scholarly journals Analysis and revision of the Miocene boreal faunae of bivalve mollusks of the South Sakhalin

2020 ◽  
Author(s):  
В.Д. ХУДИК ◽  
Ю.Д. ЗАХАРОВ
Keyword(s):  
Japan Sea ◽  
Climatic Conditions ◽  
Bivalve Mollusks ◽  
The South ◽  
The North ◽  
Initial Stage ◽  
The Japan Sea ◽  
South Sakhalin ◽  
Early Neogene ◽  
Climatic Cooling

Приведены результаты изучения остатков фаун двустворчатых моллюсков из миоценовых отложений Южного Сахалина. Их анализ позволил выделить три бореальных комплекса моллюсков: невельский, раннечеховский и курасийский, фиксирующие периоды похолодания климата в миоцене региона. Изучение неогеновых представителей родов Lucinoma и Mya позволило обозначить среди них ряд таксонов, имеющих стратиграфическое значение. Установленное присутствие тепловодных двустворок в фаунах позднечеховского времени Южного Сахалина, очевидно, отражает собой начальный этап тенденции нарастающего потепления климата в миоцене региона с климатическим оптимумом в верхнедуйско-сертунайское время. Высказывается следующее мнение: неустойчивые климатические условия в позднем палеогене – раннем неогене северной части Япономорского региона могли быть основной причиной возникновения здесь одного из мощных центров эволюции морских малакофаун бореальных районов северной Пацифики. The results on the studying of the faunae of bivalve mollusks remains from miocene deposits of the South Sakhalin are presented. The analysis of the last ones allowed distinguishing the following three boreal assemblages of mollusks: Nevelskiy, early Chekhovskiy and Kurasiiskiy, recording the period of climatic cooling in miocene of the region. Studying of Neogene representatives of Lucinoma and Mya generas allowed identifying some taxa among them which have stratigraphic significance. The detected presence of warm water bivalves in the faunae of the late Chekhovsky time of the South Sakhalin appears to reflect the initial stage of the tendency of the intensifying climate warming happened during miocene, with climatic optimum during the Verkhneduysky – Sertunaysky times. An opinion is expressed that the unstable climatic conditions in the northern part of the Japan Sea region during late Paleogene – early Neogene could have been the main reason for originating of one of the high-potential centers of evolution of the marine malacofaunae of boreal regions of the North Pacific.

scholarly journals Unusually high sea level at the south coast of Japan in September 2011 induced by the Kuroshio

2020 ◽  
Author(s):  
Norihisa Usui ◽  
Koji Ogawa ◽  
Kei Sakamoto ◽  
Hiroyuki Tsujino ◽  
Goro Yamanaka ◽  
...  
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Tide Gauge ◽  
Phase Speed ◽  
Japan Sea ◽  
South Coast ◽  
The South ◽  
Characteristic Analysis ◽  
The Japan Sea ◽  
The Kuroshio

Abstract Using a coastal assimilation model, generation mechanism of unusually high sea level (UHSL) at the south coast of Japan in September 2011 is investigated. Both model results and tide gauge observations indicate that sea level rise associated with the UHSL event occurred twice in the middle and end of September. The first one, which is localized around the eastern part of the Seto Inland Sea, is caused by a cyclonic circulation in the Kii Channel formed as a result of northward migration of the Kuroshio axis toward Cape Shionomisaki. The second sea level rise, which is the main contributor to this UHSL event, is observed in wide areas not only at the south coast of Japan, but also at the coast of the Japan Sea. It is brought about by a coastal trapped wave (CTW) induced as a result of a fluctuation of the Kuroshio path to the south of the Boso Peninsula. The CTW with positive SSH anomalies propagates westward along the south coast of Japan, and then goes into the coast of the Japan Sea. Sensitivity experiments and a modal characteristic analysis indicate that the CTW is mainly characterized by the first mode baroclinic Kelvin wave. The phase speed for the first mode is calculated at 2.96 m s$$^{-1}$$ - 1 , which compares well with that estimated by tide gauge observations.

