scholarly journals Decadal Variability of the Meridional Geostrophic Transport in the Upper Tropical North Pacific Ocean

2018 ◽  
Vol 31 (15) ◽  
pp. 5891-5910 ◽  
Author(s):  
Hui Zhou ◽  
Dongliang Yuan ◽  
Lina Yang ◽  
Xiang Li ◽  
William Dewar
Keyword(s):  
Pacific Ocean ◽  
North Pacific ◽  
General Circulation ◽  
Decadal Variability ◽  
North Pacific Ocean ◽  
Salt Content ◽  
Circulation Model ◽  
Global Ocean ◽  
Meridional Transport ◽  
Tropical Ocean

The meridional geostrophic transport (MGT) in the interior tropical North Pacific Ocean is estimated based on global ocean heat and salt content data. The decadal variations of the zonally and vertically integrated MGT in the tropical North Pacific Ocean are found to precede the Pacific decadal oscillation (PDO) by 1–3 years. The dynamics of the MGT are analyzed based on Sverdrup theory. It is found that the total meridional transport variability (MGT plus Ekman) is dominated by the MGT variability having positive correlations with the PDO index. The Sverdrup transports differ from the total meridional transport significantly and have insignificant correlations with PDO index, suggesting that the MGT variability is not controlled by the Sverdrup dynamics. In comparison, the simulated meridional transport variability in the models from phase 5 of the Coupled Model Intercomparison Project (CMIP5) and the Ocean General Circulation Model for the Earth Simulator are dominated by the Sverdrup transports, having insignificant correlations with the simulated PDO indices. The comparison suggests that the non-Sverdrup component in the MGT is important for the predictability of PDO and that significant deficiencies exist in these models in simulating a realistic structure of the tropical ocean gyre variability and predicting the decadal climate variations associated with it.

scholarly journals Interannual Variations in Summer Precipitation in Southwest China: Anomalies in Moisture Transport and the Role of the Tropical Atlantic

2020 ◽  
Vol 33 (14) ◽  
pp. 5993-6007 ◽  
Author(s):  
Chaoxia Yuan ◽  
Mengzhou Yang
Keyword(s):  
Pacific Ocean ◽  
North Pacific ◽  
Moisture Transport ◽  
General Circulation ◽  
Western North Pacific ◽  
North Pacific Ocean ◽  
Circulation Model ◽  
Summer Precipitation ◽  
Tropical Atlantic ◽  
Anomalous Anticyclone

AbstractUsing a Lagrangian trajectory model, contributions of moisture from the Indian Ocean (IO), the South China Sea (SCS), the adjacent land region (LD), and the Pacific Ocean (PO) to interannual summer precipitation variations in southwestern China (SWC) are investigated. Results show that, on average, the IO, SCS, LD, and PO contribute 48.8%, 21.1%, 23.6%, and 3.7% of the total moisture release in SWC, respectively. In summers with the above-normal precipitation, moisture release from the IO and SCS increases significantly by 41.4% and 15.1%, respectively. In summers with below-normal precipitation, moisture release from the IO and SCS decreases significantly by 44.2% and 24.6%, respectively. In addition, the moisture anomalies from the four source regions together explain 86.5% of the total interannual variances of SWC summer precipitation, and the IO and SCS only can explain 75.7%. Variations in moisture transport from the IO, SCS, and LD to SWC are not independent of one another and are commonly influenced by the anomalous anticyclone in the western North Pacific Ocean, which enhances the moisture transport from the IO and SCS by the anomalous southwesterlies over its northwestern quadrant but reduces that from the LD east of SWC by the anomalous westerlies along its northern edge. Anomalous warming in the tropical Atlantic Ocean can modify the Walker circulation, induce anomalous descending motion over the central tropical Pacific, and excite the anomalous anticyclone in the western North Pacific as the classic Matsuno–Gill response. The observed impacts of the tropical Atlantic warming on the anomalous anticyclone and summer precipitation in SWC can be well reproduced in an atmospheric general circulation model.

scholarly journals Dynamics of the Coastal Oyashio and Its Seasonal Variation in a High-Resolution Western North Pacific Ocean Model

2010 ◽  
Vol 40 (6) ◽  
pp. 1283-1301 ◽  
Author(s):  
Kei Sakamoto ◽  
Hiroyuki Tsujino ◽  
Shiro Nishikawa ◽  
Hideyuki Nakano ◽  
Tatsuo Motoi
Keyword(s):  
Seasonal Variation ◽  
Pacific Ocean ◽  
North Pacific ◽  
General Circulation ◽  
Western North Pacific ◽  
North Pacific Ocean ◽  
Maximum Velocity ◽  
Circulation Model ◽  
Okhotsk Sea ◽  
Resolution Model

