Precession cycles of the El Niño/Southern oscillation-like system controlled by Pacific upper-ocean stratification

Abstract

Modern observations have presented linkages between subsurface waters of the western Pacific warm pool and both El Niño/Southern Oscillation-related and extratropic-controlled upper-ocean stratification on interannual timescales. Moreover, studies have showed that such controls may operate on orbital cycles, although the details remain unclear. Here we present paired temperature and salinity reconstructions for the surface and thermocline waters in the central western Pacific warm pool over the past 360,000 years, as well as transit modeling results from an Earth system model. Our results show that variations in subsurface temperature and salinity in the western Pacific warm pool have consistently correlated with the shallow meridional overturning cell over the past four glacial-interglacial cycles, and they vary on eccentricity and precession cycles. The shallow meridional overturning cell regulates subsurface waters of the western Pacific warm pool by changing subtropical surface water density and thus equatorial upper-ocean stratification, acting as an El Niño/Southern Oscillation-like process in the precession band. Therefore, the western Pacific warm pool is critical in connecting the austral shallow meridional overturning cell to the Earth’s climate system on orbital timescales.

Heat Transport Processes of the Indonesian Throughflow Along the Outflow Pathway in the Eastern Indian Ocean During the Last 160 Kyr

“…(2020). The conversion from Mg/Ca to temperature for Core KX97322‐4 (Zhang et al., 2021) is different from our method. It uses the equation developed by Hollstein et al.…”

“…The two cores are both located in the main outflow pathway of the ITF in the eastern Indian Ocean. To understand the heat transport processes of the ITF from the western Pacific to the eastern Indian Ocean during the last 160 Kyr, we compared the SSTs of Core MD98-2172 and Core MD77-150 with data from Core KX97322-4 (Zhang et al, 2021) and Core MD06-3067 (Bolliet et al, 2011) in the western equatorial Pacific Ocean in the core region of the IPWP. Core MD06-3067 is located to the south of Mindanao, the main entrance area for the ITF (Figures 1 and 7, Figure S2 in Supporting Information S1).…”

Thermal coupling of the Indo-Pacific warm pool and Southern Ocean over the past 30,000 years

“…2d ), the overturning circulation that mainly formed in winter by intense vertical mixing 72 was warmed due to the rising insolation in austral winter (Fig. 2e ), and this warmer signal was further transferred to the western Pacific 69 . Preceding thermocline anomalies in the western and central deep tropical Pacific contribute to the recharge phase of ENSO 63 , 73 , and modern observations also indicate that the change in the WPWP OHC is tightly related to ENSO activity 74 .…”

“…A continuous subduction of the extratropical warm anomaly to the WPWP thermocline is hypothesized to affect ENSO-like transitions since 360 ka, paced by orbital precession 69 . The results of earlier modeling simulations have shown that orbital precession exerts a major impact on ENSO-like processes through the strength of ocean-atmosphere feedbacks 70 , 71 .…”

Precessional pacing of tropical ocean carbon export during the Late Cretaceous

“…Today this scenario occurs as an irregular periodic variation along with an opposite "La Niña" state in the tropical Pacific, with strong trade winds and more intense upwelling in the eastern tropical Pacific driving increased productivity on interannual to decadal timescales. Changes in the mean state over longer timescales can be recorded in deep-sea sediment archives (e.g., Pena et al, 2008;Zhang et al, 2021). The large range of variations in our carbon export record in the tropical Pacific (XRF-Ba elemental intensities and benthic foraminiferal accumulation rates) during the Maastrichtian greenhouse argues against the hypothesis of a continual or permanent El Niño-like state.…”