Coastal Upwelling

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Coastal Upwelling

• Equatorward winds along a coastline lead to offshore Ekman transport

• Mass conservation requires these waters replaced by cold, denser waters

• Brings nutrients into surface waters creating blooms

• Creates dynamic height gradients - currents

Coastal Upwelling

April 2000 CalCoFI Cruise

At smaller scales...

• Strong west winds

Ocean Biogeochemistry in a Nutshell

• Light energy drives the net fixation of carbon

• Within the euphotic zone, nutrients & CO2 produce CO2 & fixed carbon

• Below the euphotic zone, the rxn’s reverse

PelagicEcosystems

Fixed Carbon

Coastal Upwelling

• California Current

• April 1978

• AVHRR - SST

• CZCS Chlorophyll

SSTChl

Respiration & Remineralizati

remineralizers

CO2 O2

PlantsNUTS

Biological processes consume plants & O2 to make CO2 & nutrients

Euphotic Zone

Euphotic Zone – PP happens

Aphotic Zone - Respiration & Remineralization

Depth of Euphotic Zone is f(water clarity)

100% Light

1% Light

Euphotic Zone

• Defined as the depth where the light = 1% of the surface value

• A function of plant biomass or chlorophyll concentration

• Varies from 10 to 130 m

• Typically, Zeu = 3 * Secchi depth

CalCoFI Light Profiles

% surface light

Secchi = 7 m

Secchi = 18 m

The Upwelling Conveyor Belt

Highest NUTS & CO2

High NUTSLow NUTS

High Chl Low ChlLower Chl

Sinking Flux of Carbon

CO2(aq) (CO2 + H2O)

photosynthesisrespiration

HCO3- + H+

oceanfood web

Carbonate Chemistry

calcifiers

Increasing CO2: •Increases acidity (lowers pH)•Lowers CO3

- availability•Lowers CaCO3(s) saturation state

Acidification

Calderia & Wickett, Nature [2003]

Increasing CO2: •Increases acidity (lowers pH)•Lowers CaCO3(s) saturation state “”Multiple forms of CaCO3: aragonite, calcite, Mg-calcite with different solubility

More Seawater Chemistry

= [Ca2+][CO32-] / Ksp

Δ[CO32-] = [CO3

2-]obs - [CO32-]sat

-Shell forming plants & animals

•reduced shell formation (calcification)•lower reproduction & growth rates

-Habitat loss (reefs)-Less food for predators

•humans, fish, whales-Possible negative effects on larvae

Biological Impacts

warm-water corals

cold-water corals

lobsters, crabs some plankton

pteropodsplanktonic snails

scallops, clams, oysters

Published by AAAS

R. A. Feely et al., Science 320, 1490 -1492 (2008)

Fig. 1. Distribution of the depths of the undersaturated water (aragonite saturation < 1.0; pH < 7.75) on the continental shelf of western North America from Queen

Charlotte Sound, Canada, to San Gregorio Baja California Sur, Mexico

Published by AAAS R. A. Feely et al., Science 320, 1490 -1492 (2008)

Fig. 2. Vertical sections of (A) temperature, (B) aragonite saturation, (C) pH, (D) DIC, and (E) pCO2 on transect line 5 off Pt George

Review• Wind stress along coasts leads to divergence of surface Ekman transport

• This drives to coastal upwelling and forms a coastal jet

• This drives the productivity of eastern boundary currents

• Important for acidification of the coastal ocean

Coastal Upwelling

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