From 885310cebb8e65fa9e80ba6c0c044dcdc345d6a3 Mon Sep 17 00:00:00 2001
From: Paul Gierz <pgierz@awi.de>
Date: Tue, 12 May 2026 12:05:53 +0200
Subject: [PATCH 1/2] Silence seawater deprecation warning, document EOS-80 vs
 TEOS-10

The seawater library is deprecated in favor of gsw (TEOS-10) but a
literal swap is not safe: gsw expects Absolute Salinity (g/kg) while
this module receives Practical Salinity from PHC/WOA, and the SA<->SP
conversion is regionally varying. Until a deliberate scientific
decision is made on TEOS-10 migration, keep EOS-80 numerics and just
silence the import-time warning. Prominent comment block records why.

Verified seawater still works on Python 3.13 + numpy 2.4.x.
---
 pyfesom2/climatology.py | 35 ++++++++++++++++++++++++++++++++++-
 1 file changed, 34 insertions(+), 1 deletion(-)

diff --git a/pyfesom2/climatology.py b/pyfesom2/climatology.py
index f55b00d..f6e7fda 100644
--- a/pyfesom2/climatology.py
+++ b/pyfesom2/climatology.py
@@ -8,10 +8,43 @@
 # Add seasonal climatology
 ################################################################################
 import os
+import warnings
 
 import numpy as np
 import scipy as sc
-import seawater as sw
+
+# =============================================================================
+# WARNING: EOS-80 vs TEOS-10
+# -----------------------------------------------------------------------------
+# This module deliberately uses the (deprecated, unmaintained) `seawater`
+# library, which implements the EOS-80 equation of state. The successor
+# library `gsw` implements TEOS-10, which is the *current* international
+# standard (since 2010) for seawater thermodynamics.
+#
+# We have NOT migrated to gsw on purpose:
+#
+#   * EOS-80 takes Practical Salinity (PSS-78, unitless) as input.
+#   * TEOS-10 takes Absolute Salinity (g/kg) as input, which differs from
+#     Practical Salinity by a *regionally varying* composition anomaly that
+#     gsw retrieves from a bundled lon/lat/depth atlas (`gsw.SA_from_SP`).
+#   * Climatology inputs here are practical salinity from PHC / WOA, so a
+#     literal swap would silently change the numbers and break reproducibility
+#     against legacy pyfesom2 output.
+#
+# A proper TEOS-10 migration must (1) plumb lon/lat through to compute SA,
+# (2) decide whether to use SR (gsw.SR_from_SP) as a global-mean shortcut,
+# and (3) accept that potential temperatures will differ slightly from the
+# EOS-80 reference. Until that scientific decision is made, we keep EOS-80
+# and just silence the deprecation noise.
+# =============================================================================
+with warnings.catch_warnings():
+    warnings.filterwarnings(
+        "ignore",
+        message=".*seawater library is deprecated.*",
+        category=UserWarning,
+    )
+    import seawater as sw  # noqa: E402
+
 from netCDF4 import Dataset
 from numpy import nanmean
 

From d579505b5307c837f67f7a1a4455395e613d5c49 Mon Sep 17 00:00:00 2001
From: Paul Gierz <pgierz@awi.de>
Date: Tue, 12 May 2026 14:02:50 +0200
Subject: [PATCH 2/2] Fix cache-environment-key typo in CI workflow

---
 .github/workflows/pyfesom2_onPR.yml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.github/workflows/pyfesom2_onPR.yml b/.github/workflows/pyfesom2_onPR.yml
index 78cdfdf..aabc7a5 100644
--- a/.github/workflows/pyfesom2_onPR.yml
+++ b/.github/workflows/pyfesom2_onPR.yml
@@ -58,7 +58,7 @@ jobs:
       with:
         environment-file: main/ci/requirements-py37.yml
         environment-name: pyfesom2
-        cache-envronment-key: "${{runner.os}}-${{runner.arch}}-py${{env.PYTHON_VERSION}}-${{env.TODAY}}-${{hashFiles(env.CONDA_ENV_FILE)}}"
+        cache-environment-key: "${{runner.os}}-${{runner.arch}}-py${{env.PYTHON_VERSION}}-${{env.TODAY}}-${{hashFiles(env.CONDA_ENV_FILE)}}"
         init-shell: >-
             bash
             zsh