Modelling the Northern Humboldt Current Ecosystem: From Winds to Predators

Atmospheric models with embedded domains off Peru have been used to simulate surface winds. Coastal wind dynamics were simulated to investigate the effect of two warming conditions: impact of El Nino event and impact of regional climate change. During the 1997–1998 El Nino, a counter-intuitive coastal wind increase was observed; sensitivity experiments showed that the inhomogeneous alongshore surface warming, larger in the north, drives an enhanced alongshore pressure gradient that accelerates the alongshore wind. Under the “worst case” RCP8.5 climate change scenario, coastal summer winds decrease (<5%) whereas coastal winter winds increase (<10%), thus slightly reinforcing the seasonal cycle, these wind changes were mainly associated with changes in the intensity and position of the South Pacific Anticyclone. Physical-biogeochemical models off Peru have been used to reproduce the oceanographic conditions from 1958 to 2008. Primary productivity and dissolved oxygen were simulated to investigate the effect of El Nino events. During El Nino, the productivity decreases due to nutrient depletion associated with intense downwelling Coastal Trapped Waves and due to an enhanced light limitation in summer. The surface layer becomes more ventilated as the oxycline deepens in association with the thermocline. The enhanced eddy kinetic energy also impacts eddy fluxes of nutrient and oxygen. During the last decades, the large-scale remote forcing associated with equatorial variability mainly drives the summer chlorophyll increase and progressive deoxygenation trends during the last decades, whereas local winds play a minor role.