IMIS

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 Niño event and impact of regional climate change. During the 1997–1998 El Niño, 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 Niño events. During El Niño, 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.

Multispecific ecotrophic models of the Northern Humboldt Current Ecosystem have been used to simulate energy flows through the food web, during El Niño and La Niña conditions. Steady-state models simulated a decrease in total throughput and ecosystem organization during 1997–98 El Niño. Time dynamic models simulated contributions of several external drivers, being most important fishing rate, followed by mesopelagics immigration and phytoplankton changes. These basic models will contribute to implement the ecosystem approach to fisheries, allowing to assess the impact of fishing and environmental factors on economically important species such as anchovy and hake.