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Ask a Researcher: Can we Walk to the Islands in the Future? (Hannes Tõnisson)

15.05.2018

How many years will it take until we can walk from the mainland to the islands, and is our climate really warming? Why are Estonian summers becoming colder and colder, and will it stay that way? We asked these viewer questions from Hannes Tõnisson, Senior Researcher at the Tallinn University School of Natural Sciences and Health.

In the past, our climate has become cooler, and then again warmer. The cooler times bring about ice ages, which bring us shelf ice from the Scandinavian mountains. The last such ice age ended a bit more than 10,000 years ago. Back then Estonia was covered with a 2km thick sheet of ice.

That sheet was heavy enough to push the rigid lithosphere from under our feet into the half-liquid asthenosphere, making it flow away from the weight of the ice.

When the ice receded, the asthenosphere started to flow back toward its initial location. This is why we can witness the earth rising in Estonia by about 3 millimetres a year.

For this reason, we have observed the rising of the earth and the fall-back of the sea for thousands of years. The question whether we could soon go to Saaremaa on foot seems just here. As we look at the sea charts, we see that the deepest place between the mainland and Saaremaa is 12 metres.

However, if we plot a rout straight from Tallinn to the northern edge of Muhumaa, the deepest place will be no more than 5-6 metres. Given a 2mm/year land rising, a simple calculation says we would only have to wait another 3,000 years!

Alas, it is not that easy. We are currently witnessing global climate warming, which is melting shelf ice and raising the world’s sea levels, due to both the melting as well as heat expansion in the water. The most optimistic prognoses say the sea will rise by 25 centimetres by the year 2,100.

This is similar to the speed we are expecting Saaremaa to rise in the future. However, the more pessimistic prognoses predict an 80cm rise in sea levels. Either way, we have to admit the distance between the mainland and Saaremaa will probably increase.

Global warming will also save more heat into the oceans. More heat has the potential for bigger storms, which will reach deeper inland. Therefore, the Estonian climate is due to become a marine climate.

This will bring us cooler and windier summers, making it even harder to get to the islands; and stormier and milder winters, which will not let ice roads form. Stormy and ice-free winters will also increase the destruction of our beaches, and danger the buildings and infrastructure located at the seafront.