Adjusted Sea Level: We used to call this Gridded Sea Level but have changed the name. Adjusted Sea level (like GSL) is sea level minus astronomical tides and the ocean's response to atmospheric pressure. We make the pressure adjustment for two reasons:

  1. Our maps are made using altimeter and tide gauge data acquired over several days. Sea level changes rapidly due to the weather (rising about 10 cm for each 10 hPa fall of pressure) and the tides. To de-alias the altimeter observations we subtract the tide and the pressure response evaluated along-track by the space agencies using a barotropic ocean model, leaving the slowly changing sea level signals associated with ocean circulation and eddies. The same is done with the tide gauge data, providing daily information on the adjusted sea level variations at the coast.
  2. ASL is a measure of total pressure (being pressure due to sea level plus atmospheric pressure), the gradients of which control the dynamics of the ocean. For example, the geostrophic balance involves the adjusted sea level, not the total sea level. (If a storm passes rapidly over an eddy, the sea level rises while the pressure goes down, leaving the adjusted sea level largely unchanged.)
Terminology: The once-traditional term 'adjusted' is commonly omitted by many agencies and oceanographers. We did this, too, and now regret it, because dropping the 'adjusted' leaves no short name for 'unadjusted sea level', which is the quantity most relevant to users interested in coastal inundation. To reduce this ambiguity, we decided (in Sep 2021) to reinstate usage of 'adjusted'. Another candidate name for this quantity is Ocean dynamic sea level. Related names include: dynamic height, dynamic topography, subsurface pressure.

Adjusted Sea Level Anomaly: By 'anomaly', we mean the departure from the long-term (1993-2012) mean. We (like most users of altimetry) subtract the long-term mean of ASL from the altimeter observations in order to remove the ~100m sea level highs and lows (with respect to a smooth surface) mostly due to gravity perturbations associated with sea floor topography. This is done using a correction supplied by the space agencies, which is the Mean Sea Surface (MSS, evaluated along the precise track of the altimeter). Unfortunately this also removes the ~1m scale highs and lows of the Mean Dynamic Topography (MDT) due to the long-term mean of the ocean circulation (that causes the Coral Sea off Queensland to be about 1m higher than waters off Tasmania with respect to the geoid). We add the Bluelink ocean model estimate of the MDT to our altimetry-derived maps of ASLA (formerly known as GSLA) to produce ASL, from which we estimate velocities that include the mean. Most users, however, are more interested in the anomaly of sea level (adjusted or not) than the more abstract concept of sea level with respect to the geoid. Showing the anomaly also allows use of a more restricted colour bar, and to show the along-track altimetry data closer to its supplied form.