| Abstract: | A quantitative analysis of 37 radiolarian species in 58 deep-sea surface-sediment samples from the subtropical to the polar regions of the Indian Ocean produced four geographically distinct faunal assemblages (transitional, antarctic, subtropical, subantarctic). Geographic distributions of these assemblages coincide with present-day patterns of sea-surface temperature and water masses. The antarctic factor is almost exclusively found south of today's Antarctic Polar Front. Highest concentrations of the transitional factor are recorded at sites positioned between today's Subtropical Convergence and the Polar Front. The subtropical factor is dominant in sites north of today's Subtropical Convergence.Values of these four faunal assemblages in the surface-sediment samples were regressed onto present-day summer and winter temperatures of the surface waters overlying each of the core-top sites. Resulting transfer functions yield temperature estimates which compare favorably with observed (present-day) summer and winter sea-surface temperatures, with low standard errors of estimate (< ± 1.9°C) and no clear geographic pattern in maps of the residuals (difference between observed and estimated sea-surface temperature). |
