scholarly journals Three-Dimensional Structure and Temporal Evolution of Submesoscale Thermohaline Intrusions in the North Pacific Subtropical Frontal Zone

2010 ◽  
Vol 40 (8) ◽  
pp. 1669-1689 ◽  
Author(s):  
A. Y. Shcherbina ◽  
M. C. Gregg ◽  
M. H. Alford ◽  
R. R. Harcourt
Keyword(s):  
North Pacific ◽  
Frontal Zone ◽  
Opposite Sign ◽  
Three Dimensional ◽  
Three Dimensions ◽  
Dimensional Structure ◽  
Subtropical Front ◽  
The North ◽  
Lateral Advection ◽  
The North Pacific

Abstract Four instances of persistent intrusive deformation of the North Pacific Subtropical Front were tagged individually by a Lagrangian float and tracked for several days. Each feature was mapped in three dimensions using repeat towed observations referenced to the float. Isohaline surface deformations in the frontal zone included sheetlike folds elongated in the alongfront direction and narrow tongues extending across the front. All deformations appeared as protrusions of relatively cold, and fresh, water across the front. No corresponding features of the opposite sign or isolated lenslike structures were observed. The sheets were O(10 m) thick, protruded about 10 km into the warm saline side of the front, and were coherent for 10–30 km along the front. Having about the same thickness and cross-frontal extent as the sheets, tongues extended less than 5 km along the front. All of the intrusions persisted as long as they were followed, several days to one week. Their structures evolved on both inertial (23 h) and subinertial (∼10 days) time scales in response to differential lateral advection. The water mass surrounding the intrusions participated in gradual anticyclonic rotation as a part of a mesoscale meander of the subtropical front. The intrusions may be interpreted as a manifestation of three-dimensional submesoscale turbulence of the frontal zone, driven by the mesoscale. Absence of large features of the opposite sign may be indicative of the asymmetry of the underlying dynamics.

3D Structure of Striations in the North Pacific

2021 ◽  
Author(s):  
YU ZHANG ◽  
YU PING GUAN ◽  
RUI XIN HUANG
Keyword(s):  
North Pacific ◽  
3D Structure ◽  
Three Dimensional ◽  
Vertical Plane ◽  
Dimensional Structure ◽  
The North ◽  
Layer Analysis ◽  
Fluid Potential ◽  
The North Pacific

AbstractOcean striations are composed of alternating quasi-zonal band-like flows; this kind of organized structure of currents be found in all world’s oceans and seas. Previous studies have mainly been focused on the mechanisms of their generation and propagation. This study uses the spatial high-pass filtering to obtain the three-dimensional structure of ocean striations in the North Pacific in both the z-coordinate and σ-coordinate based on 10-yr averaged SODA3 data. First, we identify an ideal-fluid potential density domain where the striations are undisturbed by the surface forcing and boundary effects. Second, using the isopycnal layer analysis, we show that on isopycnal surfaces the orientations of striations nearly follow the potential vorticity (PV) contours, while in the meridional-vertical plane the central positions of striations are generally aligned with the latitude of zero gradient of the relative PV. Our analysis provides a simple dynamical interpretation and better understanding for the role of ocean striations.

scholarly journals Mass Footprints of the North Pacific Atmospheric Blocking Highs

2015 ◽  
Vol 28 (12) ◽  
pp. 4941-4949 ◽  
Author(s):  
Tae-Won Park ◽  
Yi Deng ◽  
Wenhong Li ◽  
Song Yang ◽  
Ming Cai
Keyword(s):  
Mass Loss ◽  
North Pacific ◽  
Three Dimensional ◽  
Low Frequency ◽  
Lower Troposphere ◽  
Decay Stage ◽  
The North ◽  
Detection And Attribution ◽  
Blocking High ◽  
The North Pacific

