El Niño-related sea surface elevation and ocean bottom pressure enhancement associated with the retreat of the Oyashio southeast of Hokkaido, Japan

• Published in: Marine geophysical researches 2019-12, Vol.40 (4), p.505-512
• Main Authors: Hasegawa, Takuya, Nagano, Akira, Matsumoto, Hiroyuki, Ariyoshi, Keisuke, Wakita, Masahide
• Format: Article
• Language: English
• Subjects: Barotropic mode; Bottom pressure; Continental shelves; Crustal deformation; Earth and Environmental Science; Earth Sciences; El Nino; El Nino phenomena; Geophysics/Geodesy; Ocean bottom; Ocean floor; Oceanic trenches; Oceanography; Oceans; Offshore; Offshore Engineering; Original Research Paper; Pycnocline; Sea surface
• ISSN: 0025-3235; 1573-0581
• DOI: 10.1007/s11001-019-09392-8

To investigate the impact of current variations of the Oyashio on bottom pressure (BP) at observation stations PG1 ( 41 . 7040 ∘ N , 144 . 4375 ∘ E ) and PG2 ( 42 . 2365 ∘ N , 144 . 8454 ∘ E ), which are located in the onshore region of the Kuril Trench off Kushiro–Tokachi, altimetric sea surface height (SSH) and ocean bottom pressure (OBP) gauge data were evaluated. Two and a half years after El Niño, during 2007–2008 and 2012–2013, the Oyashio retreated toward the northeast in association with strong warm-core rings, which were inferred from SSH elevations at both stations. BP at PG1 near the offshore edge of the continental shelf is enhanced corresponding to the SSH elevations in a barotropic manner. Meanwhile, at PG2, BP remained relatively unchanged in spite of the high SSH variability because the main pycnocline adjusted rapidly to the SSH elevations. BP changes at PG1 caused by the northeastward retreat of the Oyashio cannot be neglected to detect BP change by crustal deformations.