Dampened El Niño in the Early and Mid‐Holocene Due To Insolation‐Forced Warming/Deepening of the Thermocline. Issue 1 (8th January 2018)

• Record Type: Journal Article
• Authors: White, Sarah M.; Ravelo, A. Christina; Polissar, Pratigya J.
• Is Part Of: Geophysical research letters. Volume 45:Issue 1(2018)
• Page Start: 316
• Page End: 326
• Publication Date: 2018-01-08
• Subjects: paleoclimate -- paleoceanography -- foraminifera -- ENSO -- tropical Pacific -- insolation; Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1002/2017GL075433
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: El Niño–Southern Oscillation (ENSO) dominates interannual climate variability; thus, understanding its response to climate forcing is critical. ENSO's sensitivity to changing insolation is poorly understood, due to contrasting interpretations of Holocene proxy records. Some records show dampened ENSO during the early to mid‐Holocene, consistent with insolation forcing of ENSO amplitude, but other records emphasize decadal‐centennial fluctuations in ENSO strength, with no clear trend. To clarify Holocene ENSO behavior, we collected proxy data spanning the last ~12 kyr and find relatively low El Niño amplitude during the early to mid‐Holocene. Our data, together with published work, indicate both a long‐term trend in ENSO strength due to June insolation forcing and high‐amplitude decadal‐centennial fluctuations; both behaviors are shown in models. The best supported mechanism for insolation‐driven dampening of ENSO is weakening of the upwelling feedback by insolation‐forced warming/deepening of thermocline source waters. Elucidating the thermocline's role will help predict future ENSO change. Key Points: Our new data show a reduced amplitude of El Nino events during the early and mid‐Holocene Overall, proxy data supports both a June insolation‐forced trend in ENSO strength and decadal‐centennial variability in ENSO strength The best supported mechanism for insolation forcing of Holocene ENSO is a weaker upwelling feedback, due to a warmer/deeper thermocline