Claims that forest cutting during the last few decades has contributed significantly to the buildup in atmospheric CO2 have cast doubt on the validity of models used to estimate CO2 uptake by the ocean. In this paper we review the existing models and conclude that the box-diffusion model of Oeschger and his co-workers provides an excellent fit to the average distributions of natural and bomb-produced radiocarbon. We also take the first steps toward a more detailed ocean model which takes into account upwelling in the equatorial zone and deep water formation in the polar zone. The model is calibrated using the distribution of bomb-produced and cosmic ray-produced radiocarbon in the ocean. Preliminary calculations indicate that the fossil fuel CO2 uptake by this model will be greater than that by the box-diffusion model of Oeschger and others (1975) but not great enough to accommodate a significant decline in the mass of the terrestrial biosphere over the past two decades.

The distribution of 14C concentrations in the dissolved inorganic carbon in the surface waters of the Pacific Ocean is shown to have a primarily latitudinal pattern with Δ14C maxima at mid-latitudes in both hemispheres and a minimum at the equator. Oceanographic causes of this phenomenon are discussed.

The characteristics of a one-dimensional vertical advection-diffusion ocean mixing model were examined using temperature, salinity, and bomb 14C measurements made during the GEOSECS program. Vertical advection (W) and eddy diffusion (K) rates for the main oceanic thermocline and CO2 gas exchange rates (E) were determined from the depth distributions of salinity and bomb produced 14C measured in the upper 1000m of the Atlantic and Pacific Oceans. In the Atlantic, the results suggest that vertical diffusion rates are lower in the equatorial region (K = 0.6cm2sec—1) than in the temperate region (K = 1.6cm2sec—1). Upwelling rates were calculated for stations located between about 30° N and 30°S and average 10m yr—1, corresponding to an upward transport of about 10 Sverdrups. Model calculations of the gas exchange rate of CO2 indicate a 2 to 3-fold decrease between temperate latitudes and the equatorial latitudes of the Atlantic. For many of the Pacific GEOSECS stations, the Δ14C depth distribution is distinctly different than in the Atlantic, and cannot be used to calculate unique values of K and W that explain both the salinity and 14C depth distributions.

Additional 14C data from the atmosphere and ocean have been provided since the ninth 14C conference in 1976. At the moment, one sampling station in the troposphere in each hemisphere seems to give sufficient accuracy for exchange studies. The 14C concentration in the troposphere in December 1978 constituted a mean value of 30 ± 1 percent (Δ14C) above normal level, a concentration that has been reduced to about one half during 12 years. 14C measurements have been performed with intervals of 1 to 4 months in the surface water of the Atlantic, Pacific, and Indian Oceans. In addition to the 14C data observed, the salinity and temperature are also measured. Because of earlier objections against storing sea water in steel drums on board ships for months before treatment, the CO2 has now been flushed out immediately after collection. The reliability of previous measurements has been confirmed with 10 parallel samples. 14C concentration in ocean surface on each location shows some seasonal variation due to variable exchange of water with deeper layers.

Nuclear-weapon produced 14C (or bomb 14C) in the ocean can be traced by simultaneous tritium observations. Data are presented on the general relationship of bomb 14C and tritium in the North Atlantic. For the period 1965 to 1973, the excess 14C to tritium ratios in the surface water vary, systematically, over a factor of 10: the ratios monotonically increase with time, and decrease with latitude, particularly so for the later observations. The sub-surface water ratios show that the mid- and low-latitude water below about the 15° C isothermal horizon (~500m depth) originates from higher northern latitudes, rather than being renewed by local vertical mixing. It is further shown that in the North Atlantic, bomb 14C did not penetrate beyond the horizon where the presently observed 14C concentration is Δ14C = —75‰. Observed concentrations up to about —40‰ can be corrected for a bomb contribution if the tritium concentration is known because the bomb 14C to tritium concentration ratio is rather uniform in this range. A surface water 14C concentration versus time curve is presented for the period since 1957. This curve is based on a North Atlantic mixing model and is fitted to the 14C observations. Making use of a previously published tritium versus time curve obtained by the same model, a time curve for the average excess 14C to tritium ratio in North Atlantic surface water is given. This curve reproduces the observations well. The presented data and theoretical curves show the usefulness of simultaneous 14C and tritium observations for mixing studies and to provide corrections for bomb 14C in sub-surface 14C data in the North Atlantic.