New insights into the latitudinal ventilation variations in the Japan Sea since the Last Glacial Maximum: A radiolarian assemblage perspective

2020 ◽  
Author(s):  
Zhi Dong ◽  
Xuefa Shi ◽  
Jianjun Zou ◽  
Yanguang Liu ◽  
Ruxi Dou ◽  
...  
Keyword(s):  
Deep Water ◽  
Coastal Upwelling ◽  
Sediment Cores ◽  
Japan Sea ◽  
Volume Transport ◽  
The North ◽  
Radiolarian Assemblage ◽  
Basin Scale ◽  
Japan Sea Proper Water ◽  
The Japan Sea

<p>The formation of intermediate and deep water plays a key role in regulating climate changes at a variety of time scales through the heat redistribution and carbon cycling. The Japan Sea has unique water-mass characteristics in the North Pacific with its own deep-water formation within the Sea itself called Japan Sea Proper Water (JSPW). Latitudinal ventilation changes in the Japan Sea were reconstructed using radiolarian assemblage from three sediment cores, extending from the southwestern, central to northwestern Japan Sea. Here, we present downcore faunal records spanning the last 25 ka as well as other existing ventilation records in the Japan Sea, and provide reliable evidence to evaluate the potential controlling mechanism that lead to onset and interruption of JSPW ventilation. Taking all together, we argue that radiolarian assemblage records have revealed a distinct basin-scale transition in deep-water conditions from anoxic to oxic during the deglaciation related to changing surface hydrography. However, it should be recognized that there is significant potential for bias in the timing of the ventilation changes among regions. Deep ventilation in the central Japan Sea has been in an interglacial mode during the Bølling/Allerød presumably related to northward volume transport of the Tsushima Warm Current. Moreover, the decrease of JSPW Assemblage at the B/A in southwestern Japan Sea was attributed to higher export productivity, facilitating suboxic deepwater condition through enhanced consumption of oxygen, which was probably caused by coastal upwelling. In contrast, the weakening ventilation of the northwestern Japan Sea during the B/A and YD periods was probably caused by the blocking effect of the sea ice. Note: This study was supported by the National Natural Science Foundation of China (Grant No. 41420104005, U1606401) and National Program on Global Change and Air-Sea Interaction (GASI-GEOGE-04).</p>

scholarly journals Reconstruction of Tsunami Occurrence on Okushiri Island, Southwestern Hokkaido, Japan

2021 ◽  
Author(s):  
Atsushi Urabe ◽  
Yoshihiro Kase ◽  
Gentaro Kawakami ◽  
Kenji Nishina ◽  
Yasuhiro Takashimizu ◽  
...  
Keyword(s):  
Japan Sea ◽  
Tsunami Deposit ◽  
Fault Activity ◽  
Tsunami Deposits ◽  
Tectonic Zone ◽  
Tectonic Plates ◽  
Eastern Margin ◽  
The North ◽  
The Japan Sea ◽  
Okushiri Island

Abstract The eastern margin of the Japan Sea is located along an active convergent boundary between the North American and Eurasian tectonic plates. Okushiri Island, which is situated off the southwest coast of Hokkaido, is located in an active tectonic zone where many active submarine faults are distributed. Studying the records of past tsunamis on Okushiri Island is important for reconstructing the history and frequency of fault activity in this region, as well as the history of tsunamis in the northern part of the eastern margin of the Japan Sea. Five tsunami deposit horizons have been identified previously on Okushiri Island, including that of the 1741 tsunami, which are interbedded in the coastal lowlands and Holocene terraces. However, these known tsunami deposits date back only ~3,000 years. A much longer record of tsunami occurrence is required to consider the frequency of submarine fault activity. In this study, we cored from 7 to 25 m depth in the Wasabiyachi lowland on the southern part of Okushiri Island, where previous studies have confirmed the presence of multiple tsunami deposits on peat layer surfaces. The results indicate that the Wasabiyachi lowland comprises an area that was obstructed by coastal barriers between the lowland and the coast at ~8.5 ka and consists of muddy sediment and peat layers formed in lagoons and floodplains, respectively. In addition, event deposits and 15 tsunami horizons were observed among the turbidites and peat layers, dating back as far as 3,000 years. Combined with previous findings, Okushiri Island has sustained 20 tsunami events between ~7.5 ka and the present. These findings are critical for investigating the activities of submarine faults off the southwestern coast of Hokkaido, as well as for determining tsunami risks along the coast of the Japan Sea between North Tohoku and Hokkaido.

scholarly journals Ricker analysis of dynamics for two populations of walleye pollock in the Japan Sea

