The onset of modern-like Atlantic meridional overturning circulation at the Eocene-Oligocene transition; evidence, causes, and possible implications for global cooling

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doi: 10.1002/2017GC006826
Author(s): Abelson, Meir; Erez, Jonathan
Author Affiliation(s): Primary:
Israel Geological Survey, Jerusalem, Israel
Hebrew University, Israel
Volume Title: Geochemistry, Geophysics, Geosystems - G<sup>3</sup>
Source: Geochemistry, Geophysics, Geosystems - G>3`, 18(6), p.2177-2199. Publisher: American Geophysical Union and The Geochemical Society, United States. ISSN: 1525-2027
Note: In English. 107 refs.; illus., incl. 1 table, sketch map
Summary: A compilation of benthic δ18O from the whole Atlantic and the Southern Ocean (Atlantic sector) shows two major jumps in the interbasinal gradient of δ18O (Δδ18O) during the Eocene and the Oligocene: one at ∼40 Ma and the second concomitant with the isotopic event of the Eocene-Oligocene transition (EOT), ∼33.7 Ma ago. From previously published circulation models and proxies, we show that the first Δδ18O jump reflects the thermal isolation of Antarctica associated with the proto-Antarctic circumpolar current (ACC). The second marks the onset of interhemispheric northern-sourced circulation cell, similar to the modern Atlantic meridional overturning circulation (AMOC). The onset of AMOC-like circulation slightly preceded (100-300 kyr) the EOT, as we show by the high-resolution profiles of δ18O and δ13C previously published from DSDP/ODP sites in the Southern Ocean and South Atlantic. These events coincide with the onset of antiestuarine circulation between the Nordic seas and the North Atlantic which started around the EOT and may be connected to the deepening of the Greenland-Scotland Ridge. We suggest that while the shallow proto-ACC supplied the energy for deep ocean convection in the Southern Hemisphere, the onset of the interhemispheric northern circulation cell was due to the significant EOT intensification of deepwater formation in the North Atlantic driven by the Nordic antiestuarine circulation. This onset of the interhemispheric northern-sourced circulation cell could have prompted the EOT global cooling. Abstract Copyright (2017), . American Geophysical Union. All Rights Reserved.
Year of Publication: 2017
Research Program: DSDP Deep Sea Drilling Project
IPOD International Phase of Ocean Drilling
ODP Ocean Drilling Program
Key Words: 12 Stratigraphy, Historical Geology and Paleoecology; Angola Basin; Antarctic Circumpolar Current; Antarctica; Atlantic Meridional Overturning Circulation; Atlantic Ocean; Atlantic region; Bay of Biscay; Blake Nose; Blake Plateau; C-13/C-12; Cantabria Seamount; Cape Basin; Carbon; Cenozoic; Climate change; Convection; Cooling; DSDP Site 119; DSDP Site 360; DSDP Site 366; DSDP Site 384; DSDP Site 401; DSDP Site 522; DSDP Site 525; DSDP Site 527; DSDP Site 528; DSDP Site 549; DSDP Site 550; DSDP Site 553; DSDP Site 563; DSDP Site 608; Deep Sea Drilling Project; Eocene; Equatorial Atlantic; Global change; Greenland-Scotland Ridge; IPOD; Isotope ratios; Isotopes; Leg 108; Leg 113; Leg 114; Leg 12; Leg 171B; Leg 177; Leg 40; Leg 41; Leg 43; Leg 48; Leg 73; Leg 74; Leg 80; Leg 81; Leg 82; Leg 94; Maud Rise; Mid-Atlantic Ridge; North Atlantic; Northeast Atlantic; O-18/O-16; ODP Site 1051; ODP Site 1052; ODP Site 1053; ODP Site 1090; ODP Site 667; ODP Site 689; ODP Site 690; ODP Site 702; ODP Site 703; Ocean Drilling Program; Ocean circulation; Oligocene; Oxygen; Paleo-oceanography; Paleogene; Rockall Plateau; Sierra Leone Rise; South Atlantic; Southern Hemisphere; Southern Ocean; Stable isotopes; Tertiary; Walvis Ridge; Weddell Sea
Record ID: 2017072916
Copyright Information: GeoRef, Copyright 2017 American Geosciences Institute. Reference includes data from John Wiley & Sons, Chichester, United Kingdom, Reference includes data supplied by, and/or abstract, Copyright, American Geophysical Union

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