The effects of nonconservative sources (inputs) and sinks (outputs) of carbon are indicated by the behavior of Δ14C and δ13C of the total dissolved inorganic carbon (ΣCO2) in San Francisco Bay and Chesapeake Bay. Isotopic distributions and model calculations indicate that in North San Francisco Bay the net CO2 flux to the atmosphere and carbon utilization in the water column are balanced by benthic production. Municipal waste appears to be a dominant source in South San Francisco Bav. In Chesapeake Bay, atmospheric exchange has increased the Δ14C and δ13C in the surface water. Decomposition of organic matter in the water column is indicated to be the dominant source of excess ΣCO2 in the deep water.

Radiocarbon activity of successive parts of Pleistocene and Holocene ooids and mollusk shells from the Persian Gulf, Kuwait, was measured. The inner part of the ooids showed the lowest activity and the cement between grains the highest. Radiocarbon activities correspond to the general stratigraphy and to the position of the sediments. Radiocarbon ages of Pleistocene sediments seem to be very low due to recrystallization of aragonite. Higher radiocarbon activity of cement indicates that atmospheric carbon dioxide was involved in the subaerial diagenetic process. The radiocarbon age of well-preserved mollusk shells seems to be lower than their allegedly Pleistocene geologic age.

The reservoir effect of Scandinavian sea water has been determined by dating seals and whales killed well before man's impact on the natural 14C concentration became significant. The samples were collected at different places along the Swedish coasts and in the Gulf of Finland. They derive from ad 1657 or 1658, 1868, 1875, 1894, and 1906. The EDTA treatment of bones was used to obtain collagen free from contaminants.

An elk, originating from ad 1881 was selected for comparison. A seal from ad 1899 from the Caspian Sea was also included in the investigation.

All results have been normalized to δ13C = —25‰ vs PDB. The determinations yield values of the reservoir effect in agreement with earlier results obtained from shells and mammals. The final results are discussed in light of previous variations of 14C content in the atmosphere. Using a smoother curve, the reservoir effect is slightly smaller than was hitherto believed.

An event thought to be of cosmic origin caused the count rate of both proportional and Geiger counters to increase significantly around December 4, 1978. The correction for this has been studied. The statistics for background, oxalic acid, and unknown samples, measured repeatedly after this correction, were as good as usual.

Rates of CO2 exchange across the air-water interface in oceans and lakes measured to date by the L-DGO group are summarized. They range from 3 to 38 moles/m2/yr. The possible causes for this range include the differences in salinity, mean wind speed, and pH. Wind tunnel studies comparing fresh water and sea water are required before a satisfactory explanation can be found.

14C measurements were carried out on sea water samples collected in 1973, in the Indian ocean. The results obtained for 9 vertical profiles between 27° S and 48°S are presented. In surface water, the bomb 14C content is maximum at middle latitudes. A time lag relative to the north hemisphere bomb 14C delivery is apparent. In the more southern latitudes, 14C content remains very low.

The limits of the statistical evaluation of 14C dates by histograms are discussed. The method of the attempt to establish a global chronology of the short-term eustatic sea-level changes during the Holocene is examined as well as its correlation with the precisely determined Suess wiggles.

During Pleistocene pluvial precipitation was sufficient for the maintenance of groundwater supported lakes and for the accumulation of playa lakes in wind-scoured depressions during the early Holocene pluvial. At places where ground water reaches near to the surface, wells (birs) have been dug and maintained in historic times. These birs have been used as sampling sites for water analyses, including carbon-14 levels, carbon and oxygen stable isotope ratios, tritium concentrations, and chemical data.

All the waters from birs analyzed to date produced apparent radiocarbon ages ranging from late historic to early Holocene, and tritium analyses on some of these indicate no recharge during the Atomic age.

Sources of error for the radiocarbon analyses, including exchange with atmospheric CO2, respiration by plant roots, and contact with carbonates of considerably older age, were evaluated. None of these factors have such an extreme impact on the measurements as to render the result invalid. Two trends revealed by these data are an increase in apparent age from northwest to southwest and with subsequent extractions at the same site where the hand-dug well was bailed out and sampled four times within two days.

