The next satellite tasked with maintaining the “gold standard” measurement of sea-level rise is about to enter final testing.
Sentinel-6a will pick up from the long-running Jason series of spacecraft when it launches in November 2020. These missions track the height and shape of Earth’s oceans with microwave altimeters.
Since 1992, the orbiting instruments have observed sea level go up by an average of 3.2mm per year. This trend is accelerating, however. The most recent five-year period, from 2014 to 2019, has witnessed a 4.8mm/yr increase.
Just as air pressure tells meteorologists what is going on in the atmosphere, so ocean height will betray details about the behaviour of water below just the top layers.
The data gives clues to temperature and salinity. When combined with gravity information, it will also indicate current direction and speed.
The oceans store vast amounts of heat from the Sun, and how they move that energy around the globe and interact with the atmosphere are what drive key elements of our weather and climate systems.