Time series (2002)(2003)(2004)(2005)(2006)(2007)(2008)(2009)(2010)(2011)(2012)(2013)(2014)(2015)(2016)(2017)(2018) of a global monthly objectively analyzed fields of temperature and salinity were used to investigate the South Atlantic subtropical mode water (SASTMW). It is characterized as homogeneous layers in the temperature range of 13 to 16 • C and with low potential vorticity. Three different types of SASTMW were distinguished allowing us to evaluate their temporal volumetric variation. Each type has its distinct spatial and temporal distribution patterns and consequently dissimilar volumetric variation. This variability is seen in the volume anomaly and turnover time of each type. To examine these differences we compared two rates: the water formation in a given temperature range due to heat flux and the mode water formation. The first (13.1±2.4 Sv) is higher than the second (10.2±2.0 Sv), showing that although heat flux is essential for the formation of SASTMW, there are other factors that influence each type differently. Plain Language SummaryThis article aimed to investigate the South Atlantic subtropical mode water (SASTMW) to better understand how the volume of this mode water varies over the years (from 2002 to 2018) and in space (the South Atlantic basin). It is defined as a layer with very low vertical temperature, in a specific range (13 to 16 • C), and density variation. Three different types of SASTMW can been seen. This allowed us to independently assess the volume and its modifications over time for each one and we saw that each type has specific temperature/density characteristics and changes of its volume over time. It is understood that the formation of mode water is directly related to the processes that occur between the atmosphere and the ocean. Thus, we investigate whether the different volume variations of each type are related to these interactions. As a first approach, we investigated two rates: the rate of the amount of water that is cooled or heated to the 13-16 • C range per month and the SASTMW formation rate. By the difference between these rates, we understand that despite the importance of heat flux for the existence of SASTMW, other factors influence each type in a different way.
We investigated the formation and evolution of the South Atlantic subtropical mode water using data from profiling conductivity, temperature, and depth sensors (CTD) deployed in April–May 2015 and from two customized Argo floats that drifted from April 2015 to June 2017. From the CTD data, we observed a mode water layer below the seasonal thermocline that deepened from the southern side of the area to the north. The two Argo floats remained in the proximity of the cruise area for 2 years. Their slow displacement and recirculating patterns allowed us to observe the changes in the temperature and salinity structure before and after the formation period. We observed that the potential vorticity of newly formed mode water was O[10−1 to 10−2] of the mean value found in the whole mode water layer. There is a significant correspondence between the phases of the time integral of surface heat fluxes and the sea surface temperature. Mode water is observed to form at the integrated heat flux minimum phase. The relationship between the air‐sea fluxes and sea surface temperature promotes the necessary preconditioning for the mode water formation. Once this was established, the outcropping of the mode water, that was at about 100 m depth, coincided with the passage of an atmospheric cold frontal system. This event suggests that the mode water formation can be triggered by the passage of cold fronts.
This work describes the circulation over the continental slope and the São Paulo Plateau in the Santos Basin during the SANSED winter 2019 survey. The cruise consisted of four legs in the period between June, 11 and August, 03 2019. The observed circulation is dominated by the Atlantic southwestern boundary current regime and remotely-generated anticyclones and cyclones. The former is composed by the Brazil Current, the Intermediate Western Boundary Current and their mesoscale meanders; the latter are 300km vortical rings with origin in the eastern side of the South Atlantic Basin. A Lagrangian scheme applied over satellite altimeter maps indicate that the origin of these rings is primarily the Cape Basin off South Africa. The interaction between the boundary currents, their cyclonic meanders, and the anticyclonic rings is complex, and varies widely. During the SANSED winter 2019 survey period, three anticyclones interacted with the Brazil Current, instabilizing it, forming dipoles with the current cyclonic meanders, leading to their downstream propagation. Ancienter cyclonic eddies within Santos Basin may interfere with the propagation of the large anticyclones further south. In addition, the continuous arrival of remotely-originated anticyclones, the larger portion over the São Paulo Plateau presented a tendency of counter-clockwise circulation during the whole cruise period.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.