Land-ocean interface

Historically many oceanographers have considered the land-ocean boundary to lie at the mouth of an estuary, and some view it as being at the head of an estuary (or, said another way, at the mouth of the river). A more holistic view of the land-ocean interface, however, might include the river basins that drain into the estuary. This rather unconventional view of the land-sea interface is particularly important when considering the impact of short- and medium-term changes in land use and climate, and how they may affect the coastal and global ocean. 

Cai, W.J., Wang, Z.A., and Wang, Y. (2004) The role of marsh-dominated heterotrophic continental margins in transport of CO2 between the atmosphere, the land-sea interface and the ocean. Lirnnol. Oceanogr. 49, 348-354. 

Romero, O.E., Dupont, L., Wyputta, U., Jahns, S., and Wefer, G (2003) Temporal variability of fluxes of eolian-transported freshwater diatoms, phytoliths, and pollen grains off Cape Blanc as reflection of land-atmosphere-ocean interface in northwest Africa. J. Geophys. Res. 108, 3153. 

An important block of the MBWB is the methods of determination of various parameters of the water cycle. Such methods are based on the use of surface, satellite, and airborne measurements. The MBWB used as a global model makes it easier to understand the role of the oceans and land in the hydrological cycle, to identify the main factors that control it, as well as to trace the dynamics of its interaction with plants, soil, and topographic characteristics of the Earth surface. It is based on the interaction between the elements of the water cycle, and takes natural and anthropogenic factors into account by means of information interfaces with other units of the global model (Krapivin and Kondratyev, 2002). 

Estuaries and the mouths of large river systems are located at an important interface between land and ocean where terrestrially derived materials can be altered before entering continental shelves. Continental shelves provide an estimated net CO2 sink of 0.1 Pg C y 1 (lPg = 1015g), with an export that may be as much as 20% of the oceanic biological pump (Liu et al., 2000). Unfortunately, ocean margins have only recently started to receive the appropriate attention they deserve in the context of their importance in the global C budget (Bauer and Druffel, 1998 Liu et al., 2000) (more details on this in chapter 16). 

Estuaries and the mouths of large river systems are located at an important interface between land and ocean where terrestrially derived materials can be altered before entering continental shelves. 

As we discussed in Chapter 5 the activities of the two isotopes would be in secular equihbrium in a closed system, which is the case for Rn and Ra within the ocean s interior away from the air-water interface. At the surface, however, Rn escapes to the atmosphere because its activity in the marine atmosphere far from land is very low. Exchange to the atmosphere creates a deficit in the activity of Rn relative to the activity of Ra in the surface ocean, which is proportional to the rate of gas exchange across the air-water interface. 

Water soluble inorganic zinc species are predominant in the global ocean waters. It has been calculated that 90% of suspended and 35% of solnble riverine zinc are deposited at the ocean-land interface (Lisitsin et al, 1983). It leads to the annual accumulation of 0.6 X 10 tons ofZn in suspension and abontO.5 x 10 tons in soluble form in the pelagic part of the ocean. The average concentration of solnble Zn in the global marine waters is abont 5 /xg/L, with relevant amonnt in ocean water of 6, 800 x 10 tons. The suspended Zn amonnt is not estimated qnantitatively yet. 

Several important studies have examined the transfer of P between terrestrial and marine environments (e.g., Froelich 1988, Berner and Rao 1994, Ruttenberg and Goni 1997), but more work clearly needs to be done to quantify the interactions between dissolved and particulate P forms and the aquatic/marine interface. The net pre-human flux of dissolved P to the oceans is 1 Tg P/year, with an additional 1-2 Tg P/year of potentially soluble P, bringing the total to about 2-3 Tg P/year. Thus, the residence time of biologically available P on land is about 40-60 kyr with respect to export to the oceans. It may be no coincidence that this residence time is of a glacial timescale—later I discuss the control of climate on the terrestrial P cycle. But clearly, the interaction between biologically available P on land and loss of this P to the oceans is relatively dynamic and speaks to the relatively rapid cycling of P on land. 

The coastal interface between land masses and the ocean is an important area of environmental activity. The land along this boundary is under constant attack from... 

Figure 17.10 Cross section of the ocean/land interface along a beach.

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