Reduced ENSO Variability during Marine Isotope Stage 3
Abstract
The El Niño/Southern Oscillation (ENSO) is the largest interannual signal in Earth's climate system and its predicted response to anthropogenic climate change is debated. In order for climate scientists to forecast how ENSO will evolve in the face of future climate change, it is necessary to have accurate, comprehensive records of how the system has naturally changed in the past. Here, we use the millennial-scale climate events of the last glacial period as a natural experiment to assess how ENSO variability responded to past abrupt warming and changed under different background climate conditions.
We present records of tropical Pacific mean state and ENSO variability over the last 65 kyr reconstructed from a sediment core recovered from the Eastern Equatorial Pacific cold tongue (MV1014-17JC, 0°10.8' S, 85°52.0' W, 2846 m water depth). Mean state variability is assessed from thermocline temperatures reconstructed from Mg/Ca analyses of the thermocline dwelling foraminifera Neogloboquadrina dutertrei and organic geochemical proxies for productivity, upwelling, and sea surface temperature. ENSO variability is determined from individual shell Mg/Ca analyses of N. dutertrei across multiple Heinrich Events, stadials, and interstadials. During Marine Isotope Stage 3, we find that thermocline temperature increased by up to 3.5°C, in-step with interstadial warming events recorded in Greenland ice cores, while cooler thermocline temperatures prevailed during stadial intervals and Heinrich Events. Quantile-Quantile analyses of the individual foraminifera temperature data suggest that all of the glacial intervals had reduced ENSO variability compared to the modern/Late Holocene. We will present an analysis comparing the Quantile-Quantile results for the Heinrich Events, stadials, and interstadials to determine if ENSO variability changed in concert with these millennial-scale climate events. We will describe various hypotheses that can result in a dampened ENSO in the context of the mean state conditions present during MIS 3.- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMOS53D1560H
- Keywords:
-
- 1620 Climate dynamics;
- GLOBAL CHANGE;
- 1627 Coupled models of the climate system;
- GLOBAL CHANGE;
- 4522 ENSO;
- OCEANOGRAPHY: PHYSICAL;
- 4922 El Nino;
- PALEOCEANOGRAPHY