Multiple thermal fronts near the Patagonian shelf break

Bárbara C. Franco,Andrés L. Rivas,Juan P. Pisoni,Ana Baldoni,Alberto R. Piola

doi:10.1029/2007gl032066

Abstract

Eighteen year (1985–2002) sea surface temperature (SST) data are used to study the intraseasonal variability of the Patagonian shelf break front (SBF) in the SW South Atlantic Ocean between 39° and 44°S. The cross‐shelf break SST gradients reveal distinct, previously undocumented thermal fronts located both, offshore and inshore of the SBF. Throughout the year the main SBF, identified as a band of negative SST gradient maxima (relatively strong offshore temperature decrease), forms a persistent feature located closed to the 200 m isobath, while two distinct negative gradient maxima are located inshore and offshore of this location. Daily SST images reveal the presence of three branches of cold waters whose edges delineate the above mentioned fronts. The two offshore branches closely follow lines of constant potential vorticity (f/h) and appear to be associated with the Malvinas Current, while a third branch, located further onshore, is not steered by the bottom topography. South of 40°S the onshore branch forms a quasi permanent front parallel to the SBF.

Highlights

[1] Eighteen year (1985 – 2002) sea surface temperature (SST) data are used to study the intraseasonal variability of the Patagonian shelf break front (SBF) in the SW South Atlantic Ocean between 39° and 44°S
[8] Climatological (1985– 2002) monthly means of satellite-derived gSST were analyzed in the area between 39° and 44°S near the shelf break at 1° latitude intervals (Figure 1)
The analysis shows that the SBF is characterized by a negative gSST maximum located near the 200 m isobath

Summary

Introduction

[1] Eighteen year (1985 – 2002) sea surface temperature (SST) data are used to study the intraseasonal variability of the Patagonian shelf break front (SBF) in the SW South Atlantic Ocean between 39° and 44°S. Other studies suggest that surface chl-a blooms at the shelf break are located inshore of the thermal front [Romero et al, 2006]. Given the ecological importance of the SBF and the evidence of its seasonal zonal displacements near 39°S, in this article we discuss the seasonal and intraseasonal frontal variability based on the analysis of 18 years of monthly mean SST data.

Results

Conclusion