A revised inoceramid biozonation for the Upper Cretaceous based on high-resolution carbon isotope stratigraphy in northwestern Hokkaido, Japan

2013 ◽  
Vol 63 (2) ◽  
pp. 239-263 ◽  
Author(s):  
Tatsuya Hayakawa ◽  
Hiromichi Hirano
Keyword(s):  
High Resolution ◽  
Carbon Isotope ◽  
North Pacific ◽  
Upper Cretaceous ◽  
Northwest Pacific ◽  
Terrestrial Organic Matter ◽  
Carbon Isotope Stratigraphy ◽  
The North ◽  
Isotope Stratigraphy ◽  
The North Pacific

Abstract Hayakawa, T., Hirano, H. 2013. A revised inoceramid biozonation for the Upper Cretaceous based on high-resolution carbon isotope stratigraphy in northwestern Hokkaido, Japan. Acta Geologica Polonica, 63 (2), 239-263. Warszawa. Biostratigraphic correlations of inoceramid bivalves between the North Pacific and Euramerican provinces have been difficult because the inoceramid biostratigraphy of the Japanese strata has been based on endemic species of the northwest Pacific. In this study, carbon stable isotope fluctuations of terrestrial organic matter are assembled for the Upper Cretaceous Yezo Group in the Haboro and Obira areas, Hokkaido, Japan, in order to revise the chronology of the inoceramid biozonation in Japan. The carbon isotope curves are correlated with those of marine carbonates in English and German sections with the aid of age-diagnostic taxa. According to the correlations of the carbon isotope curves, 11 isotope events are recognised in the sections studied. As a result of these correlations, the chronology of the inoceramid biozones of the Northwest Pacific has been considerably revised. The revised inoceramid biozones suggest that the timing of the origination and extinction of the inoceramids in the North Pacific biotic province is different from the stage/substage boundaries defined by inoceramids, as used in Europe and North America.

scholarly journals Strengthened Relationship between Tropical West Pacific and Midsummer Precipitation over Northeast China after the Mid-1990s

2020 ◽  
Vol 33 (16) ◽  
pp. 6833-6848
Author(s):  
Tingting Han ◽  
Minghua Zhang ◽  
Botao Zhou ◽  
Xin Hao ◽  
Shangfeng Li
Keyword(s):  
North Pacific ◽  
Northeast China ◽  
Aleutian Islands ◽  
Northwest Pacific ◽  
West Pacific ◽  
The North ◽  
Circulation Anomalies ◽  
The Relationship ◽  
The North Pacific ◽  
Central North Pacific

AbstractThe relationship between the tropical west Pacific (TWP) and East Asian summer monsoon/precipitation has been documented in previous studies. However, the stability for the signals of midsummer precipitation in the TWP sea surface temperature (SST_TWP), which is important for climate variation, has drawn little attention. This study identifies a strengthened relationship between the leading empirical orthogonal function mode (EOF1) of midsummer precipitation over Northeast China (NEC) and the SST_TWP after the mid-1990s. The EOF1 mode shows a significant positive correlation with the SST_TWP for 1996–2016, whereas the relationship is statistically insignificant for 1961–90. Further results indicate that the North Pacific multidecadal oscillation (NPMO) shifts to a positive phase after the 1990s. In the positive NPMO phase, the anomalous circulation over the northeast Pacific expands westward over the central North Pacific–Aleutian Islands region. Concurrently, the SST_TWP-associated wavelike pattern propagates northeastward from the west Pacific to the northwest Pacific and farther to the North Pacific, facilitating the poleward expansion and intensification of the SST_TWP-related circulation anomalies over the North Pacific. Therefore, the SST_TWP has an enhanced influence on NEC precipitation through the modulation of the circulation anomalies over the central North Pacific–Aleutian Islands region after the mid-1990s. Additionally, the tropical anticyclone/cyclone associated with the SST_TWP expands westward to South China, exerting an intensified impact on meridional wind anomalies along eastern China and on moisture transport over NEC. These conditions jointly contribute to the strengthened relationship between the SST_TWP and the EOF1 mode of NEC midsummer precipitation after the mid-1990s.

