Chemical Oceanography

• Chemical Oceanography is the most interdisciplinary of all the sub-disciplines of this interdisciplinary science.– Biological processes in the ocean are controlled by

the chemistry– Chemical components of the ocean influence the

density of seawater and thus affect its circulation.– Chemical components of marine sediments and

glacial ice

Chemical oceanography is the study of ocean chemistry:

– the behavior of the chemical elements within the Earth's oceans.

The ocean is UNIQUE in that it contains - in greater or lesser quantities - nearly every element in the periodic table

What does a chemical oceanographer do?

• “Chemical oceanographers and marine chemists study the composition of seawater, its processes and cycles, and the chemical interaction of seawater with the atmosphere and sea floor. Their work may include analysis of seawater components, the effects of pollutants, and the impacts of chemical processes on marine organisms. They may also use chemistry to understand how ocean currents move seawater around the globe and how the ocean affects climate or to identify potentially beneficial ocean resources such as natural products that can be used as medicines.”

– NOAA

• In 2012, overall, geoscientists, except for hydrologists and geographers, earned median annual salaries of $90,890, according to the U.S. Bureau of Labor Statistics (BLS). The bottom 10 percent earned less than $48,270, while the top 90 percent earned more than $187,199. An individual's salary depends on several factors, such as education, experience, skill set, management ability, and employer

STARTING SALARY offers in 2010 for geological and related sciences averaged $56,689 for master's degree recipients and $58,625 for those holding doctorates. Bachelor's degree recipients' average salary offers were $37,431.

Chemical oceanographers study how ocean water chemistry interacts with the environment.

HW Writing Assignment: Chemical Oceanographer Research Review --• Submit a 3+ paragraph (1/2 - 3/4 of a page) write-up

describing the following:– 1. Who is doing the research? What credentials do they have?

What agencies, universities, or organizations are they associated with?

– 2. What is their research? What questions are they trying to answer or what problems/issues are they trying to resolve? Where?

– 3. What methods are they using? What technologies or tools are they collecting data with? How do they work?

Type this and email it in. – (Use word or GoogleDocs - size 12 font, double spaced, Times New Roman)

DUE: Friday 10/23/15

Water Chemistry.

StatesEnergy/Heat/TemperatureHeat CapacityProperties

cohesion/adhesionviscositycompressibilitydensitydissolving – solvent

Transmission of Energy

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Hydrogen Bonding

• Polarity means small negative charge at O end

• Small positive charge at H end

• Attraction between positive and negative ends of water molecules to each other or other ions

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Hydrogen Bonding

• Hydrogen bonds are weaker than covalent bonds but still strong enough to result in– High water surface tension– High solubility of chemical compounds in water– Unusual thermal properties of water– Unusual density of water

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Water’s Thermal Properties

• Water is solid, liquid, and gas at Earth’s surface.

• Water influences Earth’s heat budget.

Heat Capacity (1 g by 1 oC)• Specific Heat = Heat capacity per unit mass

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Global Thermostatic Effects• Moderate temperature on Earth’s surface

– Equatorial oceans do not boil– Polar oceans do not freeze solid

• Marine effect– Oceans moderate temperature changes from day

to night and during different seasons• Continental effect

– Land areas have greater range of temperatures from day to night and during different seasons

The thermal conductivity of seawater (3.5% dissolved salt by weight) is 0.6 W/mK at 25 °C.

The thermal conductivity:* Decreases with increasing salinity* Increases with increasing temperature

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Earth’s Water

• 97.2% in the world ocean• 2.15% frozen in glaciers and ice caps• 0.62% in groundwater and soil moisture• 0.02% in streams and lakes• 0.001% as water vapor in the atmosphere

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Pure Water vs. Seawater

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Seawater Density

• Freshwater density = 1.000 g/cm3

• Ocean surface water =1.022 to 1.030 g/cm3

• Ocean layered according to density

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Seawater Density

• Density increases with decreasing temperature– Greatest influence on density

• Density increases with increasing salinity• Density increases with increasing pressure

– Does not affect surface waters

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Temperature and Density Variation With Depth

• Pycnocline – abrupt change of density with depth• Thermocline – abrupt change of temperature with

depth

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Layered Ocean

Three distinct water masses based on density:• Mixed surface layer – above thermocline• Upper water – thermocline and pycnocline• Deep water – below thermocline to ocean

floor• High latitude oceans – thermocline and

pycnocline rarely develop– Isothermal– Isopycnal

In oceanography, a halocline (from Greek hals, halo- 'salt' and klinein 'to slope') is a subtype of chemocline caused by a strong, vertical salinity gradient within a body of water. Because salinity (in concert with temperature) affects the density of seawater, it can play a role in its vertical stratification.

A thermocline is a thin but distinct layer in a large body of fluid (e.g. water, such as an ocean or lake, or air, such as an atmosphere) in which temperature changes more rapidly with depth than it does in the layers above or below.

Exploration LAB: Modeling a Pycnocline (Density Gradient) Objective: Create three solutions (aqueous) that will represent the Mixed surface layer,

Upper water, & Deep water.

Variables: DENSITY: Your goal is to have them different enough in density that they will

remain stratified (in layers).

SALINITY: Decide the salt content (grams) and the volume (mL) of each layer. FYI -- At 100 °C (373.15 K, 212 °F), saturated sodium chloride brine is

about 28% salt by weight i.e. 39.12 g salt dissolves in 100 mL of water at 100 °C. At 0 °C (273.15 K, 32 °F), brine can only hold about 26% salt. You will want much less salt than a fully saturated brine.

TEMPERATURE: Determine if you will manipulate the temperature of the solution to increase or decrease density of your solutions.

Create the layers in 100 mL beakers – Use a drop of food coloring for visual display.Slowly combine them to model the three layers of a mid-latitude ocean pycnocline.

TO TURN IN: Write a detailed procedure with mass, volume, and density measurements. Write a conclusion ( 1 paragraph) describing your success and the result of your experiment. *Also make a note about your group’s effectiveness (did everyone do their part?).

Global Density: Thermohaline Circulation

thermo- temperature haline - referring to salt content, *factors which together determine the density of sea water

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Surface Salinity Variation by Latitude

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Surface Salinity Variation

• High latitudes– Low salinity– Abundant sea ice melting, precipitation, and runoff

• Low latitudes near equator– Low salinity– High precipitation and runoff

• Mid latitudes – High salinity– Warm, dry, descending air increases evaporation

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Global Salinity

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Seawater

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Salinity

• Expressed in parts per thousand (ppt)• Typical ocean salinity is 35 ppt (o/oo)

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Processes Affecting Salinity

• Decreasing salinity – adding fresh water to ocean– Runoff, melting icebergs, melting sea ice– Precipitation

• Increasing salinity – removing water from ocean– Sea ice formation– Evaporation

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Processes that Add/Subtract Dissolved Substances

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Earth’s Hydrologic Cycle

Temperature plays a role…

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Determining Salinity

• Evaporation• Chemical analysis–titration

– Principle of constant proportions– Major dissolved constituents in same proportion

regardless of total salinity– Measure amount of halogens (Cl, Br, I, F) (chlorinity) – Salinity = 1.80655 * Chlorinity (ppt)

• Electrical conductivity– Salinometer