scholarly journals Formation Mechanism for Isopycnal Temperature–Salinity Anomalies Propagating from the Eastern South Pacific to the Equatorial Region

2007 ◽  
Vol 20 (7) ◽  
pp. 1305-1315 ◽  
Author(s):  
Masami Nonaka ◽  
Hideharu Sasaki
Keyword(s):  
Formation Mechanism ◽  
General Circulation ◽  
Circulation Model ◽  
South Pacific ◽  
Ocean General Circulation Model ◽  
Equatorial Region ◽  
Sea Surface ◽  
Global Ocean ◽  
Decadal Time Scale ◽  
Isopycnal Surface

Abstract Equatorward propagation of temperature–salinity (or spiciness) anomalies on an isopycnal surface emanating from the eastern subtropical South Pacific and their formation mechanism are investigated based on a hindcast simulation with an eddy-resolving quasi-global ocean general circulation model. Because of density-compensating meridional distributions of temperature and salinity, the meridional density gradient is weak at the sea surface in the eastern subtropical South Pacific. With these mean fields, cool sea surface temperature anomalies (SSTAs) can make the outcrop line of an isopycnal surface migrate equatorward more than 5° and induce warm and salty anomalies on the isopycnal surface. Subducted warm, salty anomalies propagate to the equatorial region over approximately 5 yr and may influence equatorial isopycnal temperature–salinity anomalies. Although the associated effects are unclear, if these anomalies could further induce warm eastern equatorial SSTAs that are positively correlated with eastern South Pacific SSTAs, opposite sign temperature–salinity anomalies would be formed in the subtropical South Pacific, and a closed cycle having a decadal time scale might be induced.

scholarly journals A global eddying hindcast ocean simulation with OFES2

2020 ◽  
Vol 13 (7) ◽  
pp. 3319-3336 ◽  
Author(s):  
Hideharu Sasaki ◽  
Shinichiro Kida ◽  
Ryo Furue ◽  
Hidenori Aiki ◽  
Nobumasa Komori ◽  
...  
Keyword(s):  
General Circulation ◽  
Circulation Model ◽  
Ocean General Circulation Model ◽  
Sea Surface ◽  
Sea Surface Salinity ◽  
Tidal Mixing ◽  
Surface Salinity ◽  
Previous Version ◽  
Spatiotemporal Scales ◽  
The Kuroshio

Abstract. A quasi-global eddying ocean hindcast simulation using a new version of our model, called OFES2 (Ocean General Circulation Model for the Earth Simulator version 2), was conducted to overcome several issues with unrealistic properties in its previous version, OFES. This paper describes the model and the simulated oceanic fields in OFES2 compared with OFES and also observed data. OFES2 includes a sea-ice model and a tidal mixing scheme, is forced by a newly created surface atmospheric dataset called JRA55-do, and simulated the oceanic fields from 1958 to 2016. We found several improvements in OFES2 over OFES: smaller biases in the global sea surface temperature and sea surface salinity as well as the water mass properties in the Indonesian and Arabian seas. The time series of the Niño3.4 and Indian Ocean Dipole (IOD) indexes are somewhat better in OFES2 than in OFES. Unlike the previous version, OFES2 reproduces more realistic anomalously low sea surface temperatures during a positive IOD event. One possible cause of these improvements in El Niño and IOD events is the replacement of the atmospheric dataset. On the other hand, several issues remained unrealistic, such as the pathways of the Kuroshio and Gulf Stream and the unrealistic spreading of salty Mediterranean overflow. Given the worldwide use of the previous version and the improvements presented here, the output from OFES2 will be useful in studying various oceanic phenomena with broad spatiotemporal scales.

scholarly journals Global tide simulations with ICON-O: testing the model performance on highly irregular meshes

2020 ◽  
Vol 71 (1) ◽  
pp. 43-57
Author(s):  
Kai Logemann ◽  
Leonidas Linardakis ◽  
Peter Korn ◽  
Corinna Schrum
Keyword(s):  
General Circulation ◽  
Model Performance ◽  
Circulation Model ◽  
Ocean General Circulation Model ◽  
Discrete Fourier Transformation ◽  
Global Ocean ◽  
Transition Zones ◽  
Maximum Angle ◽  
Irregular Meshes

AbstractThe global tide is simulated with the global ocean general circulation model ICON-O using a newly developed tidal module, which computes the full tidal potential. The simulated coastal M2 amplitudes, derived by a discrete Fourier transformation of the output sea level time series, are compared with the according values derived from satellite altimetry (TPXO-8 atlas). The experiments are repeated with four uniform and sixteen irregular triangular grids. The results show that the quality of the coastal tide simulation depends primarily on the coastal resolution and that the ocean interior can be resolved up to twenty times lower without causing considerable reductions in quality. The mesh transition zones between areas of different resolutions are formed by cell bisection and subsequent local spring optimisation tolerating a triangular cell’s maximum angle up to 84°. Numerical problems with these high-grade non-equiangular cells were not encountered. The results emphasise the numerical feasibility and potential efficiency of highly irregular computational meshes used by ICON-O.

