SSH (DUACS)
The height of the sea surface itself, measured by satellite — not a departure from average. Use it to see where a current edge actually sits, including over permanent features an anomaly map washes out.
Updates daily
More detail
Warm eddies stand up as hills and cold ones sit in bowls, and the current is strongest where the height changes fastest. The Copernicus Marine Service, the European Union's ocean data service, makes the map with a system called DUACS. It has no cloud gaps, and a blank spot is land. The newest picture is about a day old.
Why the height itself matters. A permanent feature such as the Loop Current barely shows on SLA (DUACS).
By the provider's own figure, the smallest real feature is about 95 nautical miles across: the Loop Current and the big eddies, not a small filament. The layer covers the Gulf of America, the East Coast and Baja.
A number can change within the week: the provider publishes each day's map again three and six days later.
The colors are centered on the day's average for the whole basin. On the website the crosshair readout gives the height in whole inches when your depth unit is feet, and in meters otherwise.
How it relates to the other sea level layers. SLA (DUACS) is the same measurement shown as the difference from the usual height. Use SLA (DUACS) to find what has changed and this layer to find where the current edge sits. Currents (DUACS) is the current speed worked out from the slope of this same surface. SSH - Altimetry, from HYCOM (U.S. Navy model), is a forecast of the sea surface height with the tide still in it, so it will not match this layer. With an Observed layer up, the Altimetry button draws contour lines traced from SLA (DUACS), not from this layer, so switch to SLA (DUACS) to make them match.
The numbers
| How often it updates | Once a day, one frame per day |
| How fresh it usually is | About 1 day; a value settles after about 6 days |
| How detailed it is | About 8 nautical miles per cell, but the smallest real feature is about 95 nautical miles across |
| Where it covers | Gulf of America, East Coast and Baja |
| How far back you can look | 8 days back |
| Goes blank under cloud? | No. Blank means land |
| Observed or modeled | Measured along satellite tracks by radar, then mapped in between. The tide is taken out |
| What you see on screen | Height above or below the day's basin average. The default color range is about 18 inches (0.45 meters) either side |
Source: a satellite picture from DUACS satellite altimetry (Copernicus).