Go with the flow under a changing climate: the role of advection in marine ecosystems

Ekaterina Popova (1), Simon van Gennip (2), Andrew Yool (3)

1 National  Oceanography Centre, Empress Dock, Southampton, SO14 3ZH, UK. ekp@noc.ac.uk

2 National  Oceanography Centre, Empress Dock, Southampton, SO14 3ZH, UK. s.van.gennip@noc.ac.uk

3 National  Oceanography Centre, Empress Dock, Southampton, SO14 3ZH, UK. axy@noc.ac.uk

Ocean warming, acidification, deoxygenation and reduced productivity are widely considered to be the major stressors to ocean ecosystems induced by anthropogenic emissions of CO2 and climate change. However, a stressor overlooked in this list is the change in ocean circulation.. Strong changes in the intensity and positions of western boundary currents are already observed, and the consequences of such changes for ecosystems are beginning to emerge.

Diagnosing a change in the strength and position of major currents in future projections of ocean models is a reasonably straightforward task. What is much less clear is how to relate such change to the impacts that it may impose on ocean ecosystems. Running complex models of biological behaviour in parallel with that of climate models at resolution sufficient to meaningfully resolve current systems is not feasible given current computation resources. However, by viewing circulation change from a Lagrangian point of view, it becomes possible to investigate how circulation change may link to ecosystem dynamics.

In this study, we use a high resolution ocean model run under an extreme climate change scenario to examine climatically-induced changes in ocean circulation at the global scale. The model resolution of ¼-degree permits regional ocean circulation that is much more realistic than that possible in IPCC AR5-class models, and represents change in this circulation with direct relevance to global shelf ecosystems. Using this, we identify hotspots of circulation change and present examples of the most significant changes in ocean currents projected to occur over the current century.