Solve the inversion calving problem differently (#794)

* WIP: refactor inversion internals

* Add find inversion calving

* Add what's new

docs/whats-new.rst

@@ -16,6 +16,10 @@ Breaking changes
   affect the majority of users (which used ``run_until_and_store``), but
   the results or ``run_until`` can be affected (:pull:`726`).
   By `Matthias Dusch <https://github.com/matthiasdusch>`_.
+- ``find_inversion_calving`` has been renamed to
+  ``find_inversion_calving_loop`` and will probably be deprecated soon
+  (:pull:`794`).
+  By `Fabien Maussion <https://github.com/fmaussion>`_.
 
 Enhancements
 ~~~~~~~~~~~~
@@ -38,6 +42,11 @@ Enhancements
   to the code base as it increases the number of choices available to users
   and demonstrates the modularity of the model.
   By `Moritz Oberrauch <https://github.com/oberrauch>`_.
+- Changed the way the calving flux is computed during the ice thickness
+  inversion. This no longer relies on an iteration over mu*, but solves
+  for `h` instead. The new function is likely to replace the "old"
+  calving loop(:pull:`794`).
+  By `Fabien Maussion <https://github.com/fmaussion>`_.
 
 
 Bug fixes

oggm/cfg.py

@@ -204,7 +204,7 @@ def __setitem__(self, key, value):
 BASENAMES['model_diagnostics'] = ('model_diagnostics.nc', _doc)
 
 _doc = ('A csv file containing the output of each iteration of the '
-        'find_inversion_calving task loop.')
+        'find_inversion_calving_loop task loop.')
 BASENAMES['calving_loop'] = ('calving_loop.csv', _doc)
 
 _doc = 'Calving output (deprecated).'

oggm/core/climate.py

@@ -1332,7 +1332,7 @@ def mu_star_calibration(gdir):
 
 
 @entity_task(log, writes=['inversion_flowlines', 'linear_mb_params'])
-def apparent_mb_from_linear_mb(gdir, mb_gradient=3.):
+def apparent_mb_from_linear_mb(gdir, mb_gradient=3., ela_h=None):
     """Compute apparent mb from a linear mass-balance assumption (for testing).
 
     This is for testing currently, but could be used as alternative method
@@ -1358,8 +1358,10 @@ def to_minimize(ela_h):
         smb = mbmod.get_specific_mb(heights=h, widths=w)
         return (smb - cmb)**2
 
-    ela_h = optimization.minimize(to_minimize, [0.], bounds=((0, 10000), ))
-    ela_h = ela_h['x'][0]
+    if ela_h is None:
+        ela_h = optimization.minimize(to_minimize, [0.], bounds=((0, 10000), ))
+        ela_h = ela_h['x'][0]
+
     mbmod = LinearMassBalance(ela_h, grad=mb_gradient)
 
     # For each flowline compute the apparent MB