The zonally integrated component of surface and deep currents, known as the meridional overturning circulation (MOC), plays an important role in Earth’s climate because it provides a mechanism for ocean meridional heat transport (MHT). The observing system for the Atlantic MOC/MHT consists of several basin-wide moored arrays as well as the combination of satellite altimetry and in situ (mainly Argo and eXpendable BathyThermograph [XBT]) measurements (Fig. 3.21a; e.g., Frajka-Williams et al. 2019)...

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Abstract: The Meridional Overturning Circulation (MOC) is a primary mechanism driving oceanic heat redistribution on Earth, thereby affecting Earth’s climate and weather. However, the full-depth structure and variability of the MOC are still poorly understood, particularly in the South Atlantic. This study presents unique multiyear records of the oceanic volume transport of both the upper (<~3100 meters) and abyssal (>~3100 meters) overturning cells based on daily moored measurements in the South Atlantic at 34.5°S. The vertical structure of the time-mean flows is consistent with the limited historical observations. Both the upper and abyssal cells exhibit a high degree of variability relative to the temporal means at time scales, ranging from a few days to a few weeks. Observed variations in the abyssal flow appear to be largely independent of the flow in the overlying upper cell. No meaningful trends are detected in either cell.

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Abstract: In this study, mechanisms causing year-to-year changes in the Florida Current seasonality are investigated using controlled realistic numerical experiments designed to isolate the western boundary responses to westward propagating open ocean signals. The experiments reveal two distinct processes by which westward propagating signals can modulate the phase of the Florida Current variability, which we refer to as the “direct” and “indirect” response mechanisms. The direct response mechanism involves a two-stage response to open ocean anticyclonic eddies characterized by the direct influence of Rossby-wave barotropic anomalies, and baroclinic wall-jets that propagate through Northwest Providence Channel...

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