We conclude that recharge of shallow ground water occurred in early Holocene time, and some recharge of deeper aquifers may have occurred where infiltration paths permitted. Some recharge occurred in late Holocene (post pluvial) time, but the net trend has been toward hyper-aridity that characterizes the area today.

Shells in beach-ridge and chenier Holocene deposits from the Gulf of Carpentaria, Queensland, have been dated by radiocarbon. Possible contamination of carbonate by post-depositional diagenetic processes, isotopic fractionation, ocean reservoir environmental effect, and association of biological age of sample material with depositional event have been examined in order to validate dating of samples from this environment. A numerical methodology used for comparing ‘groups’ of 14C dates strongly supports morphostratigraphic evidence that time discontinuities occur within both chenier and beach-ridge sequences. Four episodes are recognized in each area, all younger than ca 5800 years ago, the time when sea level reached its postglacial maximum in the Gulf of Carpentaria. To some extent, these episodes are out of phase, reflecting different modes of strandline accumulation.

Detailed radiocarbon chronologies from three volcanic crater lakes (maars) in southeast Australia are examined in relationship to the magnetic mineral stratigraphies within lakes, and the magnetic secular variation stratigraphy between lakes. Some implications for magnetic dating are considered.

Chemical components in a sea sediment core from the Santa Barbara Basin show the same periodic variations as do stable isotope variations in a Japanese cedar.

Within the United States, the State of California ranks first in recorded earthquake frequencies. Annually, thousands of shocks are registered on seismometers and many hundreds are actually noticed directly by Californians. In modern times, about one quake per year, destructive to property, has occurred, yet the very large and disastrous events approaching magnitude 8 and higher on the Richter scale are spaced a few decades apart: 1857 in Southern California centered on Tejon Pass, 1872 in the Owens Valley, and 1906 in San Francisco. Unfortunately, the historical record for earthquakes is short in California when compared with accounts for Europe or China, both of which list quakes over a time period of some 2000 to 3000 years. In California, the first historically noted event dates to barely 200 years ago, when in 1769, members of an expedition of the Spanish explorer Gaspar de Portola were knocked to the ground along the Santa Ana River during a large earthquake.

The loessic deposits along with their palaeosols of the Kashmir Valley have been 14C dated using both organic and carbonate fractions. The 14C dates on both the fractions show good concordance. The 14C dates indicate that the last deglaciation in Kashmir (34° N) already started CA 18,000 ± 1000 BP at CA 1600m and CA 15,000 BP at CA 3000m altitude and thus support the recent global evidence of deglaciation having started several millennia before the Holocene.

Radiocarbon dating of mollusks and barnacles from fossil shoreline deposits in the Persian Gulf and on the coast of Iranian Makran is being used to assess the extent and rate of recent crustal deformation in the area. Samples are selected with the help of x-ray diffraction and of light and scanning electron microscopy; whenever possible, two or more ages are determined for each locality on monospecific samples. Age/height values have been used to compute local uplift rates by allowing for sea-level fluctuations, but eustatic controversy can be avoided by limiting the analysis to fault chronology and to relative vertical movements between dated sections. Short counting times on large, carefully pretreated samples would supply the numerous, cheap, low-resolution ages required to follow up the preliminary results obtained by the survey.

There are extended wind-blown sand territories in the northeastern part of the Great Hungarian Plain. Wind-blown sand migration periods were distineuished by means of radiocarbon age determination of charcoal samples found in the same type of a thin soil layer of chernozem character in different sand dune exposures. The ages of the samples were determined by proportional counter, and are around 12 000 years BP. This thin fossil soil layer, which is regionally spread in the northeast Hungarian wind-blown sand areas, presents a chronological mark between the blown sand forms evolved in the last glacial period and in the Holocene.

An 18O/16O versus 14C age curve was constructed for unrecrystallized Holocene marine shell samples from Israel that were shown to be homogeneous populations. The surprisingly large variation in the oxygen isotopic composition (1.2‰) between 2600 and 4000 years ago is most probably due to variations in the isotopic composition of the water. This implies that either the excess of evaporation over precipitation or the Nile river discharge must have varied significantly during the Holocene.