Five radiocarbon analyses were performed on 5 different sources within Soreq Cave, which was used as a model for the Judea Group Aquifer of Israel (pMC q0 ). The transit time of rainwater through the roof of the cave to sources within it had been determined with tritium. From this information, the year of deposition of rain on the roof of the cave, which later appeared in one of the sources, was estimated and the atmospheric 14C concentration at that time was ascertained (pMC a0 ). The parameter Q = pMC q0 / pMC a0 was found to be Q = 0.60 ± 0.04. This makes it possible to calculate the age of water in any well in the Judea Group Aquifer of Israel by measuring its 14C concentration (pMC qt ) by use of the decay equation and applying Q.

The radiocarbon concentration of dissolved inorganic carbon in groundwater is most logically and completely represented as the product of 5 time-variable factors; these are mutually independent, and all must be considered and evaluated to determine a groundwater residence time. In the case of one factor, the 14C/(12C+13C) ratio of atmospheric CO2, its time variability can be side-stepped by assuming it to be constant at the pre-bomb 1950 value, and assigning an apparent half-life in the radioactive decay term. Apparent half-lives are calculated here for 5 separate periods extending back to 24,000 BP, working from the INTCAL98 atmospheric calibration. This approach can be extended further back in time when the necessary atmospheric calibrations are updated with greater certainty. The procedure is applied to the recently-explored Wairau Deep Aquifer, underlying central areas of the coastal Wairau Plain, Marlborough. The evolution of dissolved inorganic carbon concentration for this river-recharged groundwater is apparent from distinct trends in 13C, and is confirmed by hydrochemical modelling. Extension to the 14C concentrations yields minimum/maximum limits for groundwater residence times to 3 wells. In all 3 cases, the maximum is uncertain due to present uncertainty of the apparent half-life applicable before 24,000 BP. Residence times for the 2 wells closest to the recharge area are at least 17,400 yr, while that for a well further down the aquifer is at least 38,500 yr. Recharge, therefore, occurred during the Otiran glaciation, while the present-day near-surface fluvioglacial deposits of the Wairau Plain were accumulating. Drawdown-recovery records over 3 yr indicate a permeable connection to compensating recharge, enabling limited exploitation for vineyard irrigation.

Radiocarbon, 18O, and chemical concentrations have been used to identify groundwater recharged during the last ice age near Nelson, New Zealand. Moutere Gravel underlies most of the Moutere Depression, a 30-km-wide system of valleys filled with Plio-Pleistocene gravel. The depression extends northwards into Tasman Bay, which was above sea level when the North and South Islands of New Zealand were connected during the last glaciation. The aquifers are tapped by bores up to 500 m deep. Shallow bores (50–100 m) tap “pre-industrial” Holocene water (termed the “modern” component) with 14C concentrations of 90 ± 10 percent modern carbon (pMC) and δ18O values of −6.8 ± 0.4, as expected for present-day precipitation. Deeper bores discharge water with lower 14C concentrations and more negative 18O values resulting from input of much older water from depth. The deep end-member of the mixing trend is identified as paleowater (termed the “glacial” component) with 14C concentration close to 0 pMC and more negative 18O values (-7.6). Mixing of the modern and glacial components gives rise to the variations observed in the 14C, 18O, and chemical concentrations of the waters. Identification of the deep groundwater as glacial water suggests that there may be a large body of such water onshore and offshore at deep levels. More generally, the influence of changing sea levels in the recent past (geologically speaking) on the disposition of groundwaters in coastal areas of New Zealand may have been far greater than we have previously realized.

In Quebrada de los Burros in coastal southern Peru (Tacna department), human settlements containing shells and charcoal deposits have been excavated since 1995. The sea surface 14C reservoir ages, estimated by calculating the difference of 14C age between marine shells and terrestrial organic materials, exhibit high values during the lower and middle Holocene and decrease abruptly after 4000 cal BP. The increase of reservoir age at around 7000–8000 cal BP suggests an enhancement of Peruvian coastal upwelling intensity and changes in ocean circulation at intermediate depth.

A total of 294 beachrock samples were collected from 116 sites on 15 islands in the Nansei Islands chain, southwestern Japan, and were radiocarbon dated. The beachrocks began to form at about 6900 BP and some are still under development in the islands. Values of isotope fractionations of different materials making up the beachrocks ranged between +9.4‰ and −5.7‰. Isotope fractionations outside the range of 0 ± 2‰ suggest that these beachrocks were strongly influenced by underground water and running freshwater when they were cemented. The sea level during the late Holocene has remained the same for at least the past 5000 yr, except for several uplifted coasts.

