[P-EM14] 太陽地球系結合過程の研究基盤形成

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

*小川 泰信¹、Magnar Johnsen²、Njål Gulbrandsen²、Andrea Løkke²、Ingrid Mann²、Ingemar Häggström³ (1.国立極地研究所、2.UiT ノルウェー北極大学、3.EISCAT本部)

キーワード：気候変動、地球温暖化、北極温暖化

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.