Oceans surface

Sinks, chemical species, or method OH, reaction with OH radical S, sedimentation P, precipitation scavenging NO, reaction with NO radical uv, photolysis by ultraviolet radiation Sr, destmction at surfaces O, adsorption or destmction at oceanic surface. 

One form of solar heat does offer interesting possibilities and is refeiTcd to as OTEC (Ocean-Thermal Energy Conversion). The OTEC power plant principle uses the solar heat of ocean surface water to vaporize ammonia as a working fluid in a Rankine cycle. After the fluid is expanded in the turbine, it is condensed by the 22°C colder... 

Ocean thermal energy conversion (OTEC) power plants generate electricity by exploiting the difference in temperature between warm water at the ocean surface and colder waters found at ocean depths. To effectively capture this solar energy, a temperature difference of 35°F or more between surface waters and water at depths of up to 3,000 feet is required. This situation can be found in most of the tropical and subtropical oceans around the world that are in latitudes between 20 degrees north and 20 degrees south. 

There are three potential types of OTEC power plants opcii-cyclc, closed-cycle, and hybrid systems. Open-cycle OTEC systems exploit the fact that water boils at temperatures below its normal boiling point when it is under lower than normal pressures. Open-cycle systems convert warm surface water into steam in a partial vacuum, and then use this steam to drive a large turbine connected to an electrical generator. Cold water piped up from deep below the oceans surface condenses the steam. Unlike the initial ocean water, the condensed steam is desalinated (free of salt) and may be collected and used for drinking or irrigation. 

Wave size is determined by wind speed and fetch, the distance over the oceans surface which the wind travels. Favorable wind energy sites are generally western coastlines facing the open ocean such as the Pacific Coast of North America and the Atlantic Coast of Northern Europe. Norway, Denmark, Japan, and the United Kingdom are the world leaders in wave energy technologies. 

Carbon in living organic matter in the ocean surface layer. 

The rate of evaporation of water from the ocean surface to the atmosphere. 

The turnover time of carbon in biota in the ocean surface water is 3 x 10 /(4 + 36) x lO yr 1 month. The turnover time with respect to settling of detritus to deeper layers is considerably longer 9 months. Faster removal processes in this case must determine the turnover time respiration and decomposition. 

An important example of non-linearity in a biogeochemical cycle is the exchange of carbon dioxide between the ocean surface water and the atmosphere and between the atmosphere and the terrestrial system. To illustrate some effects of these non-linearities, let us consider the simplified model of the carbon cycle shown in Fig. 4-12. Ms represents the sum of all forms of dissolved carbon (CO2, H2CO3, HCOi" and... 

The flux of particles in the other direction, deposition on the ocean surface, occurs intermittently in precipitation (wet deposition) and more continuously as a direct uptake by the surface (dry deposition). These flux densities may be represented by a product of the concen-... 

Many hydrologic reservoirs can be further subdivided into smaller reservoirs, each with a characteristic turnover time. For example, water resides in the Pacific Ocean longer than in the Atlantic, and the oceans surface waters cycle much more quickly than the deep ocean. Similarly, groundwater near the surface is much more active than deep reservoirs, which may cycle over thousands or millions of years, and water frozen in the soil as permafrost. Typical range in turnover times for hydrospheric reservoirs on a hillslope scale (10-10 m) are shown in Table 6-4 (estimates from Falkenmark and Chapman, 1989). Depths are estimated as typical volume averaged over the watershed area. 

On the average, the air over roughly half of the Earth s surface has an upward velocity and half has a downward velocity. This frontal activity (Section 7.5.3) and the interactions of marine air with the cold ocean surface result in about half of the Earth being covered by clouds and half being clear. As will be discussed in Chapter 17, this large fractional cloud cover is extremely important to the Earth s climate because it controls the planetary albedo (reflectivity). 

Besides these features, the formation of a layer due to an interaction of a stratified fluid with light is itself noteworthy. Analogs to this phenomenon can be found in other media. Examples include photochemical reactions in the atmosphere near the Earth s surface, photochemical reactions in the surface water of the ocean and biological activity near the ocean surface. 

The ocean surface represents the master base level for continental erosion and sedimentation. 

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. 

Over 20% of the world s open ocean surface waters are replete in light and major nutrients (nitrate, phosphate, and silicate), yet chlorophyll and productivity values remain low. These so-called "high-nitrate low-chlorophyll" or HNLC regimes (Chisholm and Morel, 1991) include the sub-arctic North Pacific (Martin and Fitzwater, 1988 Martin et al, 1989 Miller et al, 1991), the equatorial Pacific (Murray et al, 1994 Fitzwater et al, 1996) and the southern Ocean (Martin et al.,... 

Fig. 10-15 Organic carbon fluxes with depth in the water column normalized to mean annual primary production rates at the sites of sediment trap deployment. The undulating line indicates the base of the euphotic zone the horizontal error bars reflect variations in mean annual productivity as well as replicate flux measurements during the same season or over several seasons vertical error bars are depth ranges of several sediment trap deployments and uncertainities in the exact depth location. (Reproduced with permission from E. Suess (1980). Particulate organic carbon flux in the oceans - surface productivity and oxygen utilization, Nature 288 260-263, Macmillan Magazines.)...

