Oceans circulation/currents

Extrapolation of this model calculation to the future climate warming suggests that an amplification of the current rate of increase in atmospheric CO2 content could result from climate-induced changes in ocean circulation rates. 

In this section we briefly review what controls the density of seawater and the vertical density stratification of the ocean. Surface currents, abyssal circulation, and thermocline circulation are considered individually. 

As a result of these factors (wind, Ekman transport, Coriolis force) the surface ocean circulation in the mid-latitudes is characterized by clockwise gyres in the northern hemisphere and the counterclockwise gyres in the southern hemisphere. The main surface currents around these gyres for the world s oceans are shown in Fig. 10-6. The regions where Ekman transport tends to push water together are called convergences. Divergences result when surface waters are pushed apart. 

Two areas of focus within oceanography today are physical and chemical oceanography. Physical oceanography is the study of ocean basin stractures, water and sediment transportation, and the interplay between ocean water, air and sediments and how this relationship effects processes such as tides, upwellings, temperature, and salinity. Findings aid oceanic engineers, coastal planners, and military defense strategists. Current areas of research include oceanic circulation—especially ocean... 

Chemical d5mamics and mechanisms of reactions in the ocean-atmosphere system on time scales equal to and less than that of ocean circulation are evaluated by stud5nng the distribution of chemical compounds within the sea. In order to understand the processes controlling the chemical distributions and their rates, one must know something about how the ocean circulates. The following brief descriptive overview describes the main wind-driven and thermohaline current distributions. 

Surface ocean currents respond primarily to the climatic wind field. The prevailing winds supply much of the energy that drives surface water movements. This becomes clear when charts of the surface winds and ocean surface currents are superimposed. The wind-driven circulation occurs principally in the upper few hundred meters and is therefore primarily a horizontal circulation, although... 

Fig. 3.3 (a) Generalized atmospheric pressure, wind and precipitation patterns on an ocean-covered Earth (n. b. sphere is elongated to aid clarity of wind patterns), (b) Idealized major oceanic surface current systems in the Pacific and Atlantic oceans. The Coriolis effect is responsible for disruption of the meridional circulation cells between 30 and 60° in (a). 

The potential negative feedbacks tend to stabilize atmospheric C02 and 02 concentrations in the long term. However, the processes represented by boxes in Fig. 6.5 are the result of tectonic activity and so are not controlled by feedbacks. They have the potential to disrupt the carbon cycle severely, as considered in Section 6.3. As indicated in Fig. 6.5, oceanic circulation can influence the C cycle in complex ways via its influence on climate, through its impact on heat distribution over the surface of the Earth and the rate and net direction of C02 exchange with the atmosphere. Similarly, continental relief and distribution have an effect on the climate through their influence on winds and currents. All these factors are investigated in Section 6.3.1. 

Currents in the Sound are due to the tidal stream, to the estuarine circulation, and to wind stress acting on the water surface. Systematic surveys of the currents in the Sound have been made from time to time by the U.S. National Ocean Survey. Current meters have been placed in grid-pattern arrays for time intervals sufficiently long to reveal the principal tidal constituents of the current. Data obtained this way were used by G. A. Riley (1952, 1956) to describe the estuarine circulation of the Sound. The utility of these meter records in the study of sediment transport is limited because the observations were all made during the... 

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