A band of enhanced thermocline variability at 108–158N in the Pacific found in nature also occurs in an ocean general circulation model forced with observed fluxes of momentum, heat, and freshwater over the period 1958– 97. The variability in the model is primarily associated with long baroclinic Rossby waves characterized by periods in the decadal range (7–10 yr). The waves are forced by westw...

We have generated a high-resolution coral D14C record from the southwest subtropical Pacific spanning the last 50 yr. Prebomb (1950–1956) D14C values average -52‰. Values begin to increase in 1957, reaching a maximum in the early 1970s, about 10 yr after the atmospheric peak. There is a consistent 10-15‰ seasonal cycle whose relationship with vertical mixing evolves as a consequence of the pene...

The thermohaline hysteresis response to varying North Atlantic freshwater forcing is studied by means of a three-dimensional global ocean general circulation model (OGCM). The influence of vertical diffusivity is examined using a wide range of mixing coefficients. For sufficiently large vertical diffusivity the model shows a pronounced hysteresis behavior, so that two equilibrium states of the ...

The Eastern North Pacific Subtropical Mode Water (ESTMW) is a water mass of low potential vorticity (PV) and appears as a weak pycnostad or thermostad. Distinct from other subtropical mode waters, it forms in the absence of a deep winter mixed layer. The formation mechanism of this ESTMW is investigated using an ocean general circulation model that is forced by monthly climatological temperatur...

Ocean general circulation models (OGCMs) are important tools for climatological research. These models approximate the solution to the governing equations to predict horizontal velocity components, temperature, salinity, and other chosen parameters. The GFDL OGCM, or Modular Ocean Model (MOM), is an example of such a code. This code was originally developed at the Geophysical Fluids Dynamics La...

A method to initialize an ensemble, introduced by Evensen (Physica, D 77:108–129, 1994a; J Geophys Res 99(C5):10143–10162, 1994b; Ocean Dynamics 53:343–367, 2003), was applied to the Ocean General Circulation Model (OGCM) HYbrid Coordinate Ocean Model (HYCOM) for the Pacific Ocean. Taking advantage of the hybrid coordinates, an initial ensemble is created by first perturbing the layer interface...

Most of the Southern Ocean (SO) is marginally stably stratified and thus prone to enhanced convection and possibly bottom-water formation whenever the upper ocean is cooled or made more saline by ice formation. Sea ice modifies the heat and freshwater fluxes, which in turn constitute a critical surface condition in this sensitive region of intense vertical exchange. The authors investigate the ...

The authors report an interdecadal oscillation in a windand thermally-driven ocean general circulation model (OGCM). The oscillation is tantalizing in that it occursunder a relatively strong thermal damping(26.3 W m-2K-’). Examinations involving a two-dimensional OGCM, a simple thermal ‘flip-flop’ model, and a three-dimensional OGCM with and without the nonlinear effect of temperature in the st...

The possibility of generating decadal ENSO variability via an ocean teleconnection to the midlatitude Pacific is studied. This is done by analyzing the sensitivity of the equatorial stratification to midlatitude processes using an ocean general circulation model, the adjoint method, and a quasigeostrophic normal-mode stability analysis. It is found that, on timescales of 2–15 yr, the equatorial...

The properties of water mass transformation in a semi-enclosed basin, separated from the open ocean by a sill and subject to surface cooling, are analyzed both theoretically and numerically using an ocean general circulation model. This study extends previous studies of convection in a marginal sea to the case with a sill. The sill has a strong impact on both the properties of the dense water f...