浮游有孔虫壳体重量的古海洋学应用

Paleoceanographic applications of planktonic foraminiferal shell weights

海洋沉积物中浮游有孔虫壳体重量同时受到上层海洋钙化过程和深海碳酸钙溶解作用的影响,是一种潜在的古海洋代用指标。基于全球大洋表层沉积物的指标现代过程校准,发现当深海碳酸根离子饱和度<20μmol·kg-1,溶解作用开始显著影响浮游有孔虫壳体重量。易溶种的壳体重量对碳酸根离子饱和度的响应更加敏感,可以作为可靠的深海碳酸根离子饱和度代用指标。当深海碳酸根离子饱和度>20μmol·kg-1,浮游有孔虫壳体重量可反映其钙化程度。基于该指标的古海洋学研究揭示了冰期旋回中浮游有孔虫钙化过程主要响应海水碳酸盐系统和温度变化;上新世以来太平洋深海碳酸根离子饱和度演化主要受控于海平面、南大洋冰盖/海冰和全球温盐环流变化。浮游有孔虫壳体重量指标为探索海洋碳循环演化提供了有力工具。

The shell weights of planktonic foraminifera from marine sediments are influenced by both upper-ocean calcification and deep-ocean calcium carbonate dissolution,and are potential paleoceanographic proxies.Based on the global surface-sediment calibrations,dissolution begins to significantly affect planktonic foraminiferal shell weight when the deep-ocean carbonate ion saturation degree(CISD)is below 20μmol·kg^(−1).The shell weights of dissolution-susceptible species are more sensitive to CISD changes,and thus can be used as reliable deepocean CISD proxies.When the deep-ocean CISD is above 20μmol·kg^(−1),the shell weights of planktonic foraminifera can reflect the changes of their calcification degree.Previous paleoceanographic studies based on the shell weight proxies reveal that the calcifications of planktonic foraminifera mainly respond to the changes in seawater carbonate system and temperature during glacial-interglacial cycles.The evolutions of deep Pacific CISD since the Pliocene is controlled by the changes in sea level height,Southern Ocean ice-sheet/sea ice,and global thermohaline circulation.The planktonic foraminiferal shell weight proxy provides a powerful tool for exploring the evolution of ocean carbon cycle.