scholarly journals Subtropical Mode Water Variability in a Climatologically Forced Model in the Northwestern Pacific Ocean

2012 ◽  
Vol 42 (1) ◽  
pp. 126-140 ◽  
Author(s):  
Elizabeth M. Douglass ◽  
Steven R. Jayne ◽  
Synte Peacock ◽  
Frank O. Bryan ◽  
Mathew E. Maltrud
Keyword(s):  
Pacific Ocean ◽  
Mixed Layer Depth ◽  
Northwestern Pacific ◽  
Northwestern Pacific Ocean ◽  
Large Meander ◽  
The West ◽  
Mode Water ◽  
Subtropical Mode Water ◽  
South Of Japan ◽  
The Kuroshio

Abstract A climatologically forced high-resolution model is used to examine variability of subtropical mode water (STMW) in the northwestern Pacific Ocean. Despite the use of annually repeating atmospheric forcing, significant interannual to decadal variability is evident in the volume, temperature, and age of STMW formed in the region. This long time-scale variability is intrinsic to the ocean. The formation and characteristics of STMW are comparable to those observed in nature. STMW is found to be cooler, denser, and shallower in the east than in the west, but time variations in these properties are generally correlated across the full water mass. Formation is found to occur south of the Kuroshio Extension, and after formation STMW is advected westward, as shown by the transport streamfunction. The ideal age and chlorofluorocarbon tracers are used to analyze the life cycle of STMW. Over the full model run, the average age of STMW is found to be 4.1 yr, but there is strong geographical variation in this, from an average age of 3.0 yr in the east to 4.9 yr in the west. This is further evidence that STMW is formed in the east and travels to the west. This is qualitatively confirmed through simulated dye experiments known as transit-time distributions. Changes in STMW formation are correlated with a large meander in the path of the Kuroshio south of Japan. In the model, the large meander inhibits STMW formation just south of Japan, but the export of water with low potential vorticity leads to formation of STMW in the east and an overall increase in volume. This is correlated with an increase in the outcrop area of STMW. Mixed layer depth, on the other hand, is found to be uncorrelated with the volume of STMW.

North Pacific Subtropical Mode Water Controlled by the Atlantic Multi-Decadal Variability

2020 ◽  
Author(s):  
Baolan wu ◽  
Xiaopei lin ◽  
Lisan yu
Keyword(s):  
Pacific Ocean ◽  
North Pacific ◽  
Decadal Variability ◽  
Heat Content ◽  
Northwestern Pacific ◽  
Mode Water ◽  
Subtropical Mode Water ◽  
The North ◽  
Mean Temperature ◽  
The Pacific

<p><strong>The North Pacific Subtropical Mode Water (mode water hereafter) is a vertically homogeneous thermocline water mass, occupying the entire subtropical Western Pacific Ocean. By transporting mass, heat and nutrients from the surface into the subsurface ocean, it provides memory of climate variability and is a potential source of predictability. Previous studies attributed decadal variability of the mode water mean temperature to the Pacific Decadal Oscillation (PDO). Using available observations and reanalysis data, here we show that decadal to multi-decadal variability of the mode water mean temperature is controlled by the Atlantic Multi-Decadal Variability (AMV) instead. During an AMV positive phase, warm sea surface temperatures (SSTs) in the north Atlantic Ocean weaken the subtropical North</strong> <strong>Pacific westerlies, and the anomalous easterlies in the subtropical west Pacific drive an anomalous northward Ekman transport of warm water into the mode water formation area. </strong><strong>This increases the mode water temperature through subduction</strong><strong>, driving variability of the upper-layer ocean heat content and fish catches in the Northwestern Pacific. This mechanism is supported by a long pre-industrial model simulation with multiple AMV cycles and by a Pacemaker model experiment, in which the AMV forcing alone is shown to drive the variability of the mode water. Our finding suggests that the AMV is an important driver for decadal climate and ecosystem variability and provides memory for prediction in the Pacific Ocean.</strong></p>

