Air–sea heat fluxes variations in the Southern Atlantic Ocean: Present-day and future climate scenarios

Abstract

This study investigates the variations in air–sea heat fluxes and temperatures in two ocean front regions, the Southwestern Atlantic Ocean (SWA) and the Drake Passage, widely recognized as hotspot areas with significant influences on South America weather and climate. We analyse means and trends of latent and sensible heat fluxes (LHF and SHF) and their associated air–sea temperatures (SAT and SST), based on monthly ERA5 (1985–2014) and eight CMIP6 models, for historical and long-term simulations (2015–2099). The ERA5 trend for all parameters was positive over SWA, contrasting with the negative values observed in the Drake Passage, indicating surface warming and cooling, respectively. In the SWA, the ERA5 and CMIP6 multi-model ensemble (MME) align in SST and SAT values, with a historical trend of 0.1°C·decade⁻¹ and a significantly increasing trend in warming estimated by 0.4°C·decade⁻¹ up to 2099. The ERA5 LHF and SHF trends were 4 and 0.6 W·m⁻²·decade⁻¹, respectively. The MME shows historical (SSP5-8.5) trends of 0.2 (1.3) W·m⁻²·decade⁻¹ for LHF and −0.2 (−0.1) W·m⁻²·decade⁻¹ for SHF. In the Drake Passage, the models accurately reproduced the air–sea mean temperatures; however, they failed to simulate negative trends observed in SAT and SST. Under the high emissions scenario, all CMIP6 models predict an increasing warming trends of 0.1–0.4°C·decade⁻¹ and ocean heat gain of −0.2 to −1.2 (−1 to −2) W·m⁻²·decade⁻¹ for LHF (SHF). For both regions, spatial analyses of SST and SAT highlight the coupling between the ocean and the atmosphere, alongside changes in air–sea heat fluxes. Our findings reveal inhomogeneous patterns of SST warming trends by the end of the 21st century, which are approximately 2–4 times greater than historical trends. The results suggest the persistence and enhancement of these regions as hotspots with significant potential to influence oceanic and atmospheric dynamics.