Seasonal asymmetries and long-term trends in atmospheric and ionospheric temperatures in polar regions and their dependence on solar activity (SATS)

This is chapter 1 of the State of Environmental Science in Svalbard (SESS) report 2022. We have used temperature measurements from a number of observatories in and above Svalbard to study temperature variations, and their relation to solar activity. Sea temperatures from the mouth of Isfjorden, several ground stations as well as weather balloon measurements were used to study long-term trends of temperatures on ground and in the atmosphere. Radar and optical measurements were used to infer temperatures in the mesosphere and ionosphere. The measurements show a trend towards higher temperatures and less difference between summer and winter over the last decades. An increasing seasonal asymmetry between temperatures and season over the last decades is also observed; the day with maximum temperatures tends to occur later in the year. Ground and atmospheric temperatures were also compared to solar input energies, but no clear correlation between solar activity and temperatures on ground or in the lower atmosphere was found. We attribute the observed trends in the ground and atmospheric conditions to a combination of climate warming and local conditions such as sea currents and changes in the extension of the ice shelf. At higher altitudes, in the mesosphere and in the ionosphere, we observe a clear correlation between solar activity and temperatures, suggesting that a significant transfer of energy from the Sun and its solar wind to the upper part of the thermosphere takes place. This coupling can be explained by electromagnetic processes and enhanced Joule heating due to collisions between neutrals and ions.