Global variations of surface ocean productivity in low and mid latitudes: influence on C0$_2$ reservoirs of the deep

• Published in: Paleoceanography
• Main Authors: Sarnthein, Michael, Winn, Kyaw, Duplessy, Jean-Claude, Fontugne, Michael
• Other Authors: Christian-Albrechts University of Kiel, Centre des Faibles Radioactivités, Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 1988
• Subjects: [SDU.OCEAN]Sciences of the Universe [physics]/Ocean; Atmosphere; [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces; environment; Sea ice
• Online Access: https://hal.science/hal-03543888; https://hal.science/hal-03543888/document; https://hal.science/hal-03543888/file/Paleoceanography%20-%20June%201988%20-%20Sarnthein%20-%20Global%20variations%20of%20surface%20ocean%20productivity%20in%20low%20and%20mid%20latitudes%20.pdf; https://doi.org/10.1029/PA003i003p00361

International audience Based on detailed reconstructions of global distribution patterns, both paleoproductivity and the benthic δ13C record of CO$_2$, which is dissolved in the deep ocean, strongly differed between the Last Glacial Maximum and the Holocene. With the onset of Termination I about 15,000 years ago, the new (export) production of low- and mid-latitude upwelling cells started to decline by more than 2-4 Gt carbon/year. This reduction is regarded as a main factor leading to both the simultaneous rise in atmospheric CO$_2$ as recorded in ice cores and, with a slight delay of more than 1000 years, to a large-scale gradual CO$_2$ depletion of the deep ocean by about 650 Gt C. This estimate is based on an average increase in benthic δ13C by 0.4–0.5‰. The decrease in new production also matches a clear 13C depletion of organic matter, possibly recording an end of extreme nutrient utilization in upwelling cells. As shown by Sarnthein et al., [1987], the productivity reversal appears to be triggered by a rapid reduction in the strength of meridional trades, which in turn was linked via a shrinking extent of sea ice to a massive increase in high-latitude insolation, i.e., to orbital forcing as primary cause.