Trudy VNIRO ◽  
2020 ◽  
Vol 180 ◽  
pp. 156-173
Author(s):  
Yu. I. Zuenko ◽  
V. A. Nuzhdin
Keyword(s):  
Climate Change ◽  
Carrying Capacity ◽  
Japan Sea ◽  
Walleye Pollock ◽  
The North ◽  
Optimal Value ◽  
The Japan Sea ◽  
Analysis Of Dynamics ◽  
Local Ecosystem ◽  
Two Populations

Recent changes in reproduction are considered for two populations of walleye pollock which spawn in the Japan Sea at the coasts of Primorye and Hokkaido. Interannual dynamics of reproduction for both populations corresponds to the stock-recruitment dependence described by Ricker curve that determines the maximum recruitment with an optimal value of stock equal to the carrying capacity of the biotope for the species and the lower recruitment if the stock is either lower or higher than this optimal value. However, instability of the Ricker curve parameters is noted, and their recent changes were unfavorable for reproduction of both populations and caused decreasing of their stocks, with sharp decline in the early 1990s. Basing on authors results and cited data, climate change in the Japan Sea region is determined as the reason of this decreasing, in particular weakening of winter monsoon. In spite of a common nature, mechanisms of the climate change influence on two studied populations are completely different: reproduction of the Hokkaido population worsened because of increasing transfer of its eggs and larvae out of the Japan Sea in conditions of the strengthening Tsushima Current, that was explained in the terms of Ricker curve as decreasing of population fecundity, but reproduction of the Primorye population worsened because of unfavorable for pollock reconstructions in the local ecosystem located in the south periphery of the Subarctic zone in conditions of increasing water temperature that was explained in the terms of Ricker curve as shrinkage of carrying capacity for pollock (from approximately 150 .103 t to almost zero level). Note that the carrying capacity did not shrink but slightly extended (to 500 .103 t) for the Hokkaido population located in the north periphery of the Subtropic zone. Features of climate warming influence onto subarctic and subtropic ecosystems are discussed.

scholarly journals Reanalysis of 47 Years of Climate in the French Alps (1958–2005): Climatology and Trends for Snow Cover

2009 ◽  
Vol 48 (12) ◽  
pp. 2487-2512 ◽  
Author(s):  
Yves Durand ◽  
Gérald Giraud ◽  
Martin Laternser ◽  
Pierre Etchevers ◽  
Laurent Mérindol ◽  
...  
Keyword(s):  
Snow Cover ◽  
Snow Depth ◽  
Numerical Models ◽  
High Elevation ◽  
Climatic Conditions ◽  
Spatial And Temporal Variability ◽  
The South ◽  
French Alps ◽  
Mountainous Regions ◽  
The North

Abstract Since the early 1990s, Météo-France has used an automatic system combining three numerical models to simulate meteorological parameters, snow cover stratigraphy, and avalanche risk at various altitudes, aspects, and slopes for a number of mountainous regions (massifs) in the French Alps and the Pyrenees. This Système d’Analyse Fournissant des Renseignements Atmosphériques à la Neige (SAFRAN)–Crocus–Modèle Expert de Prévision du Risque d’Avalanche (MEPRA) model chain (SCM), usually applied to operational daily avalanche forecasting, is here used for retrospective snow and climate analysis. For this study, the SCM chain used both meteorological observations and guess fields mainly issued from the newly reanalyzed atmospheric model 40-yr ECMWF Re-Analysis (ERA-40) data and ran on an hourly basis over a period starting in the winter of 1958/59 until recent past winters. Snow observations were finally used for validation, and the results presented here concern only the main climatic features of the alpine modeled snowfields at different spatial and temporal scales. The main results obtained confirm the very significant spatial and temporal variability of the modeled snowfields with regard to certain key parameters such as those describing ground coverage or snow depth. Snow patterns in the French Alps are characterized by a marked declining gradient from the northwestern foothills to the southeastern interior regions. This applies mainly to both depths and durations, which exhibit a maximal latitudinal variation at 1500 m of about 60 days, decreasing strongly with the altitude. Enhanced at low elevations, snow depth shows a mainly negative temporal variation over the study period, especially in the north and during late winters, while the south exhibits more smoothed features. The number of days with snow on the ground shows also a significant general signal of decrease at low and midelevation, but this signal is weaker in the south than in the north and less visible at high elevation. Even if a statistically significant test cannot be performed for all elevations and areas, the temporal decrease is present in all the studied quantities. Concerning snow duration, this general decrease can also be interpreted as a sharp variation of the mean values at the end of the 1980s, inducing a step effect in its time series rather than a constant negative temporal trend. The results have also been interpreted in terms of potential for a viable ski industry, especially in the southern areas, and for different changing climatic conditions. Presently, French downhill ski resorts are economically viable from a range of about 1200 m MSL in the northern foothills to 2000 m in the south, but future prospects are uncertain. In addition, no clear and direct relationship between the North Atlantic Oscillation (NAO) or the ENSO indexes and the studied snow parameters could be established in this study.

