function [LakeNodes,OceanNodes,LakeElements,OceanElements] = LakeOrOcean3(CtrlVar,MUA,GF,OceanBoundaryNodes,NodesDownstreamOfGroundingLines)

narginchk(3,5)
nargoutchk(2,4)

[LakeNodes,OceanNodes] = LakeOrOcean3(CtrlVar,MUA,GF,OceanBoundaryNodes)

OceanBoundaryNodes is an optional input that allows the user to specify the node numbers of nodes in their domain that are connected to the ocean, if this input is not provided the code assumes that all floating nodes on the model boundary are connected to the ocean. This is usually a good guess but may break down in certain situations, particularly if there are holes in the model mesh.

When calling this to apply melt, the following syntax is recommended to ensure that melt is applied correctly:

[LakeNodes,OceanNodes]=LakeOrOcean3(CtrlVar,MUA,GF)
ab(~OceanNodes) = 0;

This script is designed to be used in conjunction with DefineMassBalance to only assign melt to nodes that should be melted (OceanNodes).

Note that this script does not robustly identify all possible lakes in a domain, since it only considers nodes strictly downstream of the grounding line as floating. Thus, floating nodes with an edge that crosses the grounding line, which are not considered floating, will also not be considered as lakes. In this way, very small isolated patches of floating nodes will neither be considered lakes nor ocean.

Also consider using: LakeOrOcean.m , which uses an alternative approach for the problem. ... but is painfully slow and will fail to correctly identify lakes within grounded islands

Currently, Úa users are split into LakeOrOcean.m and the LakeOrOcean3.m camps. The author of the LakeOrOcean.m prefers using LakeOrOcean3.m

load PIG-TWG-RestartFile.mat ; CtrlVar=CtrlVarInRestartFile;
[LakeNodes,OceanNodes,LakeElements,OceanElements]=LakeOrOcean3(CtrlVar,MUA,F.GF) ;

FindOrCreateFigure("LakeOrOcean3") ;
CtrlVar.WhenPlottingMesh_PlotMeshBoundaryCoordinatesToo=0;
PlotMuaMesh(CtrlVar,MUA) ;
hold on ; plot(MUA.coordinates(OceanNodes,1)/CtrlVar.PlotXYscale,MUA.coordinates(OceanNodes,2)/CtrlVar.PlotXYscale,'ob') ;
PlotGroundingLines(CtrlVar,MUA,F.GF,[],[],[],color='r') ;

GF = IceSheetIceShelves(CtrlVar,MUA,GF);

% TestIng
if nargin<5 || isempty(NodesDownstreamOfGroundingLines)

    NodesDownstreamOfGroundingLines=GF.NodesDownstreamOfGroundingLines;
else
    if isstring(NodesDownstreamOfGroundingLines)
        if contains(NodesDownstreamOfGroundingLines,"Strickt")
            NodesDownstreamOfGroundingLines=GF.NodesDownstreamOfGroundingLines;
        elseif contains(NodesDownstreamOfGroundingLines,"Relaxed")
            NodesDownstreamOfGroundingLines=GF.node < 0.5 ;
        end
    end
end


% if the user does not provide an OceanBoundaryNodes vector as input,
% assume that floating nodes on the Mesh Boundary are ocean nodes
if nargin<4 || isempty(OceanBoundaryNodes)
    OceanBoundaryNodes=MUA.Boundary.Nodes(GF.node(MUA.Boundary.Nodes)<0.5);
end

% the graph will be comprised only of fully floating elements
EleSubset = GF.ElementsDownstreamOfGroundingLines;

% find the node numbers of all of these fully floating elements
NodeSubset = unique(MUA.connectivity(EleSubset,:));


% don't include floating boundary nodes that are not part of fully floating
% elements as these will not be a part of the graph network
FloatingSubset = intersect(NodeSubset,OceanBoundaryNodes);

TRI=MUA.connectivity(EleSubset,:) ;

% create undirected graph
G=graph(TRI,TRI(:,[2 3 1]));
% calculate the connected components of the graph
bins=conncomp(G) ;

% initialise arrays
Nnum = zeros(MUA.Nnodes,1);

Nnum(FloatingSubset) = 1;
LakeNodes = NodesDownstreamOfGroundingLines;

% loop through ocean boundary nodes until each one has been checked for
% connected floating nodes, once this is done for all boundary nodes the
% only floating nodes left should be lakes
while sum(Nnum)>0

    NodeSeed = find(Nnum,1,'first');
    ID=bins(NodeSeed) ;
    % list of all connected nodes to this ocean boundary node
    nodes=find(bins==ID);
    % remove these from the Lakes list
    LakeNodes(nodes) = 0;
    % also remove these from the list of boundary nodes to save time where
    % one ice shelf has multiple nodes on the ocean boundary
    Nnum(nodes) = 0;

end

OceanNodes = NodesDownstreamOfGroundingLines & ~LakeNodes;

if nargout > 2
    LakeElements=AllElementsContainingGivenNodes(MUA.connectivity,find(LakeNodes)) ;
end

if nargout > 3
    OceanElements=AllElementsContainingGivenNodes(MUA.connectivity,find(OceanNodes)) ;
end

Published with MATLAB® R2021a