H O L LY G O N Z A L E S

D E C E M B E R 4 , 2 0 1 3

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

• 150-300m 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