Science

Global sea level rise: All roads lead to one conclusion

Oceans have risen up 3 cm per decade since 1990s

Scientists can measure a change in the height of the sea surface, via satellites. And they can use satellites to notice that glaciers have less ice now than decades ago. So they can estimate how much ice melt has gone into the ocean. Plus satellites show that the oceans themselves are warming. And with that warming comes an expansion of seawater and more sea level rise. But do the estimates for the amount of sea level rise – based on the different sorts of studies – agree? On February 10, 2022, the European Space Agency (ESA) released the results of a new comprehensive comparison. Yes, the estimates do agree, these scientists said, adding that mean global sea level has risen by more than an inch (3 cm) per decade since precise satellite measurements began in the 1990s.

The peer-reviewed journal Earth System Science Data published the new comparison study, which was led by scientists at the Dresden University of Technology. ESA explained:

A good third of this rise in sea level is down to thermal expansion. That is, as seawater warms, it expands.

Nearly two-thirds of the rise is because of freshwater being added to the ocean, mainly from the melting of glaciers and from the Antarctic and Greenland ice sheets, but also from the water added to the ocean from land, essentially as a result of groundwater storage depletion.

While we all understand that seas are rising because Earth is getting hotter, scientists need to understand exactly what’s going on. They do this by assessing how these different contributions compare with the overall change in sea level.

In other words, they ‘assess the sea-level budget.’

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Read more about some of those questions – and how scientists hope to answer them – from ESA.

A common sea level framework for experts

Martin Horwath, lead author of the new study, commented:

Assembling this coherent picture of sea-level and ocean-mass budgets not only required advanced datasets from satellite Earth observation and modeling. It also required the experts from various disciplines to arrive at a common framework.

ESA’s Jérôme Benveniste said ESA’s Climate Change Initiative helped make this research possible:

The beauty of the results lies in the coherence of all the CCI Essential Climate Variables [key indicators that describe Earth’s changing climate]. When well-prepared and assembled, they give a precise picture of our climate and its trend.

A milestone sea level study

Benveniste called this new work an “impressive milestone.” But, he said, the work doesn’t stop here:

… There are still questions to be answered regarding the climate variability and its evolution.

Indeed!

Bottom line: A new comparison of direct measurements of sea level rise with contributing factors – like ice melt and thermal expansion of seawater – shows that global mean sea level has risen by more than an inch (3 cm) per decade since precise satellite measurements began in the 1990s.

Source: Global sea-level budget and ocean-mass budget, with a focus on advanced data products and uncertainty characterization

Via ESA

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