Calculating 'IceVolumeAboveFloatation'

in-woo

Dear ISSM users,

I have a question about calculating ‘IceVolumeAboveFloatation’ in results of ‘md.results.TransientSolution’. It was easy to calculate ‘md.results.TransientSolution.IceVolume’, however, code which I used for ‘IceVolumeAboveFloatation’ was not worked well. From that code, I want to calculate initial IceVolumeAboveFloatation.


% find grounded ice
pos_gi = find(md.mask.grounded_levelset > 0 & md.mask.ice_levelset<0);
elements = zeros(md.mesh.numberofelements,3);
% find floating ice elements
for kk = 1.mesh.numberofelements 
   if find(elements(kk,1) == pos_gi)
   pos_el_gi(kk,1)=1;
   end;
   if find(elements(kk,2) == pos_gi)
   pos_el_gi(kk,2)=1;
   end;
   if find(elements(kk,3) == pos_gi)
   pos_el_gi(kk,3)=1;
   end;
end;
% calculating elements data
areas = GetAreas(elements,md.mesh.x,md.mesh.y);
surface = md.geometry.surface(elements) * ones(3,1) * 1/3;
thickness = md.geometry.thickness(elements) * ones(3,1) *1/3;
bed = bed(elements) *ones(3,1) * 1/3;
mask = md.results.TransientSolution.MaskGroundediceLevelset;
mask = mask(elements) * ones(3,1) * 1/3;

IceVolumeAboveFloatation = (surface – bed * ( 1- rho_water/rho_ice)).*areas;
IceVolumeAboveFloatation = sum(IceVolumeAboveFloatation,1);
% Or
IceVolumeAboveFloatation = mask.* areas;
IceVolumeAboveFloatation = sum(IceVolumeAboveFloatation,1);

Best,

Inwoo

mathieumorlighem

Hi InWoo,

what error message did you get when you requested IceVolumeAboveFloatation as an additional output?

Mathieu

in-woo

Dear Mathieu,

An output requestion for 'md.results.TransientSolution' works good. There is no problem. However, I want to calculate IceVolumeAboveFloatation by myself, so I want to get IceVolumeAboveFloatation at initial condition of my model for calculating equivalent sea level rise precisely. To confirm my code, I compared results of 'IceVolumeAboveFloatation' from ISSM to my result from my code at some time (i.e. if initial time = 2007, comparing time points = 2007.2 years).

When I run the transient simulation with following options,

md.timestepping.start_time = 2007;

md.timestepping.end_time = 2008;

md.timestepping.time _step = 0.2; %

md.setting.output_frequency = 1;

the time result is shown as . There is no information at 2007 year.

If I use relaxation model as initial condition for other sensitivity analysis (e.g. SMB, melting rate, or others), I just use data at end of relaxation model, which provides 'IceVolumeAboveFloatation'.

Maybe it isn't a problem.

Best,

Inwoo

mathieumorlighem

Hi InWoo,

if you are using trunk-jpl I added a function called VolumeAboveFloatation that will return the volume above floatation for your initial step.

Let me know if you have any problem.

Best

Mathieu