Comparison of the Semtner and Chervin eddy-resolving global ocean model with LUCIE and satellite observations in the Leeuwin Current region

1996 ◽  
Vol 47 (3) ◽  
pp. 509 ◽  
Author(s):  
CJC Reason ◽  
AF Pearce
Keyword(s):  
Western Australia ◽  
Satellite Data ◽  
General Circulation ◽  
Maximum Velocity ◽  
Circulation Model ◽  
Ocean General Circulation Model ◽  
Global Ocean ◽  
Western Coast ◽  
Model Output ◽  
Leeuwin Current

Output from the Semtner and Chervin eddy-resolving global ocean general circulation model is compared with observations from the Leeuwin Current Interdisciplinary Experiment (LUCIE) and satellite data for the coastal waters of Western Australia. The model output is a snapshot over the domain 9-43�S, 90-120�E for a day in mid July 1987, which is during the season that the Leeuwin Current is expected to be well established along the western and southern coasts of Western Australia. Maximum Leeuwin Current velocities in the model are of the order of 60 cm s-1 and are found in the southern part of the current on the western coast and around into the Great Australian Bight. At depths below about 200 m, and centred near 400 m, there is an equatorward-flowing undercurrent with maximum velocity of order 25 cm s-1. Comparison of temperature and salinity cross-sections with LUCIE observations reveals that the model output for this day exhibits many realistic features. In particular, the model fields display a number of prominent meanders and eddies on the Leeuwin Current as well as further offshore. Consistent with observations, mesoscale features associated with the Leeuwin Current are concentrated between 25�S and the Cape Mentelle region; the flow in the northern part of the Leeuwin Current and the North West Shelf may be too weak to induce eddy-generating instabilities. Prominent in the model output are two large meanders on the Leeuwin Current between 25�S and 29�S and two anticyclonic eddies further downstream; features similar to these are evident in satellite data during winter 1987.

scholarly journals Origin and Pathway of Equatorial 13°C Water in the Pacific Identified by a Simulated Passive Tracer and Its Adjoint*

2009 ◽  
Vol 39 (8) ◽  
pp. 1836-1853 ◽  
Author(s):  
Tangdong Qu ◽  
Shan Gao ◽  
Ichiro Fukumori ◽  
Rana A. Fine ◽  
Eric J. Lindstrom
Keyword(s):  
General Circulation ◽  
Circulation Model ◽  
South Pacific ◽  
Equatorial Region ◽  
Equatorial Pacific ◽  
Western Boundary ◽  
Passive Tracer ◽  
The South ◽  
Mode Water ◽  
Eastern Equatorial Pacific

Abstract The origin and pathway of the thermostad water in the eastern equatorial Pacific Ocean, often referred to as the equatorial 13°C Water, are investigated using a simulated passive tracer and its adjoint, based on circulation estimates of a global general circulation model. Results demonstrate that the source region of the 13°C Water lies well outside the tropics. In the South Pacific, some 13°C Water is formed northeast of New Zealand, confirming an earlier hypothesis on the water’s origin. The South Pacific origin of the 13°C Water is also related to the formation of the Eastern Subtropical Mode Water (ESTMW) and the Sub-Antarctic Mode Water (SAMW). The portion of the ESTMW and SAMW that eventually enters the density range of the 13°C Water (25.8 < σθ < 26.6 kg m−3) does so largely by mixing. Water formed in the subtropics enters the equatorial region predominantly through the western boundary, while its interior transport is relatively small. The fresher North Pacific ESTMW and Central Mode Water (CMW) are also important sources of the 13°C Water. The ratio of the southern versus the northern origins of the water mass is about 2 to 1 and tends to increase with time elapsed from its origin. Of the total volume of initially tracer-tagged water in the eastern equatorial Pacific, approximately 47.5% originates from depths above σθ = 25.8 kg m−3 and 34.6% from depths below σθ = 26.6 kg m−3, indicative of a dramatic impact of mixing on the route of subtropical water to becoming the 13°C Water. Still only a small portion of the water formed in the subtropics reaches the equatorial region, because most of the water is trapped and recirculates in the subtropical gyre.

Towards AOD1B RL07

2020 ◽  
Author(s):  
Linus Shihora ◽  
Henryk Dobslaw
Keyword(s):  
General Circulation ◽  
A Priori ◽  
Circulation Model ◽  
Ocean General Circulation Model ◽  
Temporal Variations ◽  
Ocean Dynamics ◽  
Global Ocean ◽  
Ocean Bottom ◽  
Data Set ◽  
Priori Information

<p>The Atmosphere and Ocean De-Aliasing Level-1B (AOD1B) product provides a priori information about temporal variations in the Earth's gravity field caused by global mass variability in the atmosphere and ocean and is routinely used as background model in satellite gravimetry. The current version 06 provides Stokes coefficients expanded up to d/o 180 every 3 hours. It is based on ERA-Interim and the ECMWF operational model for the atmosphere, and simulations with the global ocean general circulation model MPIOM consistently forced with the fields from the same atmospheric data-set.</p> <p>We here present preliminary numerical experiments in the development towards a new release 07 of AOD1B. The experiments are performed with the TP10 configuration of MPIOM and include (I) new hourly atmospheric forcing based on the new ERA-5 reanalysis from ECMWF; (II) an improved bathymetry around Antarctica including cavities under the ice shelves; and (III) an explicit implementation of the feedback effects of self-attraction and loading to ocean dynamics. The simulated ocean bottom pressure variability is discussed with respect to AOD1B version 6 as well as in situ ocean observations. A preliminary timeseries of hourly AOD1B-like coefficients for the year 2019 that incorporate the above mentioned improvements will be made available for testing purposes.</p>

Sign in / Sign up

Export Citation Format

Share Document