ALKENONES AND ALKENES IN SURFACE WATERS AND SEDIMENTS OF THE SOUTHERN-OCEAN - IMPLICATIONS FOR PALEOTEMPERATURE ESTIMATION IN POLAR-REGIONS

The concentration of C-37-C-39 long-chain alkenones and alkenes were d etermined in surface water and surface sediment samples from the subpo lar waters of the Southern Ocean. Distributions of these compounds wer e similar in both sample sets indicating little differential degradati on between or within compound classes. The relative amounts of the tri - to tetra-unsaturated C-37 alkenones increased with increasing temper ature for temperatures below 6 degrees C similar to the di- and tri-un saturated C-37 alkenones. The C-37 di-, tri-, and tetra-unsaturated me thyl alkenones are used in paleotemperature calculations via the U-37( K) and the U-37(K') ratios. In these datasets, the relative abundances of the C-37:2 and the C-37:3 alkenones as a proportion of the total C -37 alkenones were opposite and strongly related to temperature (the l atter with more scatter), but the abundance of the C-37:4 alkenone sho wed no relationship with temperature. The original definition of U-37( K) includes the abundance of 37:4 in both the numerator and denominato r, and thus it is perhaps not surprising that there is considerable sc atter in the values obtained for U-37(K) at low temperatures. Of the t wo, we suggest that U-37(K') is the better parameter for use in paleot emperature estimations, even in cold locations. U-37(K') values in the sediments fall on virtually the same regression line obtained for the water column samples of Sikes and Volkman (1993), indicating that the ir calibration is suitable for use in Southern Ocean sediments. The co mparison of water column data with sedimentary temperature estimates s uggests that the alkenone distributions are dominated by contributions from the summer when the biomass of Emiliania huxleyi and presumably flux to the sediment, is expected to be high. Copyright (C) 1997 Elsev ier Science Ltd.