"The persistence and extent of the high, which also extended over the North Sea, making room, as it were, for the large volume of water flowing out of the Baltic Sea, is responsible for the scale of the phenomenon," he says. "We are talking about 275 cubic kilometres of water! This exceptional situation did not happen in isolation from the large-scale processes we observe in the Earth's atmosphere. The most important of these in this context is the disintegration of the polar vortex, a circulation of air in the upper layers of the atmosphere (10-50km) which, colloquially speaking, is responsible for keeping the Arctic cold. This vortex is linked to the jet stream, the rapidity of which and the course of this current are responsible for the migration of lows and highs. Hence, deviations such as blocked highs, Arctic frost waves or heat waves in the north are the result of disturbances to this jet stream, and hence the warming of the Arctic."
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During her research between 2004 and 2020, she noted a marked decrease in the density of the endemic bryophyte species Harmeria scutulata. "This allowed me to conclude that with climate change, there is also a reorganisation of species communities in the Arctic hard bottom ecosystem."
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The disappearance of ecosystems in turn translates into the collapse of the fishing industry, says the expert. Similarly, the exploitation of underwater metal resources - so-called rare earth mines on the ocean floor - involves environmental degradation on a larger scale than land-based open-pit mines."It is not only the bottom that is destroyed, but the overburden - that part of the excavated material that on land is stored in heaps - in the Ocean disperses throughout the depths, eliminating access to light and space for ocean creatures."
The Baltic is a sea with a reputation as one of the most polluted. However, according to Kijewski, the basin's worst period of pollution is behind it."Since the common policy of the Baltic States, coordinated by HELCOM and the EU, has led to the installation of biological wastewater treatment plants and generally increased attention to the state of the environment, pollution of the Baltic has largely been halted. A prime example is the Bay of Puck, which until recently was virtually extinct, and for the past two decades we have seen a spontaneous return of seagrass meadows and even seaweed there. The state of plastic pollution is also low, which, unlike the rest of the Ocean, has not increased during the last 30 years."However, he says, the peculiarities of the Baltic's hydrology require a long time for the water to undergo a purifying exchange. An event such as the current low is conducive to this purification, but it will still take another 30 years for the Baltic Sea to undergo significant self-purification.