AOML
NOAA

Brazil Current

Interannual Variability and Regional Impacts

The Interannual Variability of the Brazil Current and Regional Impacts

Introduction

The BC is a western boundary system, with relatively weak mean flow and strong mesoscale variability, that closes the South Atlantic Subtropical gyre. The BC is originated from the southern branch of the South Equatorial Current (SEC) bifurcation off the Brazilian coast, at different latitudes and depths. At approximately 38°S, the warm salty southward-flowing BC encounters the cold, fresher northward flow of the Malvinas Current, generating a strong thermohaline front known as the Brazil-Malvinas Confluence Front. Understanding the mechanisms that control the variability of the South Atlantic western boundary will advance the regional ocean forecast skill, as well as the improve the knowledge of the processes responsible for the South Atlantic meridional overturning variability. Here we will expand on previous studies by I) Confronting the regional variability of the western boundary current with mechanisms that control the large-scale features of the South Atlantic, and II) Investigate how the importance of the BC SST front in modifying the weather patterns in South America.

Team members

  • PI
  • Marlos Goes (USA, NOAA/AOML, UM/CIMAS)
  • Post-docs
  • Yanyun Liu (USA, NOAA/AOML, UM/CIMAS)
    Sudip Majumder (USA, NOAA/AOML, UM/CIMAS)
  • Masters Students
  • Vinicius Webber (UM/RSMAS)
    Mateus Lima (UFBA/Brazil)
  • High School Interns
  • Steve Marrero (MAST)
  • Collaborators
  • Sang-Ki Lee (USA, NOAA/AOML)
    Leo Siqueira (USA, UM/RSMAS)
    Ben Kirtman (USA, UM/RSMAS)
    Shenfu Dong (USA, NOAA/AOML)
    Greg Foltz (USA, NOAA/AOML)
    Gustavo Goni (USA, NOAA/AOML)
    Molly Baringer (USA, NOAA/AOML)
    Mauro Cirano (Brazil, UFRJ)
    Mauricio Mata (Brazil, FURG)

News and Highlights

10/23/2017:

2017 OSTS meeting

PIs of the projects attended the 2017 Ocean Surface Topography Science Team Meeting, Oct 23-27, Miami, FL. (POSTER) Goes,M., S-K Lee, and S. Majumder "The Brazil Current variability from XBT data and satellite altimetry".

05/23/2017:

2017 US AMOC science team meeting

PIs of the projects attended the 2017 US AMOC science team meeting, May 23-25, Santa Fe, NM. (POSTER) Goes, M., Y. Liu, S-K Lee, S. Dong, H. Lopez "Interannual variability of the Brazil Current assessed using observations and model simulations".

05/03/2017:

Biweekly AMOC discussion meetings

PhOD has resumed the AMOC discussion meetings to discuss new papers and ideas concerning AMOC and related topics. The meeting is held biweekly at NOAA/AOML. In the first meeting (May 31st), Alexandra Gronholz led the discussion of "Impact of slowdown of Atlantic overturning circulation on heat and freshwater transports" by Kelly et al. (2016).

05/03/2017:

XBT Science workshop

PIs of the project presented talks on the XBT Science Workshop in Tokyo, Japan, during October 5-7, 2016. (TALKS) Marlos Goes: "The structure and variability of the Brazil Current", and Coll. Mauro Cirano: "Brazil Current structure and variability: the representativeness of the MOVAR-NOAA AX97 High-Density XBT transect".

Interannual Variability of the Brazil Current

PIs: Marlos Goes
Collaborators: Sang-Ki Lee, and Shenfu Dong

The broad goal of this work is to improve understanding of the Brazil Current (BC) system variability on interannual timescales, and the impact of the local and remote surface forcings on the regional variability of the BC. To achieve this goal, we will use a set of oceanographic (in-situ and satellite) data, ocean reanalysis and eddy-resolving model experiments. One of the strengths of the proposed work is that we will use a collection of over a decade long direct measurements of the BC at mesoscale sampling in two locations (22°S and 34°S). In addition, we will examine the interannual variability of the South Atlantic Ocean temperature structure, its relation to sea level and heat content variability, the relationship with the subtropical gyre variability, and their causes. BC variability will provide better climate predictability for the region. In addition, this project will promote a strong collaboration between the University of Miami and the Brazilian scientists. As follows, our research plan will detail the objectives and work tasks to be completed in order to answer the questions above described.

Air-Sea Interactions in the Western South Atlantic Region

PIs: Marlos Goes, and Leo Siqueira
Collaborators: Greg Foltz; Ben Kirtman

Current observational estimates and climate models are moving toward higher spatial and temporal resolutions, allowing for better representations of mesoscale features and their associated air-sea interactions. Western boundary currents in the subtropics are associated with intense heat transport and strong upper temperature fronts. The ability of current climate models to simulate the impact of these currents on the extreme weather events is constrained by to their generally coarse resolution. This work examines the role of increased ocean resolution and a better represented Brazil Current on the air-sea interaction in the western South Atlantic. For this, current observations and two 150-year global climate model simulations with identical atmospheric resolution but contrasting ocean resolutions are used. The boundaries in the South Atlantic ocean present intense coupling between the wind and SST gradients. The impact of the DJF rainfall variability over Subtropical South America is captured by both models, but significant regional differences arise over the Brazil Current region. Ocean temperature sections near the coast also show large differences, with the eddy-resolving model in better agreement with observational estimates. This shows the importance of the resolution of the western boundary current to improving the representation and prediction of regional summer precipitation, and extreme events such as floods and droughts.

Publications

Goes, M., et al., 2017: The variability of the Brazil Current at 22°S from high-density XBT transect and satellite altimetry J. Geophys. Res., in prep.

Siqueira, L., M. Goes, G. Foltz, B. Kirtman, and D. Putrasahan, 2017: Impact of Ocean Resolution on Western South Atlantic Air-sea Interaction during Extreme SST Events J. Climate, submitted.

Lima, M., M. Cirano, M. Mata, M. Goes, G. Goni, and M. O. Baringer, 2016: An assessment of the Brazil Current baroclinic structure and variability near 22°S in distinct Ocean Forecasting and Analysis systems, Ocean Dynamics, 66:893, doi:10.1007/s10236-016-0959-6.

Goes, M., I. Wainer, N. Signorelli, 2014: Investigation of the causes of historical changes in the sub-surface salinity minimum of the South Atlantic. J. Geophys. Res. Oceans, 119, 5654-5675, doi: 10.1002/2014JC009812.

Acknowledgments

This project is sponsored by the National Science Foundation, NOAA Climate Program Office, and NOAA/AOML.