“Eddy Resolving” Observation of the North Pacific Subtropical Mode Water

2011 ◽  
Vol 41 (4) ◽  
pp. 666-681 ◽  
Author(s):  
Eitarou Oka ◽  
Toshio Suga ◽  
Chiho Sukigara ◽  
Katsuya Toyama ◽  
Keishi Shimada ◽  
...  
Keyword(s):  
High Resolution ◽  
North Pacific ◽  
Kuroshio Extension ◽  
Uniform Structure ◽  
Mode Water ◽  
Subtropical Mode Water ◽  
The North ◽  
Late Fall ◽  
The Kuroshio ◽  
The North Pacific

Abstract Hydrographic data obtained by high-resolution shipboard observations and Argo profiling floats have been analyzed to study the mesoscale structure and circulation of the North Pacific Subtropical Mode Water (STMW). The float data show that in the late winter of 2008, STMW having a temperature of approximately 18.8°, 17.7°, and 16.6°C formed west of 140°E, at 140°–150°E, and east of 150°E, respectively, in the recirculation gyre south of the Kuroshio Extension. After spring, the newly formed STMW gradually shift southward, decreasing in thickness. Simultaneously, the STMWs of 16.6° and 17.7°C are gradually stirred and then mixed in terms of properties. In late fall, they seem to be integrated to form a single group of STMWs having a temperature centered at 17.2°C. Such STMW circulation in 2008 is much more turbulent than that in 2006, which was investigated in a previous study. The difference between the two years is attributed to the more variable state of the Kuroshio Extension in 2008, associated with stronger eddy activities in the STMW formation region, which enhance the eddy transport of STMW. High-resolution shipboard observations were carried out southeast of Japan at 141°–147°E in the early fall of 2008. To the south of the Kuroshio Extension, STMW exists as a sequence of patches with a horizontal scale of 100–200 km, whose thick portions correspond well to the mesoscale deepening of the permanent pycnocline. The western (eastern) hydrographic sections are occupied mostly by the 17.7°C (16.6°C) STMW, within which the 16.6°C (17.7°C) STMW exists locally, mostly at locations where both the permanent pycnocline depth and the STMW thickness are maximum. This structure implies that the STMW patches are transported away from their respective formation sites, corresponding to a shift in the mesoscale anticyclonic circulations south of the Kuroshio Extension. Furthermore, 20%–30% of the observed STMW pycnostads have two or three potential vorticity minima, mostly near temperatures of 16.6° and 17.7°C. The authors presume that such a structure formed as a result of the interleaving of the 16.6° and 17.7°C STMWs after they are stirred by mesoscale circulations, following which they are vertically mixed to form the 17.2°C STMW observed in late fall. These results indicate the importance of horizontal processes in destroying the vertically uniform structure of STMW after spring, particularly when the Kuroshio Extension is in a variable state.

scholarly journals SSH Wavenumber Spectra in the North Pacific from a High-Resolution Realistic Simulation

2012 ◽  
Vol 42 (7) ◽  
pp. 1233-1241 ◽  
Author(s):  
Hideharu Sasaki ◽  
Patrice Klein
Keyword(s):  
High Resolution ◽  
Kinetic Energy ◽  
North Pacific ◽  
North Pacific Ocean ◽  
Spectral Characteristics ◽  
Turbulence Theory ◽  
Realistic Simulation ◽  
The North ◽  
Altimetric Data ◽  
The North Pacific

Abstract Following recent studies based on altimetric data, this paper analyses the spectral characteristics of the sea surface height (SSH) using a new realistic simulation of the North Pacific Ocean with high resolution ( in the horizontal and 100 vertical levels). This simulation resolves smaller scales (down to ≈10 km) than altimetric data (limited to 70 km because of the noise level). In high eddy kinetic energy (EKE) regions (as in the western part), SSH spectral slope almost follows a k−4 (with k the wavenumber) or slightly steeper law in agreement with altimeter studies. The new result is that, unlike altimeter studies, such a k−4 slope is also observed in low EKE regions (as in the eastern part). In these regions, this slope mostly concerns scales not well resolved by altimetric data. Such k−4 SSH spectral slopes are weaker from what is expected from quasigeostrophic turbulence theory but closer to surface quasigeostrophic (SQG) turbulence theory. The consequence is that the small scales concerned by these spectral slopes, in particular in low EKE regions, may significantly affect the larger ones because of the inverse kinetic energy cascade. These results need to be confirmed using a longer numerical integration. They also need to be corroborated by high-resolution observations.

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