(MUA.Nnodes,1);
    II(OceanNodes)=true;
    OceanNodes=II;

    II=false(MUA.Nnodes,1);
    II(LakeNodes)=true;
    LakeNodes=II;

    OceanElements=AllElementsContainingGivenNodes(MUA.connectivity,find(OceanNodes)) ;


    if CtrlVar.doplots && CtrlVar.PlotOceanLakeNodes

        figure
        hold off


        P1=plot(x(OceanNodes)/CtrlVar.PlotXYscale,y(OceanNodes)/CtrlVar.PlotXYscale,'og','DisplayName','Ocean Nodes') ; hold on
        P2=plot(x(LakeNodes)/CtrlVar.PlotXYscale,y(LakeNodes)/CtrlVar.PlotXYscale,'or','DisplayName','Lake Nodes');


        PlotFEmesh(MUA.coordinates,MUA.connectivity,CtrlVar) ; hold on
        plot(xGL1/CtrlVar.PlotXYscale,yGL1/CtrlVar.PlotXYscale,'k','LineWidth',2);
        [xGL,yGL,GLgeo]=PlotGroundingLines(CtrlVar,MUA,GF,GLgeo,[],[],'r');
        %plot(GLgeo(:,[3 4])'/CtrlVar.PlotXYscale,GLgeo(:,[5 6])'/CtrlVar.PlotXYscale,'r','LineWidth',1);
        %plot(x(Boundary.EdgeCornerNodes)/CtrlVar.PlotXYscale,y(Boundary.EdgeCornerNodes)/CtrlVar.PlotXYscale,'k.-')
        %plot(x(Boundary.Nodes)/CtrlVar.PlotXYscale,y(Boundary.Nodes)/CtrlVar.PlotXYscale,'ro')
        axis equal tight
        hold on
        title('Ocean/Lake nodes')
        lg=legend([P1 P2]);

    end
end

end

Published with MATLAB® R2019b