Rapid Subsurface Ocean Warming in the Bay of Fundy as Measured by Free-Swimming Basking Sharks

Abstract

It is widely recognized that the western North Atlantic has recently warmed very rapidly. Sea surface temperatures (SST) in 2012 were measured to be 1–3°C higher than the 1982–2011 average (Mills et al., 2013). In particular, in continental shelf regions, such as the Gulf of Maine (GoM), there was pronounced warming, with SSTs > 2°C higher than normal, to almost 20°C, during this "ocean heat wave." Although the specific cause of this warming trend is still being debated, it may have implications for local fauna; concurrent shifts in the distributions of marine organisms associated with local climate changes have already been reported (Nye et al., 2009; Pinsky et al., 2013). Ocean warming trends are usually discussed in terms of SST changes, with few studies considering events in benthic habitats. The GoM (Figure 1) is monitored by the Northeastern Regional Association of Coastal and Ocean Observing Systems (NERACOOS, http://www.neracoos.org) buoy system that uses remote buoys with probes to 200 m, though only in a few fixed locations. The goal of this study was to determine whether the 2012 warming trend extended into subsurface habitats in the northern reaches of the GoM and adjacent Bay of Fundy (BoF). This highly productive body of water is located in the northern corner of the GoM, but has different oceanographic patterns due to its enormous tides (changing by 6–12 m twice daily). Whether BoF water column temperature profiles mirror those of the central GoM has been unclear, as there are no oceanographic sensing buoys present.

Keywords

• Gulf of Maine
• ocean warming
• basking sharks
• Bay of Fundy
• NERACOOS