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NASA – keeping an eye on sea level change from space

Earth’s seas are rising, which is a direct result of a changing climate. NASA continuously measures the sea level rise and the weight of glaciers and ice sheets – a large fraction of the Earth’s fresh water is said to be frozen. The GRACE satellites allow to observe Greenland and Antarctic ice sheets, as well as glaciers, shrinking.

NASA published a feature on 7th of July, that looks at the continuous record of ocean height, as the satellites circling our planet allow to measure sea levels. This has helped researchers forecast any future impacts of climate change around the world. It is said that now, engineers and scientists, are preparing two identical satellites, to extend the dataset.

The satellites are said to be part of the Sentinel-6/Jason-CS mission – collaboration between US and Europe that aims to deliver the most accurate measurements about the sea levels around the world. The accurate measuring of sea surface height is essential to predict sea level changes that may affect people in coastal regions.

The satellite Sentinel-6 Michael Freilich would be the first satellite to launch, which will lift off in November, whilst the Sentinel-6B will launch in 2025. Article describes the aim of the mission: “Both will assess sea levels by sending electromagnetic signals down to the ocean and measuring how long it takes for them to return to the spacecraft.”

The mission has been compared to the launch of the TOPEX/Poseidon in 1992, which has been continued with three more missions over the years. It is hoped that the Sentinel-6/Jason-CS mission in November will continue the efforts that began in 1992, to extend the sea level dataset.

In the article, Josh Willis – the mission’s project scientist at NASA’s Jet Propulsion Laboratory in Southern California – highlighted the importance of the mission, as the way to give scientists ‘a real-time indication of how Earth’s climate is changing’.

One of the studies by EarthSky says that the ocean absorbs about 90% of the excess heat from the planet’s warming climate. A study released in 2018 reported that oceans absorbed 60 percent more heat than previously thought. The article describes: “The study estimates that for each of the past 25 years, oceans have absorbed an amount of heat energy that is 150 times the energy humans produce as electricity annually.”

Moreover, the NASA study adds that seawater expands as it heats up and the melting ice accounts for the rest. The study then moves on to present satellite sea level observations from January 1993 to January 2020. The graph from NASA Goddard Space Flight Centre, shows the rate of change being 3.3 millimetres per year. This has been described as rising more than twice the rate at the start of the 20th century. The measurement has been made using data that has been collected by the TOPEX/Poseidon that continued with three more missions over the years: Jason-1, OSTM/Jason-2, and Jason-3. 

Josh Willis described the satellites as an important tool to understand how rising sea levels will affect humanity, explaining it as “they are kind of a bellwether for this creeping global warming impact that’s going to inundate coastlines around the world and affect hundreds of millions of people”. The article also gathers the quote from Craig Donlon – mission project scientist at the European Space Agency: “As more and more people move to coastal regions, and coastal megacities continue to develop, the impact of sea level change will be more profound on those societies”.

The mission in November will allow to continue the dataset’s success that started with TOPEX/Poseidon and become essential for future climate studies from space. It would allow climate scientists to account for different variations, as the long-term datasets such as ocean temperature or the height of tides are said to ‘have gaps or major changes in how data was collected(like before and after satellite records began)”.

This will provide researchers with better understanding of the rate of sea level rise, and the mentioned in the article phenomena like El Niño – that can shift ocean currents and global weather patterns. Craig Donlon said in the article:

“The global view that the Sentinel-6 Michael Freilich satellite will provide, together with sea level data from models and observing stations, will provide invaluable information for governments and local authorities tasked with planning for things like sea level rise and storms.”

By Julita Waleskiewicz

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