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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.
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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
At smaller scales... • Strong west winds
Pelagic Ecosystems 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 hn NUTS Fixed Carbon CO2 O2
Coastal Upwelling • California Current • April 1978 • AVHRR - SST • CZCS Chlorophyll Chl SST
Respiration & Remineralization hn CO2 O2 remineralizers NUTS Plants Biological processes consume plants & O2 to make CO2 & nutrients
Euphotic Zone 1% Light 100% Light Euphotic Zone – PP happens Aphotic Zone - Respiration & Remineralization Depth of Euphotic Zone is f(water clarity)
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 Secchi = 7 m Depth (m) Secchi = 18 m % surface light
The Upwelling Conveyor Belt Lower Chl High Chl Low Chl Low NUTS High NUTS Sinking Flux of Carbon Highest NUTS & CO2
Carbonate Chemistry CO2 CO2(aq) (CO2 + H2O) H2CO3 K1 photosynthesis respiration HCO3-+ H+ K2 ocean food web CO3-2+ 2H+ calcifiers
Acidification • Increasing CO2: • Increases acidity (lowers pH) • Lowers CO3- availability • Lowers CaCO3(s) saturation state Calderia & Wickett, Nature [2003]
More Seawater Chemistry • Increasing CO2: • Increases acidity (lowers pH) • Lowers CaCO3(s) saturation state “” • Multiple forms of CaCO3: aragonite, calcite, Mg-calcite with different solubility = [Ca2+][CO32-] / Ksp Δ[CO32-] =[CO32-]obs - [CO32-]sat
warm-water corals Biological Impacts • -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 lobsters, crabs some plankton cold-water corals pteropods planktonic snails scallops, clams, oysters
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 R. A. Feely et al., Science 320, 1490 -1492 (2008) Published by AAAS
Fig. 2. Vertical sections of (A) temperature, (B) aragonite saturation, (C) pH, (D) DIC, and (E) pCO2 on transect line 5 off Pt George Published by AAAS R. A. Feely et al., Science 320, 1490 -1492 (2008)
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