[ad_1]
Artist’s impression of a Sentinel satellite. With the kind permission of ESA / ATG medialab.
E.Research funded by the European Space Agency has shown a new way of measuring sea level changes in coastal areas with millimeter precision. It also works for areas covered in ice.
Satellite radar elevation data collected since 1990 has shown that the global mean sea level has risen an average of just over 3 mm each year … a rate that has been increasing in recent years.
Such averages are fine for assessments of open water regions around the world, but measurements along coastlines are more difficult due to distortion in the radar waves reflected off mountains, bays, and islands.
“In order to protect people and infrastructure – for example by building flood protection structures, securing ports or raising dikes – we need reliable predictions of sea level development,” says Florian Seitz, Director of the German Geodetic Research Institute at the Technical University of Munich
As part of the ESA project Earth Observation Science for Society Baltic Sea Level (Baltic SEAL), a team of researchers from the Technical University of Munich worked together with international partners to develop new algorithms for processing data from various satellite altitude sensors.
The aim of the work was to obtain precise and high-resolution measurements of sea level changes in coastal areas and of the “protrusions” in the sea ice.
The researchers chose the Baltic Sea as a model region.
“Data from this region is particularly suitable for developing new methods, as several factors make analysis difficult, such as the complex shape of the coast, sea ice and wind. At the same time, there are many local sea level measurements to underpin the results, â€said project manager Marcello Passaro.
“An analysis method that works in the Baltic Sea can easily be transferred to other regions.”
Mean sea level rise in the North and Baltic Seas (millimeters per year), calculated using satellite altimetry data between 1995 and 2019. With the kind permission of TUM / ESA.
The team developed a multi-step process to process hundreds of millions of radar measurements collected between 1995 and 2019 from missions such as the Jason series, Envisat, CryoSat and Copernicus Sentinel-3.
First, they calibrated the measurements from the various satellite missions so that they could be combined. With their new algorithms, they were then able to identify signals from ice-covered seawater in the radar reflections along cracks and crevices, so-called leads.
This made it possible to determine the sea level for the winter months. And with new calculation methods, they also achieved a better resolution of radar echoes near land.
The data show that sea levels in the south of the Baltic Sea on the German and Danish coasts rose annually by 2–3 mm, and in the northeast in the Gulf of Bothnia by 6 mm.
The cause of the greater north-east rise are strong south-westerly winds that drive the water north and east.
However, an above-average rise in sea level does not pose a threat to coastal residents, say the researchers, as the land area here increases by up to 1 cm per year due to the post-glacial recovery.
“With the data, researchers can, for example, verify their climate models and authorities can plan suitable protective measures,” says Dr. Seitz.
Stay in the know by getting stories like this delivered to your inbox.
Sign up to receive our free weekly Spatial Source newsletter.
[ad_2]
