The aftermath of strong instantaneous warm water volume changes — Australian Meteorological and Oceanographic Society

The aftermath of strong instantaneous warm water volume changes (#162)

Sonja Neske 1 2 , Shayne McGregor 1 3
  1. School of Earth, Atmosphere and Environment, Monash University, Clayton, Victoria, Australia
  2. ARC Centre of Excellence for Climate System Science, Clayton, Victoria, Australia
  3. ARC Centre of Excellence for Climate Extremes, Clayton, Victoria, Australia

A wind forced ocean model is used to decompose the equatorial Pacific warm water volume (WWV) between 1980-2016 into the (i) instantaneous WWV response, which are the WWV changes due to winds prevailing during the previous 3 months consistent with WWV changes due to Ekman transports and (ii) adjusted WWV response, which is the WWV contribution of winds prevailing more than 3 months ago. Separate examinations of pre- and post-2000 periods reveal: (i) nearly equal importance of instantaneous and adjusted WWV responses for the pre-2000 period; and (ii) dominance of the instantaneous WWV response during the post-2000 period, due to a 44% decrease of the post-2000 adjusted WWV standard deviation (SD).  Previous research showed that the increasing prominence of instantaneous WWV can explain the post-2000 reduction in WWV/ENSO sea surface temperature lead times (from 6-9 months pre-2000 down to 3-months post-2000). Our study focuses on understanding the apparent contradiction between the post-2000 decrease in adjusted WWV SD and the increase in instantaneous WWV SD as both are wind driven responses.

#AMOS2019