Oceanic fronts and ecosystems in the Southern Ocean: a review of recent progress

The Southern Ocean is a fundamental component of the global climate system and an important ecoregion, hosting a diverse range of interdependent flora and fauna. One unique aspect of its physical environment is that it hosts numerous fronts: sharp boundaries between waters with different characteristics.

Fronts are known to be of great importance to the Southern Ocean environment and the ecosystems it supports. The great advances in biotelemetry tools for animal tracking and the resulting fine-scale animal movement data, coupled with the availability of higher resolution ocean observations from satellites, have recently enabled identification of relationships between marine animals and complex, mesoscale ocean processes. The biota of the Southern Ocean are broadly structured around the principal frontal features of the region: The fronts, by their ability to suppress horizontal exchange of tracers, both create and delimit ecological niches occupied by particular species, supported by water masses with similar characteristics. The challenge for biologists is to integrate observations of animal movements and feeding with the fine-scale physical and biogeochemical properties of Southern Ocean fronts.

Here we review the rapid advances made in understanding Southern Ocean fronts over the last decade and discuss the implications for Southern Ocean ecosystems and the broader climate system. We address the controversy of whether the locations of Southern Ocean fronts have shifted as a result of ongoing climate change, and how the choice of frontal definition can impact the conclusions of a study. We provide a ‘Southern Ocean fronts User Guide’ aimed at the broader scientific community to facilitate future research with advice on how to best exploit new data and techniques to answer outstanding questions.