scholarly journals The Predictability Limit of Ocean Mesoscale Eddy Tracks in the Kuroshio Extension Region

2021 ◽  
Vol 8 ◽  
Author(s):  
Yao Meng ◽  
Hailong Liu ◽  
Ruiqiang Ding ◽  
Pengfei Lin ◽  
Mengrong Ding ◽  
...  
Keyword(s):  
Kuroshio Extension ◽  
Mesoscale Eddy ◽  
Growth Dynamics ◽  
Northern Region ◽  
Eastern Region ◽  
Limit Values ◽  
Surface Ocean ◽  
Large Size ◽  
High Predictability ◽  
The Kuroshio

In this study, the nonlinear local Lyapunov exponent and nonlinear error growth dynamics are employed to estimate the predictability limit of oceanic mesoscale eddy (OME) tracks quantitatively using three datasets. The results show that the mean predictability limit of OME tracks is about 53 days for cyclonic eddy (CE) and 52 days for anticyclonic eddy (AE) in the Kuroshio Extension (KE). The predictability limit varies spatially. The predictability limit of OME tracks is higher for the eastern region (about 62.5 days) than that for the western part (about 46 days). The CEs (AEs) predictability limit is relatively high in the southern (northern) region. Additionally, the lifetime, amplitude, and radius of OME are closely related to the predictability limit. The long-lived, large-amplitude, and large-sized OMEs tend to be more predictable. The eastern region often generates long-lived and large-size OMEs, thereby obtaining a higher predictability limit of OME tracks. Furthermore, the relationship between the predictability limit and the smoothness of the OME tracks was investigated using a metric to describe the track’s complexation. Usually, OMEs with high predictability limit values often show extender and smoother trajectories. The effects of the surface ocean circulations and the surface winds are also investigated. The strong and energetic currents lead to a short limitation in the west region.

scholarly journals Observations of the Subtropical Mode Water Evolution from the Kuroshio Extension System Study

2006 ◽  
Vol 36 (3) ◽  
pp. 457-473 ◽  
Author(s):  
Bo Qiu ◽  
Peter Hacker ◽  
Shuiming Chen ◽  
Kathleen A. Donohue ◽  
D. Randolph Watts ◽  
...  
Keyword(s):  
North Pacific Ocean ◽  
Kuroshio Extension ◽  
Mesoscale Eddy ◽  
Lower Boundary ◽  
Late Winter ◽  
Mode Water ◽  
Subtropical Mode Water ◽  
Budget Analysis ◽  
Recirculation Gyre ◽  
The Kuroshio

Abstract Properties and seasonal evolution of North Pacific Ocean subtropical mode water (STMW) within and south of the Kuroshio Extension recirculation gyre are analyzed from profiling float data and additional hydrographic and shipboard ADCP measurements taken during 2004. The presence of an enhanced recirculation gyre and relatively low mesoscale eddy variability rendered this year favorable for the formation of STMW. Within the recirculation gyre, STMW formed from late-winter convection that reached depths greater than 450 m near the center of the gyre. The lower boundary of STMW, corresponding to σθ ≃ 25.5 kg m−3, was set by the maximum depth of the late-winter mixed layer. Properties within the deep portions of the STMW layer remained largely unchanged as the season progressed. In contrast, the upper boundary of the STMW layer eroded steadily as the seasonal thermocline deepened from late April to August. Vertical eddy diffusivity responsible for this erosion was estimated from a budget analysis of potential vorticity to be in the range of ∼2–5 × 10−4 m2 s−1. The latitudinal extent of the STMW formation was narrow, extending from 30°N to the Kuroshio Extension jet near 35°N. South of 30°N, STMW did not form locally but was transported from the recirculation gyre by lateral induction.

Decadal variability of the Kuroshio Extension

2020 ◽  
Author(s):  
Guidi Zhou ◽  
Xuhua Cheng
Keyword(s):  
Decadal Variability ◽  
Kuroshio Extension ◽  
Relaxation Oscillation ◽  
Mesoscale Eddy ◽  
Height Anomaly ◽  
Intrinsic Variability ◽  
Mean Flow ◽  
The Real ◽  
Eddy Activity ◽  
The Kuroshio

<p>The decadal variability of the Kuroshio Extension (KE) is investigated using altimeter observations (AVISO) and the output of an ocean model (OFES). It is shown that the KE decadal variability is manifested in its strength, latitudinal position, and zonal extent, as well as the associated mesoscale eddy activity. Two differences between the two datasets are identified: (a) In OFES, the eddy activity positively correlates with the KE mode index when it leads by a few years, whereas in AVISO the two are negatively and concurrently correlated. (b) In OFES, the positive KE mode is associated with large meanders of the Kuroshio south of Japan, but in AVISO they are irrelevant. These differences indicate that the generation mechanism of KE's decadal variability is different in OFES and the real ocean. The sea surface height anomaly (SSHA) is then decomposed into major components including the wind-driven Rossby waves and residual (intrinsic) variability. The relationship between the two components are virtually the same in OFES and in AVISO, showing a negative correlation when the wind-driven part leads by a few years. Further diagnostics based on OFES reveals that the residual SSHA originates from the downstream region over the Shatsky Rise, slowly propagates westward, and is driven by eddy potential energy transfer. The OFES results partly conform to the intrinsic relaxation oscillation theory put forth by idealized model analyses, but in the latter the SSHA signal originates from the upstream Kuroshio. A new mechanism is then proposed for OFES: the decadal variability of the KE is first a result of the intrinsic relaxation oscillation probably excited by wind forcing, which regulates the strength of the KE’s inflow and thus modulates the downstream topography interaction, resulting in different downstream mesoscale eddy activity that further feeds back on the mean-flow. The mechanism for the real ocean is also reassessed.</p>

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.

