Sea Surface Height
At present, only altimeter systems are capable of measuring Sea Surface Height (SSH), with which information on ocean circulation patterns and sea levels are determined on a global scale.
SSH is the height of the sea surface with respect to the reference ellipsoid. SSH measurement includes dynamic contributions from ocean circulation and variations in the geoid with respect to the reference ellipsoid. Dynamic topography is the variation in SSH with respect to the geoid.
Sea level anomalies (a variable part of SSH) are usually derived by subtracting the Mean Sea Level (MSL) from the SSH. MSL is SSH, averaged across all the oceans of the globe. An increase in MSL is an indicator of possible global warming.
Figure 1: The variation of MSL anomalies on a global scale. Positive anomalies indicate more heat content (warmer waters, a deeper thermocline) whereas negative anomalies indicate less heat content (cooler waters, a shallower thermocline). Generally, sea level is higher than average in the northern hemisphere in July and August when waters are warmed by more direct solar radiation and is lower than average in February and March when the incoming solar flux reduces. These sea level anomalies maps derive from a combination of data coming from altimeters on-board JASON-1 and ENVISAT. Feb 2007-Dec 2008 (Credit: CNES/CLS)
The SENTINEL-3 mission SSH goal accuracy is 10 cm for Near Real-Time (NRT) products and 3-5 cm for Slow Time Critical (STC) products.