Abstract The Coastal Oyashio (CO) carries the cold, fresh, and relatively light water mass called the Coastal Oyashio Water (COW) westward along the southeastern coast of Hokkaido in winter and spring. To investigate dynamics of the CO and its seasonal variation, model experiments are executed using a western North Pacific general circulation model with horizontal resolutions of approximately 2 and 6 km. The 2-km resolution model reproduces the properties of COW with temperature of 0°–2°C and salinity of 32.2–32.6 and reproduces its distribution. COW is less dense than offshore water by 0.2 kg m−3, and it forms a surface-to-bottom density front with a width of 10 km near the shelf break. The CO appears as a baroclinic jet current along the front with a maximum velocity of approximately 40 cm s−1. The velocity and density structures and the front location relative to bathymetry indicate that the CO can be understood in terms of a simplified dynamical model developed for the shelfbreak front in the Middle Atlantic Bight. In contrast to the 2-km resolution model, the 6-km model cannot realistically reproduce the COW distribution. This is because only the 2-km model can represent the sharp density structure of the shelfbreak front and the accompanying CO. The CO exists during the limited period from January to April. This is directly connected with seasonal variation of the COW inflow from the Okhotsk Sea to the North Pacific Ocean through the Nemuro and Kunashiri Straits, indicating that the seasonal variation of the CO is ultimately controlled by the variation of the circulation in the Okhotsk Sea induced by the monsoon.

scholarly journals A modelling study of the 1976 climate regime shift in the North Pacific Ocean

1999 ◽  
Vol 56 (12) ◽  
pp. 2450-2462 ◽  
Author(s):  
Julia Qiuying Wu ◽  
William W Hsieh
Keyword(s):  
Pacific Ocean ◽  
North Pacific ◽  
General Circulation ◽  
Regime Shift ◽  
North Pacific Ocean ◽  
Circulation Model ◽  
Climate Regime ◽  
Climate Regime Shift ◽  
The North ◽  
The North Pacific

Around 1976, the North Pacific Ocean underwent a climate regime shift, with significant biological consequences. To model the changes in the ocean, an ocean general circulation model was forced by the wind stress and sea surface temperature monthly climatology of the 1952-1975 period in one numerical experiment and the 1976-1988 period in another. Changes in the ocean model between the two experiments revealed how the ocean might have changed under the 1976 climate regime shift. In winter, the intensified post-1976 Aleutian Low spun up the subarctic gyre and the subtropical gyre, except in the Gulf of Alaska, where the circulation weakened. Upwelling was generally enhanced in the subarctic and downwelling enhanced in the subtropical region, with temperature changes down to 600 m. In the post-1976 period, the meridional heat transports were also enhanced: poleward in the low latitudes, equatorward in the midlatitudes, and poleward in the high latitudes.

scholarly journals The Global Zonally Integrated Ocean Circulation, 1992–2006: Seasonal and Decadal Variability

2009 ◽  
Vol 39 (2) ◽  
pp. 351-368 ◽  
Author(s):  
Carl Wunsch ◽  
Patrick Heimbach
Keyword(s):  
Southern Ocean ◽  
Time Scales ◽  
Ocean Circulation ◽  
General Circulation ◽  
Decadal Variability ◽  
Circulation Model ◽  
Meridional Overturning Circulation ◽  
Global Ocean ◽  
Oceanic Circulation ◽  
Meridional Transport

Abstract The zonally integrated meridional and vertical velocities as well as the enthalpy transports and fluxes in a least squares adjusted general circulation model are used to estimate the top-to-bottom oceanic meridional overturning circulation (MOC) and its variability from 1992 to 2006. A variety of simple theories all produce time scales suggesting that the mid- and high-latitude oceans should respond to atmospheric driving only over several decades. In practice, little change is seen in the MOC and associated heat transport except very close to the sea surface, at depth near the equator, and in parts of the Southern Ocean. Variability in meridional transports in both volume and enthalpy is dominated by the annual cycle and secondarily by the semiannual cycle, particularly in the Southern Ocean. On time scales longer than a year, the solution exhibits small trends with complicated global spatial patterns. Apart from a net uptake of heat from the atmosphere (forced by the NCEP–NCAR reanalysis, which produces net ocean heating), the origins of the meridional transport trends are not distinguishable and are likely a combination of model disequilibrium, shifts in the observing system, other trends (real or artificial) in the meteorological fields, and/or true oceanic secularities. None of the results, however, supports an inference of oceanic circulation shifts taking the system out of the range in which changes are more than small perturbations. That the oceanic observations do not conflict with an apparent excess heat uptake from the atmosphere implies a continued undersampling of the global ocean, even in the upper layers.

