Observations of oceanic temperature in the upper 400 m reveal decadal signals that propagate in the thermocline along lines of constant potential vorticity from the ventilation region in the central North Pacific to approximately 188N in the western Pacific. The propagation path and speed are well described by the geostrophic mean circulation and by a model of the ventilated thermocline. The ap...

The North Paci c thermocline (250m to 400m) is studied using XBT observations acquired during the 1970s and 1980s. Interannual variations (3-5 year time scales) in thermocline temperature, with O(0.1 C) amplitude at 400m, are found to exhibit westward propagation throughout the extra-tropical North Paci c up to 45N. Southwards of 30N, the features propagate intact across the basin from the east...

In response to a substantial weakening of the Atlantic Meridional Overturning Circulation (AMOC) from a coupled ocean-atmosphere general circulation model experiment significant changes in the interannual variability are found over the tropical Atlantic, characterized by an increase of variance (by ~150%) in boreal late spring-early summer and a decrease of variance (by ~60%) in boreal autumn. ...

The role of tropical Pacific ocean dynamics in regulating the ocean response to thermodynamic forcing is investigated using an ocean general circulation model (GCM) coupled to a model of the atmospheric mixed layer. It is found that the basin mean sea surface temperature (SST) change is less in the presence of varying ocean heat transport than would be the case if the forcing was everywhere bal...

From the early 1970s to the mid-1980s, the main thermocline of the subarctic gyre of the North Pacific Ocean shoaled with temperatures at 200–400-m depth cooling by 18–48C over the region. The gyre-scale structure of the shoaling is quasi-stationary and intensified in the western part of the basin north of 308N, suggesting concurrent changes in gyre-scale transport. A similar quasi-stationary c...

Chemical tracers can be used to assess the simulated circulation in ocean models. Tracers that have been used in this context include tritium, chlorofluorocarbons, natural and bomb-produced radiocarbon, and to a lesser extent, oxygen, silicate, phosphate, isotopes of organic and inorganic carbon compounds, and certain noble gases (e.g., helium and argon). This paper reviews the use of chemical ...

We investigated the effects of large-scale orography on the tropical coupled atmosphere-ocean system over the Indian and Pacific Oceans in northern summer, using the Meteorological Research Institute coupled atmosphere-ocean General Circulation Model (GCM). Six different experiments were conducted with mountain heights of 100%, 80%, 60%, 40%, 20%, and 0% of the standard mountain height. The res...

[1] Changes in dissolved O2 observed across the world oceans in recent decades have been interpreted as a response of marine biogeochemistry to climate change. Little is known however about the spectrum of oceanic O2 variability. Using an idealized model, we illustrate how fluctuations in ocean circulation and biological respiration lead to low-frequency variability of thermocline oxygen. Becau...

The linear temperature trend of the last 40 yr (1955–94) in the upper Pacific Ocean above 400 m is studied using an objectively analyzed dataset and simulations of an ocean general circulation model. Both the data and simulations suggest a warming trend in the western tropical Pacific (108S–108N) near the surface and in the eastern tropical Pacific above 400 m but a cooling trend in the thermoc...

[1] Reconstruction of oceanic nutrient concentrations in the past provides information about nutrient cycling and physical circulation and the role these processes have played in past climate changes. The Cd/Ca and Zn/Ca of benthic foraminifera have been used successfully to reconstruct past deep ocean nutrient concentrations. In this study we test the ability of benthic foraminiferal Cd/Ca and...