Annual signal modulation of the Kuroshio through-flow volume transport south of Japan leading West Pacific Pattern (original) (raw)

Influence of Kuroshio Extension’s sea surface temperature variability on the North Pacific atmosphere and Pacific Decadal Precession

2024

Recent research has revealed links between a quasi-decadal mode of climate variability over the North Pacific – the Pacific Decadal Precession (PDP) – and the North Pacific’s western boundary current’s extension – the Kuroshio Extension (KE). It is suggested that on decadal time scales the PDP both responds to and influences the KE variability. A question yet to be answered is whether it is the large-scale or the mesoscale variations of the KE region that link with the PDP evolution. Using high-resolution sea surface temperature data (1981–2018) from the global ocean Operational Sea Surface Temperature (SST) and Sea Ice Analysis, low-resolution Extended Reconstructed SST (ERSST) version 3b data (1949–2018), geopotential height reanalysis data from the European Centre for Medium-Range Weather Forecasts (ECMWF) and the National Centers for Environmental Prediction (NCEP) we find that it is the large-scale variations in the KE region that correlate best with the PDP-like response in the overlying and downstream atmosphere as compared to the mesoscale variations. In particular, the second mode of the large-scale KE region, which is characterized by the warming (cooling) of the ocean south (north) of the KE, sets up a PDP-like north-south atmospheric pressure dipole over the North Pacific Ocean by altering the large-scale baroclinicity of the atmosphere and zonal intensification of the subtropical jet stream. In turn, there is a reduction in the zonal propagation of stationary wave energy and an enhancement of the climatological zonal wave heights over North America, which results in a downstream response over the North American continent and the formation of a subsequent east-west pressure dipole over the North Pacific and North American continent. As a result, there is a strong correlation between large-scale SST variations in the KE region and the evolution of the PDP over the next three years.

Stable volume and heat transports of the North Pacific subtropical gyre revealed by identifying the Kuroshio in synoptic hydrography south of Japan

Journal of Geophysical Research, 2010

1] We conducted synoptic hydrographic surveys three times under distinctly different conditions of the Kuroshio in the region off the southern coast of Japan; the large-meander (October 2004) and non-large-meander (September 2005 and September 2006) states. As a result of the water mass analysis, we could separate the volume and heat transports of the North Pacific subtropical gyre from the local recirculation gyre and mesoscale eddies. Despite the different flow conditions of the Kuroshio, the volume transport and the volume transport-averaged temperature of the subtropical gyre fluctuate within the ranges of 23.3-29.0 × 10 6 m 3 s −1 and 17.3-17.6°C, respectively, which are quite stable with respect to those for the Kuroshio south of Japan estimated in the past studies. Taking into account the decrease in the volume transport-averaged temperature in the North Pacific interior region, the net heat transport of the subtropical gyre across the latitude of 30°N was estimated to be between 0.19 and 0.22 × 10 15 W. Citation: Nagano, A., K. Ichikawa, H. Ichikawa, H. Tomita, H. Tokinaga, and M. Konda (2010), Stable volume and heat transports of the North Pacific subtropical gyre revealed by identifying the Kuroshio in synoptic hydrography south of Japan,

Influence of Kuroshio Extension Variability on the North Pacific Atmosphere and Pacific Decadal Precession

Recent research has revealed links between a quasi decadal mode of climate variability over the North Pacific – the Pacific Decadal Precession (PDP) – and the North Pacific’s western boundary currents extension – the Kuroshio Extension (KE). It is suggested that on decadal time scales the PDP both responds to and influences the KE variability. A question yet to be answered is whether it is the large-scale or the mesoscale variations of the KE region that influence the overlying and downstream atmosphere and hence the PDP evolution. Using high-resolution sea surface temperature data (1981-2018) from the global ocean Operational Sea Surface Temperature (SST) and Sea Ice Analysis, low resolution Extended Reconstructed SST (ERSST) version 3b data (1949-2018), geopotential height data from the European Centre for MediumRange Weather Forecasts (ECMWF) and the National Centers for Environmental Prediction we find that it is the large-scale variations in the KE region that correlate best wi...

