Oceanic eddy-induced modifications to air–sea heat and CO2 fluxes in the Brazil-Malvinas Confluence

Abstract

Sea surface temperature (SST) anomalies caused by a warm core eddy (WCE) in the Southwestern Atlantic Ocean (SWA) rendered a crucial influence on modifying the marine atmospheric boundary layer (MABL). During the first cruise to support the Antarctic Modeling and Observation System (ATMOS) project, a WCE that was shed from the Brazil Current was sampled. Apart from traditional meteorological measurements, we used the Eddy Covariance method to directly measure the ocean–atmosphere sensible heat, latent heat, momentum, and carbon dioxide (CO2) fluxes. The mechanisms of pressure adjustment and vertical mixing that can make the MABL unstable were both identified. The WCE also acted to increase the surface winds and heat fluxes from the ocean to the atmosphere. Oceanic regions at middle and high latitudes are expected to absorb atmospheric CO2, and are thereby considered as sinks, due to their cold waters. Instead, the presence of this WCE in midlatitudes, surrounded by predominantly cold waters, caused the ocean to locally act as a CO2 source. The contribution to the atmosphere was estimated as 0.3 ± 0.04 mmol m−2 day−1, averaged over the sampling period. The CO2 transfer velocity coefficient (K) was determined using a quadratic fit and showed an adequate representation of ocean–atmosphere fluxes. The ocean–atmosphere CO2, momentum, and heat fluxes were each closely correlated with the SST. The increase of SST inside the WCE clearly resulted in larger magnitudes of all of the ocean–atmosphere fluxes studied here. This study adds to our understanding of how oceanic mesoscale structures, such as this WCE, affect the overlying atmosphere.

The effect of Oceanic South Atlantic Convergence Zone episodes on regional SST anomalies: the roles of heat fluxes and upper-ocean dynamics

“…The region where these two currents collide is called the Brazil Malvinas Confluence (BMC). Strong modulations in MABL stability have been documented in the frontal zone separating warm BC from cold MC waters (Pezzi et al 2005 and by warm core eddy at the Atlantic Southwest (Pezzi et al 2021). Another interesting feature seen in the simulated oceanic near-surface currents is a train of cyclonic eddies extending in the same direction and region of the negative wind stress curl areas.…”

“…The SACZ can also occur in association with other atmospheric and oceanic phenomena, being influenced by local or remote factors (Kodama 1992;Kodama et al 1997;Grimm and Silva Dias 1995;Grimm et al 2007;Nogués-Peagle and Mo 1997;Jones and Horel 1990;Marton 2000;Chaves and Nobre 2004;Hirata and Grimm 2015;Pezzi et al 2016;Pezzi et al 2021). These issues have been addressed in numerical modeling studies that simulate the SACZ in its atmospheric and oceanic components (Chaves and Satyamurty 2006;Chaves and Nobre 2004), as well as in reanalysis-based studies dedicated to understanding the spatial and temporal variability of the SACZ (Carvalho et al 2004;Ferreira et al 2004;Grimm and Zilli 2009).…”

Salt marsh-atmosphere CO2 exchanges in Patos Lagoon Estuary, Southern Brazil

“…The knowledge gaps of CO 2 fluxes are particularly large for South America, where the great majority of EC studies are concentrated in the terrestrial ecosystems, with few studies performed in coastal wetlands (e.g. Tonti et al, 2018, Freire et al, 2022 and the coastal and open ocean (Pezzi et al, 2016;Oliveira et al, 2019;Santini et al, 2020;Pezzi et al, 2021;Souza et al, 2021).…”

“…using 30 min long time intervals and detrended time series derived from the original data. The methodology used here is similar to that used byOliveira et al (2019);Santini et al (2020) andPezzi et al (2021).…”

SuppressedpCO2in the Southern Ocean Due to the Interaction Between Current and Wind

“…Air-sea interaction in the oceanic mesoscale can impose another layer of complexity to CO 2 exchange in the Southern Ocean. A recent observational study by Pezzi et al (2021) reports that a warm-core eddy in the southwestern Atlantic Ocean acts as a local source of CO 2 to the atmosphere in contrast to the surrounding cold waters, which are considered as a sink. The sea surface temperature perturbation associated with the mesoscale modifies the surface wind speed (Chelton et al, 2007;Putrasahan et al, 2013;Samelson et al, 2006;Seo et al, 2007), which can alter the air-sea CO 2 exchange.…”