Mode Water Map Overlay
OceanGraph can color search-result map markers by profile-level mode water detection. This helps you inspect where individual profiles match a selected mode water type, and how thick the detected layer is.
This map overlay is separate from Visual Lab > Mode Waters. The map overlay works on the profiles in your current search results, while Visual Lab shows precomputed seasonal summaries and time series.
Accessing the Overlay
Mode water map overlay is available to signed-in users.
- Sign in and perform a search
- Open the Mode Water map control
- Choose one mode water type, such as NPSTMW or NASTMW
- Use marker colors and tooltips to compare detected layer thickness across profiles
The MLD / SOM and Mode Water controls are mutually exclusive. Selecting a mode water turns off MLD and SOM coloring, and selecting MLD or SOM turns off mode water coloring. Both controls include Off when you want to return to the default marker colors.
Marker Colors and Tooltips
When a mode water type is selected:
- Profiles with that mode water are colored by detected layer thickness.
- Profiles without that selected mode water are shown as no-data markers.
- The tooltip shows the selected mode water type, layer thickness, core depth, and that marker color represents thickness.
Thickness is mapped to color with the same cmocean deep colormap used for MLD map coloring. Color should be read as a relative visual cue for comparing profiles in the current result set, not as a separate classification variable.
Supported Mode Water Types
The region column reflects OceanGraph’s default advection processing scope, which searches broader areas that can include advected mode water signals.
| Short name | Full name | Region | Density range |
|---|---|---|---|
| NPSTMW | North Pacific Subtropical Mode Water | 20°N-38°N, 130°E-180° | 25.0-25.6 σθ |
| NPCMW | North Pacific Central Mode Water | 20°N-45°N, 145°E-145°W | 26.0-26.6 σθ |
| SPSTMW | South Pacific Subtropical Mode Water | 25°S-42°S, 150°E-170°W | 25.8-26.5 σθ |
| NASTMW | North Atlantic Subtropical Mode Water | 20°N-42°N, 85°W-35°W | 26.3-26.6 σθ |
| SASTMW | South Atlantic Subtropical Mode Water | 25°S-42°S, 60°W-20°E | 26.2-26.7 σθ |
| IOSTMW | Indian Ocean Subtropical Mode Water | 25°S-45°S, 20°E-70°E | 25.8-26.2 σθ |
All listed mode water types use a maximum potential vorticity threshold of 2 × 10⁻¹⁰ m⁻¹s⁻¹ and a minimum detected layer thickness of 10 m.
Detection Details
Mode water detection is calculated during OceanGraph data processing for each profile. The detection uses quality-controlled, interpolated pressure, potential temperature, and absolute salinity profiles. A profile is checked against the configured geographic bounds for each mode water type, then a continuous layer is detected using density, potential vorticity, and minimum-thickness criteria.
For each detected layer, OceanGraph records:
- Top pressure and bottom pressure in dbar
- Thickness in meters
- Core depth in meters
Core depth is defined as the midpoint of the detected layer after converting the top and bottom pressures to depth. It is not the depth of minimum potential vorticity.
A single profile can store more than one detected mode water type. The map, however, colors markers for the one type currently selected in the Mode Water control.
Interpreting No-Data Markers
A no-data marker does not necessarily mean the profile is unusable. It means the selected mode water type was not detected for that profile under OceanGraph’s current automatic criteria. Common reasons include:
- The profile is outside the selected mode water’s geographic bounds
- The density or potential vorticity criteria were not met
- The matching layer was thinner than the 10 m minimum required thickness
- The profile did not have enough valid data after quality control and interpolation
Mode water detection is intended as an exploration aid. For research-grade classification, inspect the original profile structure and apply the criteria appropriate to your study.