Spatial Structure of Turbulent Mixing in the Northwestern Pacific Ocean

2014 ◽  
Vol 44 (8) ◽  
pp. 2235-2247 ◽  
Author(s):  
Qingxuan Yang ◽  
Wei Zhao ◽  
Min Li ◽  
Jiwei Tian
Keyword(s):  
Pacific Ocean ◽  
Turbulent Mixing ◽  
Boundary Region ◽  
Horizontal Distribution ◽  
Northwestern Pacific ◽  
Western Boundary ◽  
Northwestern Pacific Ocean ◽  
Thorpe Scale ◽  
High Level ◽  
The Kuroshio

Abstract Turbulent mixing in the northwestern Pacific Ocean is estimated using the Gregg–Henyey–Polzin scaling and Thorpe-scale methods. The data sources are the hydrographic observations during October and November 2005. The results reveal clear spatial patterns of turbulent mixing in the study area. High-level diffusivity on the order of 10−3 m2 s−1 or larger is found within the western boundary region, where the Kuroshio flows northward. The width covered by this prominent diffusivity shows an increase from 12° to 18°N. The horizontal distribution of depth-averaged diffusivity in the top 500 m shows enhanced mixing with diffusivity of 6 × 10−3 m2 s−1 south of 9°N where the Mindanao Eddy remains a quasi-permanent feature. These two distinct patterns of diffusivity distribution suggest that the Kuroshio and the Mindanao Eddy are likely responsible for the elevated turbulent mixing in the study area.

New Climate Diagnostic Method of Activity of Typhoons over the Northwestern Pacific Ocean

2011 ◽  
Vol 71-78 ◽  
pp. 3118-3122 ◽  
Author(s):  
Ji Qing Tan ◽  
Hui Qi Li ◽  
Zhao Xia Zheng
Keyword(s):  
Pacific Ocean ◽  
Diagnostic Method ◽  
Computational Method ◽  
Northwestern Pacific ◽  
Direct Impact ◽  
Northwestern Pacific Ocean ◽  
China Meteorological Administration ◽  
Fortran Compiler ◽  
Impact Area ◽  
South Of Japan

A new conception, called the Most Direct Impact Area (MDIA) of typhoons, is put forward in this paper. After the computational method is explained in detail, the databank of 1955 typhoons of China Meteorological Administration (CMA) have been calculated on the Linux operational platform with a Fortran compiler in a computer. The results via calculating the geographic distribution of the MDIA of typhoons show that the characteristic of typhoon activity in a year can be easily identified in quantity. A most interesting feature has been found that typhoon activity is abnormally active over the ocean to the south of Japan in three typical El Niño years.

scholarly journals Influence of Kuroshio Path Variation South of Japan on Formation of Subtropical Mode Water

2014 ◽  
Vol 44 (4) ◽  
pp. 1065-1077 ◽  
Author(s):  
Shusaku Sugimoto ◽  
Kimio Hanawa
Keyword(s):  
Kuroshio Extension ◽  
Potential Temperature ◽  
Late Summer ◽  
Northwestern Part ◽  
North Pacific Subtropical Gyre ◽  
Mode Water ◽  
Subtropical Mode Water ◽  
Shikoku Basin ◽  
South Of Japan ◽  
The Kuroshio

Abstract Distributions of subtropical mode water (STMW) in the northwestern part of the North Pacific Subtropical Gyre were investigated, using temperature–salinity profiles from 2005 to 2011, with particular reference to the Kuroshio meander and non-meander path states, south of Japan. In spring of meander years, warm STMW with a potential temperature of 19°–20°C (potential density anomaly of 24.6–24.9 kg m−3) was found in the Shikoku Basin, whereas cold STMW below 19°C was distributed throughout the southern region of Japan in non-meander years. The warm STMW was formed in a spatially isolated and warm winter mixed layer (ML) in the Shikoku Basin, where a local recirculation developed in association with the Kuroshio meander path; both the absence of horizontal mixing with a cold ML south of the Kuroshio Extension because of the spatially isolated ML and an increase in horizontal heat advection due to the westward flow associated with this local recirculation caused the ML warming in the Shikoku Basin. After the spring shoaling of the ML, the warm STMW was preserved under the seasonal pycnocline until midsummer at a depth of 100–250 dbar; its thickness was approximately half that of the cold STMW in the Shikoku Basin in non-meander years. The warm STMW was rapidly eroded between the late summer and the following winter.

