[A-CG24] 北極域の科学

[ACG24-02] 西部北極海における厳冬期の亜表層暖水輸送

*渡邉 英嗣¹、小野寺 丈尚太郎¹、伊東 素代¹、西野 茂人¹、菊地 隆¹ (1.海洋研究開発機構)

キーワード：北極海、亜表層水温極大、陸棚縁ジェット

Ocean heat transport is a possible important factor for recent sea ice decline, especially in the western Arctic Ocean. It has been indicated that vertical hydrographic profiles in the Canada Basin were characterized by three temperature maxima. The near-surface temperature maximum was the shallowest one arising from summer solar heat absorption and subsequent autumn Ekman downwelling. The subsurface temperature maximum reflected intrusion of Pacific summer water. The deepest maximum was located in the Atlantic layer. Substantial parts of upper ocean heat would eventually affect sea ice freezing/melting. However, spatial and temporal variabilities of these warm layers still remain uncertainties. Recently, year-long moorings in Chukchi Abyssal Plain detected mid-winter subsurface warming, plausibly caused by lateral advection of shelf-origin water. In this study, a pan-Arctic sea ice-ocean modeling was performed to address overwinter transport of subsurface warm water. The horizontal grid size was approximately 5 km to resolve mesoscale eddies and narrow jets. The interannual experiment from 2001 to 2014 demonstrated that Barrow Canyon throughflow and westward shelf-break jet established primary pathways of subsurface heat transport toward Chukchi Borderland. Shelf-break heat was partly lost by event-like wind mixing but remained under highly stratified surface layer until mid-winter.