Seasonal Variability of SST Fronts in the Inner Sea of Chiloé and Its Adjacent Coastal Ocean, Northern Patagonia

Gonzalo S. Saldías,Wilber Hernández,Carlos Lara,Sebastián Vásquez,Luis Soto-Mardones,Cristian Rojas,Richard Muñoz,Iván Pérez-Santos

doi:10.3390/rs13020181

Abstract

Surface oceanic fronts are regions characterized by high biological activity. Here, Sea Surface Temperature (SST) fronts are analyzed for the period 2003–2019 using the Multi-scale Ultra-high Resolution (MUR) SST product in northern Patagonia, a coastal region with high environmental variability through river discharges and coastal upwelling events. SST gradient magnitudes were maximum off Chiloé Island in summer and fall, coherent with the highest frontal probability in the coastal oceanic area, which would correspond to the formation of a coastal upwelling front in the meridional direction. Increased gradient magnitudes in the Inner Sea of Chiloé (ISC) were found primarily in spring and summer. The frontal probability analysis revealed the highest occurrences were confined to the northern area (north of Desertores Islands) and around the southern border of Boca del Guafo. An Empirical Orthogonal Function analysis was performed to clarify the dominant modes of variability in SST gradient magnitudes. The meridional coastal fronts explained the dominant mode (78% of the variance) off Chiloé Island, which dominates in summer, whereas the SST fronts inside the ISC (second mode; 15.8%) were found to dominate in spring and early summer (October–January). Future efforts are suggested focusing on high frontal probability areas to study the vertical structure and variability of the coastal fronts in the ISC and its adjacent coastal ocean.

Highlights

Oceanic fronts are relatively narrow regions with high gradients of physical, chemical, biological, and optical properties
This study aims to characterize the seasonal and interannual variability of surface thermal fronts along the Inner Sea of Chiloé and its adjacent coastal ocean
There is a slight underestimation by Multi-scale Ultrahigh Resolution (MUR) sea surface temperature (SST) (Figure 1c)

Summary

Introduction

Oceanic fronts are relatively narrow regions with high gradients of physical, chemical, biological, and optical properties. They are generally associated with convergence at the surface [1] and high aggregation of organisms and biological activity e.g., [2,3]. Frontal features and currents such as jets and meanders e.g., [6,7], filaments e.g., [8,9], and river discharges e.g., [10,11] present distinct patterns of variation in strength and duration over multiple temporal scales and are identified from satellite sea surface temperature (SST) fields. High-resolution (1 km) SST images are used to analyze the variability of SST fronts in the Inner Sea of Chiloé (ISC) and adjacent coastal ocean (northern Chilean Patagonia). The development of chlorophyll patches and blooms have been suggested to develop around frontal regions [25], there are no major insights into the evolution and distribution of surface fronts along the ISC

Objectives

Results

Conclusion