A review of modern coral delta O-18 and Delta C-14 proxy records

摘要

This paper is a review of published modem coral delta O-18 and Delta C-14 isotopic records that are at least 30 and 20 years long, respectively. The data are presented to show basin-scale trends in both of these proxy records on decadal-to-centennial timescales. The goal was to qualitatively integrate the general inter-annual-to-centennial timescale variability revealed in these data, as well as the statistical and modeling output results that have been produced using these coral records. While many review papers typically include a representative subset of the data available, this review aims to include as much of the available data as possible. In general, coral delta O-18 records show a long-term warming and/or freshening throughout the tropical oceans, and agree with the NOAA Extended Reconstruction Sea Surface Temperature 2 (ERSST) on decadal timescales. hi the western Pacific, it is most likely a freshening of the seawater delta O-18 that dominates the signal. El Nino Southern Oscillation (ENSO) variability dominates Most delta O-18 records either by varying local seawater temperature or salinity, depending on the regional oceanography/climatology. Outside of the Pacific, ENSO affects seawater temperature and salinity via atmospheric or oceanic teleconnections. Post-bomb coral Delta C-14 records collectively show that the uptake of Delta C-14 has been greatest in gyrewater fed sites, followed in descending order by western boundary current areas, equatorial upwelling regions, and eastern tropical Pacific upwelling sites. These surface waterd C-Delta 14 values indicate the proportion of surface water and/or the residence time of water at the surface at a given location, and can be used to model water mass mixing rates. Such models have only begun to be run and show that the amount of eastern Pacific water entering the central South Pacific increases during El Ninos and that the Indonesian throughflow is supplied year-round by the North Pacific. Comparing ocean circulation models with coral Delta C-14-modelled circulation enables researchers to explore the mechanisms that drive seawater, Delta C-14 variability and fine-tune their models. In addition, our comparison between the rate of coral Delta C-14 increase between 1960 and 1970 and total anthropogenic CO2 uptake rates show general agreement demonstrating the value of coral records in understanding past carbon fluxes. Overall, coral delta O-18 and Delta C-14 proxy records represent natural archives of seawater conditions and are critical for studying the natural variability in local and regional patterns within, and teleconnection patterns between, the tropics, extra-tropics, temperate, and Polar Regions on intra-annual-to-centennial timescales. (c) 2006 Elsevier B.V. All rights reserved.