Possible effects of climate change to Central and Northern Europe

Keskiviikko 2.8.2023 klo 19:25 - Mikko Nikinmaa

We have been taught at school how the temperature in Central and Northern Europe is much higher than at similar latitudes elsewhere. The reason for this has been Gulf Stream, which flows northeast from the Gulf of Mexico to the Arctic, North of Norway. The stream moves a lot of heat from tropics to high latitudes. Finally the water cools and sinks to the bottom of the ocean and the cold water flows back south in southwest-directed cold streams. An important part of the dynamic water flow is that the Gulf Stream water sinks to ocean bottom, because that generates the driving force for water circulation. In the absence of water circulation, Central and Northern Europe would be much colder than presently, especially in winter. Gulf Stream water sinks, because when its temperature decreases to four degrees centigrade, the density of water is higher than the water below, which has a lower temperature. The density of water depends also on its salinity, the higher the salinity, the higher the density. Earlier on this has also contributed to the water circulation. The surface water flowing in Gulf stream from tropical areas has traditionally had higher salinity than the bottom water of the Arctic Sea.

 Climate change is now threatening to change this warmth-bringing ocean circulation. The melting of Greenland glaciers but also the sea ice of the arctic causes a significant decrease in the density of surface water in the Arctic Sea. As a result, the sinking of Gulf Stream water from the surface to the bottom can be markedly reduced. This decreases the driving force for ocean circulation, and Gulf Stream may stop flowing altogether. The result for Central and North European climate would be that we experience Siberia-like weather patterns. An additional problem associated with presently ongoing freshwater addition is that the global temperature rise observed already seems to be adequate to cause continuing glacier melting in Greenland. This suggests that even if we are able to stop temperature increase to 1.5 degrees centigrade, the weakening of Gulf Stream may occur. There is no way to know, when we reach the tipping point.

So, if climate deniers tell you after three cold winters that clearly there is no climate change, as we have cold winters, you can answer them: “On the contrary, this shows that climate change has reached another tipping point. The heat transfer from tropics to the north in the form of Gulf Stream has stopped.” The real problem with this, and the weather patterns in general, is that what has happened and is happening is increased unpredictability. That is probably the biggest problem with climate change.

Kommentoi kirjoitusta. Avainsanat: Gulf Stream, temperature rise, tipping point, Greenland, glacier melting

Extreme heat in Europe - a new normal together with cold spells in winter, if climate change is not stopped

Tiistai 20.9.2022 klo 11:29 - Mikko Nikinmaa

The climate models predict that the circulation of warm water towards north and cold water to the south can radically decrease in near future. This is mainly the result of the melting of Greenland ice sheath, which liberates a lot of fresh water to the Arctic Ocean/North Atlantic. Because of this, the surface water becomes less dense than earlier and will not sink in the water column. The downward movement of surface water is the main driver of northward current of warm water in Gulf Stream. Since Gulf Stream keeps the European climate temperate increasing especially winter temperatures, its weakening may change the climate towards Siberian-like.

Other major effectors of European climate are the jet streams at high altitude. Their movements to a large extent determine the movement and stability of low and high pressure zones, and depending of the location of the zones if tropical or arctic air is moving towards Europe. The jet stream has recently started to split more often than earlier, and between the split any weather pattern becomes more stationary that earlier. Although there is no conclusive evidence that the increased splitting of jet stream would be caused by climate change, it has only started to occur recently, more or less at the same time as the global average temperature has increased more than one degree centigrade.

The two factors, weakened Gulf stream and jet stream function, predict that Europe can expect extended heat spells in summer and cold winters. The cold winter weather may occur even though the global temperature increases markedly. So, the truth value of the following is zero. “Look, it is cold now, there is no climate change”, as climate sceptics certainly shall say. But scorching heat in future summers becomes even worse than in 2022   

Kommentoi kirjoitusta. Avainsanat: Gulf Stream, heat waves, temperature, jet stream