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  • Author or Editor: Masayo Ogi x
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Yuta Ando
,
Masayo Ogi
, and
Yoshihiro Tachibana

Abstract

Negative Arctic Oscillation (AO) and western Pacific (WP) indices persisted from October to December 2012 in the Northern Hemisphere. For the first time, the monthly AO and WP were both negative for three consecutive months since records have been kept. Although in general negative AO and WP phases cause Siberia, East Asia, and Japan to be abnormally cold, Japan was relatively warm in October 2012 even though both the AO and WP were strongly negative. The temperature of the Sea of Japan reached a record-breaking high in October 2012, and it was found that heating by these very warm waters, despite the small size of the Sea of Japan, overwhelmed the cooling effect of the strongly negative AO and WP in October. Linear regression analyses showed that Japan tends to be warm in years when the Sea of Japan is warm. Consequently, the temperature over Japan is controlled by interannual variations of small-scale oceanic phenomena as well as by large-scale atmospheric patterns. Previous studies have ignored such small-scale oceanic influences on island temperatures.

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Masayo Ogi
,
Bunmei Taguchi
,
Meiji Honda
,
David G. Barber
, and
Søren Rysgaard

Abstract

Contemporary climate science seeks to understand the rate and magnitude of a warming global climate and how it impacts regional variability and teleconnections. One of the key drivers of regional climate is the observed reduction in end of summer sea-ice extent over the Arctic. Here the authors show that interannual variations between the September Arctic sea-ice concentration, especially in the East Siberian Sea, and the maximum Okhotsk sea-ice extent in the following winter are positively correlated, which is not explained by the recent warming trend only. An increase of sea ice both in the East Siberian Sea and the Okhotsk Sea and corresponding atmospheric patterns, showing a seesaw between positive anomalies of sea level pressures over the Arctic Ocean and negative anomalies over the midlatitudes, are related to cold anomalies over the high-latitude Eurasian continent. The patterns of atmospheric circulation and air temperatures are similar to those of the annually integrated Arctic Oscillation (AO). The negative annual AO forms colder anomalies in autumn sea surface temperatures both over the East Siberian Sea and the Okhotsk Sea, which causes heavy sea-ice conditions in both seas through season-to-season persistence.

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