scholarly journals Effects of mesoscale eddies on global ocean distributions of CFC-11, CO<sub>2</sub> and Δ<sup>14</sup>C

2006 ◽  
Vol 3 (4) ◽  
pp. 1011-1063
Author(s):  
Z. Lachkar ◽  
J. C. Orr ◽  
J.-C. Dutay ◽  
P. Delecluse
Keyword(s):  
General Circulation ◽  
Circulation Model ◽  
Ocean General Circulation Model ◽  
Global Scale ◽  
Global Ocean ◽  
Residual Circulation ◽  
Mean Flow ◽  
Meridional Transport ◽  
Anthropogenic Co2 ◽  
Short Time

Abstract. Global-scale tracer simulations are typically made at coarse resolution without explicitly modeling eddies. Here we ask what role do eddies play in ocean uptake, storage, and meridional transport of transient tracers. We made global anthropogenic transient-tracer simulations in non-eddying (2°cosφ×2°, ORCA2) and eddying (½°cosφ×½°, ORCA05) versions of the ocean general circulation model OPA9. We focus on the Southern Ocean where tracer air-sea fluxes are largest. Eddies have little effect on global and regional bomb Δ14C uptake and storage. Yet for anthropogenic CO2 and CFC-11, increased eddy activity reduces southern extratropical uptake by 28% and 25% respectively. There is a similar decrease in corresponding inventories, which provides better agreement with observations. With higher resolution, eddies strengthen upper ocean vertical stratification and reduce excessive ventilation of intermediate waters by 20% between 60° S and 40° S. By weakening the Residual Circulation, i.e., the sum of Eulerian mean flow and the opposed eddy-induced flow, eddies reduce the supply of tracer-impoverished deep waters to the surface near the Antarctic divergence, thus reducing the air-sea tracer flux. Consequently, inventories for both CFC-11 and anthropogenic CO2 decrease because their mixed layer concentrations in that region equilibrate with the atmosphere on relatively short time scales (15 days and 6 months, respectively); conversely, the slow air-sea equilibration of bomb Δ14C of 6 years, gives surface waters little time to exchange with the atmosphere before they are subducted.

scholarly journals Sensitivity of the Simulated Distributions of Water Masses, CFCs, and Bomb 14C to Parameterizations of Mesoscale Tracer Transports in a Model of the North Pacific

2006 ◽  
Vol 36 (3) ◽  
pp. 273-285 ◽  
Author(s):  
Yongfu Xu ◽  
Shigeaki Aoki ◽  
Koh Harada
Keyword(s):  
North Pacific ◽  
General Circulation ◽  
Western North Pacific ◽  
North Pacific Ocean ◽  
Circulation Model ◽  
Water Masses ◽  
Intermediate Water ◽  
North Pacific Intermediate Water ◽  
The North ◽  
The North Pacific

Abstract A basinwide ocean general circulation model of the North Pacific Ocean is used to study the sensitivity of the simulated distributions of water masses, chlorofluorocarbons (CFCs), and bomb carbon-14 isotope (14C) to parameterizations of mesoscale tracer transports. Five simulations are conducted, including a run with the traditional horizontal mixing scheme and four runs with the isopycnal transport parameterization of Gent and McWilliams (GM). The four GM runs use different values of isopycnal and skew diffusivities. Simulated results show that the GM mixing scheme can help to form North Pacific Intermediate Water (NPIW). Greater isopycnal diffusivity enhances formation of NPIW. Although greater skew diffusivity can also generate NPIW, it makes the subsurface too fresh. Results from simulations of CFC uptake show that greater isopycnal diffusivity generates the best results relative to observations in the western North Pacific. The model generally underestimates the inventories of CFCs in the western North Pacific. The results from simulations of bomb 14C reproduce some observed features. Greater isopycnal diffusivity generates a longitudinal gradient of the inventory of bomb 14C from west to east, whereas greater skew diffusivity makes it reversed. It is considered that the ratio of isopycnal diffusivity to skew diffusivity is important. An increase in isopycnal diffusivity increases storage of passive tracers in the subtropical gyre.

Mean and time-varying meridional transport of heat at the tropical/subtropical boundary of the North Pacific Ocean

2001 ◽  
Vol 106 (C5) ◽  
pp. 8957-8970 ◽  
Author(s):  
Dean Roemmich ◽  
John Gilson ◽  
Bruce Cornuelle ◽  
Robert Weller
Keyword(s):  
Pacific Ocean ◽  
North Pacific ◽  
North Pacific Ocean ◽  
Time Varying ◽  
Meridional Transport ◽  
The North ◽  
The North Pacific
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