Climate-change-driven cooling can kill marine megafauna at their distributional limits

The impacts on marine species from secular warming and heatwaves are well demonstrated, however the impacts of extreme cold events are poorly understood. Here, we link the death of organisms from 81 species to an intense cold upwelling event in the Agulhas Current, and show trends of increasing frequency and intensification of upwelling in the Agulhas Current and East Australian Current. Using electronic tagging, we illustrate potential impacts of upwelling events on the movement behaviour of bull sharks, Carcharhinus leucas including alterations of migratory patterns and maintenance of shallower dive profiles when transiting through upwelling cells. Increasing upwelling could result in “bait-and-switch” situations, where climate change expands subtropical species’ distribution, while simultaneously exposing climate-migrants to increased risk of cold-stun/mortality events at poleward distributional limits. This shows the potential impacts of increased cold events, an understudied aspect..., Study areas
Both study areas are located along Western Boundary Currents (WBCs): the Agulhas Current in southern Africa and the East Australian Current in eastern Australia. In southern Africa, the area spans from the warm-temperate Breede River estuary on the south coast of South Africa (34.5°S) to northern Mozambique (16°S) (Figs. 1, 5a main MS). In eastern Australia, the area extends from the warm-temperate Sydney Harbour estuary (33.5˚S) to tropical Queensland (16.5˚S) (Fig. 5b main MS). On both continents, the study areas were divided into two distinctive zones (Fig. 5a, b main MS). First, an upwelling zone, comprising multiple coastal upwelling cells inshore of each WBC, extending from the southern limit equatorward to 32.4°S along the Agulhas Current and 28.6°S along the East Australian Current. This zone includes the Breede River and Sydney Harbour estuaries in South Africa and Australia, respectively (Fig. 5a, b main MS). The second zone, in each case, was the subtropical/tropi..., , # Climate-change-driven cooling can kill marine megafauna at their distributional limits

Bull Shark PSAT Data and example code for modeling of upwelling variables:

## Description of the Data and file structure

These data include two different data sets

Data set 1 contains 5 csv. files with raw depth and temperature data collected by PSAT-tags externally attached to bull sharks tagged in the Breede River in South Africa (n=5, 1 per shark). For this study, recorded depth (in m) and temperature (in °C) were the main variables used. For Shark ID1, ID2, ID4 and ID5 PSAT-tag series data was available. This includes the columns DeployID and PTT which are each sharks individual identifier number, DepthSensor which is the depth sensor resolution in m, a Source column which describes the source of the data, in the case of our PSAT-tags this is by Transmission, an Instrument column which describes the tag type, in our case MiniPAT, Day and Time columns provided in UTC. The Depth column provide...