low Atlantic reconstructed Lawrence2009

Core/Site name:

ODP-162-982

Elevation:

-1134.2

Archive:

marine sediments (downcore)

Proxy measurement:

SST alkenones

Sampling resolution:

millennial

Startyear:

4012.228 ka BP

Endyear:

0 ka BP

Description:

We provide the first continuous, orbital-resolution sea surface temperature (SST) record from the high latitude North Atlantic, a region critical to understanding the origin of the Plio-Pleistocene ice ages and proximal to regions that became frequently glaciated after ~2.7 Ma. We analyzed sediments from Ocean Drilling Program Site 982 over the last 4 Ma for their alkenone unsaturation index and compared this surface water signal to a benthic d18O record obtained from the same section. We find that while ocean surface temperatures were significantly warmer (~6°C) than modern temperatures during the early Pliocene, they were also as variable as those during the late Pleistocene, a surprising result in light of the subdued variance of oxygen isotopic time series during the interval of 3-5 Ma. We propose two possible explanations for the high orbital-scale SST variability observed: either that a strong, high-latitude feedback mechanism not involving large continental ice sheets alternately cooled and warmed a broad region of the northern high latitudes or that by virtue of its location near the northern margin of the North Atlantic Drift, the site was unusually sensitive to obliquity-driven climate shifts. On supraorbital time scales, a strong, sustained cooling of North Atlantic SSTs (~4.5°C) occurred from 3.5 to 2.5 Ma and was followed by an interval of more modest cooling (an additional 1.5°C) from 2.5 Ma to the present. Evolutionary orbital-scale phase relationships between North Atlantic SST and benthic d18O show that SST began to lead d18O significantly coincident with the onset of strong cooling at Site 982 (~3.5 Ma). We speculate that these changes were related to the growth and subsequent persistence of a Greenland ice sheet of approximately modern size through interglacial states.

Data entered by name:

Martrat, Belen

Data entered by email:

This email address is being protected from spambots. You need JavaScript enabled to view it.

Main reference(s):

Lawrence, K. T., Herbert, T. D., Brown, C. M., Raymo, M. E. & Haywood, A. M. High-amplitude variations in North Atlantic sea surface temperature during the early Pliocene warm period. Paleoceanography 24, PA2218, doi:10.1029/2008pa001669 (2009).Lang, N. & Wolff, E. W. Interglacial and glacial variability from the last 800 ka in marine, ice and terrestrial archives. Clim. Past 7, 361-380, doi:10.5194/cp-7-361-2011 (2011).

Link to reference 1:

http://www.agu.org/pubs/crossref/2009/2008PA001669.shtml

Link to reference 2:

http://www.clim-past.net/7/361/2011/

Data storage link 1:

https://www.ncdc.noaa.gov/paleo/study/8624

Data storage link 2:

http://www.clim-past.net/7/361/2011/

Comments:

woa09t_an0: 11.069 ºC

Current dating method:

-- select --

Annual snow acc rate:

-- select --

Category: PIGS