Unprecedented 2015/2016 Indo‐Pacific Heat Transfer Speeds Up Tropical Pacific Heat Recharge

Abstract

El Niño events are characterized by anomalously warm tropical Pacific surface waters and concurrent ocean heat discharge, a precursor of subsequent cold La Niña conditions. Here we show that El Niño 2015/2016 departed from this norm: despite extreme peak surface temperatures, tropical Pacific (30°N–30°S) upper ocean heat content increased by 9.6 ± 1.7 ZJ (1 ZJ = 1021 J), in stark contrast to the previous strong El Niño in 1997/1998 (−11.5 ± 2.9 ZJ). Unprecedented reduction of Indonesian Throughflow volume and heat transport played a key role in the anomalous 2015/2016 event. We argue that this anomaly is linked with the previously documented intensified warming and associated rising sea levels in the Indian Ocean during the last decade. Additionally, increased absorption of solar radiation acted to dampen Pacific ocean heat content discharge. These results explain the weak and short‐lived La Niña conditions in 2016/2017 and indicate the need for realistic representation of Indo‐Pacific energy transfers for skillful seasonal‐to‐decadal predictions.

Unprecedented Response of Indonesian Throughflow to Anomalous Indo‐Pacific Climatic Forcing in 2016

“…Mayer et al (), using reanalysis products, posited that ITF transport was greatly reduced during 2015–2016 and that this reduction was due to a substantial warming of the eastern Indian Ocean on decadal variability time scales. Here we argue that the reduced ITF transport in the upper layer in 2016 is a response to the extreme negative IOD event which may be sparked by the preceding boreal fall 2015 to early 2016 strong El Niño.…”

“…Determining what factors contribute to the dominance of co-occurring negative IOD events over a La Niña events, or vice versa, requires analysis of more concurrent negative IOD-La Niña cases, which is beyond the scope of this study. Mayer et al (2018), using reanalysis products, posited that ITF transport was greatly reduced during 2015-2016 and that this reduction was due to a substantial warming of the eastern Indian Ocean on decadal variability time scales. Here we argue that the reduced ITF transport in the upper layer in 2016 is a response…”

“…Similarly, model-based studies by Lim and Hendon (2017), Lu et al (2017), and Mayer et al (2018) revealed pronounced impacts of the Indian Ocean warming on the development of an extreme negative IOD and weak La Niña events during northern summer to fall 2016. Lu et al (2017) posited that the long-term increasing trend in surface and subsurface temperatures in the Indian Ocean deepened the thermocline in the eastern basin, promoting strengthened thermocline feedback favorable for the development of the negative IOD event.…”

“…Local along‐strait τ generally is not important for seasonal variation of the ITF but is influential to drive subseasonal variations of the ITF in the upper layer of Makassar Strait (Pujiana et al, ). Note that the areas used to determine η N and η S are similar to those adopted in previous studies (Mayer et al, ; Shinoda et al, ).…”

Evaluation of Five Satellite Top-of-Atmosphere Albedo Products over Land

“…TOA products based on satellite data were used to calculate the downward net radiative flux at the TOA because of their better accuracy than reanalysis datasets. In addition, several studies have used the Diagnosing Earth's Energy Pathways in the Climate system (DEEP-C) products to calculate the surface energy budget [24][25][26]. Smith et al [24] built upon the DEEP-C datasets by including estimates of the ocean heat content trends and developing a combined simulated/observation-based record of net downward TOA radiation extending back to 1960.…”