Meridional Overturning Circulation transport variability at 34.5S during 2009-2017

MEINEN, C. S.; SPEICH, S.; PIOLA, A. R.; ANSORGE, I.; CAMPOS, E.; KERSALE, M.; TERRE, T.; CHIDICHIMO, M. P.; LAMONT, T.; SATO, O.; PEREZ, R. C.; VALLA, D.; VAN DEN BERG, M.; LE HENAFF, M.; DONG, S.

Montreal

Congreso; 27th IUGG General Assembly; 2019

IUGG

Six years of simultaneous moored observations near the western and eastern boundaries of the South Atlantic are combined with satellite winds to produce a daily time series of the variability of the basin-wide meridional overturning circulation (MOC) volume transport at 34.5°S. The results show that barotropic and baroclinic signals at both boundaries cause significant transport variations, and as such must be concurrently observed. The data, spanning ~20 months during 2009-2010 and ~4 years during 2013-2017, reveal a highly energetic MOC record with a temporal standard deviation of 8.3 Sv, and strong variations at time scales ranging from a few days to years (peak-to-peak range = 54.6 Sv). Seasonal transport variations have both semi-annual (baroclinic) and annual (Ekman and barotropic) timescales. Interannual MOC variations are shown to result from both barotropic and baroclinic changes, with density profile changes at the eastern boundary having the largest impact on the year-to-year variations.