Sea surface density gradients in the Nordic Seas during the Holocene as revealed by paired microfossil and isotope proxies
| Autor: | Henning A. Bauch, Nicolas Van Nieuwenhove, Claude Hillaire-Marcel, Anne de Vernal |
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| Rok vydání: | 2016 |
| Předmět: |
Convection
Buoyancy 010504 meteorology & atmospheric sciences Paleontology Pelagic zone engineering.material 010502 geochemistry & geophysics Oceanography 01 natural sciences Isotopes of oxygen 13. Climate action Climatology Potential density engineering Seawater 14. Life underwater Surface water Geology Holocene 0105 earth and related environmental sciences |
| Zdroj: | Paleoceanography. 31:380-398 |
| ISSN: | 0883-8305 |
| DOI: | 10.1002/2015pa002815 |
| Popis: | We attempt to assess the Holocene surface-subsurface seawater density gradient on millennial time scale based on the reconstruction of potential density (σθ) by combining data from dinoflagellate cyst assemblages and planktic foraminiferal (Neogloboquadrina pachyderma (s)) stable oxygen isotopes (δ18Oc). Following several calibration exercises, the likeliness of favorable seasonal preconditioning to open ocean convection is evaluated. The reconstructed σθ values reveal unfavorable conditions for vertical convection in the western Nordic Seas prior to ~7–6.5 ka B.P., with a westward increase and persistence of surface water buoyancy. Active overturning became more likely after 6.5 ka B.P. as suggested by a reduced and recurrently inverted vertical σθ gradient, while intermittent eastward spreading of lower density surface waters continued to modulate the area of potential overturning. Despite some reservation regarding the accuracy of the σθ values reconstructed, the documentation of relative changes of σθ gradients through time and space is suggested as a helpful tool for the appraisal of past overturning likeliness. |
| Databáze: | OpenAIRE |
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