scholarly journals Recovery of Tropical Cyclone Induced SST Cooling Observed by Satellite in the Northwestern Pacific Ocean

2021 ◽  
Vol 13 (18) ◽  
pp. 3781
Author(s):  
Zheng Ling ◽  
Zhifeng Chen ◽  
Guihua Wang ◽  
Hailun He ◽  
Changlin Chen
Keyword(s):  
Pacific Ocean ◽  
Tropical Cyclones ◽  
Recovery Time ◽  
Mixed Layer Depth ◽  
Sea Surface ◽  
Northwestern Pacific ◽  
Northwestern Pacific Ocean ◽  
Layer Depth ◽  
Translation Speed ◽  
Sst Cooling

Based on the satellite observed sea surface temperature (SST), the recovery of SST cooling induced by the tropical cyclones (TCs) over the northwestern Pacific Ocean is investigated. The results show that the passage of a TC induces a mean maximum cooling in the SST of roughly −1.25 °C. It was also found that most of this cooling (~87%) is typically erased within 30 days of TC passage. This recovery time depends upon the degree of cooling, with stronger (weaker) SST cooling corresponding to longer (shorter) recovery time. Further analyses show that the mixed layer depth (MLD) and the upper layer thermocline temperature gradient (UTTG) also play an important role in the SST response to TCs. The maximum cooling increases ~0.1 °C for every 7 m decrease in the MLD or every 0.04 °C/m increase in the UTTG. The combined effects of MLD and TC intensity and translation speed on the SST response are also discussed.

scholarly journals Subtropical Mode Water in a recent persisting Kuroshio large-meander period: part I—formation and advection over the entire distribution region

2021 ◽  
Author(s):  
Eitarou Oka ◽  
Hatsumi Nishikawa ◽  
Shusaku Sugimoto ◽  
Bo Qiu ◽  
Niklas Schneider
Keyword(s):  
North Pacific ◽  
Decadal Variability ◽  
Kuroshio Extension ◽  
Formation Rate ◽  
Stable State ◽  
Large Meander ◽  
Mode Water ◽  
Subtropical Mode Water ◽  
The Kuroshio ◽  
Central North Pacific

AbstractSince August 2017, the Kuroshio has taken a large-meander (LM) path, which has forced the Kuroshio extension (KE) to be in its stable state against its wind-forced decadal variability. How such current conditions have impacted the formation and advection of North Pacific subtropical mode water (STMW) over its distribution region was examined using Argo float data during 2005–2020. Out of the whole STMW defined as a low-potential vorticity layer of 16–19.5 ºC, a relatively cold variety of 16–18 ºC, which was formed south of the KE and advected westward and southward, occupied more than 80% of the total volume. The formation rate of the 16–18 ºC variety was low during 2006–2009 in an unstable-KE period and high during 2010–2015 in a stable-KE period, and then dropped drastically in 2016 despite the KE still being in the stable state. After a short unstable-KE period in 2016–2017, the LM-forced, stable-KE period began, but the formation rate of the 16–18 ºC variety has not restored, possibly due to stronger background stratification propagated from the central North Pacific. In addition, the 16–18 ºC variety has had to make a southern detour around the LM, and its westward advection from the formation region south of the KE to the region south of Japan has been significantly decreased, possibly because it is dissipated more strongly over a southern part of the Izu–Ogasawara Ridge. Due to such decline in the formation and advection, the volume of the 16–18 ºC variety and hence that of the whole STMW have gradually decreased since 2016.

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