Over the past decade it has become apparent that the atmosphere is a significant pathway for the transport of many natural and pollutant materials from the continents to the ocean. The atmospheric input of many of these species can have an impact (either positive or negative) on biological processes in the sea and on marine chemical cycling. For example, there is now evidence that the atmosphere may be an important transport path for such essential nutrients as iron and nitrogen in some regions. In this report we assess current data in this area, develop global scale estimates of the atmospheric fluxes of trace elements, mineral aerosol, nitrogen species, and synthetic organic compounds to the ocean; and compare the atmospheric input rates of these substances to their input via rivers. Trace elements considered were Pb, Cd, Zn, Cu, Ni, As, Hg, Sn, Al, Fe, Si, and P. Oxidized and reduced forms of nitrogen were considered, including nitrate and ammonium ions and the gaseous species NO, NO2, HNO3, and NH3. Synthetic organic compounds considered included polychlorinated biphenyls (PCBs), hexachlorocyclohexanes (HCHs), DDTs, chlordane, dieldrin, and hexachlorobenzenes (HCBs). Making this assessment was difficult because there are very few actual measurements of deposition rates of these substances to the ocean. However, there are considerably more data on the atmospheric concentrations of these species in aerosol and gaseous form. Mean concentration data for 10° × 10° ocean areas were determined from the available concentration data or from extrapolation of these data into other regions. These concentration distributions were then combined with appropriate exchange coefficients and precipitation fields to obtain the global wet and dry deposition fluxes. Careful consideration was given to atmospheric transport processes as well as to removal mechanisms and the physical and physicochemical properties of aerosols and gases. Only annual values were calculated. On a global scale atmospheric inputs are generally equal to or greater than riverine inputs, and for most species atmospheric input to the ocean is significantly greater in the northern hemisphere than in the southern hemisphere. For dissolved trace metals in seawater, global atmospheric input dominates riverine input for Pb, Cd, and Zn, and the two transport paths are roughly equal for Cu, Ni, As, and Fe. Fluxes and basin‐wide deposition of trace metals are generally a factor of 5‐10 higher in the North Atlantic and North Pacific regions than in the South Atlantic and South Pacific. Global input of oxidized and reduced nitrogen species are roughly equal to each other, although the major fraction of oxidized nitrogen enters the ocean in the northern hemisphere, primarily as a result of pollution sources. Reduced nitrogen species are much more uniformly distributed, suggesting that the ocean itself may be a significant source. The global atmospheric input of such synthetic organic species as HCH,PCBs, DDT, and HCB completely dominates their input via rivers.

Based on the results obtained in the East China Sea, we propose a new term, Continental Shelf Pump, as a mechanism for the absorption of atmospheric CO2. We investigated the carbonate system of the East China Sea along a single observation line traversing its central part on 5 cruises in various seasons. The directly observed fugacity of CO2 dissolved in the surface water decreased with decreasing salinity and temperature as well as nutrient content. The relation has been expressed as a simple equation of these 3 parameters. Putting the observed data on the parameters in the various parts of the East China Sea in various months into this equation, we have obtained 55 ± 5 ppm as an annual mean fugacity deficit of CO2 in the surface water of the East China Sea, which nearly equals the directly measured mean fugacity along the observation line. The net absorption flux estimated from the fugacity deficit has agreed with the amount of carbonate transported out of the East China Sea calculated for the distributions of total dissolved carbonate and alkalinity. The distributions of density and total dissolved carbonate reveal the cause of this large deficiency, described as follows. The shallower shelf zone is more cooled than the open sea when heat is lost from the surface. This cooling produces denser water, which together with photosynthetic activity, accelerates the absorption of CO2 in the shelf zone. The absorbed CO2 is transformed to organic carbon and regenerated especially at the shallow bottom. Isopycnal mixing (advection and diffusion) transports the denser coastal water, especially the bottom water enriched in dissolved and particulate carbon, into the subsurface layer of the open oceans. The transport continues in the layer below the pycnocline even in the warm season and maintains the low fugacity of CO2 in the surface water of the shelf zone. This is the continental shelf pump. The pump would account for a net oceanic uptake of CO2 of 1 GtC/ yr, if the world continental shelf zone would absorb the atmospheric CO2 at the rate observed in the East China Sea.

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As part of a cooperative effort of the Joint Global Ocean Flux Study (JGOFS) and of the World Ocean Circulation Experiment (WOCE) program, we have measured total CO 2 (TCO 2) and total alkalinity (TA) along three sections in the northern Indian Ocean. One section through the Gulf of Aden to the Arabian Sea is parallel to the coast of Yemen. One section is across the Arabian Sea along the nominal 9N latitude and the other section is across the Bay of Bengal along the nominal 10N latitude. The measurements were performed on board R/V Knorr in September-October 1995. The primary purpose of this work is to understand the penetration of anthropogenic CO 2 along these ocean sections. Here, we present a novel approach to the calculation of anthropogenic CO 2 in the ocean based upon the fundamentals of water-sources mixing. Consequently, we rst describe the observations and mixing of water-sources before we describe the quanti cation of anthropogenic CO 2 concentrationsin these waters. The data show large spatial variations in surface seawater of both total CO 2 (up to 50 µmol kg 2 1) and total alkalinity (up to 40 µmol kg 2 1). The variations are mainly associated with physical processes characterized by water masses of different temperature and salinity. For example, at depths we observed low TCO 2 concentration at longitude 54E 6 2E associated with the low-salinity water mass owing northward. The contrasts between the sections across the Arabian Sea and the Bay of Bengal emphasize the large property differences between the two ocean basins. Multiparametric analyses on the data clearly show the relative contributions of different water-sources in each of the ocean sections. The mixing coefficients calculated from the multiparametric analyses are further used to quantify anthropogenic CO 2 concentrations in each water-source. The results indicate that the surface water-sources contain 47.8, 42.1 and 50.4 µmol kg 2 1 in the Gulf of Aden, the Arabian Sea and the Bay of Bengal, respectively. In the surface waters there is slightly more anthropogenic CO 2 across the Bay of Bengal than across the Arabian Sea. In contrast, anthropogenic CO 2 has penetrated signi cantly deeper in the Gulf of Aden than in the Arabian Sea and in the Bay of Bengal.

Enrichment of I relative to Cl and Br in the air, in rain, and in river waters has long been known. To understand this enrichment, experiments were performed to examine the possibility of free evaporation of I from the surface of sea water. The experimental results showed that I can ‘vaporize’ because of the oxidation of iodide ions to free I in sea water under irradiation by solar light of wavelength up to about 560 mμ. On the basis of these results, the rate of I escape can be estimated to be 4×1011 g/yr for the whole ocean surface. This value is in fairly good agreement with the global rate of I deposition in rain.