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Wind has a great effect on the water temperature. A sea breeze leads to warmer water at the coast, while an offshore breeze leads to colder nearshore water. This is because when the wind blows towards the land (an onshore breeze) warm surface water is forced inshore. The opposite happens when the …

A tsunami is a wave that forms in the ocean following an earthquake on the sea floor. Tsunamis can also be formed by landslides or volcano eruptions under water, or if a meteorite falls into the sea, but earthquakes are the most common cause of tsunamis.

The acidity of the sea is measured using the pH scale. Over the last few years a number of articles have been published about the decrease in the pH value of the world oceans – indicating an increase in the acidity of the sea. Measurements from Swedish sea areas indicate that the same is happening …

Large volumes of man-made waste make their way out into the sea, which can cause environmental problems and the death of many marine animals. The most famous waste zone is perhaps the Great Pacific Garbage Patch, where ocean currents have gathered huge amounts of plastic from the coasts of the US …

Have invading comb jellies spread to the Baltic? Do jellyfish eat zooplankton that would otherwise feed fish? How do jellyfish affect the food chain? BAZOOCA (Baltic Zooplankton Cascades) is a research collaboration between countries around the Baltic to find out how changes in jellyfish stocks …

SMHI's oceanographers use a number of oceanographic models. Some of the operational models are listed here together with the models that are being developed by SMHI’s research department. An operational model is one that is run regularly as part of the daily forecasting routine.

Wave measurements have been made by SMHI since 1978. For many years the instruments used were placed on the sea floor and worked like an upside-down echosounder. Some simple buoys were also used. More recently, advanced buoys have been used that can also measure wave direction.

Higher air pressure gives lower sea levels: an increase in air pressure of 1 hPa lowers the water level by 1 cm.

As well as the motion of the atmosphere and the sea, the earth's crust is also moving. During the most recent ice age the crust was pressed down as much as 300 m and in places is still on its way back up.

Human activity can lead to the over-fertilisation, or eutrophication, of the sea. This can be caused by fertilisers from farming, sewage emissions, or deforestation. The threats to the Baltic, the Skagerrak and the Kattegat do not however only come from Sweden.