Paired radiocarbon and 230Th/U dating was performed on 13 surface corals from submerged reefs in the Marquesas and from raised terraces in Vanuatu. The absolute ages of the corals analyzed ranged from 3000 to 15,000 cal yr. Estimates of the difference between the absolute and 14C ages of these corals are in agreement with previous determinations up until 11,500 cal yr. The resulting mean sea surface reservoir age R is determined at 390 ± 60 yr for the Marquesas region (9°S), which is slightly higher than the R value at 280 ± 50 yr for the Tahiti Islands (18°S). Multiple 14C analyses of 2 corals from the Marquesas present scattered 14C ages at ~12,000 and ~15,100 cal yr. This could be attributed to rapid changes of the 14C content of surface waters around the Marquesas Islands or to a subtle submarine diagenesis.

Results are presented of radiocarbon and tritium measurements along a transect between the Australian continental shelf and the Indonesian coast of Bali. The stations lie in the easternmost part of the Indian Ocean, close to the sills over which the Indonesian throughflow (ITF) makes its way to the Indian Ocean. The present data, obtained as part of the Java-Australia Dynamics Experiment (JADE) in August 1989, complement the WOCE 14C and tritium data set on both sides of the Indonesian archipelago and give us the opportunity to discuss the origin of the water masses and timescale of the throughflow. Both tracers point to a north equatorial Pacific origin of the waters. The comparison of the tritium inventories in the Pacific North Equatorial Current and along the JADE transect suggests a minimum transit time of the waters across the Indonesian seaways of the order of 5 to 6 yr, corresponding to a throughflow <18 × 106 m3/s.

In the framework of the Worldwide Marine Radioactivity Studies (WOMARS) project, water profile samples for radiocarbon measurements were taken during the IAEA'97 cruise at 10 stations in the southwestern North Pacific Ocean. While 14C concentrations were rapidly decreasing from the surface (Δ14C about 100‰) down to about 800 m at all visited stations (Δ14C about −200‰), the concentrations below 1000 m were almost constant. Some stations were in proximity to the GEOSECS stations sampled in 1973; thus, 14C profiles could be compared after a 24-yr interval. Generally, 14C concentrations had decreased in surface waters (by 50–80‰) and increased (by about the same amount) in intermediate waters when compared with GEOSECS data. In deep waters (below 1000 m), the observed 14C concentrations were similar to GEOSECS values. The bomb-produced 14C inventory had increased by more than 20% over the 24 yr from 1973 to 1997 and was estimated to be about (32 ± 5) 1012 atom m-2, with an annual 14C flux of (1.3 ± 0.3) 1012 atom m-2 yr-1. The results suggest that bomb-produced 14C has been advected northwards by the Kuroshio Current and the Kuroshio Extension and stored in the intermediate layer as North Pacific Intermediate Water.

Twenty-two annually banded samples of coral from 1977 to 1998 were collected from Daya Bay, South China Sea, and bomb 14C concentrations were determined. The interannual variation of coral Δ14C is controlled mainly by oceanic factors. In ENSO years, the coastwise upwelling current of the South China Sea has been intensified; hence, the coral Δ14C displays its minimum value. The interannual variation curve of Δ14C in coral bears a relationship with the Southern Oscillation Index (SOI) curves: the correlation coefficient between Δ14C and (SOI)w is 0.43 and the correlation coefficient between Δ14C and (SOI)y is 0.27. The coral Δ14C has no remarkable response to the variation of solar radiation energy. In the past 20 yr or so, the general situation and oceanic thermal structure of the South China Sea are still stable even though interannual variations in atmosphere-sea interaction and upwelling current driven by the tropical energy have occurred.

Known-age corals from the Cocos (Keeling) Islands, Indian Ocean, have been analyzed by accelerator mass spectrometry (AMS) for radiocarbon to determine marine reservoir age corrections. The ΔR value for the Cocos (Keeling) Islands is 66 ± 12 yr based on the analyses undertaken for this study. When our AMS and previously published dates for Cocos are averaged, they yield a ΔR of 64 ± 15 yr. This is a significant revision of an earlier estimate of the ΔR value for the Cocos (Keeling) Islands of 186 ± 66 yr (Toggweiler et al. 1991). The (revised) lower ΔR for the Cocos (Keeling) Islands is consistent with GEOSECS 14C data for the Indian Ocean, and previously published bomb 14C data for the Red Sea, Gulf of Aden, and Cocos Islands. The revised ΔR is also close to values for the eastern Indian Ocean and adjacent seas. These suggest surface waters that reach the Cocos Islands might be partly derived from the far western Pacific, via the Indonesian throughflow, and might not be influenced by the southeast flow from the Arabian Sea.

