Chlorophyll a variation in the Kuroshio Extension revealed with a mixed-layer tracking float: implication on the long-term change of Pacific saury (Cololabis saira)

2007 ◽  
Vol 16 (5) ◽  
pp. 482-488 ◽  
Author(s):  
ICHIRO YASUDA ◽  
TOMOWO WATANABE
Keyword(s):  
Chlorophyll A ◽  
Mixed Layer ◽  
Kuroshio Extension ◽  
Pacific Saury ◽  
Cololabis Saira ◽  
Term Change ◽  
The Kuroshio

scholarly journals Decadal to Multidecadal Variability of the Mixed Layer to the South of the Kuroshio Extension Region

2020 ◽  
Vol 33 (17) ◽  
pp. 7697-7714
Author(s):  
Baolan Wu ◽  
Xiaopei Lin ◽  
Lisan Yu
Keyword(s):  
Heat Flux ◽  
Pacific Ocean ◽  
Mixed Layer ◽  
Kuroshio Extension ◽  
Mixed Layer Depth ◽  
Layer Depth ◽  
Multidecadal Variability ◽  
Mixed Layer Temperature ◽  
The Kuroshio ◽  
The Western Pacific

AbstractThe decadal to multidecadal mixed layer variability is investigated in a region south of the Kuroshio Extension (130°E–180°, 25°–35°N), an area where the North Pacific subtropical mode water forms, during 1948–2012. By analyzing the mixed layer heat budget with different observational and reanalysis data, here we show that the decadal to multidecadal variability of the mixed layer temperature and mixed layer depth is covaried with the Atlantic multidecadal oscillation (AMO), instead of the Pacific decadal oscillation (PDO). The mixed layer temperature has strong decadal to multidecadal variability, being warm before 1970 and after 1990 (AMO positive phase) and cold during 1970–90 (AMO negative phase), and so does the mixed layer depth. The dominant process for the mixed layer temperature decadal to multidecadal variability is the Ekman advection, which is controlled by the zonal wind changes related to the AMO. The net heat flux into the ocean surface Qnet acts as a damping term and it is mainly from the effect of latent heat flux and partially from sensible heat flux. While the wind as well as mixed layer temperature decadal changes related to the PDO are weak in the western Pacific Ocean. Our finding proposes the possible influence of the AMO on the northwestern Pacific Ocean mixed layer variability, and could be a potential predictor for the decadal to multidecadal climate variability in the western Pacific Ocean.

scholarly journals Anatomy of a Cyclonic Eddy in the Kuroshio Extension Based on High-Resolution Observations

Atmosphere ◽  
2019 ◽  
Vol 10 (9) ◽  
pp. 553 ◽  
Author(s):  
Yongchui Zhang ◽  
Xi Chen ◽  
Changming Dong
Keyword(s):  
High Resolution ◽  
Mixed Layer ◽  
Kuroshio Extension ◽  
Mesoscale Eddies ◽  
Cyclonic Eddy ◽  
Intermediate Water ◽  
Dipole Structure ◽  
Significant Difference ◽  
The Kuroshio ◽  
Main Thermocline

Mesoscale eddies are common in the ocean and their surface characteristics have been well revealed based on altimetric observations. Comparatively, the knowledge of the three-dimensional (3D) structure of mesoscale eddies is scarce, especially in the open ocean. In the present study, high-resolution field observations of a cyclonic eddy in the Kuroshio Extension have been carried out and the anatomy of the observed eddy is conducted. The temperature anomaly exhibits a vertical monopole cone structure with a maximum of −7.3 °C located in the main thermocline. The salinity anomaly shows a vertical dipole structure with a fresh anomaly in the main thermocline and a saline anomaly in the North Pacific Intermediate Water (NPIW). The cyclonic flow displays an equivalent barotropic structure. The mixed layer is deep in the center of the eddy and thin in the periphery. The seasonal thermocline is intensified and the permanent thermocline is upward domed by 350 m. The subtropical mode water (STMW) straddled between the seasonal and permanent thermoclines weakens and dissipates in the eddy center. The salinity of NPIW distributed along the isopycnals shows no significant difference inside and outside the eddy. The geostrophic relation is approximately set up in the eddy. The nonlinearity—defined as the ratio between the rotational speed to the translational speed—is 12.5 and decreases with depth. The eddy-wind interaction is examined by high resolution satellite observations. The results show that the cold eddy induces wind stress aloft with positive divergence and negative curl. The wind induced upwelling process is responsible for the formation of the horizontal monopole pattern of salinity, while the horizontal transport results in the horizontal dipole structure of temperature in the mixed layer.

scholarly journals Preconditioning of the wintertime mixed layer at the Kuroshio Extension Observatory

2010 ◽  
Vol 115 (C12) ◽  
Author(s):  
Hiroyuki Tomita ◽  
Shin'ichiro Kako ◽  
Meghan F. Cronin ◽  
Masahisa Kubota
Keyword(s):  
Mixed Layer ◽  
Kuroshio Extension ◽  
The Kuroshio

Temporal variations of the winter mixed layer south of the Kuroshio Extension

2010 ◽  
Vol 66 (1) ◽  
pp. 147-153 ◽  
Author(s):  
Hikaru Iwamaru ◽  
Fumiaki Kobashi ◽  
Naoto Iwasaka
Keyword(s):  
Mixed Layer ◽  
Kuroshio Extension ◽  
Temporal Variations ◽  
Winter Mixed Layer ◽  
The Kuroshio

scholarly journals An Index for Depicting the Long-Term Variability of Mesoscale Eddy Activity over the Kuroshio Extension Region

