The Impact of the AMOC Resumption in the Western South Atlantic Thermocline at the Onset of the Last Interglacial

Author(s)

Santos, Thiago P. ^[1] ; Lessa, Douglas O. ^[1] ; Venancio, Igor M. ^{[2, 3]} ; Chiessi, Cristiano M. ^[4] ; Mulitza, Stefan ^[2] ; Kuhnert, Henning ^[2] ; Albuquerque, Ana Luiza S. ^[1]

Affiliation

^[1] Univ Fed Fluminense, Programa Geociencias Geoquim, Niteroi, RJ - Brazil

^[2] Univ Bremen, MARUM Ctr Marine Environm Sci, Bremen - Germany

^[3] Natl Inst Space Res INPE, Ctr Weather Forecasting & Climate Studies CPTEC, Cachoeira Paulista - Brazil

^[4] Univ Sao Paulo, Escola Artes Ciencias & Humanidades, Sao Paulo - Brazil

• Document type: Journal article
• Source: Geophysical Research Letters; v. 44, n. 22, p. 11547-11554, NOV 28 2017.
• Web of Science Citations: 2

Abstract

After glacial terminations, large amounts of heat and salt were transferred from low to high latitudes, which is a crucial phenomenon for the reestablishment of the Atlantic Meridional Overturning Circulation (AMOC). However, how different glacial terminations evolved in the (sub) tropics is still poorly documented. Here we use foraminifera oxygen (delta O-18) and carbon (delta C-13) stable isotopes to show that the North Atlantic heat piracy, following the AMOC resumption at the early Last Interglacial, affected the thermocline delta O-18 levels of the subtropical western South Atlantic. Because of the cooling imposed by this process, glacial delta O-18 persisted in the thermocline for similar to 7 kyr after the onset of the Last Interglacial, dampening the effect of sea level rise usually imprinted on foraminifera delta O-18 during terminations. Faunal composition and delta C-13 also suggest the existence of a colder and thicker South Atlantic Central Water coeval with the AMOC recovery. This process apparently did not occur during the last deglaciation. Plain Language Summary Glacial terminations are periods of fast ice sheet disintegration, elevation of global temperatures, and release of carbon dioxide from the deep ocean to the atmosphere. These conditions turn such intervals well situated to the study of global climate changes. The warming of high latitudes is supported by the transfer of heat and salt from low latitudes. However, the documentation of how glacial terminations occurred in low-latitude oceans are still poorly documented. In this study we show through oxygen isotopes of planktonic foraminifera that thermocline waters from the Brazilian margin may have worked as a source of hydrostatic instability to return the meridional circulation to its interglacial mode. The impact of this process may have produced a colder South Atlantic thermocline during the transition to the Last Interglacial (130 kyr ago). (AU)

• FAPESP's process: 12/17517-3 - Response of the Western Atlantic Ocean to changes in the Atlantic meridional overturning circulation: from millennial to seasonal variability
• Grantee: Cristiano Mazur Chiessi
• Support Opportunities: Research Program on Global Climate Change - Young Investigators