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.

Mesoscale eddy effects on temporal variability of surface chlorophyll a in the Kuroshio Extension

2015 ◽  
Vol 72 (3) ◽  
pp. 439-451 ◽  
Author(s):  
Shinya Kouketsu ◽  
Hitoshi Kaneko ◽  
Takeshi Okunishi ◽  
Kosei Sasaoka ◽  
Sachihiko Itoh ◽  
...  
Keyword(s):  
Chlorophyll A ◽  
Temporal Variability ◽  
Kuroshio Extension ◽  
Mesoscale Eddy ◽  
The Kuroshio

A Comparison of Mesoscale Eddy Heat Fluxes from Observations and a High-Resolution Ocean Model Simulation of the Kuroshio Extension

2013 ◽  
Vol 43 (12) ◽  
pp. 2563-2570 ◽  
Author(s):  
Stuart P. Bishop ◽  
Frank O. Bryan
Keyword(s):  
High Resolution ◽  
Model Simulation ◽  
Kuroshio Extension ◽  
Mesoscale Eddy ◽  
Ocean Model ◽  
Heat Fluxes ◽  
Dynamical Mechanism ◽  
Eddy Heat Flux ◽  
Conversion Rates ◽  
The Kuroshio

Abstract For the first time estimates of divergent eddy heat flux (DEHF) from a high-resolution (0.1°) simulation of the Parallel Ocean Program (POP) are compared with estimates made during the Kuroshio Extension System Study (KESS). The results from POP are in good agreement with KESS observations. POP captures the lateral and vertical structure of mean-to-eddy energy conversion rates, which range from 2 to 10 cm2 s−3. The dynamical mechanism of vertical coupling between the deep and upper ocean is the process responsible for DEHFs in POP and is in accordance with baroclinic instability observed in the Gulf Stream and Kuroshio Extension. Meridional eddy heat transport values are ~14% larger in POP at its maximum value. This is likely due to the more zonal path configuration in POP. The results from this study suggest that HR POP is a useful tool for estimating eddy statistics in the Kuroshio Extension region, and thereby provide guidance in the formulation and testing of eddy mixing parameterization schemes.

scholarly journals Oceanic mesoscale eddy in the Kuroshio Extension: comparison of four datasets

2020 ◽  
pp. 100011
Author(s):  
Yao MENG ◽  
Hailong LIU ◽  
Pengfei LIN ◽  
Mengrong DING ◽  
Changming DONG
Keyword(s):  
Kuroshio Extension ◽  
Mesoscale Eddy ◽  
The Kuroshio

scholarly journals Variability of the Kuroshio Extension Jet, Recirculation Gyre, and Mesoscale Eddies on Decadal Time Scales

2005 ◽  
Vol 35 (11) ◽  
pp. 2090-2103 ◽  
Author(s):  
Bo Qiu ◽  
Shuiming Chen
Keyword(s):  
Kinetic Energy ◽  
Kuroshio Extension ◽  
Mesoscale Eddy ◽  
Low Frequency ◽  
Eddy Kinetic Energy ◽  
Mean Flow ◽  
Flow Intensity ◽  
Frequency Changes ◽  
Recirculation Gyre ◽  
The Kuroshio

Abstract Twelve years of sea surface height (SSH) data from multiple satellite altimeters are used to investigate the low-frequency changes and the interconnections of the Kuroshio Extension (KE) jet, its southern recirculation gyre, and their mesoscale eddy field. The dominant signal is characterized by the steady weakening of the KE jet/recirculation gyre from 1993 to 1996, followed by a gradual strengthening after 1997. During the weakening period of 1993–96, the KE path migrated southward in general, and this path migration reversed in direction during the strengthening period of the KE jet and recirculation gyre after 1997. By hindcasting the SSH signals using linear vorticity dynamics, it was found that weakening (strengthening) in the KE jet and recirculation gyre is consistent with westward propagation of negative (positive) SSH anomalies generating in the eastern North Pacific and strengthening during their westward propagation. When the KE jet and recirculation gyre were in a weak mode during 1996–2001, the regional eddy kinetic energy level was observed to be higher than when the jet and recirculation gyre were in a strong mode. This negative correlation between the mean flow intensity and the level of regional eddy kinetic energy is found in both the SSH data and the linear vorticity model to result from the migration of the KE jet inflow over the Izu–Ogasawara Ridge. When it is forced southward by the impinging negative SSH anomalies, the KE jet inflow rides over the ridge through a shallow segment, leading to large-amplitude downstream meanders. Impinging of positive SSH anomalies, on the other hand, strengthens the recirculation gyre and forces the inflow northward where it passes through a deep channel, minimizing the path perturbations in the downstream region.

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