Forced and intrinsic variability in the response to increased wind stress of an idealized Southern Ocean

Wilson, Chris, Hughes, Chris W ORCID: 0000-0002-9355-0233 and Blundell, Jeffrey R (2015) Forced and intrinsic variability in the response to increased wind stress of an idealized Southern Ocean. JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS, 120 (1). pp. 113-130.

Text 2015-Wilson_et_al_JGR_QGACC_Timescales.pdf - Published version Available under License Creative Commons Attribution. Download (17MB)

Abstract

<jats:title>Abstract</jats:title><jats:p>We use ensemble runs of a three layer, quasi‐geostrophic idealized Southern Ocean model to explore the roles of forced and intrinsic variability in response to a linear increase of wind stress imposed over a 30 year period. We find no increase of eastward circumpolar volume transport in response to the increased wind stress. A large part of the resulting time series can be explained by a response in which the eddy kinetic energy is linearly proportional to the wind stress with a possible time lag, but no statistically significant lag is found. However, this simple relationship is not the whole story: several intrinsic time scales also influence the response. We find an <jats:italic>e</jats:italic>‐folding time scale for growth of small perturbations of 1–2 weeks. The energy budget for intrinsic variability at periods shorter than a year is dominated by exchange between kinetic and potential energy. At longer time scales, we find an intrinsic mode with period in the region of 15 years, which is dominated by changes in potential energy and frictional dissipation in a manner consistent with that seen by Hogg and Blundell (2006). A similar mode influences the response to changing wind stress. This influence, robust to perturbations, is different from the supposed linear relationship between wind stress and eddy kinetic energy, and persists for 5–10 years in this model, suggestive of a forced oscillatory mode with period of around 15 years. If present in the real ocean, such a mode would imply a degree of predictability of Southern Ocean dynamics on multiyear time scales.</jats:p>

Item Type:	Article
Uncontrolled Keywords:	Southern Ocean, intrinsic variability, nonlinear dynamics, wind stress, eddy saturation, decadal
Subjects:	?? GC ?? ?? QC ??
Depositing User:	Symplectic Admin
Date Deposited:	22 Jul 2015 10:42
Last Modified:	31 Oct 2023 00:44
DOI:	10.1002/2014JC010315
Related URLs:	Author Publisher
URI:	https://livrepository.liverpool.ac.uk/id/eprint/2017089