Terrigenous input and marine productivity for the Pacific sector of the Southern Ocean based on lipid biomarkers

In this study, we present a new multiproxy data set of terrigenous input, marine productivity and sea surface temperature (SST) from 52 surface sediment samples collected along E-W transects in the Pacific sector of the Southern Ocean. Allochtonous terrigenous input was characterized by the distribution of plant wax n-alkanes and soil-derived branched glycerol dialkyl glycerol tetraethers (brGDGTs). 230Th-normalized burial rates of both compound groups were highest close to the potential sources in Australia and New Zealand and are strongly related to lithogenic contents, indicating common sources and transport. Detection of both long-chain n-alkanes and brGDGTs at the most remote sites in the open ocean strongly suggests a primarily eolian transport mechanism to at least 110°W, i.e. by prevailing westerly winds. Two independent organic SST proxies were used, the UK'37 based on long-chain alkenones, and the TEX86 based on isoprenoid GDGTs. Both, UK'37 and TEX86 indices show robust relationships with temperature over a temperature range between 0.5 and 20°C, likely implying different seasonal and regional imprints on the temperature signal. While alkenone-based temperature estimates reliably reflect modern SST even at the low temperature end, large temperature residuals are observed for the polar ocean using the TEX86 index. 230Th-normalized burial rates of alkenones are highest close to the Subtropical Front and are positively related to lithogenic fluxes throughout the study area. In contrast, highest isoGDGT burial south of the Antarctic Polar Front is not related with dust flux but may be largely controlled by diatom blooms, and thus high opal fluxes during austral summer.本研究构建了一套全新的多代用指标数据集，涵盖陆源输入、海洋生产力与海表温度（SST）数据，其数据来源于南大洋太平洋海域沿东西向断面采集的52个表层沉积物样品。外源陆源输入以植物蜡正构烷烃与土壤来源的支链甘油二烷基甘油四醚（brGDGTs）的分布特征为表征依据。两类化合物经230钍校正的埋藏速率在澳大利亚与新西兰的潜在源区附近最高，且与陆源碎屑含量显著相关，表明二者具有共同的源区与搬运机制。在开阔大洋最偏远的站位也检测到了长链正构烷烃与brGDGTs，这强烈表明其主要通过风成搬运机制，至少可抵达110°W，即借助盛行西风实现搬运。本研究采用两种独立的有机海表温度代用指标：基于长链烯酮的UK'37指标，以及基于类异戊二烯甘油二烷基甘油四醚（isoprenoid GDGTs）的TEX86指标。UK'37与TEX86指标在0.5~20℃的温度范围内均与温度呈现显著相关关系，这可能意味着二者在温度信号上存在不同的季节与区域印记。尽管基于烯酮的温度估算结果即使在低温端也能可靠反映现代海表温度，但使用TEX86指标在极地海洋中则会观测到较大的温度残差。长链烯酮经230钍校正的埋藏速率在亚热带锋（Subtropical Front）附近最高，且在整个研究区均与陆源碎屑通量呈正相关。与之相反，南极极锋（Antarctic Polar Front）以南的类异戊二烯甘油二烷基甘油四醚（isoGDGTs）埋藏率峰值与粉尘通量无显著关联，其主要受硅藻水华控制，因此在南大洋夏季呈现高蛋白石通量。