Why is the Arctic relevant for our weather and climate?

Climate change in the Arctic and its consequences for nature and people are widely reported in the media. What is much less well known is that climate change is particularly pronounced in the Arctic and has a direct impact on the inhabitants of the mid-latitudes. This article aims to explain the special significance of the Arctic for the mid-latitudes.

Climate change is particularly evident in the Arctic in the form of rising temperatures. Individual studies show that temperatures have risen three to four times higher than the global average in recent decades – this is known as Arctic amplification. However, a closer look shows that the warming in the Arctic varies greatly from region to region and is particularly pronounced in winter for the Barents and Kara Sea regions, while other regions such as Greenland and other seasons show a smaller increase. The Arctic amplification interacts with the sharp decline in Arctic sea ice, the reduced duration of snow cover and the increased melting of glaciers and the Greenland ice sheet.

Some physical principles enable a better understanding of the interactions between temperature changes and changes in the cryosphere. For example, the Clausius-Clapeyron equation states that a warmer atmosphere can contain more water vapour, whereby this relationship is even exponential. However, water vapour is a very effective greenhouse gas that intensifies warming, where water vapour has the property of remaining in the atmosphere for a much shorter time than CO2. Another important effect results from the extremely different reflection of solar radiation on snow-covered ground compared to snow-free ground or even more pronounced on a water surface (approx. 90% reflection by snow compared to 10% reflection by water). This has an enormous impact on the energy absorption of solar radiation and thus on the warming of the atmosphere. However, the change in clouds is also an important process, as on the one hand a more humid atmosphere can form more clouds, while on the other hand a warmer atmosphere shifts the condensation level to higher altitudes. Increased cloud formation can mean that more sunlight is reflected by the clouds or that more energy is radiated back to earth from the atmosphere in the form of infrared radiation. With the topic of clouds, however, we are already in the midst of the great uncertainties and the current major research questions and challenges of climate science.

Arctic amplification; the figure shows the increase in mean annual temperature in the entire Arctic (latitude 66°N to 90°N) compared to Greenland and the global mean. (Data: HadCRUT data set (Morice et al. 2021) and CRU TS (Harris et al. 2020), from Shahi 2024); the Arctic amplification is reflected in the significantly stronger increase in temperature in the Arctic compared to the global temperature since around 1980.

Our weather patterns in Austria are characterised by the interplay of moving low (cyclones) and high pressure (anticyclone) systems. The formation of the cyclones and anticyclones is linked to the convergence of cold air from the north with significantly warmer air from the south. The resulting temperature gradient is very pronounced regionally and is known as the polar front. It is also associated with a strong difference in air density and thus with an air pressure gradient and strong winds – the jet stream, which is located in the area of particularly pronounced temperature contrasts at an altitude of around 10 kilometres. The jet stream is the “weather engine” in our latitudes and is (partly) responsible for generating and controlling the anticyclones and cyclones.

The temperature contrast between the Arctic and the mid-latitudes is also described by the Arctic Oscillation (AO) or indirectly by the North Atlantic Oscillation (NAO). The effects of the changing NAO on Greenland were analysed by Tiago Silva  (New insights of a warmer and moister atmosphere over the Greenland Ice Sheet in a changing climate) and for near-surface temperature inversions in the study by Sonika Shahi (Regional Variability and Trends of Temperature Inversions in Greenland).

Interaction of the polar front jet stream, polar vortex and Arctic amplification. If the Arctic polar vortex is particularly strong and stable (left-hand image), then the jet stream tends to shift northwards and the north-south exchange tends to be prevented. If the vortex is weaker (possibly even split, right-hand image), the jet stream often becomes wavy. Warm air can then flow more towards the north and cold air towards the south.

If the Arctic warms faster than the mid-latitudes, the north-south temperature gradient weakens and, as several studies have shown, so does the jet stream. However, these statements are still the subject of research and other studies cannot prove the effect. What is clear, however, is that when the jet stream weakens, cold air from the north and warm air from the south can move more easily in a north-south direction. For our weather patterns, such effects are already evident in the form of surprising cold air intrusions from the north, blocking high-pressure systems, but also pronounced dry spells or possibly heavy precipitation. Researchers are trying to better understand the role of the altered jet stream, particularly in the case of the latter events.

However, this still leaves very important processes of climate-induced environmental changes in the Arctic unmentioned. The Arctic permafrost stores huge amounts of carbon, which is increasingly being released in the form of CO2 or CH4 as a result of climate change. This is a massive driver of climate change. The melting of glaciers and the Greenland ice sheet is causing sea levels to rise. This primarily affects coastal regions, but indirectly also regions far from the coast, such as Austria, due to possible migration movements. As you can see, the Arctic’s relevance is right on our doorstep.