Jim Salinger

Tracking the extent of the South Pacific Convergence Zone since the early 1600s

(1) The South Pacific Convergence Zone (SPCZ) is the largest and most persistent spur of the Intertropical Convergence Zone. At the southeastern edge of the SPCZ near 170� W and 15� -20� S a surface ocean salinity frontal zone exists that separates fresher Western Pacific Warm Pool water from saltier and cooler waters in the east. This salinity front is known to shift east and west with the phase of the El Nino Southern Oscillation. We have generated subannually resolved and replicated coral oxygen isotopic time series from Fiji (17� S, 179� E) and Rarotonga (21.5� S, 160� W) that have recorded interannual displacements of the salinity front over the last 380 years and also indicate that at lower frequencies the decadal mean position of the salinity front, and eastern extent of the SPCZ, has shifted east-west through 10� to 20� of longitude three times during this interval. The most recent and largest shift began in the mid 1800s as the salinity front progressively moved eastward and salinity decreased at both sites. Our results suggest that sea surface salinity at these sites is now at the lowest levels recorded and is evidence for an unprecedented expansion of the SPCZ since the mid 1800s. The expansion of the SPCZ implies a gradual change in the South Pacific to more La Nina-like long-term mean conditions. This observation is consistent with the ocean thermostat mechanism for the Pacific coupled ocean-atmosphere system, whereby exogenous heating of the atmosphere would result in greater warming in the western Pacific and a greater east-west surface temperature gradient. Components: 8034 words, 7 figures, 2 tables.

Dendroclimatic interpretation of tree-rings in Agathis australis (kauri): 2. Evidence of a significant relationship with ENSO

Part 1 of this investigation (Buckley et al 2000) found consistent significant correlations between tree growth and climate for nine New Zealand kauri tree‐ring chronology sites The nature of these correlations suggests that Agathis australis (kauri) may carry a useful signal of the El Nino‐Southern Oscillation (ENSO) phenomenon We have explored the potential of kauri tor ENSO reconstruction through statistical analysis of the relationship between the Southern Oscillation Index (SOI) and the tree ring indices previously derived Results showed a consistent SOI‐kaun growth relationship for eight of the nine sites A significant negative correlation was found between kauri growth and concurrent seasonal mean SOI, and a positive correlation with the seasonal mean SOI recorded over the preceding two years The former is consistent with a hypothesised ENSO‐kaun growth model, but the two‐year lag suggests an additional relationship, perhaps associated with kauri phenology Decadal‐scale variability was evident in the strength of the SOI‐kaun growth relationships, particularly in autumn (March‐May) and winter (June‐August) Comparison of SOI and extreme kauri growth years indicated general consistency in the growth response to ENSO, but also identified some anomalies, suggesting that kauri ring‐width is an imperfect ENSO proxy However, combined with the spatial scale at which ENSO operates, and the known variability of links with regional climates, we conclude that kauri growth‐rings could provide a useful ENSO proxy, particularly within the context of multi‐proxy spatially distributed studies

Dendroclimatic interpretation of tree‐rings in Agathis australis (kauri). 1. Climate correlation functions and master chronology.

In this paper we analyse nine existing Agathis australis (kauri) chronologies for their response to climate, and compare our results with those of previous studies We update the southernmost chronology, from Katikati, which now extends to the 1997 growth ring (1997–98 growing season in Southern Hemisphere) We also employ recent standardisation procedures that have been demonstrated to eliminate the chance of biasing the chronology indices Climate correlation functions are generated for all nine kauri chronologies, by correlating chronology indices with meteorological datasets In an earlier study only a 12 month response window was analysed, combined with lagging the growth year in order to account for prior‐season growth response Our expanded dendroclimatic response window covers the 21 months from May of the year of growth (t), back to the previous September (year t ‐ 1) There are consistent significant correlations with climate for all nine kauri sites, most pronounced in the form of a positive response in season t to precipitation in the previous season (t ‐ 1), and an inverse response to temperature in the year of growth The most robust climate signal comes from the Katikati chronology, which has been updated by 16 years to the 1997 growth ring The additional years allow for more degrees of freedom and a better estimate of the climate correlation functions Correlation and Principal Component Analyses validate the combining of eight of the nine chronologies into one regional time series The results presented in this paper are encouraging for future dendroclimatic research with Agathis australis, towards the goal of long‐term reconstruction of climate

Meningococcal disease and meteorological conditions in Auckland, New Zealand

Objective: The purpose of the study was to explore and model the relationship between meteorological variables and meningococcal disease notifications in Auckland during an ongoing group B meningococcal disease epidemic.