Transect Along Equator

Figure 5.5 Left Section across the equatorial Pacific along 150 W between about 6 N and S, showing the distribution of (a) velocity (m s 1 the blue area corresponds to eastward flow) and (b) temperature ( C). Note that the core of the Cromwell Current is in the fhermocline (cf. Figure 5.1 (b)) and that in the region of the core, vigorous mixing causes the isotherms to spread apart (relative to their separation to the north and south), thus weakening the fhermocline. The vertical scale is...

The Heatbudget Equation

Ocean Circulation Distribution Heat

As discussed in Section 1.1. the Earth as a whole not only receives solar radiation, which is largely short-wave, but also re-emits long-wavelength radiation. This is because all bodies with a temperature above absolute zero emit radiation the higher the temperature of the body concerned, the greater the total amount of radiant energy emitted. In fact, the intensity ( ) of the radiation emitted increases in proportion to the fourth power of the absolute temperature (7) i.e. I oT4. This is known...

Summary Of Chapter

1 The global surface current pattern to some extent reflects the surface wind field, but ocean currents are constrained by continental boundaries and current systems are often characterized by gyral circulations. 2 Maps of wind and current flows of necessity represent average conditions only at any one time the actual flow at a given point might be markedly different from that shown. 3 The frictional force caused by the action of wind on the sea-surface is known as the wind stress. Its...

The Action Of Wind On Surface Waters

Figure 3.3 In a surface wave, water particles make orbits in the vertical plane. The particles advance slightly further in the crest (the top of the orbit) than they retreat in the trough (bottom of the orbit), so a small net forward motion (known as 'wave drift') results. In deep water, this motion may be of the order of several millimetres to several centimetres per second. When wind blows over the ocean, energy is transferred from the wind to the surface layers. Some of this energy is...

Atmospheric Circulation In Midlatitudes

Mid Latitude Cyclone Stages

Like the Hadley cells, the low and high pressure centres characteristic of mid-latitudes are a manifestation of the need for heat to be moved polewards, to compensate for the radiation imbalance between low and high latitudes (Figure l .4). Though less spectacular than tropical cyclones, mid-latitude weather systems transfer enormous amounts of heat - a single travelling depression may be transferring 10-100 times the amount of heat transported by a tropical cyclone. If, in the long term, no...

The Role Of Long Waves In Ocean Circulation

Surface Waves Ocean Circulation

The changes in the slopes of the sea-surface and thermocline along the Equator in the Indian Ocean, mentioned in Section 5.2.2, occur surprisingly fast. Exactly how fast the ocean can respond to seasonal changes in the wind has been studied in the simpler and steadier Atlantic, where the stress of the South-East Trade Winds across the equatorial ocean causes the sea-surface to slope up towards the west, and the thermocline to slope down (cf. Figure 5.3). In the Atlantic, the South-East Trades...

The Equatorial Undercurrent

The Equatorial Undercurrent (Figures 5.1(b) and 5.2) is a major feature of equatorial circulation. Such an undercurrent occurs in all three oceans, although it is only a seasonal feature in the Indian Ocean. Equatorial Undercurrents flow from west to east, below the direct influence of the wind, yet they arc w ind-driven. How can this be The effect of the wind is transmitted downwards to deeper layers via turbulence (eddy viscosity) and is mainly confined to the mixed surface layer above the...

The Global Thermohaline Conveyor

In the 1980s, Wallace Broecker suggested that the fluxes of heat and freshwater around the globe in ocean currents and water masses could be viewed as a kind of 'thermohaline conveyor belt' (Figure 6.41 ). This was not intended to be a realistic picture of warm and cold currents (although it is sometimes wrongly interpreted as such), but is a representation of the overall effect of warm and cold currents on the vertical circulation within the ocean. Its usefulness lies in the fact that because...