Abstract The mass footprints associated with atmospheric blocks over the North Pacific are evaluated by constructing daily tendencies of total mass over the blocking domain from three-dimensional mass fluxes throughout the life cycle of a composite blocking event. The results highlight the major role of mass convergence driven by low-frequency (with periods >1 week) atmospheric disturbances during both the development and decay stage of a block. Specifically, low-frequency eddies are responsible for the accelerated mass buildup 4 days prior to the peak intensity of a block, and they also account for the rapid mass loss afterward. High-frequency, subweekly scale disturbances have statistically significant positive contributions to the mass loss during the decay stage, and also show weak negative contributions to the development of the blocking high prior to the peak of the high. The majority of the mass convergence (divergence) responsible for the intensification (decay) of the blocking high occurs in the middle-to-lower troposphere and is largely attributed to mass flux driven by low-frequency meridional (zonal) winds. Also discussed are the implications of this new mass perspective of atmospheric blocks for understanding dynamics of blocking highs and for model bias detection and attribution.

scholarly journals Seasonal Evolutions of Atmospheric Response to Decadal SST Anomalies in the North Pacific Subarctic Frontal Zone: Observations and a Coupled Model Simulation

2012 ◽  
Vol 25 (1) ◽  
pp. 111-139 ◽  
Author(s):  
Bunmei Taguchi ◽  
Hisashi Nakamura ◽  
Masami Nonaka ◽  
Nobumasa Komori ◽  
Akira Kuwano-Yoshida ◽  
...  
Keyword(s):  
North Pacific ◽  
Frontal Zone ◽  
Ocean Dynamics ◽  
The North ◽  
The Pacific ◽  
Decadal Scale ◽  
Anomaly Pattern ◽  
Subarctic Frontal Zone ◽  
The North Pacific ◽  
Sst Anomalies

Abstract Potential impacts of pronounced decadal-scale variations in the North Pacific sea surface temperature (SST) that tend to be confined to the subarctic frontal zone (SAFZ) upon seasonally varying atmospheric states are investigated, by using 48-yr observational data and a 120-yr simulation with an ocean–atmosphere coupled general circulation model (CGCM). SST fields based on in situ observations and the ocean component of the CGCM have horizontal resolutions of 2.0° and 0.5°, respectively, which can reasonably resolve frontal SST gradient across the SAFZ. Both the observations and CGCM simulation provide a consistent picture between SST anomalies in the SAFZ yielded by its decadal-scale meridional displacement and their association with atmospheric anomalies. Correlated with SST anomalies persistent in the SAFZ from fall to winter, a coherent decadal-scale signal in the wintertime atmospheric circulation over the North Pacific starts emerging in November and develops into an equivalent barotropic anomaly pattern similar to the Pacific–North American (PNA) pattern. The PNA-like signal with the weakened (enhanced) surface Aleutian low correlated with positive (negative) SST anomalies in the SAFZ becomes strongest and most robust in January, under the feedback forcing from synoptic-scale disturbances migrating along the Pacific storm track that shifts northward (southward) in accord with the oceanic SAFZ. This PNA-like signal, however, breaks down in February, which is suggestive of a particular sensitivity of that anomaly pattern to subtle differences in the background climatological-mean state. Despite its collapse in February, the PNA-like signal recurs the next January. This subseasonal evolution of the signal suggests that the PNA-like anomaly pattern may develop as a response to the persistent SST anomalies that are maintained mainly through ocean dynamics.

scholarly journals Decadal Variability of Upper-Ocean Heat Content Associated with Meridional Shifts of Western Boundary Current Extensions in the North Pacific

2017 ◽  
Vol 30 (16) ◽  
pp. 6247-6264 ◽  
Author(s):  
Bunmei Taguchi ◽  
Niklas Schneider ◽  
Masami Nonaka ◽  
Hideharu Sasaki
Keyword(s):  
North Pacific ◽  
Frontal Zone ◽  
Heat Content ◽  
Ocean Heat Content ◽  
Upper Ocean ◽  
Upper Ocean Heat Content ◽  
Temperature Anomalies ◽  
The North ◽  
Subarctic Frontal Zone ◽  
The North Pacific

