Seawater Chemistry & Ocean Stratification

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Key Points

• The salt in seawater is due in part to water’s unique properties.

• Seawater density is influenced by temperature and salinity.

• The ocean has layers as a result of different densities.

How did the Ocean get so salty?• Through a combination of water’s properties

(universal solvent, adhesion) water “picks up” minerals via erosional and weathering processes

• In other words, water physically and

chemically picks up salts

• Make way to the ocean

Hydrological Cycle (Water Cycle)

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What types of elements are found in the ocean’s salts?

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How do we measure the amount of salt in the Ocean?

• Salinity vs. Conductivity

• CTD Rosette– Conductivity– Temperature– Density

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Key Points

• The salt in seawater is due in part to water’s unique properties.

• Seawater density is influenced by temperature and salinity.

• The ocean has layers as a result of different densities.

How is the Ocean Like a Red Velvet

Cake?

Ocean ModelTemperature

De

pth

Surface

Deeper

WarmerColder

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Ocean Model

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“Warm” shallow surface layer

Cold deep layer

Transition Zone

Ocean Model

12How do the layers form?

SurfaceLayer

DeepWater

TransitionZone

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Homogeneous Ocean

Ocean Temperature

Deep Water

• 90% of the total volume of ocean is this cold, deep water. •At depths greater than 1000m, temperature is approximately 4ºC (even in the tropics!!).

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Why do layers form?

Thermocline = Temperature Change

Surface Layer

Transition Zone

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Mass per unit volume

Lighter1.000 g/cm 3

Denser1.022 to 1.030 g/cm3

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Because of Density

Lighter100 kg/m3

Denser19,300 kg/m3

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http://www.youtube.com/watch?v=w_8mw-1HYFg

Ocean Density

Surface Layer

Deep Water

• Seawater density is controlled by Temperature and Salinity

•In the ocean, Temperature has a greater effect on density

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Pycnocline = Density ChangePycnocline

Transition Zone

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SurfaceLayer

DeepWater

BoundaryTransitionZone

Thermocline & Pycnocline

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SurfaceLayer

DeepWater

Boundary

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Mixed

Warmed and lit by sun

Photosynthesis

Cold, Dark, No Photosynthesis

Less Nutrients

, More Nutrients

Surface Ocean

• Warm• Lit by the sun• Has photosynthesis• Less nutrients

Deep Ocean

• Cold• Dark• No photosynthesis• More Nutrients• LOTS AND LOTS OF

PRESSURE

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Main Differences…