Oceanological studies in the northwest Pacific, Japan and Okhotsk seas in the 73th cruise of the RV Professor Gagarinskiy and 53th cruise of the RV Academic Oparin

2019 ◽  
Vol 59 (6) ◽  
pp. 1093-1096
Author(s):  
V. N. Karnaukh ◽  
A. F. Sergeev ◽  
V. B. Lobanov ◽  
P. Ya. Tishcenko
Keyword(s):  
Bottom Water ◽  
Japan Sea ◽  
Western Pacific ◽  
Northwest Pacific ◽  
The North ◽  
Water Composition ◽  
Sea Bottom ◽  
The Japan Sea ◽  
North Western ◽  
North Western Pacific

During the the 73th cruise of the RV Professor Gagarinskiy and 53th cruise of the RV Academic Oparin oceanological studies of the north-western Pacific, Japan and Okhotsk Seas were conducted. New data on the structure sea bottom, water composition as well as slope convection of the Japan Sea.

Phanerozoic accretionary history of Japan and the western Pacific margin

2018 ◽  
Vol 158 (1) ◽  
pp. 13-29 ◽  
Author(s):  
Koji Wakita ◽  
Takanori Nakagawa ◽  
Masahiro Sakata ◽  
Natsuki Tanaka ◽  
Nozomu Oyama
Keyword(s):  
North China ◽  
Japan Sea ◽  
Detrital Zircons ◽  
Oceanic Plate ◽  
The South ◽  
The North ◽  
Before And After ◽  
History Of ◽  
Japanese Islands ◽  
Plate Subduction

AbstractIt is generally accepted that oceanic plate subduction has occurred along the eastern margin of Asia since about 500 Ma ago. Therefore, the Japanese Islands have a >500 Ma history of oceanic plate subduction in their geological records. In this paper, the accretionary history of the Japanese Islands is divided into six main stages based on the mode and nature of tectonic events and the temporal gaps in the development of accretionary processes. In the first stage, oceanic plate subduction and accretion started along the margin of Gondwana. After detachment of the North and South China blocks in Devonian time, accretionary complexes developed along island arcs offshore of the South and North China blocks. After the formation of back arc basins such as the Japan Sea, accretionary processes occurred only along the limited convergent margin, e.g. Nankai Trough. Detrital zircons of sandstones revealed the accretionary history of Japan. An evaluation of a comprehensive dataset on detrital zircon populations shows that the observed temporal gaps in the development of the Japanese accretionary complexes were closely related to the intensity of igneous activity in their provenance regions. Age distributions of detrital zircons in the accretionary complexes of Japan change before and after the Middle Triassic period, when the collision of the South and North China blocks occurred.

scholarly journals A computer database for falling snowflakes

1993 ◽  
Vol 18 ◽  
pp. 11-16 ◽  
Author(s):  
Ken-ichiro Muramoto ◽  
Kohki Matsuura ◽  
Toshio Harimaya ◽  
Tatsuo Endoh
Keyword(s):  
Winter Season ◽  
Japan Sea ◽  
Primary Data ◽  
Maximum Diameter ◽  
Fall Velocity ◽  
North East ◽  
The North ◽  
The Japan Sea ◽  
Computer Based ◽  
Average Size

A computer-based measurement system for characteristics of snowfall is described. To measure the size and velocity of falling snowflakes quantitatively, images of snowflakes were input to an image processor and the primary data were analyzed in real time. In this process, maximum diameter in a horizontal plane and falling velocity were recorded in previously set intervals, then stored on a disk. Since a lot of data were obtained during a full winter season, data had to be processed to make up a database after an experiment. Using this database, the data of the distribution of size and velocity of snowflakes can be retrieved at anytime.We observed snowflakes during winter months of 1986-92 in Sapporo and Toyama, which are located near the north east and middle of the Japan Sea coast respectively. The data indicate that the average size of snowflakes in Toyama was larger than that in Sapporo, while the number concentration of snowflakes in Sapporo was rather higher. The fall velocity tends to increase with increasing size of snowflakes, as observed in both areas.

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