Climate and Antarctic intermediate water covariations on centennial-millennial timescales during MIS 3-constraining the role of the "oceanic tunnel" in abrupt climate change

Author(s): Kleiven, H. F.; Ninnemann, U.
Author Affiliation(s): Primary:
University of Bergen, Department of Earth Science and Bjerknes Centre for Climate Research, Bergen, Norway
Volume Title: AGU 2014 fall meeting
Source: American Geophysical Union Fall Meeting, Vol.2014; American Geophysical Union 2014 fall meeting, San Francisco, CA, Dec. 15-19, 2014. Publisher: American Geophysical Union, Washington, DC, United States
Note: In English
Summary: The equatorward ventilation of Southern Hemisphere extratropical water masses to the low latitude thermocline has been proposed as a window through which the high latitude ocean can modulate tropical climate on anything from decadal to orbital timescales. This hypothesis is founded largely on the observation that tropical thermocline waters originate mostly in the Southern Hemisphere and that computer simulations suggest property anomalies in these source regions can advect through the intermediate ocean, "the ocean tunnel" to influence tropical SST. However, few observational records of extratropical ocean changes are available to assess their impacts on multi-decadal and longer timescales. Here we add to the observational record using new decadally resolved planktonic and benthic foraminiferal isotopic records spanning MIS 3 (20-50 ka) from the Chilean slope ODP Site 1233 that is located on the northern margin of the Antarctic Circumpolar Current and its seafloor lies in the core of Antarctic Intermediate Water (AAIW). Thus the site is ideally situated to reconstruct both near surface and AAIW variability in the high southern latitudes. On centennial to millennial timescales, changes in intermediate water properties track those in the near surface albeit with a reduced amplitude-confirming the idea that changes in the extratropical ocean effect the oceanic tunnel on these timescales. The new benthic and plantic foraminiferal isotope results demonstrate that variations in intermediate ocean properties and climate of the southeast Pacific closely align with those recorded in the EPICA ice core from Dronning Maud Land. Such abrupt, synoptic scale changes in Antarctic climate and dynamics will have potentially widespread climatic and biogeochemical consequences along the downstream flowpath of AAIW. The broad coherence of the observed Antarctic signal supports the concept of hemispheric thermal asynchrony on millennial timescales, and the extension of this climate signal into the intermediate ocean demonstrates that AAIW is extremely sensitive and responds rapidly to climate variability in its source region on a broad spectrum of timescales.
Year of Publication: 2014
Research Program: ODP Ocean Drilling Program
Key Words: 24 Surficial Geology, Quaternary Geology; Antarctic Circumpolar Current; Antarctic Intermediate Water; Antarctica; Cenozoic; Currents; East Pacific; Leg 202; ODP Site 1233; Ocean Drilling Program; Ocean circulation; Ocean currents; Pacific Ocean; Quaternary; South Pacific; Southeast Pacific; Southern Ocean
Coordinates: S410000 S410000 W0742700 W0742700
Record ID: 2015118655
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