Time-transgressive North Atlantic productivity changes upon Northern Hemisphere glaciation

• Published in: Paleoceanography
• Main Authors: Lawrence, K., Sigman, D. M., Herbert, T. D., Riihimaki, C. A., Bolton, C. T., Martinez-Garcia, A., Rosell-Melé, A., Haug, G. H.
• Other Authors: Lafayette College Easton, Department of Geosciences Princeton, Princeton University, Brown University, Universidad de Oviedo Oviedo, Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology Zürich (ETH Zürich), Universitat Autònoma de Barcelona (UAB), Institute of Environmental Science and Technology Barcelona (ICTA)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2013
• Subjects: [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography; Pacific; Southern Ocean; North Atlantic
• Online Access: https://hal.archives-ouvertes.fr/hal-01667992; https://hal.archives-ouvertes.fr/hal-01667992/document; https://hal.archives-ouvertes.fr/hal-01667992/file/Lawrence%20et%20al%202013.pdf; https://doi.org/10.1002/2013PA002546

International audience Marine biological export productivity declined in high-latitude regions in the North Pacific and Southern Ocean 2.7 million years ago, in parallel with the intensification of Northern Hemisphere glaciation. Here we present data from the North Atlantic, which show a similar but time-transgressive pattern of high-latitude productivity decline from 3.3 to 2.5 Ma, with productivity decreasing first at 69°N, hundreds of thousands of years before it declined at 58°N. We propose that the cumulative data are best explained by an equatorward migration of the westerly winds, which caused a southward shift in the zone of Ekman divergence and upwelling-associated major nutrient supply over this time interval. We suggest that a similar equatorward migration of the westerly winds may also help explain the productivity changes observed in other high-latitude regions, particularly the Southern Ocean. At 2.7 Ma, equatorial and temperate Atlantic sites began to show orbitally paced productivity pulses, consistent with a shoaling and meridional contraction of the nutrient-poor “warm sphere” that characterizes the low latitude upper ocean. This timing coincides with observed productivity changes in Southern Ocean, consistent with previous findings that the Southern Ocean exerts a strong influence on the fertility of the low-latitude Atlantic. Finally, we propose that the unique basin geometry of the North Atlantic caused deep water formation in this region to remain relatively stable despite equatorward migration of winds and ocean fronts.