Atmosphere ◽  
2020 ◽  
Vol 11 (8) ◽  
pp. 792
Author(s):  
Peilong Yu ◽  
Chao Zhang ◽  
Lifeng Zhang ◽  
Xiong Chen ◽  
Quanjia Zhong ◽  
...  
Keyword(s):  
Activity Index ◽  
Kuroshio Extension ◽  
Mesoscale Eddy ◽  
Low Frequency ◽  
Climatic Effects ◽  
Near Surface ◽  
Eddy Activity ◽  
Frequency Changes ◽  
The Kuroshio

Using high-resolution satellite-derived sea surface temperature (SST) data from September 1981 to December 2015, the present study develops a new index to detect the long-term variation in mesoscale eddy activity over the Kuroshio Extension (KE) region. This eddy activity index (EAI) highlights the strength of eddy-induced poleward heat transport and has obvious advantages over the other existing KE indices in depicting the low-frequency changes in KE eddy activity. An analysis of the EAI shows that over the long term, the KE eddy activity variability presents a significant spectral peak of about 8 years and is not directly modulated by wind-driven oceanic Rossby waves generated in the central North Pacific. When the EAI is positive, the strengthened KE eddy activity significantly enhances the heat release from ocean to atmosphere over the Kuroshio–Oyashio confluence region (KOCR). This induces an anomalous dipole pattern of near-surface baroclinicity over this region that can persist for up to 6 months, favoring a weakened and northward-moving East Asian jet, and vice versa. It is believed that the new EAI will facilitate future studies focusing on the climatic effects of the KE eddy activity variation.

Decadal Variation in Winter Mixed Layer Depth South of the Kuroshio Extension and Its Influence on Winter Mixed Layer Temperature

2016 ◽  
Vol 29 (3) ◽  
pp. 1237-1252 ◽  
Author(s):  
Shusaku Sugimoto ◽  
Shin’ichiro Kako
Keyword(s):  
Mixed Layer ◽  
North Pacific ◽  
Kuroshio Extension ◽  
Mixed Layer Depth ◽  
Positive Anomaly ◽  
Surface Cooling ◽  
Layer Depth ◽  
Mixed Layer Temperature ◽  
Winter Mixed Layer ◽  
The Kuroshio

Abstract The long-term behavior of the wintertime mixed layer depth (MLD) and mixed layer temperature (MLT) are investigated in a region south of the Kuroshio Extension (KE) (30°–37°N, 141°–155°E), an area of the North Pacific subtropical gyre where the deepest MLD occurs, using historical temperature profiles of 1968–2014. Both the MLD and MLT in March have low-frequency variations, which show significant decadal (~10 yr) variations after the late 1980s. Observational data and simulation outputs from a one-dimensional turbulent closure model reveal that surface cooling is the main control on winter MLD in the late 1970s and 1980s, whereas there is a change in the strength of subsurface stratification is the main control after ~1990. In the latter period, a weak (strong) subsurface stratification is caused by a straight path (convoluted path) of the KE and by a deepening (shallowing) of the main thermocline depth due to oceanic Rossby waves formed as a result of positive (negative) anomalies of wind stress curl associated with a southward (northward) movement of the Aleutian low in the central North Pacific. During deeper (shallower) periods of winter MLD, the strong (weak) vertical entrainment process, resulting from a rapid (slow) deepening of the mixed layer (ML) in January and February, forms a negative (positive) anomaly of temperature tendency. Consequently, the decadal variations in wintertime MLT are formed.

Variation of Surface Radiocarbon in the North Pacific During Summer Season 2004–2016

Radiocarbon ◽  
2019 ◽  
Vol 61 (5) ◽  
pp. 1367-1375 ◽  
Author(s):  
T Aramaki ◽  
S Nakaoka ◽  
Y Terao ◽  
S Kushibashi ◽  
T Kobayashi ◽  
...  
Keyword(s):  
North Pacific ◽  
Kuroshio Extension ◽  
Deep Convection ◽  
Subtropical Region ◽  
Subarctic Region ◽  
Surface Ocean ◽  
The North ◽  
The Kuroshio ◽  
The North Pacific

ABSTRACTSurface radiocarbon (Δ14C) in the North Pacific has been monitored using a commercial volunteer observation ship since the early 2000s. Here we report the temporal and spatial variations in Δ14C in the summer surface water when the surface ocean is vertically stratified over a 13-yr period, 2004–2016. The long-term Δ14C decreasing trend after the late 1970s in the subtropical region has continued to the present and the rate of decrease of the Kuroshio and Kuroshio Extension, North Pacific and California current areas is calculated to be –3.3, –5.2 and –3.3 ‰/yr, respectively. After 2012 the Δ14C of the Kuroshio and Kuroshio Extension area, however, has remained at an approximately constant value of around 50‰. The result may indicate that subtropical surface Δ14C in the western North Pacific has reached an equilibrium with atmospheric Δ14CO2. The Δ14C in the subarctic region is markedly lower than values in the subtropical region and it seems that the decreasing tendency of surface Δ14C has changed to an increasing tendency after 2010. The results may indicate that bomb-produced 14C, which has accumulated below the mixed layer in the past few decades, has been entrained into the surface layer by deep convection.

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