scholarly journals Winter mixed layer depth and spring bloom along the Kuroshio front: implications for the Japanese sardine stock

2013 ◽  
Vol 487 ◽  
pp. 217-229 ◽  
Author(s):  
H Nishikawa ◽  
I Yasuda ◽  
K Komatsu ◽  
H Sasaki ◽  
Y Sasai ◽  
...  
Keyword(s):  
Mixed Layer ◽  
Spring Bloom ◽  
Mixed Layer Depth ◽  
Layer Depth ◽  
Japanese Sardine ◽  
Winter Mixed Layer ◽  
Kuroshio Front ◽  
The Kuroshio

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.

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 Subduction over the Southern Indian Ocean in a High-Resolution Atmosphere–Ocean Coupled Model

2011 ◽  
Vol 24 (15) ◽  
pp. 3830-3849 ◽  
Author(s):  
Mei-Man Lee ◽  
A. J. George Nurser ◽  
I. Stevens ◽  
Jean-Baptiste Sallée
Keyword(s):  
Indian Ocean ◽  
Mixed Layer ◽  
Current System ◽  
Mixed Layer Depth ◽  
Coupled Model ◽  
Horizontal Resolution ◽  
Layer Depth ◽  
Mode Water ◽  
Coarse Resolution ◽  
Winter Mixed Layer

Abstract This study examines the subduction of the Subantarctic Mode Water in the Indian Ocean in an ocean–atmosphere coupled model in which the ocean component is eddy permitting. The purpose is to assess how sensitive the simulated mode water is to the horizontal resolution in the ocean by comparing with a coarse-resolution ocean coupled model. Subduction of water mass is principally set by the depth of the winter mixed layer. It is found that the path of the Agulhas Current system in the model with an eddy-permitting ocean is different from that with a coarse-resolution ocean. This results in a greater surface heat loss over the Agulhas Return Current and a deeper winter mixed layer downstream in the eddy-permitting ocean coupled model. The winter mixed layer depth in the eddy-permitting ocean compares well to the observations, whereas the winter mixed layer depth in the coarse-resolution ocean coupled model is too shallow and has the wrong spatial structure. To quantify the impacts of different winter mixed depths on the subduction, a way to diagnose local subduction is proposed that includes eddy subduction. It shows that the subduction in the eddy-permitting model is closer to the observations in terms of the magnitudes and the locations. Eddies in the eddy-permitting ocean are found to 1) increase stratification and thus oppose the densification by northward Ekman flow and 2) increase subduction locally. These effects of eddies are not well reproduced by the eddy parameterization in the coarse-resolution ocean coupled model.

Winter Extreme Mixed Layer Depth South of the Kuroshio Extension

2020 ◽  
Vol 33 (24) ◽  
pp. 10419-10436
Author(s):  
Jingjie Yu ◽  
Bolan Gan ◽  
Zhao Jing ◽  
Lixin Wu
Keyword(s):  
Heat Flux ◽  
Mixed Layer ◽  
Kuroshio Extension ◽  
Mixed Layer Depth ◽  
Surface Cooling ◽  
Layer Depth ◽  
Mode Water ◽  
Surface Warming ◽  
Mechanical Stirring ◽  
The Kuroshio

AbstractChange in the extratropical wintertime-mean mixed layer has been widely studied, given its importance to both physical and biogeochemical processes. With a focus on the south of the Kuroshio Extension region where the mixed layer is deepest in March, this study shows that variation of the synoptic-scale extreme mixed layer depth (MLD) is a better precursor than the monthly mean (or nonextreme) MLD for change in the subtropical mode water formation in spring, based on the NCEP Climate Forecast System Reanalysis (1979–2010). It is found that the extreme MLD events are attributable to the accumulation of excessive surface cooling driven by the synoptic storms that characterize cold-air outbreaks. Particularly, the difference between the extreme and nonextreme MLD is primarily related to differences in the cumulative synoptic heat flux anomalies, while a change in the preconditioning upper-ocean stratification contributes almost equally to both cases. Relative contributions of oceanic and atmospheric forcing to the interannual variation of the extreme MLD are quantified using a bulk mixed layer model. Results show comparable contributions: the preconditioning stratification change accounts for ~44% of total variance of the extreme MLD, whereas the convective mixing by surface heat flux and the mechanical stirring by wind stress account for ~35% and ~13%, respectively. In addition, both the reanalysis and observational data reveal that the extreme and nonextreme MLD has been shallowed significantly during 1979–2010, which is accounted for by the strengthened stratification due to the enhanced ocean surface warming by the Kuroshio heat transport.

scholarly journals Mixed layer depth and chlorophyll a: Profiling float observations in the Kuroshio–Oyashio Extension region

2015 ◽  
Vol 151 ◽  
pp. 1-14 ◽  
Author(s):  
Sachihiko Itoh ◽  
Ichiro Yasuda ◽  
Hiroaki Saito ◽  
Atsushi Tsuda ◽  
Kosei Komatsu
Keyword(s):  
Chlorophyll A ◽  
Mixed Layer ◽  
Mixed Layer Depth ◽  
Layer Depth ◽  
Profiling Float ◽  
The Kuroshio
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