As a result of global warming, the seas warm and ice melts. Naturally, Earth’s oceans have risen steadily – or at least, it was thought so. According to a new study based on 25 years of NASA and European satellite data, rather than increasing steadily, global sea-level rise has been accelerating in recent decades. If this trend continues, by the year 2100, sea-level rise will be around 65 cm (25.6 in), twice as big as previously thought. This is more than enough to cause significant problems for coastal cities.
Satellite altimetry (see notes 1) has shown that since 1993, the global mean sea level has been rising at a rate of ∼3 ± 0.4 millimeters per year. Researchers show that this rate is accelerating at 0.084 ± 0.025 mm/y2, which agrees well with climate model projections. This acceleration is driven mainly by increased melting in Greenland and Antarctica because of global warming. If sea level continues to change at this rate and acceleration, sea-level rise by 2100 (∼65 cm ± 12 cm, compared with 2005) will be more than double the amount if the rate was constant at 3 mm/y, researchers conclude.
Video: The acceleration of the global sea-level rise
Understanding how fast the sea level is rising can help being prepared for the effects in coastal areas around the world. Video published by NASA Goddard channel.
- Researchers used satellite altimeter data from TOPEX/Poseidon, Jason-1, Jason-2, and Jason-3. Launched on August 10, 1992, TOPEX/Poseidon was a joint satellite mission between NASA, the U.S. space agency; and CNES, the French space agency, to map ocean surface topography. A malfunction ended normal satellite operations in January 2006. Launched in 2001, Jason-1, the successor of TOPEX/Poseidon which measured ocean surface topography from 1992 through 2005, was a satellite oceanography mission to monitor global ocean circulation, study the ties between the ocean and the atmosphere, improve global climate forecasts and predictions, and monitor events such as El Niño and ocean eddies. The lineage of the name begins with the JASO1 meeting (JASO = Journées Altimétriques Satellitaires pour l’Océanographie) in Toulouse, France to study the problems of assimilating altimeter data in models. Jason as an acronym also stands for “Joint Altimetry Satellite Oceanography Network”. Additionally, it is used to reference the mythical quest for knowledge of Jason and the Argonauts. In early 2012, having helped cross-calibrate the Jason-2 replacement mission, Jason-1 was maneuvered into its graveyard orbit and all remaining fuel was vented. The mission was still able to return science data, measuring Earth’s gravity field over the ocean. On 21 June 2013, contact with Jason-1 was lost; multiple attempts to re-establish communication failed. It was determined that the last remaining transmitter onboard the spacecraft had failed. Operators sent commands to the satellite to turn off remaining functioning components on 1 July 2013, rendering it decommissioned. It is estimated that the spacecraft will remain in orbit for at least 1,000 years. OSTM/Jason-2 was launched at 07:46 UTC on June 20, 2008. It is an international Earth observation satellite mission that continues the sea level measurements. The fourth spacecraft to be part of the Ocean Surface Topography Mission is Jason-3. It is the result of a four-agency international partnership consisting of NOAA, NASA, the French Space Agency CNES (Centre National d’Etudes Spatiales), and EUMETSAT (the European Organization for the Exploitation of Meteorological Satellites). The spacecraft was built by Thales Alenia Space and launched by SpaceX on the 21st Falcon 9 flight on January 17, 2016.
- Study: “Climate-change-driven accelerated sea-level rise detected in the altimeter era.” R. S. Nerem, B. D. Beckley, J. T. Fasullo, B. D. Hamlington, D. Masters and G. T. Mitchum. pnas.org (PNAS: Proceedings of the National Academy of Sciences of the United States of America)
- “New Study Finds Sea-Level Rise Accelerating” on NASA.gov
- Future sea level on Wikipedia
- TOPEX/Poseidon on Wikipedia
- Jason-1 on Wikipedia
- Jason-2 on Wikipedia
- Jason-3 on Wikipedia