Earth Observation Mission News
25 years of global sea level data and counting
10 August 2017
Today marks the 25th anniversary of the launch of a revolutionary ocean research vessel -- a space "ship". As the NASA/CNES Topex-Poseidon satellite ascended into orbit, it ushered in a new era of oceanography with the first highly accurate, global measurements of sea levels. That mission and its three successors, all named Jason, have continuously mapped global ocean currents and tides; opened our eyes to the global reach of El Niño and other climate events; created a quarter-century-long, extraordinarily precise record of global and regional sea level rise; and enabled improved forecasts of extreme weather events such as hurricanes, floods and droughts.
In 1992, when Topex-Poseidon launched, no one foresaw that its record of precision ocean height measurements would continue through three decades and four spacecraft. In fact, many oceanographers at the time weren't convinced that Topex-Poseidon's sensors would be accurate enough to reveal the signal of sea level rise out of the noise of waves, tides and other changes. But the radar altimeter and radiometer measurement system outperformed expectations from the start. In 25 years of continuous operation, Topex-Poseidon and its successors have recorded 2.8 inches (07 centimetres) of global average sea level rise.
Image credit: NASA/JPL-Caltech - Topex-Poseidon illustration.