Interannual Agulhas leakage variability and its regional climate imprints

Yu Cheng, Lisa M. Beal, Ben P. Kirtman, Dian Putrasahan

Research output: Contribution to journalArticle

2 Scopus citations

Abstract

We investigate the interannual variability of Agulhas leakage in an ocean-eddy-resolving coupled simulation and characterize its influence on regional climate.Many observational leakage estimates are based on the study of Agulhas rings, whereas recent model studies suggest that rings and eddies carry less than half of leakage transport.While leakage variability is dominated by eddies at seasonal time scales, the noneddy leakage transport is likely to be constrained by large-scale forcing at longer time scales. To investigate this, leakage transport is quantified using an offline Lagrangian particle tracking approach.We decompose the velocity field into eddying and large-scale fields and then recreate a number of total velocity fields by modifying the eddying component to assess the dependence of leakage variability on the eddies.We find that the resulting leakage time series show strong coherence at periods longer than 1000 days and that 50%of the variance at interannual time scales is linked to the smoothed, large-scale field.As shown previously in oceanmodels, we findAgulhas leakage variability to be related to a meridional shift and/or strengthening of the westerlies. High leakage periods are associated with east-west contrasting patterns of sea surface temperature, surface heat fluxes, and convective rainfall, with positive anomalies over the retroflection region and negative anomalies within the IndianOcean to the east. High leakage periods are also related to reduced inland convective rainfall over southeastern Africa in austral summer.

Original languageEnglish (US)
Pages (from-to)10105-10121
Number of pages17
JournalJournal of Climate
Volume31
Issue number24
DOIs
StatePublished - Dec 1 2018

Keywords

  • Atmosphere-ocean interaction
  • Coupled models
  • Interannual variability
  • Lagrangian circulation/transport
  • Large-scale motions
  • Ocean circulation

ASJC Scopus subject areas

  • Atmospheric Science

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