We assessed the evidence for variations in the marine radiocarbon reservoir effect (MRE) at coastal, archaeological Iron Age sites in north and west Scotland by comparing AMS measurements of paired marine and terrestrial materials (4 pairs per context). ΔR values were calculated from measurements on material from 3 sites using 6 sets of samples, all of which were deposited around 2000 BP. The weighted mean of the ΔR determinations was −79 ± 17 14C yr, which indicates a consistent, reduced offset between atmospheric and surface ocean 14C specific activity for these sites during this period, relative to the present day (ΔR = ∼0 14C yr). We discuss the significance of this revised ΔR correction by using the example of wheelhouse chronologies at Hornish Point and their development in relation to brochs. In addition, we assess the importance of using the concepts of MRE correction and ΔR variations when constructing chronologies using 14C measurements made on materials that contain marine-derived carbon.

Lake sediments have the potential to preserve proxy records of past climate change. Organic material suitable for radiocarbon dating often provides age control of such proxy records. Six shallow freshwater lakes on the sub-Antarctic island of South Georgia were investigated for carbon reservoir effects that may influence age-depth profiles from lake sediment records in this important region. Paired samples of particulate organic matter (POM) from the water column and surface sediment (bulk organic carbon) were analyzed by accelerator mass spectrometry 14C. POM in 4 lakes was found to be in equilibrium with the atmosphere (~107% modern), whereas 2 lakes showed significant depletion of 14C. In each lake, the surface sediment ages were older than the paired POM age. Surface sediment ages showed a much greater range of ages compared to the equivalent POM ages, even for lakes located in close proximity. We conclude that sediment disturbance during coring, bioturbation, and periodic resuspension of sediments are likely factors causing the difference in the apparent age of surface sediments.

Radiocarbon (Δ14C) measurements of monthly samples from a Galapagos surface coral are among the first data sets from the new Keck Carbon Cycle Accelerator Mass Spectrometry laboratory at the University of California, Irvine. An average Δ14C value of −62 is obtained for 144 measurements of samples from monthly coral bands that lived from about AD 1760–1771 (±6 yr). High Δ14C values were found during January through March, when upwelling was weak or absent at the Galapagos Islands. Low Δ14C values were obtained mid-year during strong upwelling. The average seasonal variability of Δ14C was 15–25, which is greater than that at other tropical and subtropical locations in the Pacific Ocean because of intense seasonal upwelling at this site. Periods of sustained high Δ14C values were found during 1762–1763 and 1766. A spectral analysis revealed that the spectral density for the Δ14C data displays most of its variance at the 5-yr cycle, which is reflective of El Niño periodicity during the 20th century.

In this study, we aim to characterize the main processes controlling 14CDIC concentrations in porewater at the shallow shelf (water depth less than 120 m) off the Mediterranean coast of Israel. At these water depths, we expected to find evidence for seawater penetration toward the coast, since this area was flooded by seawater only some 18,000 yr ago (the end of the Last Glacial period).

Measurements of the chemical composition (14CDIC) and stable carbon isotopic composition (δ13CDIC) were performed in several sediment cores (40–250 cm long) at water depths between 6 and 115 m. At water depths of 60 m, represented by a 2.5-m-long sediment core, the porewater 14CDIC levels (85–87 pMC) were lower than the corresponding sediment values in each layer (92–95 pMC), mainly due to the oxidation of relatively old organic matter (about 70 pMC) with no evidence to advection. In contrast, sediment cores from water depths shallower than 50 m showed only slight anaerobic oxidation and high 14CDIC values of approximately 100 pMC, indicating possible downward advection. These geochemical observations support the perception that the penetration of seawater into the coastal aquifer occurs at the shallow water zone (<50 m), while further verification by deeper cores is required.

A coral radiocarbon (Δ14C) investigation with a high time-resolution is crucial for reconstructing secular and seasonal Δ14C changes in the surface seawater which potentially reflect ocean circulations and dynamic ocean-atmosphere interactions. The Δ14C values of a modern coral (Porites sp.) from Kikai Island, southern Japan, in the subtropical northwestern Pacific, were determined for the period of 1991-1998 at a monthly resolution. A coral Δ14C time series for the 8 yr indicated seasonal cycles superimposed on a secular decreasing trend of 3.8 per yr. The seasonal amplitude of the coral Δ14C was about 18 on the average, and the minimum Δ14C was observed in late spring and summer. The Δ14C changes were tentatively explained by horizontal oceanic advections around Kikai Island or over the wide range of the equatorial and sub-equatorial Pacific.

The Holocene Dead Sea and the late Pleistocene Lake Lisan were characterized by varying radiocarbon reservoir ages ranging between 6 and 2 ka in the Dead Sea and between 2 ka and zero in Lake Lisan. These changes reflect the hydrological conditions in the drainage system as well as residence time of 14C in the mixed surface layer of the lake and its lower brine. Long-term isolation of the lower brine led to 14C decay and an increase in the reservoir age. Yet, enhanced runoff input with atmospheric 14C brings the reservoir age down. The highest reservoir age of 6 ka was recorded after the sharp fall of the Dead Sea at ~8.1 ka cal BP. The lower reservoir age of zero was recorded between 36 and 32 ka cal BP, when the Lake Lisan mixed layer was frequently replenished by runoff.

