Strong middepth warming and weak radiocarbon imprints in the equatorial Atlantic during Heinrich 1 and Younger Dryas

Type Article
Date 2016-08
Language English
Author(s) Weldeab Syee1, Friedrich Tobias2, Timmermann AxelORCID2, Schneider Ralph R.3
Affiliation(s) 1 : Univ Calif Santa Barbara, Dept Earth Sci, Santa Barbara, CA 93106 USA.
2 : Univ Hawaii Manoa, Sch Ocean & Earth Sci & Technol, Int Pacific Res Ctr, Honolulu, HI USA.
3 : Univ Kiel, Inst Geosci, Kiel, Germany.
Source Paleoceanography (0883-8305) (Amer Geophysical Union), 2016-08 , Vol. 31 , N. 8 , P. 1070-1082
DOI 10.1002/2016PA002957
WOS© Times Cited 19
Keyword(s) deglacial tropical Atlantic, middepth warming, Heinrich events 1 and Younger Dryas, Mg, Ca paleothermometry, heat accumulation, interhemispheric heat exchange
Abstract

We present a benthic foraminiferal multiproxy record of eastern equatorial Atlantic (EEA) middepth water (1295m) covering the last deglacial. We show that EEA middepth water temperatures were elevated by 3.90.5 degrees C and 5.21.2 degrees C during Heinrich event 1 (H1) and Younger Dryas (YD), respectively. The radiocarbon content of the EEA middepth during H1 and YD is relatively low and comparable to the values of the pre-H1 episode and BOlling-AllerOd, respectively. A transient Earth system model simulation, which mimics the observed deglacial Atlantic Meridional Overturning Circulation (AMOC) history, qualitatively reproduces the major features of the EEA proxy records. The simulation results suggest that fresh water-induced weakening of the AMOC leads to a vertical shift of the horizon of Southern Ocean-sourced water and a stronger influence of EEA sea surface temperatures via mixing. Our findings reaffirm the lack of a distinctive signature of radiocarbon depletion and therefore do not support the notion of interhemispheric exchanges of strongly radiocarbon-depleted middepth water across the tropical Atlantic during H1 and YD. Our temperature reconstruction presents a critical zonal and water depth extension of existing tropical Atlantic data and documents a large-scale and basin-wide warming across the thermocline and middepth of the tropical Atlantic during H1 and YD. Significant difference in the timing and pace of H1 middepth warming between tropical Atlantic and North Atlantic likely points to a limited role of the tropical Atlantic middepth warming in the rapid heat buildup in the North Atlantic middepth.

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