Oceanic surface waters are efficiently stripped of nutrients by phytoplankton. If phytoplankton biomass was not reconverted into simple dissolved nutrients, the entire marine water column would be depleted in nutrients and growth would stop. But as we saw from the carbon balance presented earlier, more than 90% of the primary productivity is released back to the water column as a reverse RKR equation. This reverse reaction is called remineralization and is due to respiration. An important point is that while production via photosynthesis can only occur in surface waters, the remineralization by heterotrophic organisms can occur over the entire water column and in the underlying sediments. 

Oceanic circulation. The process of ocean circulation described earlier yields an ocean circulation pattern that results in progressively older deep water as the water passes, in sequence from the Atlantic, Indian, to the Pacific Ocean. Surface water returns relatively quickly to the place of origin for the deep water. 

Emerson, S., Quay, P., Karl, D. et al. (1997). Experimental determination of the organic carbon flux from open-ocean surface waters. Nature 389, 951-954. 

Suess, E. (1980). Particulate organic carbon flux in the oceans-surface productivity and oxygen utilization. Nature 288, 260-263. 

Oceanic surface water is everywhere supersaturated with respect to the two solid calcium carbonate species calcite and aragonite. Nevertheless carbonate precipitation is exclusively controlled by biological processes, specifically... 

Fig. 11-24 Carbon-14 in the troposphere and the ocean surface water 1962-1981. values for ocean surface water during this period range from 0-15% with no trend over time. (Modified with permission from R. Nydal and K. Lovseth (1983). Tracing bomb in the atmosphere. /. Geophys. Res. 88, 3621-3642, American Geophysical Union.)...

The definition of turnover time is total burden within a reservoir divided by the flux out of that reservoir - in symbols, t = M/S (see Chapter 4). A typical value for the flux of non-seasalt sulfate (nss-SOl"") to the ocean surface via rain is 0.11 g S/m per year (Galloway, 1985). Using this value, we may consider the residence time of nss-S04 itself and of total non-seasalt sulfur over the world oceans. Appropriate vertical column burdens (derived from the data review of Toon et ai, 1987) are 460 fxg S/m for nss-801 and 1700 jig S/m for the sum of DMS, SO2, and nss-S04. These numbers yield residence times of about 1.5 days for nss-S04 and 5.6 days for total non-seasalt sulfur. We might infer that the oxidation process is frequently... 

Figure 13-5 is the box model of the remote marine sulfur cycle that results from these assumptions. Many different data sets are displayed (and compared) as follows. Each box shows a measured concentration and an estimated residence time for a particular species. Fluxes adjoining a box are calculated from these two pieces of information using the simple formula, S-M/x. The flux of DMS out of the ocean surface and of nss-SOl back to the ocean surface are also quantities estimated from measurements. These are converted from surface to volume fluxes (i.e., from /ig S/(m h) to ng S/(m h)) by assuming the effective scale height of the atmosphere is 2.5 km (which corresponds to a reasonable thickness of the marine planetary boundary layer, within which most precipitation and sulfur cycling should take place). Finally, other data are used to estimate the factors for partitioning oxidized DMS between the MSA and SO2 boxes, for SO2 between dry deposition and oxidation to sulfate, and for nss-SO4 between wet and dry deposition. 

We begin our analysis by comparing the surface fluxes. According to the indicated partitioning factors, 74% of the 11 Mg DMS-S/m /h emitted from the ocean surface should be returned as nss-SO in rain. This leads to a predicted wet deposition flux of nss-SO of 8.1 Mg S/(m /h), which is 37% lower than the measured flux of 13 Mg S/(m /h). Since the estimated accuracy of the DMS emission flux is 50% (Andreae, 1986), this is about as good agreement as can be expected. It indicates that our "closed system" assumption is at least a reasonable first approximation. (A more sophisticated treatment would consider sulfur oxida-... 

Table 16-2 presents what might be termed the minimum set of constituents that must be considered in the case of cloud/rainwater. If we consider the amount of water, L, to be fixed by atmospheric physical processes, the minimum number of input components that can vary are SO2, NH3, CO2, and whatever solute is present from the CCN, often one or another sulfate compound between H2SO4 and (NH4)2S04. Occasionally, salt particles from the ocean surface may be sufficiently abundant to provide enough solute to influence the pH via the inherent alkalinity of seawater, and we will consider that as a second, somewhat more complicated possibility. 

Jouzel, J., Merlivat, L., and Lorius, C. (1982). Deuterium excess in an East Antarctic ice core suggests higher relative humidity at the oceanic surface during the last glacial maximum. Nature 299, 688-691. 

Besides, these measurements allow us to determine an elevation of the geoid, quite ocean surface, over the reference ellipsoid. The idea of this method is very... 

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