We measured radiocarbon in an annually-banded coral core collected from Con Dao Island, Vietnam, 90 km from the mouth of the Mekong River, and estimated the regional correction of the marine reservoir age (ΔR value). Twelve samples were continuously taken from the annual bands (AD 1949–1960) which were clearly identified under UV light (∼352 nm) as well as by X-radiography. The 14C content of the samples was determined using an accelerator mass spectrometer at the National Institute for Environmental Studies, Tsukuba, Japan. Results provide a Δ14C time series showing a relatively steady value of −48.6 ± 4.6‰ for the period of 1949–1955 and an abrupt increase starting from 1956 that indicates a quick response to the atmospheric testing of nuclear bombs. Using the prebomb 14C data, the ΔR value in the south of Vietnam is estimated to be −74 ± 39 yr.

The analysis of both paleo- and archeomagnetic data and magnetic properties of continental and marine sediments has shown that around 2700 BP, the geomagnetic Sterno-Etrussia excursion took place in 15 regions of the Northern Hemisphere. The study of magnetic properties of sediments of the Barents, Baltic, and White Seas demonstrates that the duration of this excursion was not more than 200–300 yr.

Paleoclimatic data provide extensive evidence for a sharp global cooling around 2700 B P. The causes of natural climate variation are discussed. Changes of the galactic cosmic ray intensity may play a key role as the causal mechanism of climate change. Since the cosmic ray intensity (reflected by the cosmogenic isotope level in the earth's atmosphere) is modulated by the solar wind and by the terrestrial magnetic field, this may be an important mechanism for long-term solar climate variability. The Sterno-Etrussia excursion may have amplified the climate shift, which, in the first place, was the effect of a decline of solar activity. During excursions and inversions, the magnetic moment decreases, which leads to an increased intensity of cosmic rays penetrating the upper atmosphere. Global changes in the electromagnetic field of the earth result in sharp changes in the climate-determining factors in the atmosphere, such as temperatures, total pressure field, moisture circulation, intensity of air flows, and thunderstorm activity. In addition, significant changes in the ocean circulation patterns and temperature regimes of oceans will have taken place.

Concentrations of 10Be in ice cores and marine sediments exhibit 2 peaks with significant enhancements at 35,000 and 60,000 BP. This radioisotope is produced in the upper atmosphere by spallation of cosmic-ray protons and secondary neutrons on atmospheric nitrogen and oxygen. Previously suggested explanations for the increases include geomagnetic field reversals, a decrease in solar activity, and a supernova explosion. We propose an alternative explanation which involves a change in the galactic environment of the solar system. The structure of the heliosphere is investigated for a period when the Sun enters a cold, dense, unmagnetized interstellar cloud. Under these conditions, the heliosphere contracts to 25% its present size, significantly affecting galactic cosmic ray modulation and increasing anomalous cosmic ray fluxes. A tenfold increase in anomalous cosmic ray flux and a twofold increase in galactic cosmic ray intensity at Earth are possible in this high-density case if heliosheath modulation is reduced. We show that this increase in galactic cosmic ray intensity could be responsible for the peaks in 10Be records.

We review the reasons for change in paleoecological conditions and their effects on different cultures at the beginning and during the Holocene period in western Hungary using radiocarbon data combined with paleoecological and paleolimnological results. Two sites were investigated in the southern and northern part of the ancient bay of Balaton Lake: Keszthely-Úsztatómajor and Főnyed I. 14C dating of 2 core samples represented a chronology from 11,000 cal BC to 2000 cal BC (10,700 BP to 3700 BP) and from 6200 cal BC to 1200 cal BC (7300 BP to 3000 BP), respectively. A relatively constant inverse sediment accumulation rate was observed in both cases (23 yr/cm and 33 yr/cm, respectively). In the case of Főnyed I, a sharp break was observed in the sedimentation curve around 6000–4800 cal BC (6000 BP). Changes in the vegetation due to human activity were observed in a larger extent only at the end of Late Neolithic, with the most significant changes detected in the landscape coinciding with the presence of Lengyel III culture in the region. The appearance of higher amounts of pollen of cereals at the sites proved the presence of crop cultivation. However, the role of plant cultivation may have been limited for the ancient inhabitants of the Kis-Balaton region due to a limited amount of soil suitable for agriculture and due to the extensive water table. Further changes in vegetation were observed during the Late Copper Age (Baden culture) and the period of Early and Middle Bronze Age, respectively. Signs of forest clearing during the period have not been detected and the increased peak of Fagus indicates climatic change. The low intensity of anthropogenic activity should not be attributed to geographic isolation.