Late Pliocene glaciation of southern Greenland and ice/ocean interactions

Author(s): Walczak, Maureen H.; Carlson, Anders E.; Stoner, Joseph Stephen; Hatfield, Robert G.; Mathias, Aspen; Wolhowe, Matthew D.
Author Affiliation(s): Primary:
Oregon State University, College of Earth, Ocean, and Atmospheric Sciences, Corvallis, OR, United States
Volume Title: AGU 2016 fall meeting
Source: American Geophysical Union Fall Meeting, Vol.2016; American Geophysical Union 2016 fall meeting, San Francisco, CA, Dec. 12-16, 2016. Publisher: American Geophysical Union, Washington, DC, United States
Note: In English
Summary: Greenland is home to the only persistent northern hemisphere ice-sheet, existing for much of the past 3.5 million years and yet likely to disappear if global temperatures rise another 2-3°C. The best analogue for the ice-sheet's current vulnerable state is likely near the time of its inception in the late Pliocene, when global surface temperatures are thought to have been 2-3°C higher than today. Although few proxy records exist for the pre-Quaternary, IODP Expedition 303 site U1307 captures the late-Pliocene warm period adjacent to the southern Greenland ice sheet. The sand fraction lithology in the Late Pliocene is dominated by well-sorted granitic material, likely sourced via runoff from the nascent southeastern ice sheet. Interpreted on a paleomagnetic reversal age model, this material shows ∼100 ka cyclicity between 3.6-3.1 Ma, with the exception of a period from 3.44-3.36 Ma. In that window, all lithologic evidence of material eroded from Greenland bedrock disappears. Poor carbonate preservation in conjunction with consistent siliceous microfossil presence suggests benthic hypoxia driven by reduced regional deep-water ventilation, and may reflect a shutdown of the Atlantic Meridional Overturning Circulation (AMOC) through this interval. The appearance of glacial ice-rafted debris immediately prior supports the brief existence (<2 ka) of a marine-terminating ice margin at ∼3.45 Ma; freshwater input to the surface ocean associated with the disappearance of this larger ice sheet may have triggered changes in regional ocean circulation. Recovery from apparent benthic hypoxia begins at ∼3.36 Ma, accompanied by lithologic evidence for regrowth of the ice sheet. This episode of apparent AMOC shutdown provides insight on the feedbacks that exist between southern Greenlandic ice-sheet behavior and the AMOC.
Year of Publication: 2016
Research Program: IODP Integrated Ocean Drilling Program
Key Words: 12 Stratigraphy, Historical Geology and Paleoecology; Atlantic Ocean; Cenozoic; Expedition 303; Expeditions 303/306; Glacial environment; IODP Site U1307; Integrated Ocean Drilling Program; Neogene; North Atlantic; Northwest Atlantic; Paleoenvironment; Pliocene; Tertiary; Upper Pliocene
Coordinates: N583000 N583000 W0462400 W0462400
Record ID: 2018008232
Copyright Information: GeoRef, Copyright 2018 American Geosciences Institute. Reference includes data supplied by, and/or abstract, Copyright, American Geophysical Union, Washington, DC, United States