The Antarctic area produces bottom waters that ventilate the vast majority of the deep basins in the rest of the world ocean. The rate of formation in the source area and the strength of these cold bottom waters affect their flow toward the equator and are key factors affecting the Global Thermohaline Circulation during modern and past climate conditions. We present the results of a multidisciplinary study carried out on a core collected in 2377m of water depth on the slope off the Drygalski Basin (Ross Sea), along the modern path of the bottom waters. The goal of this research is to detect a qualitative signal of possible changes in the rate of bottom water production during the Late Pleistocene-Holocene by integrating micropaleontological and geochemical variables. The micropaleontological signal is represented by the quantitative and qualitative variations of the agglutinated benthic foraminifera assemblages, while the amount of TOC, nitrogen, ?13C, ?15N, CaCO3 in the sediment, along with the total rock and clay mineralogy, provide information on the paleoproductivity and allow reconstruction of changes in the paleocirculation. The chronology is supported by 14C AMS datings on organic matter. The agglutinated benthic foraminifera assemblage shows several oscillations clearly visible in the total number of specimens within a general increasing trend upward. The strong dominance of Trochammina multiloculata may reflect selected dissolution of other more delicate organically-cemented species; however, the concurrent oscillations of the total number of specimens suggests the switch in of the path of the more corrosive bottom waters. These oscillations are generally paralleled by other variables, among which TOC and nitrogen, indicating increased productivity during the positive peaks of the total number of forams, in turn suggesting open marine conditions and/or more efficient CDW upwelling.
Bottom water production variability in the ross sea slope during the late pleistocene-holocene as revealed by benthic foraminifera and sediment geochemistry
Asioli A;Langone L;Giannossi ML;Summa V;Tateo F;Ridente D;Trincardi F
2008
Abstract
The Antarctic area produces bottom waters that ventilate the vast majority of the deep basins in the rest of the world ocean. The rate of formation in the source area and the strength of these cold bottom waters affect their flow toward the equator and are key factors affecting the Global Thermohaline Circulation during modern and past climate conditions. We present the results of a multidisciplinary study carried out on a core collected in 2377m of water depth on the slope off the Drygalski Basin (Ross Sea), along the modern path of the bottom waters. The goal of this research is to detect a qualitative signal of possible changes in the rate of bottom water production during the Late Pleistocene-Holocene by integrating micropaleontological and geochemical variables. The micropaleontological signal is represented by the quantitative and qualitative variations of the agglutinated benthic foraminifera assemblages, while the amount of TOC, nitrogen, ?13C, ?15N, CaCO3 in the sediment, along with the total rock and clay mineralogy, provide information on the paleoproductivity and allow reconstruction of changes in the paleocirculation. The chronology is supported by 14C AMS datings on organic matter. The agglutinated benthic foraminifera assemblage shows several oscillations clearly visible in the total number of specimens within a general increasing trend upward. The strong dominance of Trochammina multiloculata may reflect selected dissolution of other more delicate organically-cemented species; however, the concurrent oscillations of the total number of specimens suggests the switch in of the path of the more corrosive bottom waters. These oscillations are generally paralleled by other variables, among which TOC and nitrogen, indicating increased productivity during the positive peaks of the total number of forams, in turn suggesting open marine conditions and/or more efficient CDW upwelling.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