Temporal variations of net Kuroshio transport based on a repeated hydrographic section along 137°E

Climate Dynamics

Temporal variations of net Kuroshio transport are examined for 1972–2018 based on a repeated hydrographic section along 137°E, which is maintained by the Japan Meteorological Agency. The net Kuroshio transport obtained by integration of geostrophic current velocity relative to 1000 dbar depth fluctuates on inter-annual and decadal timescales. The predominant timescale of the net Kuroshio transport changes with time; the inter-annual variation is pronounced in 1972–1990 and 2000–2018, and the decadal variation is detected only before 2000. We find that a winter wind stress curl variation in the central North Pacific which reflects meridional movements of the Aleutian Low and intensity fluctuations of the North Pacific subtropical high on an inter-annual timescale and intensity fluctuations of the Aleutian Low on a decadal timescale, causes the net Kuroshio transport variation. In addition to the inter-annual and decadal variations, we further pointed out a bi-decadal-scale variation ...

Intra-Annual Sea Level Fluctuations and Variability of Mesoscale Processes in the Northern Japan/East Sea From Satellite Altimetry Data

Frontiers in Marine Science, 2022

Intra-annual sea level fluctuations and variability of mesoscale processes based on eddy kinetic energy (EKE) were studied in the northern (northward of 41 N) Japan/East Sea (JES) using data from satellite altimetry for 1993-2020. Decomposition to empirical orthogonal functions (EOF) was performed of the high-pass filtered, with the cutoff period of 250 days, sea level anomalies. The leading mode accounting for the major fraction of the variance yielded sea level fluctuations which were simultaneous in the entire sea and occurred in the range from 70 to 250 days without any preferable timescale. EKE in the northern sea was also expanded to EOF and yielded the leading mode capturing mesoscale variability within the Primorye (Liman) Current and the Tsushima Warm Current. The seasonal signal was found in the simultaneous intra-annual sea level fluctuations, which matches that of EKE, and, as found in the earlier studies, of the mean currents. The sea level rises, the mean currents intensify and EKE increases in summer and fall and the opposite changes occur in winter and spring, with the seasonal extremes in October/ November and March/April, respectively. This is in line with the EKE generation by instability of the mean currents. The intra-annual sea level fluctuations and EKE manifest rich variability on quasi-biennial, interannual and decadal timescales. However, in contrast with the seasonal signal, the low-frequency variability does not match, implying different kinds of forcing, probably by local wind in the northern JES and by the transport variations in the Korea-Tsushima Strait (KTS) in the southern JES. Intra-annual simultaneous SLA reveal changing relationship with Pacific Decadal Oscillation (PDO): both were in-phase in 1993-1994 and from late 2007 to 2013 and out-of-phase from 1997 to 2002, while there was no specific relationship in other times. However, the relationship of these SLA with the interannual KTS transport variation seems inconclusive.

Are Sea Surface Temperature Variations in the Kuroshio Extension and Subarctic Frontal Zones in the Western North Pacific Ocean Coherent?

2007

The western North Pacific region is one of the centers of action of decadal time scale variations in the atmosphere and ocean, and also oceanic ecosystem can be strongly influenced by the variations. One of the key variable of the decadal variations is sea surface temperature (SST) that varies as a result of interaction between the atmosphere and ocean. To improve our understanding of the key element, SST variaions in the two frontal zones in the western North Pacific Ocean, the Kuroshio Extension and subarctic frontal zones, are investigated on the basis of an in situ observational dataset. Interannual-to-decadal variations in these two frontal zones are not highly correlated, indicating that to some extent different mechanisms induce the SST variations in the frontal zones and those two frontal zone cannot be considered as a single frontal zone as has been done in most of previous studies. Meanwhile, the results are consistent with the recent studies that suggest different mechanisms for the variations in the two frontal zones on the basis of a solution to an eddy-resolving, i.e., very high horizontal resolution, ocean general circulation model.

Intraseasonal variability in the far-east pacific: investigation of the role of air–sea coupling in a regional coupled model

2011

Abstract Intraseasonal variability in the eastern Pacific warm pool in summer is studied, using a regional ocean–atmosphere model, a linear baroclinic model (LBM), and satellite observations. The atmospheric component of the model is forced by lateral boundary conditions from reanalysis data. The aim is to quantify the importance to atmospheric deep convection of local air–sea coupling. In particular, the effect of sea surface temperature (SST) anomalies on surface heat fluxes is examined.

Anatomy of North Pacific Decadal Variability

Journal of Climate, 2002

A systematic analysis of North Pacific decadal variability in a full-physics coupled ocean-atmosphere model is executed. The model is an updated and improved version of the coupled model studied by Latif and Barnett. Evidence is sought for determining the details of the mechanism responsible for the enhanced variance of some variables at 20-30-yr timescales. The possible mechanisms include a midlatitude gyre ocean-atmosphere feedback loop, stochastic forcing, remote forcing, or sampling error.