Rising sea levels started in the 60s

According to a study conducted by researchers from the University of Siegen, Germany, sea level rise would have started as early as the 60s of the last century. The study, published in Nature Climate Change, made use of various data relating to phenomena such as coastal tides and data from satellites.

In particular since the early 90s of the last century, satellites around the Earth have begun to measure the sea level with extreme precision, as reported by Sönke Dangendorf, researcher at the German University and principal author of the study, who adds: “So far it has not been clear when this acceleration began, in which region it was started and which processes contributed most to it. The answer to these questions was hampered by the fact that before the advent of satellite altimetry in 1992, our knowledge was based mainly on a few hundred tide gauges that record sea level along the coasts of the world and that our available approaches to reconstructing sea levels globally from these measurements were too inaccurate.”

The new approach, based on data relating to tidal registers and those provided by satellites, shows that the acceleration of sea-level rise began already in the 60s when the level itself began to increase by just under a millimeter per year (60 years), an acceleration that then reached more than 3 mm per year today, as reported by Carling Hay, geophysicist at Boston College and another author of the study.

The researchers also found that most of this level rise comes from the southern hemisphere, particularly from the subtropical southeastern marine areas of Australia and New Zealand. In these regions, this acceleration is even five times greater than the global average.

This differentiation, according to the same researchers, is due to the changing winds strongly influencing sea levels. They move northward from the warm masses of the ocean waters and control the absorption of heat by the underlying ocean, as Dangendorf explains: “When the westerly winds of the southern hemisphere intensify, more heat is pumped from the atmosphere into the ocean, leading to an expansion of the water column and therefore to an increase in the global sea level.”

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