Generation Mechanisms of SST Anomalies Associated with the Canonical El Niño Focusing on Vertical Mixing

Author:

Nakamura Kouya1,Kido Shoichiro2,Ijichi Takashi1,Tozuka Tomoki12ORCID

Affiliation:

1. a Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo, Tokyo, Japan

2. b Application Laboratory, Research Institute for Value‐Added‐Information Generation, Japan Agency for Marine‐Earth Science and Technology (JAMSTEC), Yokohama, Japan

Abstract

Abstract The mean vertical advection of anomalous vertical temperature gradient is considered the dominant generation mechanism of positive sea surface temperature (SST) anomalies associated with the canonical El Niño. However, most past studies had a residual term in their heat budget analysis and/or did not quantify the role of vertical mixing even though active vertical turbulent mixing in the upper ocean is observed in the eastern equatorial Pacific. To quantitatively assess the importance of vertical mixing, a mixed layer heat budget analysis is performed using a hindcast simulation forced by daily mean atmospheric reanalysis data. It is found that when the mixed layer depth is defined as the depth at which potential density increases by 0.125 kg m−3 from the sea surface, the development of positive SST anomalies is predominantly governed by reductions in the cooling by vertical mixing, and their magnitude is much larger than those by vertical advection. The anomalous warming by vertical mixing may be partly explained by an anomalous deepening of the thermocline that leads to a decrease in the vertical temperature gradient, giving rise to suppression of the climatological cooling by vertical mixing. Also, an anomalously thick mixed layer reduces sensitivity to cooling by the mean vertical mixing and contributes to the anomalous SST warming. On the other hand, the dominant negative feedbacks are attributed to both anomalous surface heat loss and anomalous deepening of the mixed layer that weakens warming by the mean surface heat flux.

Funder

Japan Society for the Promotion of Science

Publisher

American Meteorological Society

Reference64 articles.

1. An, S.-I., E. Tziperman, Y. M. Okumura, and T. Li, 2020: ENSO irregularity and asymmetry. El Niño Southern Oscillation in a Changing Climate, A. Santoso et al., Eds., Geophysical Monograph Series, Vol. 253, Amer. Geophys. Union, 153–172, https://doi.org/10.1002/9781119548164.ch7.

2. El Niño Modoki and its possible teleconnection;Ashok, K.,2007

3. Evaluation of the ECMWF ocean reanalysis system ORAS4;Balmaseda, M. A.,2013

4. ENSO atmospheric feedbacks under global warming and their relation to mean-state changes;Bayr, T.,2023

5. Walker circulation controls ENSO atmospheric feedbacks in uncoupled and coupled climate model simulations;Bayr, T.,2020

同舟云学术

1.学者识别学者识别

2.学术分析学术分析

3.人才评估人才评估

"同舟云学术"是以全球学者为主线,采集、加工和组织学术论文而形成的新型学术文献查询和分析系统,可以对全球学者进行文献检索和人才价值评估。用户可以通过关注某些学科领域的顶尖人物而持续追踪该领域的学科进展和研究前沿。经过近期的数据扩容,当前同舟云学术共收录了国内外主流学术期刊6万余种,收集的期刊论文及会议论文总量共计约1.5亿篇,并以每天添加12000余篇中外论文的速度递增。我们也可以为用户提供个性化、定制化的学者数据。欢迎来电咨询!咨询电话:010-8811{复制后删除}0370

www.globalauthorid.com

TOP

Copyright © 2019-2024 北京同舟云网络信息技术有限公司
京公网安备11010802033243号  京ICP备18003416号-3