HOLLY GONZALES DECEMBER 4, 2013 Humboldt Current System

Characteristics Eastern boundary of subtropical South Pacific Gyre Bordering Chile and Peru Cold water current Mean surface speed: 6 cm/s Shallow: ~100 m Driven by alongshore equatorward winds Ekman offshore transport creates upwelling zone High primary productivity

Current System ACC = Antarctic Circumpolar Current splits north and south HC = Humboldt Current Subantarctic Water (SAAW) Chile Coastal Current CHC = Cape Horn Current PC = Peru Countercurrent Warmer, saltier transported south (Subtropical Water) PCU = Peru-Chile Undercurrent m depth subsurface salinity maximum (Equatorial Subsurface Water) N. Silva et al., 2009

T-S Plot of Region Subtropical Water (STW) – Salty and warm Subantarctic Water (SAAW) – Fresher and cold Equatorial Subsurface Water (ESSW) – Salinity maximum and cold Antarctic Intermediate Water (AAIW) – Fresher and very cold Pacific Deep Water (PDW) – very cold and saltier N. Silva Et al., 2009

Water Masses Water mass percentages (A) Longitudinal Section (B) Latitudinal Section at 28° S (C) Latitudinal Section at 43° S STW=Subtropical Water, SAAW=Subantarctic Water, ESSW=Equatorial Subsurface Water, AAIW=Antarctic Intermediate Water, PDW=Pacific Deep Water N. Silva Et al., 2009

Seasonal Variability – Chile Coastal Current Spring and summer - coastal jet structure Fall – Jet moves farther from shore Winter – Weak equatorward flow Winter, South of 36° S -poleward flow, downwelling AGUIRRE ET AL.: SEASONAL DYNAMICS OF THE ALONGSHORE FLOW

El Niño Water temperatures increase by 2 to 3° C Sea level rises 40 to 50 cm Weakened upwelling Reduced nutrient availability Anchovy and other fish populations collapse