diff --git a/src/glide/assets/core.yml b/src/glide/assets/core.yml
index 076ed94..2a4739c 100644
--- a/src/glide/assets/core.yml
+++ b/src/glide/assets/core.yml
@@ -383,6 +383,20 @@ CT:
     valid_max: 50.0
     observation_type: calculated
 
+
+sound_speed:
+  track_qc: True
+  dtype: f4
+  CF:
+    long_name: Sound speed
+    standard_name: speed_of_sound_in_sea_water
+    units: m s-1
+    instrument: instrument_ctd
+    valid_min: 1400.0
+    valid_max: 1600.0
+    observation_type: calculated
+
+
 N2:
   track_qc: True
   dtype: f4
diff --git a/src/glide/process_l1.py b/src/glide/process_l1.py
index b06eb82..c8bcd4f 100644
--- a/src/glide/process_l1.py
+++ b/src/glide/process_l1.py
@@ -255,6 +255,9 @@ def calculate_thermodynamics(ds: xr.Dataset, config: dict) -> xr.Dataset:
     CT = gsw.CT_from_t(ds.SA, ds.temperature, ds.pressure)
     ds["CT"] = (dims, CT.values, variable_specs["CT"]["CF"])
 
+    sound_speed = gsw.sound_speed(ds.SA, ds.CT, ds.pressure)
+    ds["sound_speed"] = (dims, sound_speed.values, variable_specs["sound_speed"]["CF"])
+
     new_variables = ["salinity", "SA", "density", "rho0", "CT"]
     ds = qc.init_qc(ds, new_variables, ds.conductivity_qc.values, config)
     ds = qc.apply_bounds(ds, new_variables)