[P-EM14] Study of coupling processes in solar-terrestrial system

[PEM14-P11] Variations in the Arctic upper atmosphere since the early 20th century: Relation to Arctic surface warming and cooling

*Yasunobu Ogawa¹, Magnar G. Johnsen², Njål Gulbrandsen², Andrea D. Løkke², Ingrid Mann², Ingemar Häggström³ (1.National Institute of Polar Research, 2.UiT the Arctic University of Norway, 3.EISCAT Headquarters)

Keywords:Climate change, Global warming, Arctic warming

We have investigated long-term ionospheric variations using data from the Tromsø ionosonde since 1932. To study Arctic ionospheric variations in relation to Arctic warming and cooling before the 1970s, we have developed a Tromsø ionosonde database that allows us to study daily variations over about 90 years. During the 1940s to 1960s, when the Arctic surface was cooling, a gradually increasing trend in the critical frequency of the F2 layer, foF2, was observed in the Tromsø ionosonde data at a rate of 0.022 ± 0.011 MHz/year. This can be explained by the global energy balance of the Earth's atmosphere. As for the trend of foF2 since 2001, there is a clear decrease with a rate of -0.046 ± 0.007 MHz/year. These trends are qualitatively consistent with the changes in the upper atmosphere that can be inferred from the cooling and warming of the Arctic surface. In addition, EISCAT UHF radar data from Tromsø, the same location as the ionosonde, clearly show a decrease in F-layer ion temperature since 1981. Further studies will require verification of the plausible scenario using global models and associated observational data.