Testing the Tropical Trigger Hypothesis of Abrupt Climate Variability

Abstract

Dansgaard-Oeschger oscillations (DOs) are abrupt shifts in climate, which are dramatic temperature fluctuations observed in Greenland and recorded globally. These abrupt changes are associated with the slowing and shutting down of the Atlantic Meridional Overturning Circulation (AMOC), but despite their importance the driving forces of DOs are not fully understood. Here we assess the role of the AMOC during DOs, the Northern vs Southern Hemisphere control on AMOC, and the possibility of neotropical moisture as a driver for abrupt climate variability. During DOs, South America has recorded a disparity between the degree of warming, and the change in precipitation at different sites. Based on our current understanding, we propose likely oceanic and continental changes in tropical South America that can help disentangle the triggers of these events. With the margins of error associated with dating sources of palaeo-data, the need for an independent chronology with multiple proxies recorded in the same record, could offer the information needed to understand the driving forces of DOs.

Indian Summer Monsoon variability 140–70 thousand years ago based on multi-proxy records from the Bay of Bengal

“…Our ISM rainfall reconstructions show that monsoon rainfall remained strong throughout the MIS 5 interstadials despite progressive background climate cooling. This sustained monsoonal strength may have been conducive in facilitating high latitude ice sheet growth via moisture export to higher, cooler latitudes (Khodri et al, 2001), lending support to previous hypotheses invoking low-latitude controls on global climate changes (Ivanochko et al, 2005;Kaboth-Bahr et al, 2018;Kudrass et al, 2001;Oughton and Urrego, 2021). (Loulergue et al, 2008) h) Antarctic composite CO 2 ice-core record (Lüthi et al, 2008) i) EDC ice-core δD (Jouzel et al, 2007) j) Eccentricity (Laskar et al, 2004) k) Obliquity (Laskar et al, 2004) and l) 21st June NHSI at 65°N and 23°N (Laskar et al, 2004).…”

“…Despite the role of high-latitude climate processes in forcing internal climate perturbations (Broecker et al, 1992;Markle et al, 2017;Pedro et al, 2018), previous studies have revealed the importance of the lowlatitudes in determining and amplifying the subsequent global climate response through possible greenhouse gas feedbacks and global dissemination of heat and moisture (Cheng et al, 2020;Clement and Peterson, 2008;Ivanochko et al, 2005;Kudrass et al, 2001;Leduc et al, 2007;Nilsson-Kerr et al, 2019;Oughton and Urrego, 2021;Rohling et al, 2002;Sánchez Goñi et al, 2016). This has been attributed to the fact that the tropics are the primary absorber of the majority of incoming solar radiation (Chiang and Friedman, 2012).…”