Generation and propagation processes of upper-ocean heat content (OHC) in the North Pacific are investigated using oceanic subsurface observations and an eddy-resolving ocean general circulation model hindcast simulation. OHC anomalies are decomposed into physically distinct dynamical components (OHC ρ) due to temperature anomalies that are associated with density anomalies and spiciness components (OHC χ) due to temperature anomalies that are density compensating with salinity. Analysis of the observational and model data consistently shows that both dynamical and spiciness components contribute to interannual–decadal OHC variability, with the former (latter) component dominating in the subtropical (subpolar) North Pacific. OHC ρ variability represents heaving of thermocline, propagates westward, and intensifies along the Kuroshio Extension, consistent with jet-trapped Rossby waves, while OHC χ variability propagates eastward along the subarctic frontal zone, suggesting advection by mean eastward currents. OHC χ variability tightly corresponds in space to horizontal mean spiciness gradients. Meanwhile, area-averaged OHC χ anomalies in the western subarctic frontal zone closely correspond in time to meridional shifts of the subarctic frontal zone. Regression coefficient of the OHC χ time series on the frontal displacement anomalies quantitatively agree with the area-averaged mean spiciness gradient in the region, and suggest that OHC χ is generated via frontal variability in the subarctic frontal zone.

Isopycnal mixing and the distribution of particles across the North Pacific Subtropical Front

1989 ◽  
Vol 36 (11) ◽  
pp. 1607-1620 ◽  
Author(s):  
Libe Washburn ◽  
David A. Siegel ◽  
Tommy D. Dickey ◽  
Michael K. Hamilton
Keyword(s):  
North Pacific ◽  
Subtropical Front ◽  
The North ◽  
The North Pacific ◽  
Isopycnal Mixing

scholarly journals Mechanisms for the Maintenance of the Wintertime Basin-Scale Atmospheric Response to Decadal SST Variability in the North Pacific Subarctic Frontal Zone

2017 ◽  
Vol 31 (1) ◽  
pp. 297-315 ◽  
Author(s):  
Satoru Okajima ◽  
Hisashi Nakamura ◽  
Kazuaki Nishii ◽  
Takafumi Miyasaka ◽  
Akira Kuwano-Yoshida ◽  
...  
Keyword(s):  
North Pacific ◽  
Frontal Zone ◽  
Atmospheric Response ◽  
The North ◽  
Model Response ◽  
Basin Scale ◽  
Sst Anomaly ◽  
Subarctic Frontal Zone ◽  
The North Pacific ◽  
Sst Anomalies

Abstract Mechanisms for the maintenance of a large-scale wintertime atmospheric response to warm sea surface temperature (SST) anomalies associated with decadal-scale poleward displacement of the North Pacific subarctic frontal zone (SAFZ) are investigated through the following two ensemble experiments with an atmospheric general circulation model (AGCM): one with climatological-mean SST and the other with positive SST anomalies along the SAFZ prescribed on top of the climatological-mean SST. As actually observed, the simulated January ensemble response over the North Pacific is anticyclonic throughout the depth of the troposphere, although its amplitude is smaller. This response is maintained through energy conversion from the ensemble climatological-mean circulation realized under the climatological SST as well as feedback from anomalous transient eddy activity, suggesting that the response may have characteristics as a preferred mode of variability (or “dynamical mode”). Conversions of both available potential energy and kinetic energy from the climatological-mean state are important for the observed anomaly, while the latter is less pronounced for the model response. Net transient feedback forcing is also important for both the observed anomaly and simulated response. These results imply that a moderate-resolution (~1°) AGCM may be able to simulate a basin-scale atmospheric response to the SAFZ SST anomaly through synoptic- and basin-scale dynamical processes. Weaker PNA-like internal variability in the model may lead to the weaker response, suggesting that misrepresentation of intrinsic atmospheric variability can affect the model response to the SST anomaly.

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