diff --git a/environment.yml b/environment.yml
index 994ab6cf..3fd6422d 100644
--- a/environment.yml
+++ b/environment.yml
@@ -3,7 +3,7 @@ channels:
   - conda-forge
 dependencies:
   - click
-  - parcels >3, <3.1.0
+  - parcels >3.1.0
   - pyproj >= 3, < 4
   - sortedcontainers == 2.4.0
   - opensimplex == 0.4.5
diff --git a/src/virtualship/expedition/input_data.py b/src/virtualship/expedition/input_data.py
index 7af9ef72..037d007f 100644
--- a/src/virtualship/expedition/input_data.py
+++ b/src/virtualship/expedition/input_data.py
@@ -97,7 +97,7 @@ def _load_default_fieldset(cls, directory: str | Path) -> FieldSet:
 
         # make depth negative
         for g in fieldset.gridset.grids:
-            g.depth = -g.depth
+            g.negate_depth()
 
         # add bathymetry data
         bathymetry_file = directory.joinpath("bathymetry.nc")
@@ -137,7 +137,7 @@ def _load_drifter_fieldset(cls, directory: str | Path) -> FieldSet:
 
         # make depth negative
         for g in fieldset.gridset.grids:
-            g.depth = -g.depth
+            g.negate_depth()
 
         # read in data already
         fieldset.computeTimeChunk(0, 1)
@@ -169,7 +169,7 @@ def _load_argo_float_fieldset(cls, directory: str | Path) -> FieldSet:
         # make depth negative
         for g in fieldset.gridset.grids:
             if max(g.depth) > 0:
-                g.depth = -g.depth
+                g.negate_depth()
 
         # read in data already
         fieldset.computeTimeChunk(0, 1)