Heaving Modes in the World Oceans
Circulation in the world oceans is a complicated system, and it involves the transport of water masses, heat and freshwater in the three dimensional space. To describe such complicated phenomena, many two-dimensional maps, one-dimensional profiles or zero
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Heaving Modes in the World Oceans
4.1
Heaving Induced by Wind Stress Anomaly
4.1.1 Introduction Circulation in the world oceans is a complicated system, and it involves the transport of water masses, heat and freshwater in the three dimensional space. To describe such complicated phenomena, many two-dimensional maps, onedimensional profiles or zero-dimensional indexes have been used. For example, to describe the transport of water mass and heat, the meridional overturning circulation (MOC), the meridional heat flux (MHF), the zonal overturning circulation (ZOC), the zonal heat flux (ZHF) and the vertical heat flux (VHF) have been widely used in previous studies. The thermohaline circulation plays a crucial role in regulating the MOC and MHF; in addition, the quasi-horizontal circulation associated with wind-driven gyres in a stratified ocean also play a role in transporting heat poleward, as discussed in many previous studies, e.g., Schmitz (1996a, b), Ganachaud and Wunsch (2000), Talley et al. (2011), Talley (2013) and Huang (2010). Our discussion in this chapter is focused on the change and transport of heat content in the ocean. The same method can be used to analyze the change and transport of salt (or freshwater) content in the ocean, and the transport of salt is closely related to the hydrological cycle in the ocean.
In a steady state, the MHF is intimately linked to heat transport through the air-sea interface or between water parcels. As such, MHF is directly linked to the diabatic processes in the ocean. The basic pattern of air-sea heat flux and the implied horizontal heat fluxes in the world oceans is shown in Fig. 4.1, based on the annual mean climatology of the GODAS data (Behringer et al. 1998). As shown in Fig. 4.1, the net air-sea heat flux in the world oceans is non-uniformly distributed. The most outstanding features are the strong heat flux into the cold tongues in the equatorial Pacific and Atlantic Oceans, plus the strong heat release to the atmosphere in the Kuroshio, the Gulf Stream and the Labrador Sea. This map implies that ocean currents transport strong heat fluxes in both the meridional and zonal directions. The corresponding strong MHF and ZHF are shown in Fig. 4.1b, c. The MHF in the Northern Hemisphere reaches the maximum value of 1.5 PW (1 PW = 1015 W). Because the world oceans are separated into three major basins, except the periodic channel between 40° S and 70° S, we calculate the ZHF for each basin. The ZHF for each basin is defined as zero at the east most oceanic grid of each basin, and the eastward heat flux is defined as positive. As shown in Fig. 4.1c, in the steady state, there is a huge ZHF in each basin. In both the Pacific and Atlantic Oceans, the ZHF reaches the maximum amplitude of −1.0 and −0.40 PW respectively; whereas the ZHF is positive in the
© Higher Education Press and Springer Nature Singapore Pte Ltd. 2020 R. X. Huang, Heaving, Stretching and Spicing Modes, https://doi.org/10.1007/978-981-15-2941-2_4
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Heaving Modes in the World Oceans
Fig. 4.1 A
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